Annual review of selected scientific literature 1

The Journal of Prosthetic Dentistry

11July 2009

Donovan et alDonovan et al

Annual review of selected scientific literature: Report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry

Terence E. Donovan, DDS,a Maxwell Anderson, DDS, MS, MEd,b William Becker, DDS,c David R. Cagna, DMD, MS,d

Thomas J. Hilton, DDS, MS,e and Jeffrey Rouse, BS, DDSf

University of North Carolina, Chapel Hill, NC; University of Southern California, Los Angeles, Los Angeles, Calif; University of Tennessee Health Science Center, Memphis, Tenn; University of Oregon Health and Science University, Portland, Ore; University of Texas Health Science Center at San Antonio, San Antonio, Tex

aChair, Committee on Scientific Investigation, AARD; Professor and Section Head for Biomaterials, Department of Operative Den-tistry, University of North Carolina. bPrivate practice, Sequim, Wash.cClinical Professor, Advanced Education in Prosthodontics, University of Southern California, Los Angeles; private practice, Tucson, Ariz.dProfessor and Director, Advanced Prosthodontics, University of Tennessee Health Science Center, College of Dentistry.eAlumni Centennial Professor in Operative Dentistry, Oregon Health and Science University.fPrivate practice; San Antonio, Tex.(J Prosthet Dent 2009;102:10-45)

In the past decade, there has been an explosion in the volume of dental literature. New journals have been introduced on a regular basis and are competing with many of the es-tablished journals with a long history of publication. Dentists are urged to practice evidence-based dentistry at a time when commercialization of the profession has become rampant and materials are routinely brought to the marketplace with little or no clinical documentation.

While the volume of scientific lit-erature has increased dramatically, the quality of the evidence produced leaves much to be desired. Many ar-ticles are simply clinical reports that, while they may be of interest to clini-cians, are low in the desired hierarchy of evidence. Many clinical trials are neither randomized nor controlled, and also are underpowered by virtue of relatively small samples sizes. Most authors of systematic reviews lament the fact that there are not enough properly conducted randomized con-

trolled clinical trials (RCTs) to answer the primary question posed by the re-view.

The primary purpose of this re-view is to assist practicing dentists in clinical decision making and to guide them to the best scientific evidence published in 2008. The Committee on Scientific Investigation has care-fully reviewed and selected articles published in 2008 because they be-lieve the resultant data contributes to the advancement of the practice of evidence-based dentistry. Comments on study design, statistical analysis, and the relative strengths of the find-ings are included to aid the reader in interpretation of the results.

The analysis of the scientific lit-erature published in 2008 is divided into 6 sections: (1) caries and pulp pathology; (2) periodontics; (3) dental materials; (4) occlusion, tem-poromandibular disorders, and sleep-disordered breathing; (5) prostho-dontics; and (6) implant dentistry.

CARIES AND PULP PATHOLOGY

A number of studies were pub-lished last year on pulp capping, particularly on the effect of different materials on pulp capping outcomes. One such study evaluated the expres-sion of fibronectin and type III col-lagen in human pulps following pulp capping with calcium hydroxide (cal-cium hydroxide powder followed by placement of Dycal; Dentsply Caulk, Milford, Del) or a 2-step, etch-and-rinse adhesive (Single Bond; 3M ESPE, St. Paul, Minn).1 Fibronectin is con-sidered to be a marker for reparative dentin, and type III collagen is synthe-sized during the initial healing phase of tissue repair. Forty-six healthy pre-molars indicated for orthodontic ex-traction were randomly assigned to 1 of 3 groups: (1) control, no pulp cap; (2) pulps exposed and capped with adhesive; or (3) pulps exposed and capped with calcium hydroxide. Pulp caps were covered with resin-modi-

fied glass ionomer and restored with composite resin. Teeth were extracted 7 or 30 days after treatment.

The results showed that calcium hydroxide-capped pulps had similar type III collagen and fibronectin ex-pression as the control (noncapped) pulps, and both of these were signifi-cantly greater than the expression in the adhesive-capped pulps. Further-more, the adhesive-capped pulps showed persistent inflammatory process throughout the study period. This study demonstrated that healthy pulps, even in the absence of bacte-rial contamination, did not produce extracellular matrix elements when capped with a 2-step, etch-and-rinse adhesive.

Another study evaluated the re-sponse of human pulps when capped with a self-etch adhesive system.2 Thirty-four healthy human premolars scheduled to be extracted for orth-odontic reasons had the pulps inten-tionally exposed and capped with 1 of 2 self-etch adhesives (Liner Bond 2V; Kuraray Co, Ltd, Osaka, Japan, or Clearfil SE Bond; Kuraray Co, Ltd) or calcium hydroxide (Dycal; Dentsply Caulk). All teeth were restored with self-etch adhesive and composite res-in. Teeth were extracted at 30 or 90 days and assessed histologically. The results showed significantly more den-tin bridge formation and significantly less inflammation in teeth capped with calcium hydroxide compared to those capped with the self-etch adhesive. There was no difference in the performance of the 2 adhesives. These results occurred despite there being little to no bacterial contamina-tion of the specimens.

The use of mineral trioxide aggre-gate (MTA) (ProRoot MTA; Dentsply Tulsa Dental Specialties, Tulsa, Okla) has captured the attention of the pro-fession. Its use, initially for sealing root ends after surgery, has expanded and now includes pulp capping. A number of studies using MTA for pulp capping have been published recently. One such study observed 40 subjects with 53 direct pulp caps due to car-

ies (49 recalled) over periods of 1 to 9 years (mean, 3.94 years).3 No teeth exhibited abnormal radiographic or periodontal findings, and no teeth had pain in response to percussion. Bleeding was controlled with sodium hypochlorite; MTA was placed over the exposure and sealed in place with a moist cotton pellet for 5-10 days be-fore final restoration with a bonded composite resin restoration. Recall data were based on self-reports from patients, periapical radiographs, and testing with a cold stimulus. The over-all survival rate was 98%. The authors note that the outcomes suggest that MTA is a more predictable pulp-cap-ping material than calcium hydroxide. However, calcium hydroxide was not evaluated in this study, there was no control group (or any other group pulp capped with any other material), the subjects were not randomized to groups, all clinical procedures were accomplished by a single operator, and no histological evaluation was in-cluded. Therefore, the results provide a low level of evidence, and no clear justification for this statement.

Several other studies compared the outcomes of pulp capping with MTA or calcium hydroxide. Most of these studies were performed using healthy teeth, typically premolars scheduled for extraction for orthodontics. In-vestigators in 1 study intentionally exposed the pulps of 40 premolars, controlled hemorrhage with saline, and capped the exposures with either MTA or calcium hydroxide powder and calcium hydroxide cement (Life; Kerr Corp, Orange, Calif ).4 The au-thors restored the preparations with a reinforced zinc-oxide eugenol cement (IRM; Dentsply Caulk), extracted the teeth after 30 or 60 days, and evaluat-ed the pulps histologically. There were no significant differences between the 2 groups in terms of inflammation or dentin bridge formation, although there was a trend towards superior performance in the calcium hydrox-ide specimens in terms of dentin bridge formation after 30 days, and a tendency towards less inflamma-

tion in the MTA groups after 30 and 60 days.

Another study by the same lead investigator used a methodology similar to the previous study.5 Again, 40 healthy premolars had the pulps intentionally exposed, hemorrhage was controlled with saline, and expo-sures were capped with either MTA or calcium hydroxide. In this study, the calcium hydroxide group was directly pulp capped with calcium hydroxide cement (Life; Kerr Corp) without the intervening layer of calcium hydroxide powder. The capping materials were sealed with resin-modified glass iono-mer (Vitrebond; 3M ESPE), bonded with a 3-step, etch-and-rinse adhe-sive (Scotchbond Multi-Purpose; 3M ESPE), and restored with composite resin (Z100; 3M ESPE). Teeth were extracted after 30 or 60 days and evaluated histologically. In this study, the MTA showed significantly better dentin bridge formation and other pulpal findings (particles of capping materials in pulp tissue) at 30 days compared to calcium hydroxide, but these differences disappeared after 60 days. There were no significant differences in the other assessed cat-egory of pulpal inflammation.

In a study that evaluated the effect of MTA and calcium hydroxide on re-parative dentin bridge formation fol-lowing pulp capping, the researchers evaluated markers for odontoblast differentiation (dentin sialoprotein, DSP) and cellular protection (heme oxygenase, HO-1).6 Intentional pulp exposures were made in 20 healthy third molars, bleeding was controlled with saline, pulp capping was per-formed with MTA or calcium hydrox-ide cement (Dycal; Dentsply Caulk), resin-modified glass ionomer (Fuji II LC; GC America, Alsip, Ill) was used for sealing, and the preparations were restored with bonded compos-ite resin. Teeth were extracted after 2 months and subjected to histological evaluation and immunochemistry. There were no differences between the 2 groups in terms of inflamma-tion, but the MTA group showed a


11July 2009


Annual review of selected scientific literature: Report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry

Terence E. Donovan, DDS,a Maxwell Anderson, DDS, MS, MEd,b William Becker, DDS,c David R. Cagna, DMD, MS,d

Thomas J. Hilton, DDS, MS,e and Jeffrey Rouse, BS, DDSf

University of North Carolina, Chapel Hill, NC; University of Southern California, Los Angeles, Los Angeles, Calif; University of Tennessee Health Science Center, Memphis, Tenn; University of Oregon Health and Science University, Portland, Ore; University of Texas Health Science Center at San Antonio, San Antonio, Tex

aChair, Committee on Scientific Investigation, AARD; Professor and Section Head for Biomaterials, Department of Operative Den-tistry, University of North Carolina. bPrivate practice, Sequim, Wash.cClinical Professor, Advanced Education in Prosthodontics, University of Southern California, Los Angeles; private practice, Tucson, Ariz.dProfessor and Director, Advanced Prosthodontics, University of Tennessee Health Science Center, College of Dentistry.eAlumni Centennial Professor in Operative Dentistry, Oregon Health and Science University.fPrivate practice; San Antonio, Tex.(J Prosthet Dent 2009;102:10-45)

In the past decade, there has been an explosion in the volume of dental literature. New journals have been introduced on a regular basis and are competing with many of the es-tablished journals with a long history of publication. Dentists are urged to practice evidence-based dentistry at a time when commercialization of the profession has become rampant and materials are routinely brought to the marketplace with little or no clinical documentation.

While the volume of scientific lit-erature has increased dramatically, the quality of the evidence produced leaves much to be desired. Many ar-ticles are simply clinical reports that, while they may be of interest to clini-cians, are low in the desired hierarchy of evidence. Many clinical trials are neither randomized nor controlled, and also are underpowered by virtue of relatively small samples sizes. Most authors of systematic reviews lament the fact that there are not enough properly conducted randomized con-

trolled clinical trials (RCTs) to answer the primary question posed by the re-view.

The primary purpose of this re-view is to assist practicing dentists in clinical decision making and to guide them to the best scientific evidence published in 2008. The Committee on Scientific Investigation has care-fully reviewed and selected articles published in 2008 because they be-lieve the resultant data contributes to the advancement of the practice of evidence-based dentistry. Comments on study design, statistical analysis, and the relative strengths of the find-ings are included to aid the reader in interpretation of the results.

The analysis of the scientific lit-erature published in 2008 is divided into 6 sections: (1) caries and pulp pathology; (2) periodontics; (3) dental materials; (4) occlusion, tem-poromandibular disorders, and sleep-disordered breathing; (5) prostho-dontics; and (6) implant dentistry.

CARIES AND PULP PATHOLOGY

A number of studies were pub-lished last year on pulp capping, particularly on the effect of different materials on pulp capping outcomes. One such study evaluated the expres-sion of fibronectin and type III col-lagen in human pulps following pulp capping with calcium hydroxide (cal-cium hydroxide powder followed by placement of Dycal; Dentsply Caulk, Milford, Del) or a 2-step, etch-and-rinse adhesive (Single Bond; 3M ESPE, St. Paul, Minn).1 Fibronectin is con-sidered to be a marker for reparative dentin, and type III collagen is synthe-sized during the initial healing phase of tissue repair. Forty-six healthy pre-molars indicated for orthodontic ex-traction were randomly assigned to 1 of 3 groups: (1) control, no pulp cap; (2) pulps exposed and capped with adhesive; or (3) pulps exposed and capped with calcium hydroxide. Pulp caps were covered with resin-modi-

fied glass ionomer and restored with composite resin. Teeth were extracted 7 or 30 days after treatment.

The results showed that calcium hydroxide-capped pulps had similar type III collagen and fibronectin ex-pression as the control (noncapped) pulps, and both of these were signifi-cantly greater than the expression in the adhesive-capped pulps. Further-more, the adhesive-capped pulps showed persistent inflammatory process throughout the study period. This study demonstrated that healthy pulps, even in the absence of bacte-rial contamination, did not produce extracellular matrix elements when capped with a 2-step, etch-and-rinse adhesive.

Another study evaluated the re-sponse of human pulps when capped with a self-etch adhesive system.2 Thirty-four healthy human premolars scheduled to be extracted for orth-odontic reasons had the pulps inten-tionally exposed and capped with 1 of 2 self-etch adhesives (Liner Bond 2V; Kuraray Co, Ltd, Osaka, Japan, or Clearfil SE Bond; Kuraray Co, Ltd) or calcium hydroxide (Dycal; Dentsply Caulk). All teeth were restored with self-etch adhesive and composite res-in. Teeth were extracted at 30 or 90 days and assessed histologically. The results showed significantly more den-tin bridge formation and significantly less inflammation in teeth capped with calcium hydroxide compared to those capped with the self-etch adhesive. There was no difference in the performance of the 2 adhesives. These results occurred despite there being little to no bacterial contamina-tion of the specimens.

The use of mineral trioxide aggre-gate (MTA) (ProRoot MTA; Dentsply Tulsa Dental Specialties, Tulsa, Okla) has captured the attention of the pro-fession. Its use, initially for sealing root ends after surgery, has expanded and now includes pulp capping. A number of studies using MTA for pulp capping have been published recently. One such study observed 40 subjects with 53 direct pulp caps due to car-

ies (49 recalled) over periods of 1 to 9 years (mean, 3.94 years).3 No teeth exhibited abnormal radiographic or periodontal findings, and no teeth had pain in response to percussion. Bleeding was controlled with sodium hypochlorite; MTA was placed over the exposure and sealed in place with a moist cotton pellet for 5-10 days be-fore final restoration with a bonded composite resin restoration. Recall data were based on self-reports from patients, periapical radiographs, and testing with a cold stimulus. The over-all survival rate was 98%. The authors note that the outcomes suggest that MTA is a more predictable pulp-cap-ping material than calcium hydroxide. However, calcium hydroxide was not evaluated in this study, there was no control group (or any other group pulp capped with any other material), the subjects were not randomized to groups, all clinical procedures were accomplished by a single operator, and no histological evaluation was in-cluded. Therefore, the results provide a low level of evidence, and no clear justification for this statement.

Several other studies compared the outcomes of pulp capping with MTA or calcium hydroxide. Most of these studies were performed using healthy teeth, typically premolars scheduled for extraction for orthodontics. In-vestigators in 1 study intentionally exposed the pulps of 40 premolars, controlled hemorrhage with saline, and capped the exposures with either MTA or calcium hydroxide powder and calcium hydroxide cement (Life; Kerr Corp, Orange, Calif ).4 The au-thors restored the preparations with a reinforced zinc-oxide eugenol cement (IRM; Dentsply Caulk), extracted the teeth after 30 or 60 days, and evaluat-ed the pulps histologically. There were no significant differences between the 2 groups in terms of inflammation or dentin bridge formation, although there was a trend towards superior performance in the calcium hydrox-ide specimens in terms of dentin bridge formation after 30 days, and a tendency towards less inflamma-

tion in the MTA groups after 30 and 60 days.

Another study by the same lead investigator used a methodology similar to the previous study.5 Again, 40 healthy premolars had the pulps intentionally exposed, hemorrhage was controlled with saline, and expo-sures were capped with either MTA or calcium hydroxide. In this study, the calcium hydroxide group was directly pulp capped with calcium hydroxide cement (Life; Kerr Corp) without the intervening layer of calcium hydroxide powder. The capping materials were sealed with resin-modified glass iono-mer (Vitrebond; 3M ESPE), bonded with a 3-step, etch-and-rinse adhe-sive (Scotchbond Multi-Purpose; 3M ESPE), and restored with composite resin (Z100; 3M ESPE). Teeth were extracted after 30 or 60 days and evaluated histologically. In this study, the MTA showed significantly better dentin bridge formation and other pulpal findings (particles of capping materials in pulp tissue) at 30 days compared to calcium hydroxide, but these differences disappeared after 60 days. There were no significant differences in the other assessed cat-egory of pulpal inflammation.

In a study that evaluated the effect of MTA and calcium hydroxide on re-parative dentin bridge formation fol-lowing pulp capping, the researchers evaluated markers for odontoblast differentiation (dentin sialoprotein, DSP) and cellular protection (heme oxygenase, HO-1).6 Intentional pulp exposures were made in 20 healthy third molars, bleeding was controlled with saline, pulp capping was per-formed with MTA or calcium hydrox-ide cement (Dycal; Dentsply Caulk), resin-modified glass ionomer (Fuji II LC; GC America, Alsip, Ill) was used for sealing, and the preparations were restored with bonded compos-ite resin. Teeth were extracted after 2 months and subjected to histological evaluation and immunochemistry. There were no differences between the 2 groups in terms of inflamma-tion, but the MTA group showed a

12 Volume 102 Issue 1


13July 2009

Donovan et al Donovan et al

significantly thicker dentin bridge. The authors attributed this to the fact that the MTA-capped pulps also exhibited significantly greater expres-sion of HO-1 and DSP, resulting in a better healing environment in the early stages of pulp repair.

Pulp capping in primary molars was also investigated in a study pub-lished in 2008.7 Twenty-five subjects with symmetrical pairs of primary molars with carious pulp exposures received 1 pulp cap with MTA and 1 pulp cap with calcium hydroxide (Dy-cal; Dentsply Caulk), followed by a zinc-oxide eugenol (ZOE) base (Kal-zinol; Dentsply DeTrey GmbH, Kon-stanz, Germany) and an amalgam restoration. The patients were fol-lowed clinically and radiographically for 24 months. During this time, no teeth exhibited failure, showing equal outcomes as a result of pulp capping primary molars with either MTA or calcium hydroxide.

While some differences in the per-formance of pulps capped with MTA versus calcium hydroxide do appear in some studies, the trend appears to be towards similar performance of teeth following pulp capping with either MTA or calcium hydroxide. The ratio-nale for this may be explained in part by a study that characterized the hy-dration products of MTA.8 MTA was evaluated using radiographic diffrac-tion analysis. Both unhydrated and hydrated specimens were evaluated, and chemical analysis of the products released into solution was performed. The results showed that the primary hydration product of MTA is calcium hydroxide. Prior research by this same author has demonstrated that the high concentration of calcium hydrox-ide eluted from MTA resulted in cell proliferation, accounting for MTA’s biocompatibility. Since MTA is a source of calcium hydroxide, it seems reasonable that MTA and calcium hy-droxide would provide similar clinical outcomes in regard to pulp capping.

Dental caries continue to receive attention from researchers in the ar-

eas of incidence and prevalence, di-agnosis, prevention, treatment, and microbiology.

Incidence and prevalence

A number of authors investigated the incidence and prevalence of den-tal caries in countries throughout the world. Most studies were stratified by age or focused on a unique age group-ing and by what is seen as the emerg-ing needs of a population. Caries prevalence in children has continued to decline in many countries, while the disease disproportionately af-fects smaller segments of society and is ever further sequestered to occlusal surfaces.9 Emerging countries, where cariogenic diets are being introduced, are exceptions to this decreasing car-ies trend. Research on the emerging elder populations shows seniors are increasingly retaining their teeth and, as a consequence, have more teeth at risk for root caries and periodontal diseases. Higher socioeconomic sta-tus and independent living both pro-mote better oral and overall health.10 Dementia and other cognitive impair-ment conditions have demonstrated a high association with both coronal and root caries.11 Interesting tech-niques for the uniform gathering of incidence and prevalence data are also emerging, including the use of teledentistry. In a study of Early Head Start children, investigators used im-ages made with an intraoral camera by telehealth assistants to provide visual information to a calibrated pe-diatric dentist.12 They concluded that this is a viable technique for efficiently screening preschool children for early signs of caries. These data make it clear that researchers throughout the world are engaged in understanding the distribution of dental caries and the early identification of those who need interceptive and preventive ser-vices.

Diagnosis

Research focused on diagnosing

dental caries, especially pit and fissure caries, continues to reflect the cur-rent state of uncertainty concerning whether a demineralized pit or fissure is, in fact, active or inactive. Research-ers continue to make progress in this quest for objectivity and this year have reported use of lasers, visible light, fluidic probes, neural nets, radiovisi-ography, bio-impedance, digital cam-eras, infrared phothermography, the use of a Raman spectrascope, bacte-rial acid production, and cone-beam and x-ray fluorescence as tools to help objectify clinical decision making.

Laser fluorescence (LF) studies continue to show mixed results. Re-searchers performed a clinical study comparing LF with a visual examina-tion system.13 The visual system used was that of Ekstrand and colleagues,14 which has demonstrated a reasonable degree of accuracy when compared to histologic findings. The method is also reportedly training intensive, which limits its utility for nonresearch clinicians. These kinds of surrogate comparisons, while interesting, beg the question as to whether or not the LF system improves diagnostic accu-racy with respect to the true condition of the tooth. The authors note that accurate occlusal caries diagnosis is difficult, with false-positive and false-negative findings occurring frequently, and then use surrogate visual scores as the comparative reference for the LF. Despite these limitations, results are consistent with the findings of other investigators, which show that LF is significantly better at identifying healthy surfaces than those judged to be carious and that LF is not particu-larly valuable for diagnosing early car-ious lesions.15 A positive finding was found for detection of interproximal caries with LF.16 However, the clinical utility is questionable in an area that is not normally considered diagnosti-cally difficult.

The application of the science from a number of developing allied fields to caries diagnosis continued to be demonstrated in 2008. Whether any of these will become clinically use-

ful adjuncts to diagnosis for a clinical practice is uncertain. It does, however, demonstrate that the well-recognized problems associated with diagnosis of caries in specific locations and de-grees of demineralization remain clini-cal problems of importance. One such investigation was the application of fluidic probes measuring impedance variation between sound and cari-ous tooth structure.17 The researchers successfully applied this technology to the measurement of both pit and fissure and interproximal lesions in a prototype model.

A neural net (artificial intelligence) to improve radiographic interpreta-tion was successfully used to enhance the diagnostic accuracy of the best of 25 test examiners from a receiver operating characteristic (ROC) curve value of 0.717 to an ROC of 0.884 when measured against the histology of sectioned teeth viewed through a microscope. ROC is a useful metric. The calculations were developed in World War II as a way to optimize the models for radar detection of enemy targets. ROC has subsequently been applied to other fields and is increas-ingly used in medicine and dentistry to optimize models and discard those that are suboptimal. In this case, the researchers used this methodology to optimize a neural net (the model sys-tem) for the radiographic diagnosis of caries on the basis of its accuracy compared to microscopic examina-tion of the tooth after sectioning. The neural net improved the diagnostic accuracy by a substantial 39.4% com-pared to all examiners. The diagnostic improvement when combined with the previously discussed teledentistry may be a sign of future practices.

Of clinical interest to dentists is a study of the early detection of white spot lesions with digital radiography conducted in Australia.18 This investi-gation reported both an in vitro and a clinical study that investigated the use of digital photography and a software program on remineralization therapy, demonstrating that the studied remin-eralization protocol was, in fact, use-

ful. The message for the nonresearch clinician is that digital photography is useful in documenting white spot situations and the results of in-office or take-home remineralizing medica-ments.

In keeping with emerging medical trends, researchers in Japan examined a caries activity test (Cariostat; Dent-sply-Sankin, Tokyo, Japan) combined with a questionnaire to determine the prognostic capacity in Japanese children over a 3.5-year period.19 The group clinically examined 1206 chil-dren, born in 2000, at 18 months, 2 years, and 3.5 years of age. The clini-cal findings were correlated to the Cariostat test and the responses to the questionnaire. The caries activity test was successfully able to predict the direction of caries incidence at the examination time intervals. If this is a repeatable experimental result in other populations, this “prognostic” may provide a mechanism for direct-ing scarce resources to those at great-est risk for adverse outcomes (caries requiring restoration).

Finally, there is information for those considering purchasing a cone-beam computed tomography scan for detection of dental caries. The 2 cone-beam units tested against both digital and conventional radiographic cap-ture showed lower diagnostic accura-cy for caries detection by cone beam than electronic capture or film.20

Prevention

Traditional methods for caries pre-vention continued to receive research attention in 2008. These included fluoride, chlorhexidine, pit and fissure sealants, xylitol, arginine, and calcium phosphate applications. Recently, in-vestigators examined the effective-ness of 3 preventive approaches in a 2-year trial comparing school-based application of chlorhexidine varnish or sodium fluoride gel versus dental health education alone in “high-risk adolescents.”21 The inclusion criteria for “high-risk adolescents” were chil-dren aged 11 to 13 years with a de-

cayed, missing, filled surfaces (DMFS) index of 0. As might be expected, the study did not show differences be-tween treatment groups.

Fluorides

Guidelines for the use of fluorides in children were published in the Jour-nal of Clinical Pediatric Dentistry.22 This article extends the 2006 work of the American Dental Association (ADA) Council on Scientific Affairs23 by offering clinical recommendations for professionally applied fluorides. The application sequence recommen-dation is that the teeth receive either a tooth brush or prophylaxis with a rubber cup before application of a fluoride varnish to dried teeth, fol-lowed by no tooth brushing and a soft diet for 12 hours. This is reason-ably consistent with the ADA Coun-cil’s findings. It should be noted that the evidence for the 12-hour hiatus is not strong.

It is clear from an Australian sys-tematic review that when considering populations, fluoridation of water supplies remains the most effective and socially equitable mechanism available when compared to incor-poration in milk or salt.24 A well-done systematic review of fluoride varnish25 in concert with similar reviews of pit and fissure sealants was published. The findings of the review are that for those considered at high risk for den-tal caries (including previous caries, low socioeconomic status) a twice-yearly application of unit-dosed fluo-ride varnish should be used with as many other proven preventive strate-gies such as possible. The use of non-dental personnel to apply varnishes at well-baby visits showed a 35% decrease in DMFS for babies receiv-ing 4 or more treatments between 9 and 30 months.26 While most fluoride studies were conducted in young co-horts, 1 study investigated 3 different fluoride strategies for frail individuals older than 75.27 They found that fluo-ride varnishes applied by a hygienist or 5000-ppm fluoride dentifrice used



13July 2009


significantly thicker dentin bridge. The authors attributed this to the fact that the MTA-capped pulps also exhibited significantly greater expres-sion of HO-1 and DSP, resulting in a better healing environment in the early stages of pulp repair.

Pulp capping in primary molars was also investigated in a study pub-lished in 2008.7 Twenty-five subjects with symmetrical pairs of primary molars with carious pulp exposures received 1 pulp cap with MTA and 1 pulp cap with calcium hydroxide (Dy-cal; Dentsply Caulk), followed by a zinc-oxide eugenol (ZOE) base (Kal-zinol; Dentsply DeTrey GmbH, Kon-stanz, Germany) and an amalgam restoration. The patients were fol-lowed clinically and radiographically for 24 months. During this time, no teeth exhibited failure, showing equal outcomes as a result of pulp capping primary molars with either MTA or calcium hydroxide.

While some differences in the per-formance of pulps capped with MTA versus calcium hydroxide do appear in some studies, the trend appears to be towards similar performance of teeth following pulp capping with either MTA or calcium hydroxide. The ratio-nale for this may be explained in part by a study that characterized the hy-dration products of MTA.8 MTA was evaluated using radiographic diffrac-tion analysis. Both unhydrated and hydrated specimens were evaluated, and chemical analysis of the products released into solution was performed. The results showed that the primary hydration product of MTA is calcium hydroxide. Prior research by this same author has demonstrated that the high concentration of calcium hydrox-ide eluted from MTA resulted in cell proliferation, accounting for MTA’s biocompatibility. Since MTA is a source of calcium hydroxide, it seems reasonable that MTA and calcium hy-droxide would provide similar clinical outcomes in regard to pulp capping.

Dental caries continue to receive attention from researchers in the ar-

eas of incidence and prevalence, di-agnosis, prevention, treatment, and microbiology.

Incidence and prevalence

A number of authors investigated the incidence and prevalence of den-tal caries in countries throughout the world. Most studies were stratified by age or focused on a unique age group-ing and by what is seen as the emerg-ing needs of a population. Caries prevalence in children has continued to decline in many countries, while the disease disproportionately af-fects smaller segments of society and is ever further sequestered to occlusal surfaces.9 Emerging countries, where cariogenic diets are being introduced, are exceptions to this decreasing car-ies trend. Research on the emerging elder populations shows seniors are increasingly retaining their teeth and, as a consequence, have more teeth at risk for root caries and periodontal diseases. Higher socioeconomic sta-tus and independent living both pro-mote better oral and overall health.10 Dementia and other cognitive impair-ment conditions have demonstrated a high association with both coronal and root caries.11 Interesting tech-niques for the uniform gathering of incidence and prevalence data are also emerging, including the use of teledentistry. In a study of Early Head Start children, investigators used im-ages made with an intraoral camera by telehealth assistants to provide visual information to a calibrated pe-diatric dentist.12 They concluded that this is a viable technique for efficiently screening preschool children for early signs of caries. These data make it clear that researchers throughout the world are engaged in understanding the distribution of dental caries and the early identification of those who need interceptive and preventive ser-vices.

Diagnosis

Research focused on diagnosing

dental caries, especially pit and fissure caries, continues to reflect the cur-rent state of uncertainty concerning whether a demineralized pit or fissure is, in fact, active or inactive. Research-ers continue to make progress in this quest for objectivity and this year have reported use of lasers, visible light, fluidic probes, neural nets, radiovisi-ography, bio-impedance, digital cam-eras, infrared phothermography, the use of a Raman spectrascope, bacte-rial acid production, and cone-beam and x-ray fluorescence as tools to help objectify clinical decision making.

Laser fluorescence (LF) studies continue to show mixed results. Re-searchers performed a clinical study comparing LF with a visual examina-tion system.13 The visual system used was that of Ekstrand and colleagues,14 which has demonstrated a reasonable degree of accuracy when compared to histologic findings. The method is also reportedly training intensive, which limits its utility for nonresearch clinicians. These kinds of surrogate comparisons, while interesting, beg the question as to whether or not the LF system improves diagnostic accu-racy with respect to the true condition of the tooth. The authors note that accurate occlusal caries diagnosis is difficult, with false-positive and false-negative findings occurring frequently, and then use surrogate visual scores as the comparative reference for the LF. Despite these limitations, results are consistent with the findings of other investigators, which show that LF is significantly better at identifying healthy surfaces than those judged to be carious and that LF is not particu-larly valuable for diagnosing early car-ious lesions.15 A positive finding was found for detection of interproximal caries with LF.16 However, the clinical utility is questionable in an area that is not normally considered diagnosti-cally difficult.

The application of the science from a number of developing allied fields to caries diagnosis continued to be demonstrated in 2008. Whether any of these will become clinically use-

ful adjuncts to diagnosis for a clinical practice is uncertain. It does, however, demonstrate that the well-recognized problems associated with diagnosis of caries in specific locations and de-grees of demineralization remain clini-cal problems of importance. One such investigation was the application of fluidic probes measuring impedance variation between sound and cari-ous tooth structure.17 The researchers successfully applied this technology to the measurement of both pit and fissure and interproximal lesions in a prototype model.

A neural net (artificial intelligence) to improve radiographic interpreta-tion was successfully used to enhance the diagnostic accuracy of the best of 25 test examiners from a receiver operating characteristic (ROC) curve value of 0.717 to an ROC of 0.884 when measured against the histology of sectioned teeth viewed through a microscope. ROC is a useful metric. The calculations were developed in World War II as a way to optimize the models for radar detection of enemy targets. ROC has subsequently been applied to other fields and is increas-ingly used in medicine and dentistry to optimize models and discard those that are suboptimal. In this case, the researchers used this methodology to optimize a neural net (the model sys-tem) for the radiographic diagnosis of caries on the basis of its accuracy compared to microscopic examina-tion of the tooth after sectioning. The neural net improved the diagnostic accuracy by a substantial 39.4% com-pared to all examiners. The diagnostic improvement when combined with the previously discussed teledentistry may be a sign of future practices.

Of clinical interest to dentists is a study of the early detection of white spot lesions with digital radiography conducted in Australia.18 This investi-gation reported both an in vitro and a clinical study that investigated the use of digital photography and a software program on remineralization therapy, demonstrating that the studied remin-eralization protocol was, in fact, use-

ful. The message for the nonresearch clinician is that digital photography is useful in documenting white spot situations and the results of in-office or take-home remineralizing medica-ments.

In keeping with emerging medical trends, researchers in Japan examined a caries activity test (Cariostat; Dent-sply-Sankin, Tokyo, Japan) combined with a questionnaire to determine the prognostic capacity in Japanese children over a 3.5-year period.19 The group clinically examined 1206 chil-dren, born in 2000, at 18 months, 2 years, and 3.5 years of age. The clini-cal findings were correlated to the Cariostat test and the responses to the questionnaire. The caries activity test was successfully able to predict the direction of caries incidence at the examination time intervals. If this is a repeatable experimental result in other populations, this “prognostic” may provide a mechanism for direct-ing scarce resources to those at great-est risk for adverse outcomes (caries requiring restoration).

Finally, there is information for those considering purchasing a cone-beam computed tomography scan for detection of dental caries. The 2 cone-beam units tested against both digital and conventional radiographic cap-ture showed lower diagnostic accura-cy for caries detection by cone beam than electronic capture or film.20

Prevention

Traditional methods for caries pre-vention continued to receive research attention in 2008. These included fluoride, chlorhexidine, pit and fissure sealants, xylitol, arginine, and calcium phosphate applications. Recently, in-vestigators examined the effective-ness of 3 preventive approaches in a 2-year trial comparing school-based application of chlorhexidine varnish or sodium fluoride gel versus dental health education alone in “high-risk adolescents.”21 The inclusion criteria for “high-risk adolescents” were chil-dren aged 11 to 13 years with a de-

cayed, missing, filled surfaces (DMFS) index of 0. As might be expected, the study did not show differences be-tween treatment groups.

Fluorides

Guidelines for the use of fluorides in children were published in the Jour-nal of Clinical Pediatric Dentistry.22 This article extends the 2006 work of the American Dental Association (ADA) Council on Scientific Affairs23 by offering clinical recommendations for professionally applied fluorides. The application sequence recommen-dation is that the teeth receive either a tooth brush or prophylaxis with a rubber cup before application of a fluoride varnish to dried teeth, fol-lowed by no tooth brushing and a soft diet for 12 hours. This is reason-ably consistent with the ADA Coun-cil’s findings. It should be noted that the evidence for the 12-hour hiatus is not strong.

It is clear from an Australian sys-tematic review that when considering populations, fluoridation of water supplies remains the most effective and socially equitable mechanism available when compared to incor-poration in milk or salt.24 A well-done systematic review of fluoride varnish25 in concert with similar reviews of pit and fissure sealants was published. The findings of the review are that for those considered at high risk for den-tal caries (including previous caries, low socioeconomic status) a twice-yearly application of unit-dosed fluo-ride varnish should be used with as many other proven preventive strate-gies such as possible. The use of non-dental personnel to apply varnishes at well-baby visits showed a 35% decrease in DMFS for babies receiv-ing 4 or more treatments between 9 and 30 months.26 While most fluoride studies were conducted in young co-horts, 1 study investigated 3 different fluoride strategies for frail individuals older than 75.27 They found that fluo-ride varnishes applied by a hygienist or 5000-ppm fluoride dentifrice used



15July 2009


twice daily significantly reduced root caries progression compared to an untreated cohort or to those brushing twice daily with a 1450-ppm fluoride toothpaste. Given the aging of the world’s populations with increasing retention of teeth, studies such as this are useful for clinicians and care facil-ity administrators in preventive plan-ning and policy/guideline making.

Chlorhexidine

The use of chlorhexidine for caries control continues to be controversial. One review28 concludes that the data are suggestive but incomplete when examining the literature relative to rinses, gels, and chlorhexidine varnish-es. The review also notes that many studies use the surrogate outcome measure of S. mutans count reduction rather than actual caries incidence measures. As noted later in this re-view, S. mutans is not the only putative pathogen for dental caries. This use of a bacterial surrogate is a reflection of the cost of longitudinal caries trials and continues to be a research issue. The results of this report confirm the findings of a number of previous sys-tematic reviews that found a lack of well-conducted research that would verify chlorhexidine’s effectiveness.29-

31 The results do not indicate that the preventive and management methods reviewed are not efficacious; rather, they demonstrate that not enough is known through well-performed studies to determine their efficacy. Chlorhexidine’s side effects: taste al-teration, staining, and sore mouth and/or throat, were evaluated. 32,33 In uncontrolled diabetic patients in the Veteran’s Administration system with a glycosylated hemoglobin test value of hemoglobin A1c ≥8.5%, 31% of those enrolled in a clinical trial reported 1 or more of these adverse events. These effects were transient and resolved with the discontinuation of the chlorhexidine rinse.

calcium phosphate (CPP-ACP) ar-rive at different conclusions.37,38 One of the studies concludes that while 7 of 9 clinical studies reviewed (involv-ing delivery by sugar-free pellet or slab chewing gum, lozenges, milk, or mouth rinse) demonstrated efficacy in preventing dental caries by remin-eralizing subsurface carious lesions in situ in a dose-response fashion, there was not sufficient strength of evidence to form a conclusion regarding long-term effectiveness.37 The other study found that reviewed literature of a dif-ferent delivery system (Tooth Mousse; GC Corp, Tokyo, Japan) showed good remineralization effect, especially when applied after the use of a fluo-ridated toothpaste.38

Two in situ trials39,40 showed ef-ficacy for CPP-ACP in remineralizing artificial caries lesions, while a clini-cal trial41 of 2720 adolescents inves-tigated sugar-free gum containing CPP-ACP and demonstrated an 18% less progression of clinical interproxi-mal lesions than in those chewing the same gum without the casein deriva-tive over 24 months.

Treatment

With the advent of minimally in-vasive dentistry, the concurrent ad-vancement of materials science and better designed clinical trials create the potential to treat dental caries by traditional surgical techniques and nonsurgical or minimally invasive methods and materials. Two reports of the use of an “infiltrating” resin technology and protocol appeared in 2008.42,43 In these in vitro studies, ei-ther artificially induced demineraliza-tion or naturally occurring uncavitated smooth surface lesions were treated for 2 minutes with 15% HCl to remove an intact surface layer of enamel, in an approach similar to the abrasive techniques for white spot treatment. After water rinsing, reagent-grade ethanol was applied as a desiccant. Following ethanol evaporation, res-ins of varying penetration coefficients were applied. The resins were then

Arginine

For a number of years it has been reported that the generation of alkali products by oral biofilm bacteria fed a suitable metabolic substrate is a factor in the homeostasis of the pH of the oral biofilm.34 The semi-essential amino acid, L-arginine, when me-tabolized by specific intraoral bacte-rial species, creates a pH rise that is thought to offset the pH fall caused by acid-producing bacteria.35 Re-search to leverage this reaction in a commercial product was reported in 2008.36 This 1-year study of 200 children examined the development of caries in the primary molars and first permanent molars in 10.5- to 11-year-old children exhibiting previous clinical signs of caries. Two groups were tested. One received a sugarless mint (control group) and the other a sugarless mint containing an arginine bicarbonate calcium carbonate mix-ture (treatment group). Based on the DMFS scores, the treatment group showed a reduction of 75.6% at 6 months with a 50.7% reduction at 12 months. The combined DMFS and decayed, exfoliated, filled surfaces (DEFS) primary teeth reductions were 76.2% at 6 months and 74.8% at 12 months. These mints appear to be un-dergoing the Food and Drug Admin-istration (FDA) approval process in the United States and, therefore, are not yet commercially available. Other arginine-containing products are be-ing developed by dental manufactur-ers and merit watching as clinical tri-als are reported.

Calcium phosphate

The use of calcium phosphate as a remineralizing agent has been stud-ied in vitro, in situ, and in vivo for a number of years. The 2008 literature describing the efficacy of various cal-cium phosphate agents shows mixed results, with a tendency toward suc-cessful remineralization of demineral-ized enamel. Two reviews on the use of casein phosphopeptide amorphous

visible light polymerized. The higher penetration coefficient formulations were successful in penetrating well into the demineralized areas. This is an extension of earlier work inves-tigating the surface sealing of these types of early lesions.44 If the clinical trials of these penetrating resins dem-onstrate reasoned efficacy without undue work-burden, these new mate-rials and techniques have significant practice implications. Since no irre-versible procedure is performed, most practice acts in the United States would permit a hygienist or other in-dividual with conformant training to place these restorations. Additionally, while not reported in these research efforts, the use of similar methodol-ogy for pits and fissures and for what is currently termed preventive resin res-torations45 would seem highly probable as this technology evolves.

A similar strategy for treating root caries seems likely. In 2008, a group tested the concept of surface seal-ing of roots with all-in-one bonding agents to limit the adherence of an S. mutans-containing biofilm.46 A fluo-ride-containing bonding agent proved superior to nonfluoride-containing agents in this short-term test.

One additional clinical trial testing materials and methods for minimally invasive dentistry (MID) was reported in 2008.47 This study showed no dif-ference in retention and acceptance criteria for teeth minimally restored with glass ionomer using a chemome-chanical preparation technique ver-sus a standard atraumatic restorative technique (ART); the point being that neither technique used rotary instru-ments.

At the other end of the depth of preparation spectrum, 1 author re-viewed the materials choices for vital pulp therapy in primary teeth for di-rect and indirect pulp caps and pul-potomies.48 Formocreosol remains the most frequently used medicament for pulpotomies, while mineral triox-ide aggregate and ferric sulfate were found to be viable alternatives.

Microbiology of caries

The 2008 research continued to support the concept of bacterial communities being integral to dental health or dental caries initiation and progression. Research demonstrates that the bacterial community is not identical for all dental caries.49 The investigators demonstrated that the microbial flora they identified using 16S rRNA varied based on the state of progression of a lesion, from white-spot to advanced dentinal caries, as well as variations in microbial flora be-tween individuals in the same disease state. This is consistent with previous studies that show differences between enamel and dentin caries flora. The weakness of this type of study is that it does not record longitudinal history of the ecology. Rather, it takes indi-vidual pictures or snapshots at points in time. These snapshots provide no information as to whether the lesion is actively progressing at the time of sampling or quiescent. Therefore, the association of specific bacteria and disease progression is lacking. A study of preschool children using similar analyses showed direct correlations between caries status and the concen-trations of S. mutans and S. sobrinus.50

A study examining the effect of Listerine (Johnson and Johnson Healthcare Products, Skillman, NJ) or chlorhexidine on the dental biofilm51 noted that the variance in bacterial biofilm members between examined subjects elicited changes in the mi-crobial response to the studied an-tiseptics. Resistance of S. mutans to antimicrobial agents was further ex-plored in a study that examined the susceptibility of S. mutans to antimi-crobial agents in the presence of vary-ing concentrations of sucrose. The investigators found that antimicro-bial susceptibility decreased with in-creasing availability of sucrose.52 Ad-vising patients to lower the frequency of sucrose consumption continues to be a viable suggestion, albeit for more than just the reduction of acid production. Investigators also exam-

ined exposing S. mutans to increased levels of one of its own quorum-sens-ing signals, competence-stimulating peptide (CSP),53 and found that sig-nificant overexpression of the signal resulted in growth arrest and eventual S. mutans cell death, thus paving the way for CSP-mediated targeted killing of S. mutans. This concept of modula-tion of the dental biofilm by selective killing or enrichment seems to hold promise for more effective control of the caries process.

PERIODONTICS

In periodontics and implant den-tistry, there is continued interest in the relationships between systemic diseases and periodontal diseases as well as gingival augmentation and socket preservation. This review will attempt to evaluate these interesting and sometimes controversial sub-jects in an objective manner. Most papers reviewed were not the result of randomized, controlled clinical tri-als. Most are clinical series, clinical reports, and studies performed on a limited number of animals.

Periodontal disease and systemic dis-ease relationships

Periodontal diseases are inflam-matory conditions that were once thought to have manifestations lo-calized to the oral cavity alone, and were considered the concern of only dentists and other oral health profes-sionals.54 Emerging evidence suggests that periodontal diseases may have a role in numerous conditions that im-pact systemic well being, including diabetes mellitus. Periodontal inflam-mation is associated with an elevated systemic inflammatory state and an increased risk of major cardiovascular events such as myocardial infarction and stroke, adverse pregnancy out-comes such as preeclampsia, low birth weight, and preterm birth, and altered glycemic control in people with dia-betes. Intervention trials suggest that periodontal therapy, which decreases



15July 2009


twice daily significantly reduced root caries progression compared to an untreated cohort or to those brushing twice daily with a 1450-ppm fluoride toothpaste. Given the aging of the world’s populations with increasing retention of teeth, studies such as this are useful for clinicians and care facil-ity administrators in preventive plan-ning and policy/guideline making.

Chlorhexidine

The use of chlorhexidine for caries control continues to be controversial. One review28 concludes that the data are suggestive but incomplete when examining the literature relative to rinses, gels, and chlorhexidine varnish-es. The review also notes that many studies use the surrogate outcome measure of S. mutans count reduction rather than actual caries incidence measures. As noted later in this re-view, S. mutans is not the only putative pathogen for dental caries. This use of a bacterial surrogate is a reflection of the cost of longitudinal caries trials and continues to be a research issue. The results of this report confirm the findings of a number of previous sys-tematic reviews that found a lack of well-conducted research that would verify chlorhexidine’s effectiveness.29-

31 The results do not indicate that the preventive and management methods reviewed are not efficacious; rather, they demonstrate that not enough is known through well-performed studies to determine their efficacy. Chlorhexidine’s side effects: taste al-teration, staining, and sore mouth and/or throat, were evaluated. 32,33 In uncontrolled diabetic patients in the Veteran’s Administration system with a glycosylated hemoglobin test value of hemoglobin A1c ≥8.5%, 31% of those enrolled in a clinical trial reported 1 or more of these adverse events. These effects were transient and resolved with the discontinuation of the chlorhexidine rinse.

calcium phosphate (CPP-ACP) ar-rive at different conclusions.37,38 One of the studies concludes that while 7 of 9 clinical studies reviewed (involv-ing delivery by sugar-free pellet or slab chewing gum, lozenges, milk, or mouth rinse) demonstrated efficacy in preventing dental caries by remin-eralizing subsurface carious lesions in situ in a dose-response fashion, there was not sufficient strength of evidence to form a conclusion regarding long-term effectiveness.37 The other study found that reviewed literature of a dif-ferent delivery system (Tooth Mousse; GC Corp, Tokyo, Japan) showed good remineralization effect, especially when applied after the use of a fluo-ridated toothpaste.38

Two in situ trials39,40 showed ef-ficacy for CPP-ACP in remineralizing artificial caries lesions, while a clini-cal trial41 of 2720 adolescents inves-tigated sugar-free gum containing CPP-ACP and demonstrated an 18% less progression of clinical interproxi-mal lesions than in those chewing the same gum without the casein deriva-tive over 24 months.

Treatment

With the advent of minimally in-vasive dentistry, the concurrent ad-vancement of materials science and better designed clinical trials create the potential to treat dental caries by traditional surgical techniques and nonsurgical or minimally invasive methods and materials. Two reports of the use of an “infiltrating” resin technology and protocol appeared in 2008.42,43 In these in vitro studies, ei-ther artificially induced demineraliza-tion or naturally occurring uncavitated smooth surface lesions were treated for 2 minutes with 15% HCl to remove an intact surface layer of enamel, in an approach similar to the abrasive techniques for white spot treatment. After water rinsing, reagent-grade ethanol was applied as a desiccant. Following ethanol evaporation, res-ins of varying penetration coefficients were applied. The resins were then

Arginine

For a number of years it has been reported that the generation of alkali products by oral biofilm bacteria fed a suitable metabolic substrate is a factor in the homeostasis of the pH of the oral biofilm.34 The semi-essential amino acid, L-arginine, when me-tabolized by specific intraoral bacte-rial species, creates a pH rise that is thought to offset the pH fall caused by acid-producing bacteria.35 Re-search to leverage this reaction in a commercial product was reported in 2008.36 This 1-year study of 200 children examined the development of caries in the primary molars and first permanent molars in 10.5- to 11-year-old children exhibiting previous clinical signs of caries. Two groups were tested. One received a sugarless mint (control group) and the other a sugarless mint containing an arginine bicarbonate calcium carbonate mix-ture (treatment group). Based on the DMFS scores, the treatment group showed a reduction of 75.6% at 6 months with a 50.7% reduction at 12 months. The combined DMFS and decayed, exfoliated, filled surfaces (DEFS) primary teeth reductions were 76.2% at 6 months and 74.8% at 12 months. These mints appear to be un-dergoing the Food and Drug Admin-istration (FDA) approval process in the United States and, therefore, are not yet commercially available. Other arginine-containing products are be-ing developed by dental manufactur-ers and merit watching as clinical tri-als are reported.

Calcium phosphate

The use of calcium phosphate as a remineralizing agent has been stud-ied in vitro, in situ, and in vivo for a number of years. The 2008 literature describing the efficacy of various cal-cium phosphate agents shows mixed results, with a tendency toward suc-cessful remineralization of demineral-ized enamel. Two reviews on the use of casein phosphopeptide amorphous

visible light polymerized. The higher penetration coefficient formulations were successful in penetrating well into the demineralized areas. This is an extension of earlier work inves-tigating the surface sealing of these types of early lesions.44 If the clinical trials of these penetrating resins dem-onstrate reasoned efficacy without undue work-burden, these new mate-rials and techniques have significant practice implications. Since no irre-versible procedure is performed, most practice acts in the United States would permit a hygienist or other in-dividual with conformant training to place these restorations. Additionally, while not reported in these research efforts, the use of similar methodol-ogy for pits and fissures and for what is currently termed preventive resin res-torations45 would seem highly probable as this technology evolves.

A similar strategy for treating root caries seems likely. In 2008, a group tested the concept of surface seal-ing of roots with all-in-one bonding agents to limit the adherence of an S. mutans-containing biofilm.46 A fluo-ride-containing bonding agent proved superior to nonfluoride-containing agents in this short-term test.

One additional clinical trial testing materials and methods for minimally invasive dentistry (MID) was reported in 2008.47 This study showed no dif-ference in retention and acceptance criteria for teeth minimally restored with glass ionomer using a chemome-chanical preparation technique ver-sus a standard atraumatic restorative technique (ART); the point being that neither technique used rotary instru-ments.

At the other end of the depth of preparation spectrum, 1 author re-viewed the materials choices for vital pulp therapy in primary teeth for di-rect and indirect pulp caps and pul-potomies.48 Formocreosol remains the most frequently used medicament for pulpotomies, while mineral triox-ide aggregate and ferric sulfate were found to be viable alternatives.

Microbiology of caries

The 2008 research continued to support the concept of bacterial communities being integral to dental health or dental caries initiation and progression. Research demonstrates that the bacterial community is not identical for all dental caries.49 The investigators demonstrated that the microbial flora they identified using 16S rRNA varied based on the state of progression of a lesion, from white-spot to advanced dentinal caries, as well as variations in microbial flora be-tween individuals in the same disease state. This is consistent with previous studies that show differences between enamel and dentin caries flora. The weakness of this type of study is that it does not record longitudinal history of the ecology. Rather, it takes indi-vidual pictures or snapshots at points in time. These snapshots provide no information as to whether the lesion is actively progressing at the time of sampling or quiescent. Therefore, the association of specific bacteria and disease progression is lacking. A study of preschool children using similar analyses showed direct correlations between caries status and the concen-trations of S. mutans and S. sobrinus.50

A study examining the effect of Listerine (Johnson and Johnson Healthcare Products, Skillman, NJ) or chlorhexidine on the dental biofilm51 noted that the variance in bacterial biofilm members between examined subjects elicited changes in the mi-crobial response to the studied an-tiseptics. Resistance of S. mutans to antimicrobial agents was further ex-plored in a study that examined the susceptibility of S. mutans to antimi-crobial agents in the presence of vary-ing concentrations of sucrose. The investigators found that antimicro-bial susceptibility decreased with in-creasing availability of sucrose.52 Ad-vising patients to lower the frequency of sucrose consumption continues to be a viable suggestion, albeit for more than just the reduction of acid production. Investigators also exam-

ined exposing S. mutans to increased levels of one of its own quorum-sens-ing signals, competence-stimulating peptide (CSP),53 and found that sig-nificant overexpression of the signal resulted in growth arrest and eventual S. mutans cell death, thus paving the way for CSP-mediated targeted killing of S. mutans. This concept of modula-tion of the dental biofilm by selective killing or enrichment seems to hold promise for more effective control of the caries process.

PERIODONTICS

In periodontics and implant den-tistry, there is continued interest in the relationships between systemic diseases and periodontal diseases as well as gingival augmentation and socket preservation. This review will attempt to evaluate these interesting and sometimes controversial sub-jects in an objective manner. Most papers reviewed were not the result of randomized, controlled clinical tri-als. Most are clinical series, clinical reports, and studies performed on a limited number of animals.

Periodontal disease and systemic dis-ease relationships

Periodontal diseases are inflam-matory conditions that were once thought to have manifestations lo-calized to the oral cavity alone, and were considered the concern of only dentists and other oral health profes-sionals.54 Emerging evidence suggests that periodontal diseases may have a role in numerous conditions that im-pact systemic well being, including diabetes mellitus. Periodontal inflam-mation is associated with an elevated systemic inflammatory state and an increased risk of major cardiovascular events such as myocardial infarction and stroke, adverse pregnancy out-comes such as preeclampsia, low birth weight, and preterm birth, and altered glycemic control in people with dia-betes. Intervention trials suggest that periodontal therapy, which decreases



17July 2009


the intraoral bacterial bioburden and reduces periodontal inflammation, can have a significant impact on sys-temic inflammatory status. Evidence suggests that periodontal therapy is associated with improved glycemic control in many patients with both di-abetes and periodontal diseases. Rec-ognition of the bilateral relationships between oral and systemic health will challenge physicians and dentists to work together closely when managing patients with diabetes and periodon-tal disease.

Bacterial plaque is the main etio-logic agent related to periodontal tis-sue destruction. Diabetes is consid-ered an important risk factor, not only for the onset but also for progression of the disease. The aim of 1 study55 was to analyze structural changes in the rat gingival epithelium and connective tissue in response to the experimental periodontal disease induced by the ligature technique, under the influ-ence of diabetes. The results showed that experimental periodontal disease is characterized by marked inflamma-tion, affecting both the epithelial and connective tissues, causing degenera-tion of the dermal papilla, increase in the number of inflammatory cells, destruction of reticulin fibers, and ac-cumulation of dense collagen fibers. These changes were worsened by dia-betes, apparently by hampering the inflammatory response and affecting tissue repair of the affected tissues.

A MEDLINE-PubMed Central search for evidence of an association between diabetes and periodontal and periimplant conditions and the impact of periodontal therapy in sub-jects with diabetes was performed.56 The search included articles published up to December 2007. Evidence on the association between diabetes and periodontitis supports the con-cept of increased severity but not ex-tent of periodontitis in subjects with poorly controlled diabetes. Subjects with controlled diabetes do not show an increase in extent and severity of periodontitis. Periodontitis is associ-ated with poor glycemic control and

diabetes-related complications. It is inconclusive that periodontal therapy with or without the use of antibiotics results in improvements of glycemic control and of markers of systemic inflammation. Evidence is lacking to indicate that implant therapy in sub-jects with diabetes yields long-term outcomes comparable with those of nondiabetic subjects. Poorly con-trolled diabetes may be considered a risk factor for increased severity of periodontitis. The effects of periodon-tal therapy on glycemic control and systemic inflammation are not proven and require confirmation in large-scale randomized controlled clinical trials. Large variations in study design and study populations contribute to the inconsistencies of findings related to the effect of glycemic control.

The effect of nonsurgical peri-odontal treatment, with or without systemic administration of doxycy-cline, on the metabolic control of pa-tients with type 1 diabetes was stud-ied.57 Sixty type 1 diabetic subjects with moderate to severe periodon-titis were recruited. Periodontal pa-rameters were measured, and blood specimens were obtained to evaluate glycosylated hemoglobin.58,59 Group 1 (30 patients) was treated with scaling, root planing, and chlorhexidine rinses for 3 months in conjunction with sys-temic administration of doxycycline (100 mg once per day for 15 days). Group 2 (30 patients) received the same periodontal treatment but with-out the use of doxycycline. The paired Student t test was used to detect dif-ferences between glycosylated hemo-globin means before and 3 months after periodontal treatment in group 1 and group 2, separately. Changes in mean HbA1c after treatment were 0.07% in group 1 and -0.06% in group 2, which were not statistically sig-nificant after 3 months. Significant changes were not found even in pa-tients with the best response to peri-odontal treatment. Periodontal treat-ment in type 1 diabetic patients after a 3-month follow-up did not improve metabolic control of diabetes as mea-

sured by glycosylated hemoglobin.

Extraction socket healing

Extraction socket healing has become the focus for many animal and clinical studies. Previous studies indicate that there are dimensional changes in bone and soft tissue after tooth extraction.60-63 Five dogs were used to study dimensional altera-tions of the alveolar ridge that occur following implant placement in fresh extraction sockets.60 Following flap elevation in mandibular posterior re-gions, the distal roots of molars were removed. In the right jaw quadrants, implants with an airborne-particle-abraded and acid-etched surface were placed in the fresh extraction sockets, while in the left jaws, the correspond-ing sockets were left for spontaneous healing. The mesial roots were re-tained as surgical control teeth. After 3 months, the animals were examined clinically, sacrificed, and tissue blocks containing the implant sites, the ad-jacent tooth sites (mesial root), and the edentulous socket sites were dis-sected, prepared for ground section-ing, and examined with a microscope. Results at implant sites revealed the level of bone-to-implant contact (BC) was located 2.6 ±0.4 mm (buc-cal aspect) and 0.2 ±0.5 mm (lingual aspect) apical of the implant level. At the edentulous sites, the mean verti-cal distance between the marginal termination of the buccal and lingual bone walls was 2.2 ±0.9 mm. Marked dimensional alterations occurred in the edentulous ridge after 3 months of healing following the extraction of the distal root of mandibular premo-lars. The placement of an implant in the fresh extraction site failed to pre-vent the remodeling that occurred in the walls of the socket. The resulting height of the buccal and lingual walls at 3 months was similar for implants and edentulous sites, and vertical bone loss was more pronounced at the buccal than at the lingual aspect of the residual ridge. It is suggested that the resorption of the socket walls

that occurs following tooth removal must be considered in conjunction with implant placement in fresh ex-traction sockets.

Implants placed immediately af-ter tooth extraction offer several ad-vantages, but authors have reported problems in filling the residual gap between the implant and the socket walls.64 Barrier and grafting tech-niques have been evaluated and yield varying results, so it has been sug-gested that the timing of implant placement may be important for suc-cess. Bone healing and coronal bone remodeling around 35 implants, 20 placed immediately after tooth re-moval and 15 placed 6 to 8 weeks after extraction, were evaluated.64 All implants were submerged and placed within the alveolar confines, leaving circumferential defects because the implants did not contact the bone at the coronal aspects. All implants were stable. After implant placement the mean distance from buccal bone to lingual bone was 10 mm (SD 2.47) for immediate implants and 8.86 mm (SD 2.36) for delayed implants. No membrane or filling materials were used. Primary flap closure was accom-plished in all instances. At second-stage surgery, all periimplant defects were filled, and the mean distance from buccal bone to lingual bone was 8.1 mm (SD 1.3) for immediate implants and 5.8 mm (SD 1.3) for delayed implants. This pattern of cor-onal bone remodeling showed a nar-rowing of the buccolingual width and was clinically similar for the 2 groups. It was noted that the delayed implants exhibited smaller buccolingual bone width at the first measurement. This study suggests that circumferential defects could heal clinically without any guided bone regeneration (GBR) in both experimental groups, and that the procedure was free from compli-cations in the postoperative period, probably because of the absence of barrier membranes and/or grafting materials. Histologically, periimplant defects of over 1.5 mm heal by con-nective tissue apposition, rather than

by direct bone-to-implant contact, but clinically this healing may be suc-cessful. No histological analysis was performed in the study, but even the largest residual gaps were filled with hard tissue that could not be probed.

The effect on hard tissue modeling and remodeling of the placement of a xenograft in fresh extraction sockets in dogs was evaluated.65 Five mongrel dogs were used. Two mandibular pre-molars were hemisected in each dog, and the distal roots were carefully removed. In one socket, a graft (Bio-Oss Collagen; Geistlich Pharma AG, Wolhusen, Switzerland) was placed, whereas the contralateral site was left without grafting. After 3 months of healing, the dogs were euthanized and biopsy specimens were obtained. From each experimental site, 4 ground sections (2 from the mesial root and 2 from the healed socket) were pre-pared, stained, and examined un-der the microscope. The presence of Bio-Oss Collagen failed to inhibit the processes of modeling and remodel-ing that occurred in the socket walls following tooth extraction. However, it apparently promoted de novo hard tissue formation, particularly in the cortical region of the extraction site. Thus, the dimension of the hard tissue was maintained and the profile of the residual ridge was better preserved. The placement of a biomaterial in an extraction socket may promote bone modeling and compensate, at least temporarily, for marginal ridge con-traction.

A recent study offered somewhat conflicting results as compared to studies that demonstrated extraction socket healing occurs uneventfully without augmentation or grafting.66 The authors evaluated whether tooth extraction without the elevation of a mucoperiosteal flap has advanta-geous effects on the resorption rate after tooth extraction. In 5 beagle dogs, polyether impressions were made before the surgery. The roots of the first and second premolars were extracted and the sites were assigned to one of the following groups: treat-

ment group (Tx) 1, no treatment; Tx 2, surgical trauma (flap elevation and repositioning); Tx 3, the extrac-tion socket was filled with Bio-Oss Collagen (Geistlich Pharma AG) and closed with a free soft-tissue graft; Tx 4, after flap elevation and reposition-ing, the extraction socket was treated with Bio-Oss Collagen and a free soft-tissue graft. Impressions were made 2 and 4 months after surgery. The casts were scanned, matched together with baseline casts, and evaluated with dig-ital image analysis. Results indicated that the group without flap elevation demonstrated significantly lower re-sorption rates both with and without socket-preservation techniques. Fur-thermore, socket-preservation techniques yielded better results com-pared with no treatment of the socket. The results demonstrated that leav-ing the periosteum in place decreases the resorption rate of the extraction socket. Also, the treatment of the ex-traction socket with Bio-Oss Collagen and a free gingival graft seems benefi-cial in limiting the resorption process after tooth extraction.

Another study assessed contour changes after socket preservation techniques.67 The distal root of the third and fourth mandibular premo-lars were extracted in 5 beagle dogs. The following treatments were ran-domly assigned for the extraction socket. Tx 1: placement of Bio-Oss Collagen (Geistlich Pharma AG); Tx 2: placement of Bio-Oss Collagen and a free soft tissue graft; Tx 3: no treatment; and Tx 4: the internal buc-cal aspect was covered with an ex-perimental collagen membrane, the extraction socket was filled with Bio-Oss Collagen, and the membrane was folded on top of the graft. Impres-sions were obtained at baseline and 2 and 4 months after surgery. Buccolin-gual measurements were performed using digital imaging analysis. All groups displayed contour shrinkage at the buccal aspect. The differences between the 2 test groups (Tx 1, Tx 2) and the control group (Tx 3) were only significant at the buccal aspect



17July 2009


the intraoral bacterial bioburden and reduces periodontal inflammation, can have a significant impact on sys-temic inflammatory status. Evidence suggests that periodontal therapy is associated with improved glycemic control in many patients with both di-abetes and periodontal diseases. Rec-ognition of the bilateral relationships between oral and systemic health will challenge physicians and dentists to work together closely when managing patients with diabetes and periodon-tal disease.

Bacterial plaque is the main etio-logic agent related to periodontal tis-sue destruction. Diabetes is consid-ered an important risk factor, not only for the onset but also for progression of the disease. The aim of 1 study55 was to analyze structural changes in the rat gingival epithelium and connective tissue in response to the experimental periodontal disease induced by the ligature technique, under the influ-ence of diabetes. The results showed that experimental periodontal disease is characterized by marked inflamma-tion, affecting both the epithelial and connective tissues, causing degenera-tion of the dermal papilla, increase in the number of inflammatory cells, destruction of reticulin fibers, and ac-cumulation of dense collagen fibers. These changes were worsened by dia-betes, apparently by hampering the inflammatory response and affecting tissue repair of the affected tissues.

A MEDLINE-PubMed Central search for evidence of an association between diabetes and periodontal and periimplant conditions and the impact of periodontal therapy in sub-jects with diabetes was performed.56 The search included articles published up to December 2007. Evidence on the association between diabetes and periodontitis supports the con-cept of increased severity but not ex-tent of periodontitis in subjects with poorly controlled diabetes. Subjects with controlled diabetes do not show an increase in extent and severity of periodontitis. Periodontitis is associ-ated with poor glycemic control and

diabetes-related complications. It is inconclusive that periodontal therapy with or without the use of antibiotics results in improvements of glycemic control and of markers of systemic inflammation. Evidence is lacking to indicate that implant therapy in sub-jects with diabetes yields long-term outcomes comparable with those of nondiabetic subjects. Poorly con-trolled diabetes may be considered a risk factor for increased severity of periodontitis. The effects of periodon-tal therapy on glycemic control and systemic inflammation are not proven and require confirmation in large-scale randomized controlled clinical trials. Large variations in study design and study populations contribute to the inconsistencies of findings related to the effect of glycemic control.

The effect of nonsurgical peri-odontal treatment, with or without systemic administration of doxycy-cline, on the metabolic control of pa-tients with type 1 diabetes was stud-ied.57 Sixty type 1 diabetic subjects with moderate to severe periodon-titis were recruited. Periodontal pa-rameters were measured, and blood specimens were obtained to evaluate glycosylated hemoglobin.58,59 Group 1 (30 patients) was treated with scaling, root planing, and chlorhexidine rinses for 3 months in conjunction with sys-temic administration of doxycycline (100 mg once per day for 15 days). Group 2 (30 patients) received the same periodontal treatment but with-out the use of doxycycline. The paired Student t test was used to detect dif-ferences between glycosylated hemo-globin means before and 3 months after periodontal treatment in group 1 and group 2, separately. Changes in mean HbA1c after treatment were 0.07% in group 1 and -0.06% in group 2, which were not statistically sig-nificant after 3 months. Significant changes were not found even in pa-tients with the best response to peri-odontal treatment. Periodontal treat-ment in type 1 diabetic patients after a 3-month follow-up did not improve metabolic control of diabetes as mea-

sured by glycosylated hemoglobin.

Extraction socket healing

Extraction socket healing has become the focus for many animal and clinical studies. Previous studies indicate that there are dimensional changes in bone and soft tissue after tooth extraction.60-63 Five dogs were used to study dimensional altera-tions of the alveolar ridge that occur following implant placement in fresh extraction sockets.60 Following flap elevation in mandibular posterior re-gions, the distal roots of molars were removed. In the right jaw quadrants, implants with an airborne-particle-abraded and acid-etched surface were placed in the fresh extraction sockets, while in the left jaws, the correspond-ing sockets were left for spontaneous healing. The mesial roots were re-tained as surgical control teeth. After 3 months, the animals were examined clinically, sacrificed, and tissue blocks containing the implant sites, the ad-jacent tooth sites (mesial root), and the edentulous socket sites were dis-sected, prepared for ground section-ing, and examined with a microscope. Results at implant sites revealed the level of bone-to-implant contact (BC) was located 2.6 ±0.4 mm (buc-cal aspect) and 0.2 ±0.5 mm (lingual aspect) apical of the implant level. At the edentulous sites, the mean verti-cal distance between the marginal termination of the buccal and lingual bone walls was 2.2 ±0.9 mm. Marked dimensional alterations occurred in the edentulous ridge after 3 months of healing following the extraction of the distal root of mandibular premo-lars. The placement of an implant in the fresh extraction site failed to pre-vent the remodeling that occurred in the walls of the socket. The resulting height of the buccal and lingual walls at 3 months was similar for implants and edentulous sites, and vertical bone loss was more pronounced at the buccal than at the lingual aspect of the residual ridge. It is suggested that the resorption of the socket walls

that occurs following tooth removal must be considered in conjunction with implant placement in fresh ex-traction sockets.

Implants placed immediately af-ter tooth extraction offer several ad-vantages, but authors have reported problems in filling the residual gap between the implant and the socket walls.64 Barrier and grafting tech-niques have been evaluated and yield varying results, so it has been sug-gested that the timing of implant placement may be important for suc-cess. Bone healing and coronal bone remodeling around 35 implants, 20 placed immediately after tooth re-moval and 15 placed 6 to 8 weeks after extraction, were evaluated.64 All implants were submerged and placed within the alveolar confines, leaving circumferential defects because the implants did not contact the bone at the coronal aspects. All implants were stable. After implant placement the mean distance from buccal bone to lingual bone was 10 mm (SD 2.47) for immediate implants and 8.86 mm (SD 2.36) for delayed implants. No membrane or filling materials were used. Primary flap closure was accom-plished in all instances. At second-stage surgery, all periimplant defects were filled, and the mean distance from buccal bone to lingual bone was 8.1 mm (SD 1.3) for immediate implants and 5.8 mm (SD 1.3) for delayed implants. This pattern of cor-onal bone remodeling showed a nar-rowing of the buccolingual width and was clinically similar for the 2 groups. It was noted that the delayed implants exhibited smaller buccolingual bone width at the first measurement. This study suggests that circumferential defects could heal clinically without any guided bone regeneration (GBR) in both experimental groups, and that the procedure was free from compli-cations in the postoperative period, probably because of the absence of barrier membranes and/or grafting materials. Histologically, periimplant defects of over 1.5 mm heal by con-nective tissue apposition, rather than

by direct bone-to-implant contact, but clinically this healing may be suc-cessful. No histological analysis was performed in the study, but even the largest residual gaps were filled with hard tissue that could not be probed.

The effect on hard tissue modeling and remodeling of the placement of a xenograft in fresh extraction sockets in dogs was evaluated.65 Five mongrel dogs were used. Two mandibular pre-molars were hemisected in each dog, and the distal roots were carefully removed. In one socket, a graft (Bio-Oss Collagen; Geistlich Pharma AG, Wolhusen, Switzerland) was placed, whereas the contralateral site was left without grafting. After 3 months of healing, the dogs were euthanized and biopsy specimens were obtained. From each experimental site, 4 ground sections (2 from the mesial root and 2 from the healed socket) were pre-pared, stained, and examined un-der the microscope. The presence of Bio-Oss Collagen failed to inhibit the processes of modeling and remodel-ing that occurred in the socket walls following tooth extraction. However, it apparently promoted de novo hard tissue formation, particularly in the cortical region of the extraction site. Thus, the dimension of the hard tissue was maintained and the profile of the residual ridge was better preserved. The placement of a biomaterial in an extraction socket may promote bone modeling and compensate, at least temporarily, for marginal ridge con-traction.

A recent study offered somewhat conflicting results as compared to studies that demonstrated extraction socket healing occurs uneventfully without augmentation or grafting.66 The authors evaluated whether tooth extraction without the elevation of a mucoperiosteal flap has advanta-geous effects on the resorption rate after tooth extraction. In 5 beagle dogs, polyether impressions were made before the surgery. The roots of the first and second premolars were extracted and the sites were assigned to one of the following groups: treat-

ment group (Tx) 1, no treatment; Tx 2, surgical trauma (flap elevation and repositioning); Tx 3, the extrac-tion socket was filled with Bio-Oss Collagen (Geistlich Pharma AG) and closed with a free soft-tissue graft; Tx 4, after flap elevation and reposition-ing, the extraction socket was treated with Bio-Oss Collagen and a free soft-tissue graft. Impressions were made 2 and 4 months after surgery. The casts were scanned, matched together with baseline casts, and evaluated with dig-ital image analysis. Results indicated that the group without flap elevation demonstrated significantly lower re-sorption rates both with and without socket-preservation techniques. Fur-thermore, socket-preservation techniques yielded better results com-pared with no treatment of the socket. The results demonstrated that leav-ing the periosteum in place decreases the resorption rate of the extraction socket. Also, the treatment of the ex-traction socket with Bio-Oss Collagen and a free gingival graft seems benefi-cial in limiting the resorption process after tooth extraction.

Another study assessed contour changes after socket preservation techniques.67 The distal root of the third and fourth mandibular premo-lars were extracted in 5 beagle dogs. The following treatments were ran-domly assigned for the extraction socket. Tx 1: placement of Bio-Oss Collagen (Geistlich Pharma AG); Tx 2: placement of Bio-Oss Collagen and a free soft tissue graft; Tx 3: no treatment; and Tx 4: the internal buc-cal aspect was covered with an ex-perimental collagen membrane, the extraction socket was filled with Bio-Oss Collagen, and the membrane was folded on top of the graft. Impres-sions were obtained at baseline and 2 and 4 months after surgery. Buccolin-gual measurements were performed using digital imaging analysis. All groups displayed contour shrinkage at the buccal aspect. The differences between the 2 test groups (Tx 1, Tx 2) and the control group (Tx 3) were only significant at the buccal aspect



19July 2009


(P≤.001). It was concluded that the preservation techniques used were not able to entirely compensate for the alterations after tooth extraction. However, incorporation of Bio-Oss Collagen seems to have the potential to limit but not avoid the postopera-tive contour shrinkage.

Another study investigated the clinical regeneration of extraction sockets using high-density polytetra-fluoroethylene (dPTFE) membranes without the use of a graft material.68 A total of 276 extraction sockets were evaluated in 276 subjects (151 males and 125 females; mean age, 50.2 years; age range: 24 to 73 years). Af-ter extraction, flaps were elevated and a dPTFE membrane was placed over the extraction site. The flaps were re-positioned and sutured into place. Primary closure was not obtained over the membranes. The cemento-enamel junctions of the adjacent teeth were used as reference points. Measure-ments were made postextraction and 12 months after surgery in the same areas with the help of a guide and were defined as the distance from the reference points to the bone level. Hard tissue biopsies were made from 10 representative subjects during implant placement 12 months after socket preservation. The bone core samples were submitted for histologic evaluation. A stringent plaque-control regimen was enforced in all subjects during the 12-month observation pe-riod. A significant regeneration of the volume of sockets could be noted by histologic evaluation, indicating that the newly formed tissue in extraction sites was mainly bone. No influence of gender, smoking, age, or clinical bone level before treatment was found on the percentage of bone gain. It was concluded that use of dPTFE mem-branes predictably resulted in the preservation of soft and hard tissue in extraction sites.

Recognizing the variation in results following extraction socket healing, another study was designed to evalu-ate healing in all tissue compartments during healing of extraction sockets.69

The purpose of the study was to moni-tor, during a 6-month period, the heal-ing of human extraction sockets and include a semiquantitative analysis of tissues and cell populations involved in various stages of the processes of modeling/remodeling. Twenty-seven biopsies, representative of the early, intermediate (6-8 weeks, n=6), and late phase (12-24 weeks, n=11) of healing, were collected and analyzed. Granulation tissue that was present in comparatively large amounts in the early healing phase of socket healing was, in the interval between the early and intermediate observation phase, replaced with provisional matrix and woven bone. The density of vascular structures and macrophages slowly decreased from 2 to 4 weeks over time. The presence of osteoblasts peaked at 6-8 weeks and remained al-most stable thereafter; a small num-ber of osteoclasts were present in a few specimens at each observation interval. The study findings demon-strated that great variability exists in humans with respect to hard tissue formation within extraction sockets. Thus, whereas a provisional connec-tive tissue consistently forms within the first weeks of healing, the interval during which mineralized bone is laid down is much less predictable.

Soft tissue augmentation

Soft tissue augmentation for peri-odontal situations as well as dental implants is always of interest and occasionally controversial. Soft tis-sue augmentation frequently involves treatment of recession defects; there-fore, it is important to understand the classification of these defects.70 In Miller Classification Class I defects, the marginal recession does not ex-tend beyond the mucogingival junc-tion. For Class II defects, the marginal tissue extends to or beyond the mu-cogingival junction with no loss of in-terdental bone or soft tissue. In Class III defects, the recession extends to or beyond the mucogingival junction, and there is bone or tissue loss api-

cal to the cemento-enamel junction. For Class IV defects, marginal tissue recession extends beyond the muco-gingival junction. Loss of interdental bone extends to a level apical to the extent of marginal tissue recession.

New techniques as well as mate-rials offer clinicians and patients a myriad of treatment choices. It is not clear whether 1 method or material is superior to another. This review will attempt to answer this question.

An electronic search (MEDLINE, EMBASE, and PubMed Central) for randomized controlled clinical trials with at least 6 months of follow-up comparing subepithelial connective tissue grafts (SCTG) with other pro-cedures for the treatment of gingival recession was performed for articles published up to December 2007.71 To be eligible to be included in this review, patients had to present a di-agnosis of gingival recession with the following characteristics: (1) reces-sion areas selected for treatment, classified as Miller Class I or Class II, of at least 2 mm; (2) recession areas containing teeth with no caries or res-torations; and (3) at least 10 partici-pants per group at final examination. From a total of 568 references, 23 studies were considered relevant. The results indicated a statistically signifi-cantly greater reduction in gingival recession for SCTG, when compared to acellular dermal matrix grafts and guided tissue regeneration with re-sorbable membranes (GTR rm). For clinical attachment level changes, dif-ferences between all groups were not significant. For changes in the kerati-nized tissue (KT), the results showed a statistically significant gain in the width of KT for SCTG when compared to GTR rm. The results of this review show that subepithelial connective tissue grafts provided significant root coverage, clinical attachment, and keratinized tissue gain. Overall com-parisons allow the conclusion to be drawn that subepithelial connective tissue grafts are the gold-standard procedure in the treatment of reces-sion-type defects.

The decision whether to leave con-nective tissue grafts exposed or to cover them with coronally positioned flaps is a surgical dilemma. A study was designed to evaluate changes in gingival dimensions and root cover-age using the same procedure but varying the amount of connective tis-sue graft left uncovered.72 Twenty-five Miller Class I or II recession defects in 20 healthy subjects were randomly as-signed to test (exposed connective tis-sue group; E group) or control (fully covered connective tissue group; FC group) groups and treated with a connective tissue graft procedure. In the E group, 1 to 2 mm of the graft was left uncovered at the completion of the surgery, whereas the FC group had the graft completely covered by the flap. Clinical parameters assessed included probing depth, recession depth, and clinical attachment level, width of keratinized tissue, mobility, and plaque score. At 12 weeks, the mean root coverage percentages for FC and E groups were 93% and 88%, respectively. The difference between the groups was not statistically signifi-cant (P=.48). Complete root coverage was observed in 79% and 64% of the subjects in FC and E groups, respec-tively. There was greater increase in the width of keratinized tissue in the E group (1.5 ±1.1 mm) than the FC group (0.9 ±0.9 mm), although this difference did not reach statistical significance (P=.16). There were no statistically significant differences be-tween the groups for the changes in other parameters. Both procedures resulted in successful root coverage with an increase in the width of kera-tinized tissue. Leaving a portion of the graft exposed resulted in a greater in-crease of keratinized tissue, and com-plete coverage of the graft resulted in greater root coverage. However, these differences did not reach statistical significance.

Platelet-rich plasma (PRP) applied at the time of gingival augmentation may promote periodontal regenera-tion at the grafted site. The aim of one study was to compare connective

tissue graft (CTG) plus PRP with CTG alone in the treatment of gingival re-cession.73 Forty patients with Miller Class I or II recessions were included. Each recession was randomly treated with either CTG plus PRP or CTG alone. Clinical variables were recorded at baseline and at 6 weeks and 6 and 12 months. Root coverage (RC) and attachment gain (AG) were also cal-culated. Study results indicated that probing depth, recession depth, clini-cal attachment level, keratinized tis-sue width, and recession width (RW) were improved in both study groups. However, no difference was observed between groups, except in recession width. Recession in the control group was statistically lower than the test group at all follow-up periods. Treat-ment of recession with CTG or a CTG-PRP combination resulted in favorable clinical outcomes. However, no differ-ence could be found between CTG and CTG plus PRP. Whether much longer follow-up studies with higher statistical power may provide differ-ing results remains questionable.

With root coverage procedures, it has been speculated that the time required for additional gain in the amount of keratinized tissue may be greater for the acellular dermal matrix than for the connective tissue. Differ-ent techniques have been proposed for the treatment of gingival reces-sion. This study compared the clini-cal results of gingival recession treat-ment using a subepithelial connective tissue graft and an acellular dermal matrix allograft.74 Seven patients with bilateral Miller Class I or II gingival recession were selected. Twenty-six recessions were treated and randomly assigned to the test group. In each subject, the contralateral recession was assigned to the control group. In the control group, a connective tissue graft in combination with a coronally positioned flap was used; in the test group, an acellular dermal matrix al-lograft was used as a substitute for palatal donor tissue. Probing depth, clinical attachment level, gingival re-cession, and width of keratinized tis-

sue were measured 2 weeks prior to surgery and at 6 and 12 months post-surgery. There were no statistically significant differences between the groups in terms of recession reduc-tion, clinical attachment gain, prob-ing pocket depth, and increase in the width of the keratinized tissue after 6 or 12 months. There was no statisti-cally significant increase in the width of keratinized tissue between 6 and 12 months for either group. Within the limitations of this study, it can be suggested that the acellular dermal matrix allograft may be a substitute for palatal donor tissue in root pro-cedures.

The primary purpose of a random-ized, controlled, masked clinical trial was to compare the percentage of root coverage obtained with a coro-nally positioned flap plus acellular dermal matrix (ADM) allograft to that of a tunnel technique plus ADM 4 months postsurgically.75 Twenty-four subjects with 1 site with 3 mm or greater Miller Class I or II reces-sion were treated and followed for 4 months. Twelve patients received a coronally positioned flap plus ADM and were considered the positive con-trol group. The test group consisted of 12 subjects treated with a coronal-ly positioned tunnel technique plus ADM (TUN). Subjects were randomly selected by a coin toss to receive the test or control treatment. The mean facial recession defect at the initial examination for the TUN group was 3.1 ±0.3 mm; this was reduced to 0.7 ±0.9 mm at the 4-month examina-tion, for a gain of 2.4 ±1.0 mm or 78% defect coverage (P<.05). The mean fa-cial recession defect at the initial ex-amination for the CPF group was 3.4 ±0.8 mm; it was reduced to 0.2 ±0.3 mm at the 4-month examination, for a gain of 3.2 ±0.9 mm or 95% de-fect coverage (P<.05). There was no statistically significant difference be-tween groups (P>.05). The coronally positioned flap plus ADM produced a defect coverage of 95%, whereas the tunnel technique plus ADM produced only 78% coverage. This difference



19July 2009


(P≤.001). It was concluded that the preservation techniques used were not able to entirely compensate for the alterations after tooth extraction. However, incorporation of Bio-Oss Collagen seems to have the potential to limit but not avoid the postopera-tive contour shrinkage.

Another study investigated the clinical regeneration of extraction sockets using high-density polytetra-fluoroethylene (dPTFE) membranes without the use of a graft material.68 A total of 276 extraction sockets were evaluated in 276 subjects (151 males and 125 females; mean age, 50.2 years; age range: 24 to 73 years). Af-ter extraction, flaps were elevated and a dPTFE membrane was placed over the extraction site. The flaps were re-positioned and sutured into place. Primary closure was not obtained over the membranes. The cemento-enamel junctions of the adjacent teeth were used as reference points. Measure-ments were made postextraction and 12 months after surgery in the same areas with the help of a guide and were defined as the distance from the reference points to the bone level. Hard tissue biopsies were made from 10 representative subjects during implant placement 12 months after socket preservation. The bone core samples were submitted for histologic evaluation. A stringent plaque-control regimen was enforced in all subjects during the 12-month observation pe-riod. A significant regeneration of the volume of sockets could be noted by histologic evaluation, indicating that the newly formed tissue in extraction sites was mainly bone. No influence of gender, smoking, age, or clinical bone level before treatment was found on the percentage of bone gain. It was concluded that use of dPTFE mem-branes predictably resulted in the preservation of soft and hard tissue in extraction sites.

Recognizing the variation in results following extraction socket healing, another study was designed to evalu-ate healing in all tissue compartments during healing of extraction sockets.69

The purpose of the study was to moni-tor, during a 6-month period, the heal-ing of human extraction sockets and include a semiquantitative analysis of tissues and cell populations involved in various stages of the processes of modeling/remodeling. Twenty-seven biopsies, representative of the early, intermediate (6-8 weeks, n=6), and late phase (12-24 weeks, n=11) of healing, were collected and analyzed. Granulation tissue that was present in comparatively large amounts in the early healing phase of socket healing was, in the interval between the early and intermediate observation phase, replaced with provisional matrix and woven bone. The density of vascular structures and macrophages slowly decreased from 2 to 4 weeks over time. The presence of osteoblasts peaked at 6-8 weeks and remained al-most stable thereafter; a small num-ber of osteoclasts were present in a few specimens at each observation interval. The study findings demon-strated that great variability exists in humans with respect to hard tissue formation within extraction sockets. Thus, whereas a provisional connec-tive tissue consistently forms within the first weeks of healing, the interval during which mineralized bone is laid down is much less predictable.

Soft tissue augmentation

Soft tissue augmentation for peri-odontal situations as well as dental implants is always of interest and occasionally controversial. Soft tis-sue augmentation frequently involves treatment of recession defects; there-fore, it is important to understand the classification of these defects.70 In Miller Classification Class I defects, the marginal recession does not ex-tend beyond the mucogingival junc-tion. For Class II defects, the marginal tissue extends to or beyond the mu-cogingival junction with no loss of in-terdental bone or soft tissue. In Class III defects, the recession extends to or beyond the mucogingival junction, and there is bone or tissue loss api-

cal to the cemento-enamel junction. For Class IV defects, marginal tissue recession extends beyond the muco-gingival junction. Loss of interdental bone extends to a level apical to the extent of marginal tissue recession.

New techniques as well as mate-rials offer clinicians and patients a myriad of treatment choices. It is not clear whether 1 method or material is superior to another. This review will attempt to answer this question.

An electronic search (MEDLINE, EMBASE, and PubMed Central) for randomized controlled clinical trials with at least 6 months of follow-up comparing subepithelial connective tissue grafts (SCTG) with other pro-cedures for the treatment of gingival recession was performed for articles published up to December 2007.71 To be eligible to be included in this review, patients had to present a di-agnosis of gingival recession with the following characteristics: (1) reces-sion areas selected for treatment, classified as Miller Class I or Class II, of at least 2 mm; (2) recession areas containing teeth with no caries or res-torations; and (3) at least 10 partici-pants per group at final examination. From a total of 568 references, 23 studies were considered relevant. The results indicated a statistically signifi-cantly greater reduction in gingival recession for SCTG, when compared to acellular dermal matrix grafts and guided tissue regeneration with re-sorbable membranes (GTR rm). For clinical attachment level changes, dif-ferences between all groups were not significant. For changes in the kerati-nized tissue (KT), the results showed a statistically significant gain in the width of KT for SCTG when compared to GTR rm. The results of this review show that subepithelial connective tissue grafts provided significant root coverage, clinical attachment, and keratinized tissue gain. Overall com-parisons allow the conclusion to be drawn that subepithelial connective tissue grafts are the gold-standard procedure in the treatment of reces-sion-type defects.

The decision whether to leave con-nective tissue grafts exposed or to cover them with coronally positioned flaps is a surgical dilemma. A study was designed to evaluate changes in gingival dimensions and root cover-age using the same procedure but varying the amount of connective tis-sue graft left uncovered.72 Twenty-five Miller Class I or II recession defects in 20 healthy subjects were randomly as-signed to test (exposed connective tis-sue group; E group) or control (fully covered connective tissue group; FC group) groups and treated with a connective tissue graft procedure. In the E group, 1 to 2 mm of the graft was left uncovered at the completion of the surgery, whereas the FC group had the graft completely covered by the flap. Clinical parameters assessed included probing depth, recession depth, and clinical attachment level, width of keratinized tissue, mobility, and plaque score. At 12 weeks, the mean root coverage percentages for FC and E groups were 93% and 88%, respectively. The difference between the groups was not statistically signifi-cant (P=.48). Complete root coverage was observed in 79% and 64% of the subjects in FC and E groups, respec-tively. There was greater increase in the width of keratinized tissue in the E group (1.5 ±1.1 mm) than the FC group (0.9 ±0.9 mm), although this difference did not reach statistical significance (P=.16). There were no statistically significant differences be-tween the groups for the changes in other parameters. Both procedures resulted in successful root coverage with an increase in the width of kera-tinized tissue. Leaving a portion of the graft exposed resulted in a greater in-crease of keratinized tissue, and com-plete coverage of the graft resulted in greater root coverage. However, these differences did not reach statistical significance.

Platelet-rich plasma (PRP) applied at the time of gingival augmentation may promote periodontal regenera-tion at the grafted site. The aim of one study was to compare connective

tissue graft (CTG) plus PRP with CTG alone in the treatment of gingival re-cession.73 Forty patients with Miller Class I or II recessions were included. Each recession was randomly treated with either CTG plus PRP or CTG alone. Clinical variables were recorded at baseline and at 6 weeks and 6 and 12 months. Root coverage (RC) and attachment gain (AG) were also cal-culated. Study results indicated that probing depth, recession depth, clini-cal attachment level, keratinized tis-sue width, and recession width (RW) were improved in both study groups. However, no difference was observed between groups, except in recession width. Recession in the control group was statistically lower than the test group at all follow-up periods. Treat-ment of recession with CTG or a CTG-PRP combination resulted in favorable clinical outcomes. However, no differ-ence could be found between CTG and CTG plus PRP. Whether much longer follow-up studies with higher statistical power may provide differ-ing results remains questionable.

With root coverage procedures, it has been speculated that the time required for additional gain in the amount of keratinized tissue may be greater for the acellular dermal matrix than for the connective tissue. Differ-ent techniques have been proposed for the treatment of gingival reces-sion. This study compared the clini-cal results of gingival recession treat-ment using a subepithelial connective tissue graft and an acellular dermal matrix allograft.74 Seven patients with bilateral Miller Class I or II gingival recession were selected. Twenty-six recessions were treated and randomly assigned to the test group. In each subject, the contralateral recession was assigned to the control group. In the control group, a connective tissue graft in combination with a coronally positioned flap was used; in the test group, an acellular dermal matrix al-lograft was used as a substitute for palatal donor tissue. Probing depth, clinical attachment level, gingival re-cession, and width of keratinized tis-

sue were measured 2 weeks prior to surgery and at 6 and 12 months post-surgery. There were no statistically significant differences between the groups in terms of recession reduc-tion, clinical attachment gain, prob-ing pocket depth, and increase in the width of the keratinized tissue after 6 or 12 months. There was no statisti-cally significant increase in the width of keratinized tissue between 6 and 12 months for either group. Within the limitations of this study, it can be suggested that the acellular dermal matrix allograft may be a substitute for palatal donor tissue in root pro-cedures.

The primary purpose of a random-ized, controlled, masked clinical trial was to compare the percentage of root coverage obtained with a coro-nally positioned flap plus acellular dermal matrix (ADM) allograft to that of a tunnel technique plus ADM 4 months postsurgically.75 Twenty-four subjects with 1 site with 3 mm or greater Miller Class I or II reces-sion were treated and followed for 4 months. Twelve patients received a coronally positioned flap plus ADM and were considered the positive con-trol group. The test group consisted of 12 subjects treated with a coronal-ly positioned tunnel technique plus ADM (TUN). Subjects were randomly selected by a coin toss to receive the test or control treatment. The mean facial recession defect at the initial examination for the TUN group was 3.1 ±0.3 mm; this was reduced to 0.7 ±0.9 mm at the 4-month examina-tion, for a gain of 2.4 ±1.0 mm or 78% defect coverage (P<.05). The mean fa-cial recession defect at the initial ex-amination for the CPF group was 3.4 ±0.8 mm; it was reduced to 0.2 ±0.3 mm at the 4-month examination, for a gain of 3.2 ±0.9 mm or 95% de-fect coverage (P<.05). There was no statistically significant difference be-tween groups (P>.05). The coronally positioned flap plus ADM produced a defect coverage of 95%, whereas the tunnel technique plus ADM produced only 78% coverage. This difference



21July 2009


was considered clinically significant but was not statistically significant.

Another study evaluated the safety and effectiveness of a tissue-engi-neered skin product composed of via-ble neonatal keratinocytes and fibro-blasts isolated from human foreskin and compared it to a free gingival graft (FGG) in a procedure to enhance ker-atinized tissue (KT) and wound heal-ing around teeth that do not require root coverage.76 Twenty-five subjects were enrolled who had at least 2 non-adjacent teeth in contralateral quad-rants exhibiting an insufficient zone of attached gingiva requiring soft tis-sue grafting where root coverage was not desired. One tooth was random-ized to receive an FGG, and the other was randomized to receive bilayered cell therapy (BCT). The amount of KT was measured at baseline and 3 and 6 months, and the texture and color of the grafted tissue were compared to the surrounding tissue at 1, 3, and 6 months. A questionnaire was used to determine subject preference at 6 months. Biopsies and persistence studies were performed on a sub-set of the subjects. The FGG group generated statistically significantly (P<.001) more KT than the test de-vice (BCT) (4.5 ±0.80 mm versus 2.4 ±1.02 mm); no significant difference in recession or clinical attachment level was detected between treatment groups (P=.212 and P=.448, respec-tively), and no significant differences were detected at any time point for bleeding on probing (BOP), resis-tance to muscle pull, or inflamma-tion. The BCT group had significantly better color and texture match with surrounding tissue (P<.001), and subject preference was significantly greater for the BCT group (P=.041). No device-related adverse events or safety issues occurred during the course of the study. The tissue-engi-neered graft BCT was safe and capa-ble of generating de novo KT without the morbidity and potential clinical difficulties associated with donor-site surgery. The amount of KT generated with FGG was greater than that gen-

erated with BCT. Several points must be mentioned concerning this study. One issue is whether the treated sites were diseased. There was no evidence of continued attachment loss for ei-ther test or control groups. It appears the greatest improvement, other than color match, was for the free gingival graft sites.

DENTAL MATERIALS

Sealants

Sealants have been a proven pre-ventive approach for several decades. However, a number of aspects regard-ing sealants remain unknown or con-troversial. Several articles addressed some of these issues. Two articles reported on practice-based data ob-tained in Finland that dealt with the issue of generalized versus targeted sealant application. One study77 retrospectively compared the cost-effectiveness in 2 community dental practices, 1 in which sealants were routinely placed versus 1 in which sealants were targeted to patients at high risk for caries. The study popula-tion consisted of 3816 children in the 2 communities, assessed at the age of 12. Sealants were applied shortly after tooth eruption. In both groups, sealants were not placed in children who failed to make their routine seal-ing appointments. Additionally, in the targeted-placement group, sealants were not placed on the teeth of those patients designated as being at low risk for caries. Preventive measures, such as oral hygiene instructions, dietary counseling, and fluoride var-nish, were similar in both communi-ties, except for supervised xylitol gum use in the targeted group, which was accounted for in the statistical analy-sis. Caries risk analysis was assessed on the basis of dental caries and pres-ence of S. mutans in dental plaque at age 2. The applied sealant (Delton, Light Cure-Clear; Dentsply Intl, York, Pa) was the same for all subjects. Cost effectiveness was calculated using the cost of sealants and restorations on

permanent first molars, based upon a standardized fee schedule. The cu-mulative cost of treatment (sealants plus restorations plus preventive mea-sures) was 184.20€ (251.26 USD) per subject in the targeted group, and 234.30€ (319.60 USD) per sub-ject in the all-sealed group. Almost all of this difference was due to the considerably higher cost of restoring nonsealed teeth in the nontargeted community versus the targeted com-munity, emphasizing the need to di-rect sealant placement to those indi-viduals at greater risk for caries. The weakness of this study, as with most practice-based research, is that it was not possible to completely account for all confounding factors.

Using additional data from the previous study, a survival analysis was performed on the effectiveness and timing of restorative treatment in sealed versus nonsealed teeth.78 A survival analysis was conducted, in which survival was defined as the time during which the mandibular first permanent molars survived without caries or restorative treatment. The mean survival time of sealed molars was significantly (P<.001) longer than that of the nonsealed teeth in the blanket sealant group, whereas the nonsealed teeth in the targeted group actually showed the best survival time of all groups. Only 60% of nonsealed molars in the blanket treatment group survived without restoration, while 80% of nonsealed permanent man-dibular first molars in the targeted group survived without restoration.

To assist clinicians in the clini-cal decision-making process, the American Dental Association (ADA) published its evidence-based clinical recommendations for pit and fissure sealants.79 The ADA recognizes the effectiveness of dental sealants, but also the confusion and controver-sies that are associated with sealant placement. The Council on Scientific Affairs undertook a critical evaluation of the published scientific evidence re-garding sealants, weighed their find-ings on strength of the evidence, and

graded their clinical recommenda-tions (A-D) on the basis of this weight-ing. Among some of their higher rated recommendations (A, B) were the fol-lowing: sealants should be placed on permanent teeth when the tooth or patient is determined to be at risk for experiencing caries; sealants should be placed on early (noncavitated) le-sions to limit lesion progression; resin sealants are the first choice material for sealants; use of a primer/adhesive after acid etching will enhance seal-ant retention; routine mechanical preparation before acid etching is not recommended. This review also rein-forced the concept that use of sharp explorers is not necessary for the de-tection of early lesions, and forceful use of explorers can damage tooth surfaces.

A group of authors, in conjunc-tion with the Center for Disease Con-trol Dental Sealant Systematic Review Work Group, undertook an analysis to evaluate lesion progression under sealants.80 This paper reported on a meta-analysis designed to examine the effectiveness of sealants on pre-venting pit and fissure caries lesion progression of permanent teeth. The review was limited to randomized and nonrandomized controlled trials and cohort studies that evaluated the percentage of lesions that progressed. From an initial group of 1872 records and associated references, 311 ar-ticles were reviewed, 6 of which had information on the percentage of le-sions progression compared to a con-current control group. This represent-ed 384 persons, 840 teeth, and 1090 surfaces. The studies included both resin and glass ionomer sealants. Ap-proximately 90% of the lesions were noncavitated. The median annualized lesion progression rate was 5.0% for sealed lesions, compared to 16.1% for unsealed lesions. Overall, sealants prevented progression in 73.2% to 75.0% of the lesions evaluated in the data. The consistency and direction of the findings across the studies was consistent. An interesting finding was that while the probability of a sealed,

noncavitated lesion progressing was 2.6%, the probability of a nonsealed, noncavitated lesion progressing was only 12.6%. The authors suggested that this indicated that immediate surgical intervention in noncavitated lesions may not be indicated. The overall conclusion was that the evi-dence supports placing sealants over noncavitated caries lesions in the permanent teeth of children, adoles-cents, and young adults.

An area of concern that has resur-faced is the potential adverse health effects of bisphenol-A (BPA). In a sys-tematic review,81 the authors noted that BPA is used as a plasticizer in many products, such as polycarbon-ate plastic food-storage containers. In dentistry, BPA is used in the man-ufacture of dental resins for dental composite resins and sealants. This review found that none of the 7 ADA-approved sealants released detect-able amounts of BPA. The authors recommended that clinicians use 1 of the following procedures following the placement of a sealant to remove the air-inhibited layer and reduce the potential leaching of BPA from this unpolymerized surface layer: (1) use a mild abrasive such as pumice with a prophy cup or on a cotton tip ap-plicator; (2) have the patient gargle with tepid water for 30 seconds; (3) use an air-water spray to rinse the surface of the sealant for 30 seconds while suctioning fluids from the pa-tient’s mouth. Another group of re-searchers82 evaluated degradation products over a 2-week period from an experimental composite using liquid chromatography mass spec-trometry. They found no BPA in any of the specimens analyzed. In the pre-viously mentioned American Dental Association evidence-based clinical recommendations for pit and fissure sealants,79 the reviewers noted that some studies found trace amounts of BPA in the saliva of patients immedi-ately after sealant administration, but that no systemic levels of BPA were detected, and there was no evidence of estrogenicity with such low levels of

BPA exposure.

Amalgam

Much of the scientific research ef-fort pertaining to amalgam revolves around health concerns. An interesting controlled clinical trial83 was designed to assess the effectiveness of 3 treat-ment strategies applied to patients with subjective health complaints who attributed their health problems to dental amalgam restorations. Sub-jects between the ages of 20 and 50 who reported at least 10 symptoms, and who did not exhibit relevant ex-clusionary criteria, including mental disorders and drug or alcohol abuse, were randomized to 1 of 3 treatments: (1) all amalgam restorations were re-moved and replaced with ceramic, gold, or composite resin restorations; (2) in addition to having all amalgam restorations removed and replaced, this group also received high doses of vitamins and trace elements (recom-mended by the International Associa-tion of Holistic Dental Medicine) de-signed to enhance mercury excretion; (3) no amalgam restorations were re-moved and the subjects participated in a health promotion program to aid in developing self-management skills for a healthy lifestyle. The primary outcome was the difference in com-plaints at baseline and 12 months later. There was no significant differ-ence in the primary outcomes among the 3 groups, despite the fact that the amalgam removal groups showed sig-nificantly lower levels of blood and urine mercury compared to the no-removal group, demonstrating that a low mercury level was not a prerequi-site for subjective improvement.

The New England Children’s Amal-gam Trial84 evaluated the psychosocial health of children who received amal-gam restorations versus those who received composite resin restorations. A total of 534 children between the ages of 6 and 10 with at least 2 car-ies lesions were randomly assigned to have their caries restored with either amalgam or composite resin. After 5



21July 2009


was considered clinically significant but was not statistically significant.

Another study evaluated the safety and effectiveness of a tissue-engi-neered skin product composed of via-ble neonatal keratinocytes and fibro-blasts isolated from human foreskin and compared it to a free gingival graft (FGG) in a procedure to enhance ker-atinized tissue (KT) and wound heal-ing around teeth that do not require root coverage.76 Twenty-five subjects were enrolled who had at least 2 non-adjacent teeth in contralateral quad-rants exhibiting an insufficient zone of attached gingiva requiring soft tis-sue grafting where root coverage was not desired. One tooth was random-ized to receive an FGG, and the other was randomized to receive bilayered cell therapy (BCT). The amount of KT was measured at baseline and 3 and 6 months, and the texture and color of the grafted tissue were compared to the surrounding tissue at 1, 3, and 6 months. A questionnaire was used to determine subject preference at 6 months. Biopsies and persistence studies were performed on a sub-set of the subjects. The FGG group generated statistically significantly (P<.001) more KT than the test de-vice (BCT) (4.5 ±0.80 mm versus 2.4 ±1.02 mm); no significant difference in recession or clinical attachment level was detected between treatment groups (P=.212 and P=.448, respec-tively), and no significant differences were detected at any time point for bleeding on probing (BOP), resis-tance to muscle pull, or inflamma-tion. The BCT group had significantly better color and texture match with surrounding tissue (P<.001), and subject preference was significantly greater for the BCT group (P=.041). No device-related adverse events or safety issues occurred during the course of the study. The tissue-engi-neered graft BCT was safe and capa-ble of generating de novo KT without the morbidity and potential clinical difficulties associated with donor-site surgery. The amount of KT generated with FGG was greater than that gen-

erated with BCT. Several points must be mentioned concerning this study. One issue is whether the treated sites were diseased. There was no evidence of continued attachment loss for ei-ther test or control groups. It appears the greatest improvement, other than color match, was for the free gingival graft sites.

DENTAL MATERIALS

Sealants

Sealants have been a proven pre-ventive approach for several decades. However, a number of aspects regard-ing sealants remain unknown or con-troversial. Several articles addressed some of these issues. Two articles reported on practice-based data ob-tained in Finland that dealt with the issue of generalized versus targeted sealant application. One study77 retrospectively compared the cost-effectiveness in 2 community dental practices, 1 in which sealants were routinely placed versus 1 in which sealants were targeted to patients at high risk for caries. The study popula-tion consisted of 3816 children in the 2 communities, assessed at the age of 12. Sealants were applied shortly after tooth eruption. In both groups, sealants were not placed in children who failed to make their routine seal-ing appointments. Additionally, in the targeted-placement group, sealants were not placed on the teeth of those patients designated as being at low risk for caries. Preventive measures, such as oral hygiene instructions, dietary counseling, and fluoride var-nish, were similar in both communi-ties, except for supervised xylitol gum use in the targeted group, which was accounted for in the statistical analy-sis. Caries risk analysis was assessed on the basis of dental caries and pres-ence of S. mutans in dental plaque at age 2. The applied sealant (Delton, Light Cure-Clear; Dentsply Intl, York, Pa) was the same for all subjects. Cost effectiveness was calculated using the cost of sealants and restorations on

permanent first molars, based upon a standardized fee schedule. The cu-mulative cost of treatment (sealants plus restorations plus preventive mea-sures) was 184.20€ (251.26 USD) per subject in the targeted group, and 234.30€ (319.60 USD) per sub-ject in the all-sealed group. Almost all of this difference was due to the considerably higher cost of restoring nonsealed teeth in the nontargeted community versus the targeted com-munity, emphasizing the need to di-rect sealant placement to those indi-viduals at greater risk for caries. The weakness of this study, as with most practice-based research, is that it was not possible to completely account for all confounding factors.

Using additional data from the previous study, a survival analysis was performed on the effectiveness and timing of restorative treatment in sealed versus nonsealed teeth.78 A survival analysis was conducted, in which survival was defined as the time during which the mandibular first permanent molars survived without caries or restorative treatment. The mean survival time of sealed molars was significantly (P<.001) longer than that of the nonsealed teeth in the blanket sealant group, whereas the nonsealed teeth in the targeted group actually showed the best survival time of all groups. Only 60% of nonsealed molars in the blanket treatment group survived without restoration, while 80% of nonsealed permanent man-dibular first molars in the targeted group survived without restoration.

To assist clinicians in the clini-cal decision-making process, the American Dental Association (ADA) published its evidence-based clinical recommendations for pit and fissure sealants.79 The ADA recognizes the effectiveness of dental sealants, but also the confusion and controver-sies that are associated with sealant placement. The Council on Scientific Affairs undertook a critical evaluation of the published scientific evidence re-garding sealants, weighed their find-ings on strength of the evidence, and

graded their clinical recommenda-tions (A-D) on the basis of this weight-ing. Among some of their higher rated recommendations (A, B) were the fol-lowing: sealants should be placed on permanent teeth when the tooth or patient is determined to be at risk for experiencing caries; sealants should be placed on early (noncavitated) le-sions to limit lesion progression; resin sealants are the first choice material for sealants; use of a primer/adhesive after acid etching will enhance seal-ant retention; routine mechanical preparation before acid etching is not recommended. This review also rein-forced the concept that use of sharp explorers is not necessary for the de-tection of early lesions, and forceful use of explorers can damage tooth surfaces.

A group of authors, in conjunc-tion with the Center for Disease Con-trol Dental Sealant Systematic Review Work Group, undertook an analysis to evaluate lesion progression under sealants.80 This paper reported on a meta-analysis designed to examine the effectiveness of sealants on pre-venting pit and fissure caries lesion progression of permanent teeth. The review was limited to randomized and nonrandomized controlled trials and cohort studies that evaluated the percentage of lesions that progressed. From an initial group of 1872 records and associated references, 311 ar-ticles were reviewed, 6 of which had information on the percentage of le-sions progression compared to a con-current control group. This represent-ed 384 persons, 840 teeth, and 1090 surfaces. The studies included both resin and glass ionomer sealants. Ap-proximately 90% of the lesions were noncavitated. The median annualized lesion progression rate was 5.0% for sealed lesions, compared to 16.1% for unsealed lesions. Overall, sealants prevented progression in 73.2% to 75.0% of the lesions evaluated in the data. The consistency and direction of the findings across the studies was consistent. An interesting finding was that while the probability of a sealed,

noncavitated lesion progressing was 2.6%, the probability of a nonsealed, noncavitated lesion progressing was only 12.6%. The authors suggested that this indicated that immediate surgical intervention in noncavitated lesions may not be indicated. The overall conclusion was that the evi-dence supports placing sealants over noncavitated caries lesions in the permanent teeth of children, adoles-cents, and young adults.

An area of concern that has resur-faced is the potential adverse health effects of bisphenol-A (BPA). In a sys-tematic review,81 the authors noted that BPA is used as a plasticizer in many products, such as polycarbon-ate plastic food-storage containers. In dentistry, BPA is used in the man-ufacture of dental resins for dental composite resins and sealants. This review found that none of the 7 ADA-approved sealants released detect-able amounts of BPA. The authors recommended that clinicians use 1 of the following procedures following the placement of a sealant to remove the air-inhibited layer and reduce the potential leaching of BPA from this unpolymerized surface layer: (1) use a mild abrasive such as pumice with a prophy cup or on a cotton tip ap-plicator; (2) have the patient gargle with tepid water for 30 seconds; (3) use an air-water spray to rinse the surface of the sealant for 30 seconds while suctioning fluids from the pa-tient’s mouth. Another group of re-searchers82 evaluated degradation products over a 2-week period from an experimental composite using liquid chromatography mass spec-trometry. They found no BPA in any of the specimens analyzed. In the pre-viously mentioned American Dental Association evidence-based clinical recommendations for pit and fissure sealants,79 the reviewers noted that some studies found trace amounts of BPA in the saliva of patients immedi-ately after sealant administration, but that no systemic levels of BPA were detected, and there was no evidence of estrogenicity with such low levels of

BPA exposure.

Amalgam

Much of the scientific research ef-fort pertaining to amalgam revolves around health concerns. An interesting controlled clinical trial83 was designed to assess the effectiveness of 3 treat-ment strategies applied to patients with subjective health complaints who attributed their health problems to dental amalgam restorations. Sub-jects between the ages of 20 and 50 who reported at least 10 symptoms, and who did not exhibit relevant ex-clusionary criteria, including mental disorders and drug or alcohol abuse, were randomized to 1 of 3 treatments: (1) all amalgam restorations were re-moved and replaced with ceramic, gold, or composite resin restorations; (2) in addition to having all amalgam restorations removed and replaced, this group also received high doses of vitamins and trace elements (recom-mended by the International Associa-tion of Holistic Dental Medicine) de-signed to enhance mercury excretion; (3) no amalgam restorations were re-moved and the subjects participated in a health promotion program to aid in developing self-management skills for a healthy lifestyle. The primary outcome was the difference in com-plaints at baseline and 12 months later. There was no significant differ-ence in the primary outcomes among the 3 groups, despite the fact that the amalgam removal groups showed sig-nificantly lower levels of blood and urine mercury compared to the no-removal group, demonstrating that a low mercury level was not a prerequi-site for subjective improvement.

The New England Children’s Amal-gam Trial84 evaluated the psychosocial health of children who received amal-gam restorations versus those who received composite resin restorations. A total of 534 children between the ages of 6 and 10 with at least 2 car-ies lesions were randomly assigned to have their caries restored with either amalgam or composite resin. After 5



23July 2009


years, the psychosocial scores on the Child Behavior Checklist were com-pared to the baseline scores. In most measured areas, there were no signifi-cant differences between the groups. Several areas (internalizing and total problem behaviors, activities, anx-ious/depressed and delinquent be-havior) showed significantly greater improvement in the amalgam group compared to the composite resin group.

Two more articles were published from the comprehensive study accom-plished by the Universities of Washing-ton and Lisbon assessing the effects of amalgam restorations on various health parameters in children. In the first report,85 507 children between the ages of 8 and 12 with at least 1 posterior caries lesion were randomly assigned to receive either amalgam or composite resin restorations. The results of systematic neurological ex-aminations carried out at baseline and over 7 years of follow-up were reported. Individuals in the amalgam group averaged between 7.7 and 10.7 restored surfaces. The neurological examination was standardized, and assessed measures of neurological hard signs (NHSs) such as mental sta-tus, cranial nerve function, plantar re-sponses, cerebellar functions, touch, joint position, vibration senses, in-voluntary movements, and tremor; as well as neurological soft signs (NSSs) such as mirror movements, synkinesias, fine finger movements, heel-to-toe walking, motor impersis-tence, restlessness, or hyperactivity. While there was an increase in NHSs over the course of the study, there were no significant differences in the outcomes between the groups in any year of the study. The second article86 evaluated a subset of the above pop-ulation to determine if amalgam res-torations had an impact on mercury- and antibiotic-resistant bacteria from baseline levels compared to compos-ite resin restorations. The concern is that mercury released from amalgam could cause an increase in bacteria resistant to antibiotics, thereby in-

creasing the susceptibility to bacterial diseases resistant to usual drug ther-apy. One hundred and fifty children were cultured at baseline, after den-tal treatment, and annually over the 7-year period of the study. Both oral and urine specimens were analyzed. There were no significant differences between children with amalgam or composite resin restorations in either oral or urinary levels of antibiotic- or mercury-resistant bacteria, providing evidence that treating children with amalgam restorations does not influ-ence the level of antibiotic-resistant bacteria.

Composite resin

An interesting clinical study evalu-ated the efficacy of various minimal intervention techniques to increase the longevity of both amalgam and composite resin restorations.87 Six-ty-six patients having 271 defective restorations (193 amalgam, 78 com-posite resin) exhibiting marginal de-ficiencies (marginal crevice, marginal staining, but not caries) were assessed for 7 Ryge criteria at baseline and at 2 years following 1 of 5 randomly as-signed treatments: (1) repair: defec-tive margins were prepared with car-bide burs and restored with the same material as the original restoration (amalgam for amalgam restorations or adhesive/composite resin for com-posite resin restorations); (2) seal-ing of margins: defective areas were etched with 35% phosphoric acid and had a resin-based sealant applied; (3) refurbishing: defective areas were smoothed and polished; (4) replace-ment: the existing restoration was completely removed and replaced with a new amalgam or new com-posite restorations; (5) untreated: no additional treatment. While the particular categories of change varied among the various treatments, all of the treatment groups showed signifi-cant improvement from baseline to the 2-year recall, while the untreated group showed significant deteriora-tion. The importance of this study

was to demonstrate that minimal in-tervention techniques could provide similar outcomes as total replacement over 2 years, while reducing cost and invasive intervention.

An area of interest in recent years regarding composite resin has been the use of composite resin that has been warmed to reduce viscosity and improve adaptation. One in vitro study evaluated the use of preheated composite resin on restoration micro-leakage.88 Extracted third molars re-ceived 2 Class II preparations with the gingival margin on dentin, and were randomly assigned to 1 of 4 groups: (1) control: composite resin (Es-thet-X; Dentsply Caulk) placed and polymerized in 2-mm increments; (2) preheated: composite resin warmed to 130°F, then placed and polymer-ized as for the control group; (3) de-layed: composite resin warmed and placed as for preheated group, but polymerization was delayed for 15 seconds; (4) flowable: 1-mm-thick layer of flowable composite resin (Es-thet-X Flow; Dentsply Intl) was placed and polymerized, then composite res-in was placed and polymerized as for the control group. All teeth were ther-mal cycled, stored in dye for 24 hours, sectioned, and evaluated for microle-akage. There were no differences at occlusal (enamel) margins among the groups. At the gingival (dentin) mar-gins, the preheated group, in which the composite resin was immediately polymerized after placement, showed significantly reduced microleakage compared to the other 3 groups, con-firming previous findings.

Fracture is a major cause of fail-ure in composite resin restorations. A study evaluated whether the cervico-occlusal shape of Class II composite resin restorations affected marginal ridge fracture strength.89 Standardized Class II preparations were performed in artificial mandibular first molars. The preparations were restored with an adhesive, and 3 different compos-ite resins of varying filler composition and resultant elastic modulus, using 2 different matrices: a straight ma-

trix (standard Tofflemire; Kerr Hawe, Bioggio, Switzerland) or a contoured matrix (Palodent; Dentsply Intl). The marginal ridge was stressed with a universal testing machine. The con-toured proximal surfaces demonstrat-ed significantly more resistance to fracture than did the straight surfaces for all tested composite resins. The fracture resistance was not related to the modulus of elasticity of the com-posite resins. The authors conjectured that the greater volume of composite resin below the marginal ridge in the contoured restorations explained the outcome.

Clinicians are concerned with which system is the best to polish res-in restorations. The latest addition to the dentist’s armamentarium for pol-ishing composite resins is the 1-step polishing systems. An in vitro study evaluated 2 of these systems on nano-filler-containing composites.90 Stan-dardized composite specimens were fabricated from 6 nanofiller-contain-ing composite resins, and randomly assigned to 1 of 4 groups: (1) control: composite resin polymerized against a Mylar strip (no finishing); (2) PoGo (Dentsply Caulk): following abrasion with 1200-grit silicon carbide paper, the surface was finished for 30 sec-onds with PoGo disc; (3) OptraPol (Ivoclar Vivadent, Amherst, NY): same procedure as PoGo group but using OptraPol; (4) Sof-Lex (3M ESPE): af-ter initial surface preparation as for the previous 2 groups, the surface was finished with medium, fine, and superfine Sof-Lex discs for 30 seconds each. The surface roughness for each specimen was assessed with a profi-lometer, and the Vickers hardness was determined for each specimen. The Mylar strip provided the smoothest surface. While there were some sta-tistical differences among the various composites, in general, the two 1-step systems provided a surface finish and surface hardness that was comparable to the multistep polishing system.

Another concern with respect to composite resin restorations relates to light-polymerization systems and

techniques. Turbo tip light guides are popular because of their abil-ity to concentrate light emission. A well-executed study evaluated the influence of light guide type on light emission and composite resin micro-hardness.91 A laser beam analyzer was used to evaluate light distribution across the emission tip of standard and turbo-style light guides. Two-millimeter thick specimens of a hybrid composite resin (Z100; 3M ESPE) and microfill composite resin (Filtek A110; 3M ESPE) were polymerized, and the Knoop hardness was tested across the top and bottom surfaces. The results showed that the standard light guide demonstrated significantly more uniform light emission than did the turbo light guide. While both light tip guides provided a higher polymer-ization at the center of the composite resin specimen than at the periphery, there was significantly less decrease in polymerization from center to pe-riphery with the standard light guide as compared to the turbo light guide. This lack of uniformity of the compos-ite resin polymerization produced by the turbo guide was more pronounced on the bottom surface of the compos-ite resin than on the top surface. This study demonstrated that while the turbo-style light guide may increase ir-radiance, additional exposures might be needed when polymerizing larger restorations to compensate for the reduced polymerization at the periph-ery of the turbo-style guide.

Another study also evaluated the impact of light guide geometry on polymerization efficacy.92 Four light guides of varying “R” value (entry diameter/exit diameter ratio) were used with 2 different LED curing lights (FreeLight 2; 3M ESPE, and L.E.Demetron 1; KerrHawe) to po-lymerize composite resin specimens. The initial polymerization regimen was accomplished with the end of the light guide against the composite resin specimen. Subsequent compos-ite resin specimens were polymerized with the light guide moved away from the composite resin surface in 1-mm

increments. The depth of polymeriza-tion of the composite resin specimens was assessed and statistically corre-lated with the “R” value. The results showed that when the light guide was close to the composite resin surface, the guide with the higher “R” value (turbo-style) was more efficient at polymerizing composite resin. How-ever, as the distance from the end of the light guide to the surface of the composite resin increased past 4-5 mm, the standard-style guide was more efficacious at polymerizing the composite resin specimens. Consider-ing the limitation on how close a light guide would be able to come to the bottom of a proximal box in a Class II preparation, this study emphasizes the shortcomings of the turbo tip light guide as compared to the stan-dard light guide.

Various polymerizing regimens have been suggested to reduce po-lymerization shrinkage stress of com-posite resins in the belief that this will promote enhanced marginal seal. While some laboratory studies have shown that reduced irradiance during the initial stages of polymerization can improve marginal integrity, clini-cal verification of this has been lack-ing, particularly in composite resin restorations other than Class V resto-rations. A recently published clinical study addressed this shortcoming.93

Twenty patients each received at least 1 pair of Class I or II restorations. One restoration of the pair was polymer-ized with a plasma arc curing (PAC) light (2000 mW/cm2 for 10 seconds for each 1.5- to 2-mm increment), and the other restoration was polym-erized with a soft start regimen (200 mW/cm2 for 20 seconds for each 1.5- to 2-mm internal increment, then 200 mW/cm2 for 3 seconds, a wait-ing period of 3 minutes; 200 mW/cm2 for 3 seconds, a waiting period of 5 minutes; 600 mW/cm2 for 20 seconds from multiple angles, and a waiting period of 3 minutes for the fi-nal increment). Each restoration was evaluated at intervals of 2 weeks and 3, 12, and 24 months for evidence



23July 2009


years, the psychosocial scores on the Child Behavior Checklist were com-pared to the baseline scores. In most measured areas, there were no signifi-cant differences between the groups. Several areas (internalizing and total problem behaviors, activities, anx-ious/depressed and delinquent be-havior) showed significantly greater improvement in the amalgam group compared to the composite resin group.

Two more articles were published from the comprehensive study accom-plished by the Universities of Washing-ton and Lisbon assessing the effects of amalgam restorations on various health parameters in children. In the first report,85 507 children between the ages of 8 and 12 with at least 1 posterior caries lesion were randomly assigned to receive either amalgam or composite resin restorations. The results of systematic neurological ex-aminations carried out at baseline and over 7 years of follow-up were reported. Individuals in the amalgam group averaged between 7.7 and 10.7 restored surfaces. The neurological examination was standardized, and assessed measures of neurological hard signs (NHSs) such as mental sta-tus, cranial nerve function, plantar re-sponses, cerebellar functions, touch, joint position, vibration senses, in-voluntary movements, and tremor; as well as neurological soft signs (NSSs) such as mirror movements, synkinesias, fine finger movements, heel-to-toe walking, motor impersis-tence, restlessness, or hyperactivity. While there was an increase in NHSs over the course of the study, there were no significant differences in the outcomes between the groups in any year of the study. The second article86 evaluated a subset of the above pop-ulation to determine if amalgam res-torations had an impact on mercury- and antibiotic-resistant bacteria from baseline levels compared to compos-ite resin restorations. The concern is that mercury released from amalgam could cause an increase in bacteria resistant to antibiotics, thereby in-

creasing the susceptibility to bacterial diseases resistant to usual drug ther-apy. One hundred and fifty children were cultured at baseline, after den-tal treatment, and annually over the 7-year period of the study. Both oral and urine specimens were analyzed. There were no significant differences between children with amalgam or composite resin restorations in either oral or urinary levels of antibiotic- or mercury-resistant bacteria, providing evidence that treating children with amalgam restorations does not influ-ence the level of antibiotic-resistant bacteria.

Composite resin

An interesting clinical study evalu-ated the efficacy of various minimal intervention techniques to increase the longevity of both amalgam and composite resin restorations.87 Six-ty-six patients having 271 defective restorations (193 amalgam, 78 com-posite resin) exhibiting marginal de-ficiencies (marginal crevice, marginal staining, but not caries) were assessed for 7 Ryge criteria at baseline and at 2 years following 1 of 5 randomly as-signed treatments: (1) repair: defec-tive margins were prepared with car-bide burs and restored with the same material as the original restoration (amalgam for amalgam restorations or adhesive/composite resin for com-posite resin restorations); (2) seal-ing of margins: defective areas were etched with 35% phosphoric acid and had a resin-based sealant applied; (3) refurbishing: defective areas were smoothed and polished; (4) replace-ment: the existing restoration was completely removed and replaced with a new amalgam or new com-posite restorations; (5) untreated: no additional treatment. While the particular categories of change varied among the various treatments, all of the treatment groups showed signifi-cant improvement from baseline to the 2-year recall, while the untreated group showed significant deteriora-tion. The importance of this study

was to demonstrate that minimal in-tervention techniques could provide similar outcomes as total replacement over 2 years, while reducing cost and invasive intervention.

An area of interest in recent years regarding composite resin has been the use of composite resin that has been warmed to reduce viscosity and improve adaptation. One in vitro study evaluated the use of preheated composite resin on restoration micro-leakage.88 Extracted third molars re-ceived 2 Class II preparations with the gingival margin on dentin, and were randomly assigned to 1 of 4 groups: (1) control: composite resin (Es-thet-X; Dentsply Caulk) placed and polymerized in 2-mm increments; (2) preheated: composite resin warmed to 130°F, then placed and polymer-ized as for the control group; (3) de-layed: composite resin warmed and placed as for preheated group, but polymerization was delayed for 15 seconds; (4) flowable: 1-mm-thick layer of flowable composite resin (Es-thet-X Flow; Dentsply Intl) was placed and polymerized, then composite res-in was placed and polymerized as for the control group. All teeth were ther-mal cycled, stored in dye for 24 hours, sectioned, and evaluated for microle-akage. There were no differences at occlusal (enamel) margins among the groups. At the gingival (dentin) mar-gins, the preheated group, in which the composite resin was immediately polymerized after placement, showed significantly reduced microleakage compared to the other 3 groups, con-firming previous findings.

Fracture is a major cause of fail-ure in composite resin restorations. A study evaluated whether the cervico-occlusal shape of Class II composite resin restorations affected marginal ridge fracture strength.89 Standardized Class II preparations were performed in artificial mandibular first molars. The preparations were restored with an adhesive, and 3 different compos-ite resins of varying filler composition and resultant elastic modulus, using 2 different matrices: a straight ma-

trix (standard Tofflemire; Kerr Hawe, Bioggio, Switzerland) or a contoured matrix (Palodent; Dentsply Intl). The marginal ridge was stressed with a universal testing machine. The con-toured proximal surfaces demonstrat-ed significantly more resistance to fracture than did the straight surfaces for all tested composite resins. The fracture resistance was not related to the modulus of elasticity of the com-posite resins. The authors conjectured that the greater volume of composite resin below the marginal ridge in the contoured restorations explained the outcome.

Clinicians are concerned with which system is the best to polish res-in restorations. The latest addition to the dentist’s armamentarium for pol-ishing composite resins is the 1-step polishing systems. An in vitro study evaluated 2 of these systems on nano-filler-containing composites.90 Stan-dardized composite specimens were fabricated from 6 nanofiller-contain-ing composite resins, and randomly assigned to 1 of 4 groups: (1) control: composite resin polymerized against a Mylar strip (no finishing); (2) PoGo (Dentsply Caulk): following abrasion with 1200-grit silicon carbide paper, the surface was finished for 30 sec-onds with PoGo disc; (3) OptraPol (Ivoclar Vivadent, Amherst, NY): same procedure as PoGo group but using OptraPol; (4) Sof-Lex (3M ESPE): af-ter initial surface preparation as for the previous 2 groups, the surface was finished with medium, fine, and superfine Sof-Lex discs for 30 seconds each. The surface roughness for each specimen was assessed with a profi-lometer, and the Vickers hardness was determined for each specimen. The Mylar strip provided the smoothest surface. While there were some sta-tistical differences among the various composites, in general, the two 1-step systems provided a surface finish and surface hardness that was comparable to the multistep polishing system.

Another concern with respect to composite resin restorations relates to light-polymerization systems and

techniques. Turbo tip light guides are popular because of their abil-ity to concentrate light emission. A well-executed study evaluated the influence of light guide type on light emission and composite resin micro-hardness.91 A laser beam analyzer was used to evaluate light distribution across the emission tip of standard and turbo-style light guides. Two-millimeter thick specimens of a hybrid composite resin (Z100; 3M ESPE) and microfill composite resin (Filtek A110; 3M ESPE) were polymerized, and the Knoop hardness was tested across the top and bottom surfaces. The results showed that the standard light guide demonstrated significantly more uniform light emission than did the turbo light guide. While both light tip guides provided a higher polymer-ization at the center of the composite resin specimen than at the periphery, there was significantly less decrease in polymerization from center to pe-riphery with the standard light guide as compared to the turbo light guide. This lack of uniformity of the compos-ite resin polymerization produced by the turbo guide was more pronounced on the bottom surface of the compos-ite resin than on the top surface. This study demonstrated that while the turbo-style light guide may increase ir-radiance, additional exposures might be needed when polymerizing larger restorations to compensate for the reduced polymerization at the periph-ery of the turbo-style guide.

Another study also evaluated the impact of light guide geometry on polymerization efficacy.92 Four light guides of varying “R” value (entry diameter/exit diameter ratio) were used with 2 different LED curing lights (FreeLight 2; 3M ESPE, and L.E.Demetron 1; KerrHawe) to po-lymerize composite resin specimens. The initial polymerization regimen was accomplished with the end of the light guide against the composite resin specimen. Subsequent compos-ite resin specimens were polymerized with the light guide moved away from the composite resin surface in 1-mm

increments. The depth of polymeriza-tion of the composite resin specimens was assessed and statistically corre-lated with the “R” value. The results showed that when the light guide was close to the composite resin surface, the guide with the higher “R” value (turbo-style) was more efficient at polymerizing composite resin. How-ever, as the distance from the end of the light guide to the surface of the composite resin increased past 4-5 mm, the standard-style guide was more efficacious at polymerizing the composite resin specimens. Consider-ing the limitation on how close a light guide would be able to come to the bottom of a proximal box in a Class II preparation, this study emphasizes the shortcomings of the turbo tip light guide as compared to the stan-dard light guide.

Various polymerizing regimens have been suggested to reduce po-lymerization shrinkage stress of com-posite resins in the belief that this will promote enhanced marginal seal. While some laboratory studies have shown that reduced irradiance during the initial stages of polymerization can improve marginal integrity, clini-cal verification of this has been lack-ing, particularly in composite resin restorations other than Class V resto-rations. A recently published clinical study addressed this shortcoming.93

Twenty patients each received at least 1 pair of Class I or II restorations. One restoration of the pair was polymer-ized with a plasma arc curing (PAC) light (2000 mW/cm2 for 10 seconds for each 1.5- to 2-mm increment), and the other restoration was polym-erized with a soft start regimen (200 mW/cm2 for 20 seconds for each 1.5- to 2-mm internal increment, then 200 mW/cm2 for 3 seconds, a wait-ing period of 3 minutes; 200 mW/cm2 for 3 seconds, a waiting period of 5 minutes; 600 mW/cm2 for 20 seconds from multiple angles, and a waiting period of 3 minutes for the fi-nal increment). Each restoration was evaluated at intervals of 2 weeks and 3, 12, and 24 months for evidence



25July 2009


of “marginal stress” (cracked tooth syndrome, postoperative sensitivity, secondary caries, interfacial stain-ing, marginal discrepancy). At the end of the 2-year evaluation period, there were no significant differences between the groups. This reinforces the belief that current polymerization shrinkage stress reduction procedures are not effective in clinically relevant time regimens.

A critical review of the literature was published on failure of dental composite resin restorations, and focused primarily on the effects of laboratory variables and testing pro-cedures on the mechanical properties of these materials.94 This article also reviewed the failures of composite resins in clinical studies, and con-cluded that failures in the first 5 years after restoration placement were pri-marily related to restoration factors (technique or material selection), while failures after this initial period were usually due to secondary caries. This review reemphasizes the need for clinicians to incorporate appropriate materials with proper technique and patient selection to enhance clinical success with composite resin restora-tions.

Dental adhesives

The trend in recent years has been towards simplification of adhesives, as manufacturers have marketed sys-tems that combine the etchant, prim-er, and resin components to reduce the number of application steps. Both in vitro and in vivo research evidence has suggested that there may be some reduced efficacy with the simplified systems. Two clinical studies reported results comparing the performance of simplified systems to the 3-step, etch-and-rinse “gold-standard” ad-hesive systems. In the first study,95 52 patients with 267 noncarious cervi-cal lesions were randomly restored with a 3-step etch-and-rinse adhe-sive (OptiBond FL; Kerr Corp) or a 1-step self-etch system (GC G-Bond; GC America), followed by a compos-

ite resin restoration (Gradia Direct Anterior; GC America). For each pa-tient, half the lesions were treated with the 3-step system, and half were treated with the 1-step system. Dur-ing restoration, teeth were isolated with cotton rolls and saliva suction. Baseline, 6-month, and 1-year evalu-ations were performed by examiners blinded to the adhesives used. After 1 year of service, lesions restored with both adhesives provided comparable results in terms of retention, second-ary caries, and sensitivity. Both adhe-sives showed an increase in marginal defects from baseline to 1 year; how-ever, those restorations done with the 1-step system showed a significantly greater increase in marginal defects at the enamel margin compared to the etch-and-rinse system. The authors suggested that this result may be due to an inferior enamel etch for the 1-step self-etch system compared to the 3-step, total-etch system. In addi-tion, there was a slightly significant in-crease in marginal discoloration with the 1-step system compared to the 3-step system.

The second study was of similar design,96 with 30 patients receiving a total of 105 restorations, divided into 4 groups, for noncarious cervical le-sions of varying degrees of sclerosis. The 1-step adhesive (iBond; Heraeus Kulzer, Armonk, NY) was used in 3 groups: restorations with no to mild sclerosis, restorations with moderate to significant sclerosis, and restora-tions with moderate to significant sclerosis that received acid etching pri-or to adhesive application. The con-trol was a 3-step, total-etch adhesive (Gluma Solid Bond; Heraeus Kulzer) used to restore lesions with no to mild sclerosis. All lesions received the same composite resin (Durafill VS; Heraeus Kulzer), and teeth were isolated with either cotton rolls or a rubber dam, depending on access. Restorations were evaluated at baseline, and at 6, 18, and 36 months after placement using standardized Ryge criteria. No significant differences were found among the groups for retention rate,

secondary caries, or sensitivity. How-ever, the quality of marginal seal as measured by marginal adaptation and/or marginal discoloration de-creased over the 3-year study period for all of the 1-step restorations, but not for the 3-step restorations. While not statistically significant when com-pared to the 3-step adhesive, all of the lost restorations came from the 1-step adhesive groups. When the 3-year marginal discoloration scores were compared between the 1-step group that received the additional etch prior to application compared to the group that did not, those restorations that received the phosphoric acid etch performed significantly better, al-though still significantly worse than the restorations that were placed with the 3-step, total-etch adhesive.

Another study compared the clini-cal performance of noncarious cer-vical lesions restored using an etch-and-rinse adhesive versus a self-etch adhesive.97 Twenty-nine patients with at least 2 pairs of similar sized non-carious cervical lesions (116 resto-rations) were restored with a 2-step self-etch adhesive (Tyrian SPE; Bisco, Inc, Schaumburg, Ill) or a 2-step etch-and-rinse adhesive (One-Step Plus; Bisco, Inc). With both systems, the adhesives were divided into 2 groups: those that were applied per manu-facturer’s instructions (2 coats), and those that received a double applica-tion of the second-step component (4 coats). All lesions were restored with a microfilled composite resin (Micronew; Bisco, Inc). Restorations were evaluated at baseline, and af-ter 6, 12, and 18 months of clinical performance using modified Ryge criteria. Of the 4 groups, only those lesions restored with the etch-and-rinse adhesive and the double ap-plication did not show a significant decrease in retention over the study period. All other groups, including both adhesives applied using manu-facturer’s instructions, did not meet ADA guidelines. The results suggest that the combination of a phosphoric acid etch and additional application

of the primer/adhesive component al-lows better penetration and improved resin concentration in the demineral-ized dentin surface. In an additional finding of note, the study found that marginal discoloration was an early indicator of restoration loss.

Taken together, these clinical studies confirm that, in general, the simplified adhesive system perfor-mance is inferior when compared to the etch-and-rinse, 3-step adhesive systems. This appears to be particu-larly true when the 3-step systems are compared to the 1-step, all-in-one ad-hesives.

Laboratory studies have also eval-uated various parameters of adhesive performance to determine if modifi-cation of self-etch application proce-dures can improve their performance. One of the disadvantages associated with self-etch systems is their inability, relative to etch-and-rinse systems, to adequately etch and adhere to enamel. To address this shortcoming, 1 study evaluated the shear bond strength to enamel of an etch-and-rinse adhesive to several self-etch systems, applied following manufacturer instructions and with prior phosphoric acid etch-ing.98 The proximal surfaces of human molars were ground flat and random-ly divided into 2 groups: 1 group was etched with 37% phosphoric acid and the other was not. These 2 groups were further divided among the 4 adhesives tested: an etch-and-rinse adhesive (Syntac Classic; Ivoclar Viva-dent), two 2-step self-etch adhesives (AdheSE; Ivoclar Vivadent, and Xeno III; Dentsply Intl), and a 1-step self-etch adhesive (Futurabond NR; VOCO America, Inc, Sunnyside, NY), which were applied according to manufac-turers’ instructions. Statistical analy-sis of the shear bond strength testing showed that phosphoric acid etching of the enamel surface significantly im-proved bond strength compared to self-etching alone, regardless of the system.

In a similar study comparing shear bond strength of self-etch adhesives applied with or without prior phos-

phoric etching, the authors added a thermal cycling step to assess the du-rability of any bond strength increase to enamel.99 Following bovine enamel surface preparation, teeth were ran-domly assigned to receive 37% phos-phoric etching or no etching. Three 1-step systems (Absolute; Dentsply Intl, or Clearfil Tri-S Bond; Kuraray Co, Ltd, or GC G-Bond; GC America) and two 2-step systems (Fluoro Bond Shake One; Shofu, San Marcos, Calif, or One-Up Bond F Plus; Tokuyama America, Inc, Encinitas, Calif ) were applied according to manufactur-er instructions and stored for 24 hours. One half of the specimens in each group were then tested in shear mode, and the other half were ther-mal cycled 10,000 times between 5°C and 55°C before being tested in shear mode. All of the adhesives showed an increase in bond strength with prior phosphoric acid etching, regardless of whether thermal cycling was done, and the increase was significant for 3 of the adhesives (Absolute, Clearfil Tri-S Bond, and Fluoro Bond Shake One). This confirms the previous study results, and shows that there is the potential that a phosphoric etch prior to self-etch adhesive application can provide a durable improvement to enamel bond strength, with at least some self-etch systems.

Other research focused on the ef-fects of other modifications of appli-cation technique on adhesive perfor-mance. One such study evaluated the impact of air stream temperature on bond strength and microleakage of 2 etch-and-rinse adhesives that con-tained different solvents.100 Flat den-tin surfaces were prepared on human teeth, and 2 etch-and-rinse adhesives (Single Bond; 3M ESPE, and Prime & Bond 2.1; Dentsply Intl) were ap-plied. After each adhesive coat was applied, the dentin surface was dried with either a warm (60°C) or cool (20°C) air stream. After light polym-erizing the adhesive, composite resin was added and polymerized in 1-mm increments, and then sectioned into sticks. Most sticks were subjected to

microtensile bond strength testing, but 3-4 sticks from each tooth were stored in silver nitrate and evaluated for microleakage. Results of the bond strength testing showed that the bond strength was higher for both adhe-sives when warm air drying had been used; this difference was significant for Single Bond. Likewise, microleak-age was reduced for both adhesives when warm air drying was done prior to light polymerization. These results confirmed the concept that it is essen-tial to maximize solvent evaporation to maximize bond strength.

The use of lasers for cavity prepa-ration has received much attention in recent years. This has prompted re-search to determine if laser prepara-tion has an effect on the bond of ad-hesives to tooth structure compared to preparations made with burs. One such study evaluated the hybrid layer in dentin following preparation with a diamond rotary cutting instrument or an Er:YAG laser at 2 different pulse energies and 2 different frequencies.101 Flat dentin surfaces were prepared for 10 seconds, bonded with 1 of 4 differ-ent adhesives: a 3-step etch-and-rinse system (Scotchbond Multi-Purpose; 3M ESPE), two 2-step etch-and-rinse systems (Single Bond 2; 3M ESPE, and Prime & Bond 2.1; Dentsply Intl), and one 1-step all-in-one system (Xeno III; Dentsply Intl), and restored with composite resin. The specimens were sectioned, sputter coated, and the hybrid layer was evaluated quan-titatively (thickness) and qualitatively (consistency) by scanning electron mi-croscopy (SEM). The results showed that the hybrid layer of the diamond rotary cutting instrument-prepared dentin was significantly thicker and more regular than the hybrid layer of the laser-prepared dentin, and there were many laser-prepared specimens in which no hybrid layer was found at all.

Another investigation determined the effect of laser preparation on den-tin microtensile bond strength.102 Flat dentin surfaces were created on bo-vine incisors with a diamond saw, then



25July 2009


of “marginal stress” (cracked tooth syndrome, postoperative sensitivity, secondary caries, interfacial stain-ing, marginal discrepancy). At the end of the 2-year evaluation period, there were no significant differences between the groups. This reinforces the belief that current polymerization shrinkage stress reduction procedures are not effective in clinically relevant time regimens.

A critical review of the literature was published on failure of dental composite resin restorations, and focused primarily on the effects of laboratory variables and testing pro-cedures on the mechanical properties of these materials.94 This article also reviewed the failures of composite resins in clinical studies, and con-cluded that failures in the first 5 years after restoration placement were pri-marily related to restoration factors (technique or material selection), while failures after this initial period were usually due to secondary caries. This review reemphasizes the need for clinicians to incorporate appropriate materials with proper technique and patient selection to enhance clinical success with composite resin restora-tions.

Dental adhesives

The trend in recent years has been towards simplification of adhesives, as manufacturers have marketed sys-tems that combine the etchant, prim-er, and resin components to reduce the number of application steps. Both in vitro and in vivo research evidence has suggested that there may be some reduced efficacy with the simplified systems. Two clinical studies reported results comparing the performance of simplified systems to the 3-step, etch-and-rinse “gold-standard” ad-hesive systems. In the first study,95 52 patients with 267 noncarious cervi-cal lesions were randomly restored with a 3-step etch-and-rinse adhe-sive (OptiBond FL; Kerr Corp) or a 1-step self-etch system (GC G-Bond; GC America), followed by a compos-

ite resin restoration (Gradia Direct Anterior; GC America). For each pa-tient, half the lesions were treated with the 3-step system, and half were treated with the 1-step system. Dur-ing restoration, teeth were isolated with cotton rolls and saliva suction. Baseline, 6-month, and 1-year evalu-ations were performed by examiners blinded to the adhesives used. After 1 year of service, lesions restored with both adhesives provided comparable results in terms of retention, second-ary caries, and sensitivity. Both adhe-sives showed an increase in marginal defects from baseline to 1 year; how-ever, those restorations done with the 1-step system showed a significantly greater increase in marginal defects at the enamel margin compared to the etch-and-rinse system. The authors suggested that this result may be due to an inferior enamel etch for the 1-step self-etch system compared to the 3-step, total-etch system. In addi-tion, there was a slightly significant in-crease in marginal discoloration with the 1-step system compared to the 3-step system.

The second study was of similar design,96 with 30 patients receiving a total of 105 restorations, divided into 4 groups, for noncarious cervical le-sions of varying degrees of sclerosis. The 1-step adhesive (iBond; Heraeus Kulzer, Armonk, NY) was used in 3 groups: restorations with no to mild sclerosis, restorations with moderate to significant sclerosis, and restora-tions with moderate to significant sclerosis that received acid etching pri-or to adhesive application. The con-trol was a 3-step, total-etch adhesive (Gluma Solid Bond; Heraeus Kulzer) used to restore lesions with no to mild sclerosis. All lesions received the same composite resin (Durafill VS; Heraeus Kulzer), and teeth were isolated with either cotton rolls or a rubber dam, depending on access. Restorations were evaluated at baseline, and at 6, 18, and 36 months after placement using standardized Ryge criteria. No significant differences were found among the groups for retention rate,

secondary caries, or sensitivity. How-ever, the quality of marginal seal as measured by marginal adaptation and/or marginal discoloration de-creased over the 3-year study period for all of the 1-step restorations, but not for the 3-step restorations. While not statistically significant when com-pared to the 3-step adhesive, all of the lost restorations came from the 1-step adhesive groups. When the 3-year marginal discoloration scores were compared between the 1-step group that received the additional etch prior to application compared to the group that did not, those restorations that received the phosphoric acid etch performed significantly better, al-though still significantly worse than the restorations that were placed with the 3-step, total-etch adhesive.

Another study compared the clini-cal performance of noncarious cer-vical lesions restored using an etch-and-rinse adhesive versus a self-etch adhesive.97 Twenty-nine patients with at least 2 pairs of similar sized non-carious cervical lesions (116 resto-rations) were restored with a 2-step self-etch adhesive (Tyrian SPE; Bisco, Inc, Schaumburg, Ill) or a 2-step etch-and-rinse adhesive (One-Step Plus; Bisco, Inc). With both systems, the adhesives were divided into 2 groups: those that were applied per manu-facturer’s instructions (2 coats), and those that received a double applica-tion of the second-step component (4 coats). All lesions were restored with a microfilled composite resin (Micronew; Bisco, Inc). Restorations were evaluated at baseline, and af-ter 6, 12, and 18 months of clinical performance using modified Ryge criteria. Of the 4 groups, only those lesions restored with the etch-and-rinse adhesive and the double ap-plication did not show a significant decrease in retention over the study period. All other groups, including both adhesives applied using manu-facturer’s instructions, did not meet ADA guidelines. The results suggest that the combination of a phosphoric acid etch and additional application

of the primer/adhesive component al-lows better penetration and improved resin concentration in the demineral-ized dentin surface. In an additional finding of note, the study found that marginal discoloration was an early indicator of restoration loss.

Taken together, these clinical studies confirm that, in general, the simplified adhesive system perfor-mance is inferior when compared to the etch-and-rinse, 3-step adhesive systems. This appears to be particu-larly true when the 3-step systems are compared to the 1-step, all-in-one ad-hesives.

Laboratory studies have also eval-uated various parameters of adhesive performance to determine if modifi-cation of self-etch application proce-dures can improve their performance. One of the disadvantages associated with self-etch systems is their inability, relative to etch-and-rinse systems, to adequately etch and adhere to enamel. To address this shortcoming, 1 study evaluated the shear bond strength to enamel of an etch-and-rinse adhesive to several self-etch systems, applied following manufacturer instructions and with prior phosphoric acid etch-ing.98 The proximal surfaces of human molars were ground flat and random-ly divided into 2 groups: 1 group was etched with 37% phosphoric acid and the other was not. These 2 groups were further divided among the 4 adhesives tested: an etch-and-rinse adhesive (Syntac Classic; Ivoclar Viva-dent), two 2-step self-etch adhesives (AdheSE; Ivoclar Vivadent, and Xeno III; Dentsply Intl), and a 1-step self-etch adhesive (Futurabond NR; VOCO America, Inc, Sunnyside, NY), which were applied according to manufac-turers’ instructions. Statistical analy-sis of the shear bond strength testing showed that phosphoric acid etching of the enamel surface significantly im-proved bond strength compared to self-etching alone, regardless of the system.

In a similar study comparing shear bond strength of self-etch adhesives applied with or without prior phos-

phoric etching, the authors added a thermal cycling step to assess the du-rability of any bond strength increase to enamel.99 Following bovine enamel surface preparation, teeth were ran-domly assigned to receive 37% phos-phoric etching or no etching. Three 1-step systems (Absolute; Dentsply Intl, or Clearfil Tri-S Bond; Kuraray Co, Ltd, or GC G-Bond; GC America) and two 2-step systems (Fluoro Bond Shake One; Shofu, San Marcos, Calif, or One-Up Bond F Plus; Tokuyama America, Inc, Encinitas, Calif ) were applied according to manufactur-er instructions and stored for 24 hours. One half of the specimens in each group were then tested in shear mode, and the other half were ther-mal cycled 10,000 times between 5°C and 55°C before being tested in shear mode. All of the adhesives showed an increase in bond strength with prior phosphoric acid etching, regardless of whether thermal cycling was done, and the increase was significant for 3 of the adhesives (Absolute, Clearfil Tri-S Bond, and Fluoro Bond Shake One). This confirms the previous study results, and shows that there is the potential that a phosphoric etch prior to self-etch adhesive application can provide a durable improvement to enamel bond strength, with at least some self-etch systems.

Other research focused on the ef-fects of other modifications of appli-cation technique on adhesive perfor-mance. One such study evaluated the impact of air stream temperature on bond strength and microleakage of 2 etch-and-rinse adhesives that con-tained different solvents.100 Flat den-tin surfaces were prepared on human teeth, and 2 etch-and-rinse adhesives (Single Bond; 3M ESPE, and Prime & Bond 2.1; Dentsply Intl) were ap-plied. After each adhesive coat was applied, the dentin surface was dried with either a warm (60°C) or cool (20°C) air stream. After light polym-erizing the adhesive, composite resin was added and polymerized in 1-mm increments, and then sectioned into sticks. Most sticks were subjected to

microtensile bond strength testing, but 3-4 sticks from each tooth were stored in silver nitrate and evaluated for microleakage. Results of the bond strength testing showed that the bond strength was higher for both adhe-sives when warm air drying had been used; this difference was significant for Single Bond. Likewise, microleak-age was reduced for both adhesives when warm air drying was done prior to light polymerization. These results confirmed the concept that it is essen-tial to maximize solvent evaporation to maximize bond strength.

The use of lasers for cavity prepa-ration has received much attention in recent years. This has prompted re-search to determine if laser prepara-tion has an effect on the bond of ad-hesives to tooth structure compared to preparations made with burs. One such study evaluated the hybrid layer in dentin following preparation with a diamond rotary cutting instrument or an Er:YAG laser at 2 different pulse energies and 2 different frequencies.101 Flat dentin surfaces were prepared for 10 seconds, bonded with 1 of 4 differ-ent adhesives: a 3-step etch-and-rinse system (Scotchbond Multi-Purpose; 3M ESPE), two 2-step etch-and-rinse systems (Single Bond 2; 3M ESPE, and Prime & Bond 2.1; Dentsply Intl), and one 1-step all-in-one system (Xeno III; Dentsply Intl), and restored with composite resin. The specimens were sectioned, sputter coated, and the hybrid layer was evaluated quan-titatively (thickness) and qualitatively (consistency) by scanning electron mi-croscopy (SEM). The results showed that the hybrid layer of the diamond rotary cutting instrument-prepared dentin was significantly thicker and more regular than the hybrid layer of the laser-prepared dentin, and there were many laser-prepared specimens in which no hybrid layer was found at all.

Another investigation determined the effect of laser preparation on den-tin microtensile bond strength.102 Flat dentin surfaces were created on bo-vine incisors with a diamond saw, then



27July 2009


prepared with Er:YAG laser or a #245 carbide bur. A 2-step etch-and-rinse adhesive (Single Bond; 3M ESPE) was applied as called for by the manu-facturer, and composite resin was added incrementally and polymer-ized. The specimens were assigned to 1 of 4 storage groups: 24-hour water storage; or 500 thermal cycles/week (5°C/55°C) and water storage for 1 week, 1 month, or 6 months. After water storage/thermal cycling, speci-mens were sectioned and subjected to microtensile bond strength testing. In general, the bur-prepared dentin surfaces demonstrated higher bond strengths than the laser-prepared sur-faces, with the laser-prepared surfaces subjected to 6-month thermal cycling and water storage showing significant-ly lower bond strength than any other group. In addition, adhesive failure was the predominant mode of failure in the laser-treated groups (62.1%), whereas mixed or cohesive failures ac-counted for the major mode of failure in the bur-prepared groups (77.1%). SEM analysis of the specimens after bond strength testing showed that the bur-prepared dentin produced more uniform, thicker hybrid layers with less morphological changes even after the simulated aging procedure (water storage/thermal cycling) than the laser-prepared dentin.

While the data would indicate that laser preparation has a negative effect on dentin adhesion, it has been suggested that such negative effects would not be seen on enamel, par-ticularly if an Er,Cr:YSGG laser (Wa-terlase; Biolase, Irvine, Calif ) is used rather than an Er:YAG laser. A study by a Belgian research group evaluated the micromorphological characteristics and bond strength of laser-prepared enamel.103 The enamel of human mo-lars was flattened with a diamond rotary cutting instrument; half of the specimens were further prepared with the Er,Cr:YSGG laser. One 3-step ad-hesive (OptiBond FL; Kerr Corp), one 2-step self-etch adhesive (Clearfil SE Bond; Kuraray Co, Ltd), and 2 all-in-one adhesives (Adper Prompt L-Pop;

3M ESPE, and Clearfil S3 Bond; Kura-ray Co, Ltd) were applied per manu-facturer’s instructions, then restored with composite resin. After 24-hour water storage, the specimens were sectioned for microtensile strength testing, following which several speci-mens from each group were analyzed with SEM. All adhesives showed lower bond strength to the laser-prepared enamel versus diamond rotary cut-ting instrument-prepared enamel, with all but one (Clearfil S3 Bond) of these being significantly lower. Evalu-ation of the bonding surfaces demon-strated a higher incidence of adhesive failures among the laser-prepared enamel surfaces compared to the dia-mond rotary cutting instrument-pre-pared enamel surfaces, including the presence of small pieces of enamel on the composite resin side of the speci-mens. The authors surmise that the results were due to the ablative effects of laser on the tooth surface, result-ing in microcracks that weakened the subsequent bond.

OCCLUSION, TEMPOROMANDIBULARDISORDERS, AND SLEEP-DISORDERED BREATHING

Occlusion

Investigation into the art and sci-ence of occlusion continues as the profession strives to better under-stand that which so fundamentally af-fects oral function, oral dysfunction, and any therapeutic efforts to suc-cessfully restore oral health. Though not addressed in detail in this review of occlusion literature, readers are encouraged to examine a recent sum-mary of occlusal concepts in fixed prosthodontics.104 The historical development of important consid-erations in this subject area, such as gnathology and competing occlusal concepts, centric relation, maximum intercuspation, anterior guidance, and occlusal vertical dimension, are discussed. The authors of this report

acknowledge the need for higher-or-der scientific research to validate the-ories of occlusal restorative therapy. The authors also state that the lack of a universally accepted evidence-based model should not diminish profes-sionally responsible goals of precision and excellence in the clinical delivery of fixed prosthodontics.

Made challenging by expected vari-ability in patients, functional condi-tions, and developmental dynamics, the organization of natural dentitions remains of substantial interest to the profession. A longitudinal report was presented105 on development of the curvature of the human occlusal plane as viewed from a sagittal perspective, a characteristic first described by Fer-dinand Graf von Spee in the late 19th century. Dental casts from 16 male and 17 female participants were in-vestigated. Casts originated in the Iowa Facial Growth Study (subjects were predominantly of Northern Eu-ropean descent, with Class I occlu-sions and normal faces, and were followed from 3 to 26 years of age). Mandibular impressions were made on young children through to age 26, and mandibular dental casts were ob-tained and analyzed at 7 approximate time points: at 3.5 to 5 years of age, the oldest casts with deciduous sec-ond molars and incisors, the young-est casts with permanent first molars and incisors, the oldest casts prior to second molar eruption, the youngest casts with second molars, at 16 years of age, and at 26 years of age.

A digital caliper mounted on a dental surveyor was used to analyze and measure each cast. Mandibular casts were oriented parallel to a ref-erence plane defined by the distal-facial cusp tips of the most posterior teeth and the incisal edge of the most erupted central incisor. The occlusal curvature was measured as the maxi-mum perpendicular distance between the reference plane and any of the fa-cial cusp tips on that side of the den-tal arch.

Findings did not reveal significant differences in occlusal curvature be-

tween left and right sides in individu-als studied, nor were there significant gender differences. The deciduous dentition was found to have a relative-ly flat occlusal plane, with the largest increase in curvature occurring after eruption of the permanent first mo-lars. Occlusal plane curvature again increases with eruption of the perma-nent second molars and then remains relatively stable into early adulthood. The authors suggested that character-izations arising from this investigation yield guidelines descriptive of the nor-mal curve of Spee for reference dur-ing orthodontic and comprehensive restorative therapy.

The need for prosthodontic re-placement of missing posterior teeth has historically been the subject of much debate. One consequence of failure to replace missing teeth in a timely manner is positional changes in adjacent and opposing dentition resulting in occlusal interferences. One study was designed to identify clinical parameters associated with occlusal contacts in centric relation and the development of occlusal in-terferences associated with posterior tooth loss.106

One hundred consecutive patients with an unopposed posterior tooth served as the experimental group. “Unopposed” was defined as 20% or less of the occlusal surface in con-tact with opposing dentition in the maximum intercuspal position for a minimum of 5 years. One hundred age- and gender-matched controls also participated. Involvement of the unopposed tooth in centric relation contact, as well as in working, non-working, and protrusive occlusal in-terferences, was identified with 8-µm articulating film. Occlusal contacts were recorded with patients in the supine position, following a period of anterior deprogramming, and us-ing bimanual manipulation guided closures. Diagnostic dental casts were analyzed to characterize the malposition of the unopposed tooth. Data analysis included examination of means and distributions, scatter

plots, box plots, relative risk tables, and generalized linear modeling. In-terexaminer reliability was evaluated to be acceptable.

The general finding was that un-opposed teeth were more likely to be involved with functional occlusal interferences than their matched con-trols. The overall incidence of occlus-al interferences in the experimental groups was 53%, as compared to only 12% in the control group. Compar-ing the presence of specific occlusal interferences between experimental and control groups, the following fre-quencies were recorded: 30% and 2% respectively for centric relation inter-ferences, 22% and 3% respectively for protrusive interferences, 19% and 1% respectively for working interferences, and 11% and 7% respectively for non-working interferences. The data also demonstrated associations between characteristic movements of adja-cent/opposing teeth and the presence of occlusal interferences. Centric rela-tion contacts were associated with the extent of unopposed supraeruption. Protrusive interferences were more prevalent when the site of tooth loss was bounded. Mesial tipping of teeth distal to the edentulous site reduced this effect. Working side interferences were significantly associated with tip-ping of teeth mesial to the edentulous site.

The authors concluded that the presence of multiple occlusal inter-ferences resulting from missing teeth and unopposed dentition may sig-nificantly impact efforts to restore healthy continuity to the dental arch. Both functional and restorative con-siderations must be given to occlusal stability, direct occlusal trauma, and the complexity of restoring both the unopposed tooth and other teeth that may share occlusal relationships.

Recently, a number of scientifically valid investigations into complete denture occlusion have appeared in the professional literature. One group studied the influence of bilateral bal-anced occlusion and canine guidance on initial patient satisfaction with

conventional complete dentures.107 Using a single-blind crossover study design, 38 edentulous patients (24 women, 14 men, 50 to 87 years of age) were each provided a single maxillary complete denture and 2 nearly iden-tical mandibular complete dentures. The 2 mandibular dentures differed only in that one possessed a bilateral balanced occlusal arrangement, while the other provided canine protected articulation. Following adjustment and placement of the dentures, pa-tients alternated daily between the 2 mandibular dentures.

At 2 weeks, patient preference was recorded using a standardized ques-tionnaire. Next, all complete dentures were subjected to laboratory remount procedures. The canine protected ar-ticulation mandibular dentures were subtractively adjusted to yield bilat-eral balanced occlusions. Simultane-ously, acrylic resin was added to the mandibular canines on the bilateral balanced dentures to arrive at ca-nine protected articulation. Patients, uninformed about these alterations, wore their dentures for an additional 2 weeks. Patient satisfaction was then again surveyed.

Results indicated that a significant number of patients preferred the bi-lateral balanced dentures after the initial 2 weeks of wear. Following the second 2 weeks, most patients either preferred the bilateral balanced den-tures, or expressed no preference. Au-thors concluded that the bilateral bal-anced occlusal scheme appears to be preferred by patients during the initial adaptation phase following complete denture therapy.

Compared to natural tooth res-torations or implant-supported res-torations, management of occlusal contact precision during complete denture therapy is complicated by denture base instability. This is espe-cially evident in edentulous mandi-bles. Clinical experience suggests that occlusal errors can contribute to func-tional denture instability, subsequent irritation of the denture foundation, and patient discomfort. The ability to



27July 2009


prepared with Er:YAG laser or a #245 carbide bur. A 2-step etch-and-rinse adhesive (Single Bond; 3M ESPE) was applied as called for by the manu-facturer, and composite resin was added incrementally and polymer-ized. The specimens were assigned to 1 of 4 storage groups: 24-hour water storage; or 500 thermal cycles/week (5°C/55°C) and water storage for 1 week, 1 month, or 6 months. After water storage/thermal cycling, speci-mens were sectioned and subjected to microtensile bond strength testing. In general, the bur-prepared dentin surfaces demonstrated higher bond strengths than the laser-prepared sur-faces, with the laser-prepared surfaces subjected to 6-month thermal cycling and water storage showing significant-ly lower bond strength than any other group. In addition, adhesive failure was the predominant mode of failure in the laser-treated groups (62.1%), whereas mixed or cohesive failures ac-counted for the major mode of failure in the bur-prepared groups (77.1%). SEM analysis of the specimens after bond strength testing showed that the bur-prepared dentin produced more uniform, thicker hybrid layers with less morphological changes even after the simulated aging procedure (water storage/thermal cycling) than the laser-prepared dentin.

While the data would indicate that laser preparation has a negative effect on dentin adhesion, it has been suggested that such negative effects would not be seen on enamel, par-ticularly if an Er,Cr:YSGG laser (Wa-terlase; Biolase, Irvine, Calif ) is used rather than an Er:YAG laser. A study by a Belgian research group evaluated the micromorphological characteristics and bond strength of laser-prepared enamel.103 The enamel of human mo-lars was flattened with a diamond rotary cutting instrument; half of the specimens were further prepared with the Er,Cr:YSGG laser. One 3-step ad-hesive (OptiBond FL; Kerr Corp), one 2-step self-etch adhesive (Clearfil SE Bond; Kuraray Co, Ltd), and 2 all-in-one adhesives (Adper Prompt L-Pop;

3M ESPE, and Clearfil S3 Bond; Kura-ray Co, Ltd) were applied per manu-facturer’s instructions, then restored with composite resin. After 24-hour water storage, the specimens were sectioned for microtensile strength testing, following which several speci-mens from each group were analyzed with SEM. All adhesives showed lower bond strength to the laser-prepared enamel versus diamond rotary cut-ting instrument-prepared enamel, with all but one (Clearfil S3 Bond) of these being significantly lower. Evalu-ation of the bonding surfaces demon-strated a higher incidence of adhesive failures among the laser-prepared enamel surfaces compared to the dia-mond rotary cutting instrument-pre-pared enamel surfaces, including the presence of small pieces of enamel on the composite resin side of the speci-mens. The authors surmise that the results were due to the ablative effects of laser on the tooth surface, result-ing in microcracks that weakened the subsequent bond.

OCCLUSION, TEMPOROMANDIBULARDISORDERS, AND SLEEP-DISORDERED BREATHING

Occlusion

Investigation into the art and sci-ence of occlusion continues as the profession strives to better under-stand that which so fundamentally af-fects oral function, oral dysfunction, and any therapeutic efforts to suc-cessfully restore oral health. Though not addressed in detail in this review of occlusion literature, readers are encouraged to examine a recent sum-mary of occlusal concepts in fixed prosthodontics.104 The historical development of important consid-erations in this subject area, such as gnathology and competing occlusal concepts, centric relation, maximum intercuspation, anterior guidance, and occlusal vertical dimension, are discussed. The authors of this report

acknowledge the need for higher-or-der scientific research to validate the-ories of occlusal restorative therapy. The authors also state that the lack of a universally accepted evidence-based model should not diminish profes-sionally responsible goals of precision and excellence in the clinical delivery of fixed prosthodontics.

Made challenging by expected vari-ability in patients, functional condi-tions, and developmental dynamics, the organization of natural dentitions remains of substantial interest to the profession. A longitudinal report was presented105 on development of the curvature of the human occlusal plane as viewed from a sagittal perspective, a characteristic first described by Fer-dinand Graf von Spee in the late 19th century. Dental casts from 16 male and 17 female participants were in-vestigated. Casts originated in the Iowa Facial Growth Study (subjects were predominantly of Northern Eu-ropean descent, with Class I occlu-sions and normal faces, and were followed from 3 to 26 years of age). Mandibular impressions were made on young children through to age 26, and mandibular dental casts were ob-tained and analyzed at 7 approximate time points: at 3.5 to 5 years of age, the oldest casts with deciduous sec-ond molars and incisors, the young-est casts with permanent first molars and incisors, the oldest casts prior to second molar eruption, the youngest casts with second molars, at 16 years of age, and at 26 years of age.

A digital caliper mounted on a dental surveyor was used to analyze and measure each cast. Mandibular casts were oriented parallel to a ref-erence plane defined by the distal-facial cusp tips of the most posterior teeth and the incisal edge of the most erupted central incisor. The occlusal curvature was measured as the maxi-mum perpendicular distance between the reference plane and any of the fa-cial cusp tips on that side of the den-tal arch.

Findings did not reveal significant differences in occlusal curvature be-

tween left and right sides in individu-als studied, nor were there significant gender differences. The deciduous dentition was found to have a relative-ly flat occlusal plane, with the largest increase in curvature occurring after eruption of the permanent first mo-lars. Occlusal plane curvature again increases with eruption of the perma-nent second molars and then remains relatively stable into early adulthood. The authors suggested that character-izations arising from this investigation yield guidelines descriptive of the nor-mal curve of Spee for reference dur-ing orthodontic and comprehensive restorative therapy.

The need for prosthodontic re-placement of missing posterior teeth has historically been the subject of much debate. One consequence of failure to replace missing teeth in a timely manner is positional changes in adjacent and opposing dentition resulting in occlusal interferences. One study was designed to identify clinical parameters associated with occlusal contacts in centric relation and the development of occlusal in-terferences associated with posterior tooth loss.106

One hundred consecutive patients with an unopposed posterior tooth served as the experimental group. “Unopposed” was defined as 20% or less of the occlusal surface in con-tact with opposing dentition in the maximum intercuspal position for a minimum of 5 years. One hundred age- and gender-matched controls also participated. Involvement of the unopposed tooth in centric relation contact, as well as in working, non-working, and protrusive occlusal in-terferences, was identified with 8-µm articulating film. Occlusal contacts were recorded with patients in the supine position, following a period of anterior deprogramming, and us-ing bimanual manipulation guided closures. Diagnostic dental casts were analyzed to characterize the malposition of the unopposed tooth. Data analysis included examination of means and distributions, scatter

plots, box plots, relative risk tables, and generalized linear modeling. In-terexaminer reliability was evaluated to be acceptable.

The general finding was that un-opposed teeth were more likely to be involved with functional occlusal interferences than their matched con-trols. The overall incidence of occlus-al interferences in the experimental groups was 53%, as compared to only 12% in the control group. Compar-ing the presence of specific occlusal interferences between experimental and control groups, the following fre-quencies were recorded: 30% and 2% respectively for centric relation inter-ferences, 22% and 3% respectively for protrusive interferences, 19% and 1% respectively for working interferences, and 11% and 7% respectively for non-working interferences. The data also demonstrated associations between characteristic movements of adja-cent/opposing teeth and the presence of occlusal interferences. Centric rela-tion contacts were associated with the extent of unopposed supraeruption. Protrusive interferences were more prevalent when the site of tooth loss was bounded. Mesial tipping of teeth distal to the edentulous site reduced this effect. Working side interferences were significantly associated with tip-ping of teeth mesial to the edentulous site.

The authors concluded that the presence of multiple occlusal inter-ferences resulting from missing teeth and unopposed dentition may sig-nificantly impact efforts to restore healthy continuity to the dental arch. Both functional and restorative con-siderations must be given to occlusal stability, direct occlusal trauma, and the complexity of restoring both the unopposed tooth and other teeth that may share occlusal relationships.

Recently, a number of scientifically valid investigations into complete denture occlusion have appeared in the professional literature. One group studied the influence of bilateral bal-anced occlusion and canine guidance on initial patient satisfaction with

conventional complete dentures.107 Using a single-blind crossover study design, 38 edentulous patients (24 women, 14 men, 50 to 87 years of age) were each provided a single maxillary complete denture and 2 nearly iden-tical mandibular complete dentures. The 2 mandibular dentures differed only in that one possessed a bilateral balanced occlusal arrangement, while the other provided canine protected articulation. Following adjustment and placement of the dentures, pa-tients alternated daily between the 2 mandibular dentures.

At 2 weeks, patient preference was recorded using a standardized ques-tionnaire. Next, all complete dentures were subjected to laboratory remount procedures. The canine protected ar-ticulation mandibular dentures were subtractively adjusted to yield bilat-eral balanced occlusions. Simultane-ously, acrylic resin was added to the mandibular canines on the bilateral balanced dentures to arrive at ca-nine protected articulation. Patients, uninformed about these alterations, wore their dentures for an additional 2 weeks. Patient satisfaction was then again surveyed.

Results indicated that a significant number of patients preferred the bi-lateral balanced dentures after the initial 2 weeks of wear. Following the second 2 weeks, most patients either preferred the bilateral balanced den-tures, or expressed no preference. Au-thors concluded that the bilateral bal-anced occlusal scheme appears to be preferred by patients during the initial adaptation phase following complete denture therapy.

Compared to natural tooth res-torations or implant-supported res-torations, management of occlusal contact precision during complete denture therapy is complicated by denture base instability. This is espe-cially evident in edentulous mandi-bles. Clinical experience suggests that occlusal errors can contribute to func-tional denture instability, subsequent irritation of the denture foundation, and patient discomfort. The ability to



29July 2009


provide an accurate prosthetic occlu-sion is both necessary and challeng-ing. Investigators evaluated available complete denture occlusal refinement procedures to ascertain the most ap-propriate clinical approach for pro-viding accurate complete denture therapy.108

In this prospective clinical trial, 30 edentulous patients (21 female, 9 male, 50 to 84 years of age, reasonable residual ridge anatomy, no TMJ prob-lems) were provided new complete dentures fabricated with balanced articulations. Patients were divided into 3 equal experimental groups: group LCRO received prostheses sub-jected to both laboratory and clinical remount procedures for occlusal cor-rection, group LRO received dentures subjected to only laboratory remount procedures, and group OOC received complete dentures for which occlusal corrections were accomplished exclu-sively by intraoral procedures when required. Routine denture placement and intaglio surface adjustments were provided. Recall examinations were performed after 48 hours and after 1 week.

The objective of the study was to identify the denture occlusal refine-ment regimen associated with opti-mal prosthesis comfort and the fewest required postinsertion appointments. At each postinsertion appointment requested by patients, examinations were accomplished, tissue irritations were identified, necessary intaglio surface adjustments were made, and patient pain/comfort was graded on a 5-point scale. Analysis for statisti-cal differences between treatment groups involved the chi-square test and Kruskal-Wallis test at a 95% con-fidence level.

Results revealed that the LCRO group required significantly fewer postinsertion adjustment appoint-ments, experienced fewer soft tissue irritations, had less pain during mas-tication, and enjoyed more mastica-tory comfort when compared to the other experimental groups. When considering postinsertion adjustment

appointments and patient comfort as indicators of treatment success, the authors concluded that, within study limitations, the combined use of lab-oratory and clinical remount proce-dures to effect occlusal refinement of complete dentures is preferred to lab-oratory remounts alone or intraoral occlusal corrections.

Temporomandibular disorders

Literature appearing in the broad subject area of temporomandibular disorders (TMDs) was again volu-minous in 2008. Of note were 2 re-view/summation articles likely to be of interest to those seeking detailed, state-of-the-art information on tem-poromandibular disorders (TMD). The first addressed the relationship between TMDs and bruxism in child-hood and adolescence.109 This review included 30 scientifically valid reports published between 1970 and 2007. Bruxism was identified as a possible causal factor, via functional man-dibular overload, in childhood TMD. Though the relationship between bruxism and TMD in young patients remains unsettled in the literature, this report provides an excellent, comprehensive, up-to-date review for interested readers.

A second article110 reviewed cur-rent understandings of the unique anatomy and physiology of the tem-poromandibular joint (TMJ) and the pathogenesis of joint degeneration. The authors then probe future inno-vations in TMJ diagnostics and thera-peutics by reviewing novel tools avail-able to the profession in the broad fields of biomedicine, imaging, and computer technology. Cone-beam computed tomography has been shown to be a dose-conservative, cost-effective, and accurate alterna-tive to more conventional 3-dimen-sional imaging modalities. Identifica-tion of biomarkers associated with TMJ diseases using synovial lavage and powerful new microarray tech-nologies is a promising biomedi-cal tool that may result in effective

therapeutic interventions. Since ge-netic factors likely have a role in TMD pronicity and severity, genotyping to identify risk holds promise for future diagnostic identification and sub-sequent preventive and therapeutic interventions. The development of high-throughput genome sequenc-ing will provide future clinicians with ready access to individual patient in-formation so that highly specific and therapeutically targeted interventions can be rendered.

Intraoral palpation of the lateral pterygoid muscle area is often in-cluded as a recommended element in the clinical examination of myo-fascial pain patients. However, ample intraoral clinical access to effectively accomplish this procedure has been questioned, and the anatomic avail-ability of the lateral pterygoid to intraoral palpation is suspect. To clarify this important diagnostic con-sideration, investigators performed a blind, controlled, clinical trial de-signed to evaluate the validity of in-traoral lateral pterygoid palpation as a diagnostic instrument.111

Using the Research Diagnostic Cri-teria for Temporomandibular Disor-ders (RDC/TMD),112 44 women clas-sified as RDC/TMD Diagnostic I were selected into the study. Thirty-three asymptomatic, age-matched women served as controls. Subjects ranged from 15 to 55 years of age. A single ex-aminer, blinded to patient allocation, performed all muscle palpations. In-traoral palpations of the lateral ptery-goid area were attempted by placing the forefinger, or the little finger, over the buccal area in the maxillary third molar region and exerting posterior, superior, and medially directed pres-sure behind the maxillary tuberocity. Patients’ indications of pain, or the absence of pain, on palpation were noted. Descriptive statistics were used to compare the groups studied. Sensitivity, specificity, and likelihood ratios were calculated for the muscle site palpations performed.

Results indicated that intraoral palpation in the lateral pterygoid area

presented an unacceptably low speci-ficity yielding an increased frequency of false-positive palpation responses. The authors pointed out the 22.73% false-positive response rate may be attributed to pain originating from oral mucosal compression, buccina-tor muscle compression, palpation of the tendonous insertion of the tem-poral muscle at the medial surface of the coronoid process, or pressure to medial pterygoid muscle fibers. The authors concluded that intraoral pal-pation in the lateral pterygoid region should be discouraged due to ana-tomic inaccessibility and a high level of false-positive responses. Within the study’s limitations, authors suggested that intraoral palpation of the lateral pterygoid area does not reach accept-able values of specificity. Therefore, caution in judging positive patient responses to this examination tech-nique is necessary.

Understanding functional biome-chanics of the temporomandibular joint is critical to managing patients affected by joint dysfunction. In healthy patients, normal movement of the condyle-disc assembly within joint spaces incurs low frictional load-ing due to lubrication derived from synovial fluid. However, in diseased tissues and under excessive loading conditions, the coefficient of friction within joint spaces may increase due to deterioration of the lubrication mechanism or reduction of synovial fluid viscosity. It has been suggested that, from a biomechanical point of view, prolonged clenching in the pres-ence of increased TMJ friction might contribute to anterior displacement of the disc within the joint space. Inves-tigators constructed a finite element (FE) model to investigate possible relationships between joint friction, prolonged clenching, and TMJ disc displacement.113

FE modeling of a glenoid fossa, ar-ticular disc, and mandibular condyle was performed using information de-rived from magnetic resonance imag-ing of a 23-year-old woman with no history of TMJ disorders or parafunc-

tional habits. The model consisted of 17,548 elements (1136 bone, 1273 disc, and 13,825 surrounding soft tissue nodes). Frictional coefficients used ranged from 0.001 to 0.1 µm, covering values previously observed in synovial joints. Joint loading was simulated with forces derived from 4 unilateral muscles (masseter, tempo-ralis, medial pterygoid, and lateral pterygoid). Clenching was simulated by simultaneous activation of all muscles at 20% of their maximum. FE analysis was accomplished during 10 minutes of clenching.

In general, results indicated that, regardless of the frictional coefficient used, the disc appeared to be loaded predominantly in the intermediate zone at the onset of clenching, with steady-state levels reached at 2 min-utes. After 10 minutes, the largest stress appeared in the central inter-mediate zone and the posterior band. Maximum stress produced in the disc (125.3 g/mm2) occurred when the frictional coefficient was increased to 0.1 µm. Upon tracking 5 distinct points in the disc for movement, it was demonstrated that all 5 points were displaced forward during the first 1 to 3 minutes of clench. Maxi-mum forward disc movement of 0.32 mm was found after 10 minutes of clench as the frictional coefficient in-creased.

The authors concluded that, based on evidence derived from this FE model of the TMJ, habitual and prolonged clenching might induce, or contribute to, anterior disc move-ment. Additionally, this forward disc movement may be accentuated by increases in the frictional coefficient within the joint space.

In 1992, the Research Diagnostic Criteria for Temporomandibular Dis-orders (RDC/TMD)112 was introduced as a standardized diagnostic instru-ment for classifying TMD patients during scientific research efforts. To be useful, all clinical measures within this instrument must be both reliable and valid. To date, the validity of the RDC/TMD examination has not been

scientifically demonstrated. Investiga-tors sought to determine the relative significance of various components of the RDC/TMD clinical examination in distinguishing healthy from diseased joints and whether these components possess predictive accuracy for distin-guishing healthy from symptomatic subjects.114

The experimental population con-sisted of 149 patients with symptom-atic temporomandibular joints (65% female, mean 34.4 years of age) and 43 symptom-free controls (75% fe-male, mean 38.5 years of age). All subjects were examined by 2 calibrat-ed examiners using RDC/TMD pro-cedures and other tests. Assessments included evaluations for joint sounds and pain, standardized muscle palpa-tions, range of mandibular motion measurements, psychosocial assess-ment, and dynamic and static com-pression of the TMJs. Bilateral joint MRIs were accomplished in both open and closed positions. Images were as-sessed in 2 diagnostic categories: disc displacement with reduction, disc displacement without reduction, or no disc displacement; and arthrosis or no arthrosis.

Sophisticated statistical manage-ment involved random forest analysis to evaluate the importance of differ-ent variables in the classification pro-cess. This statistical approach was used because it effectively covers all components of the clinical examina-tion, weighing the contribution of each to the diagnosis.

To distinguish between healthy joints and joints with disc displace-ment, forest plot analysis revealed overjet measurement, somatization, depression, opening pattern, and joint sounds during opening under TMJ compression to be important vari-ables. To distinguish between anterior disc displacement with and without reduction, the following examination variables were identified as impor-tant: facial pain, tenderness of lateral pterygoid area, overjet measurement, maximum unassisted opening, maxi-mum assisted opening, history of



29July 2009


provide an accurate prosthetic occlu-sion is both necessary and challeng-ing. Investigators evaluated available complete denture occlusal refinement procedures to ascertain the most ap-propriate clinical approach for pro-viding accurate complete denture therapy.108

In this prospective clinical trial, 30 edentulous patients (21 female, 9 male, 50 to 84 years of age, reasonable residual ridge anatomy, no TMJ prob-lems) were provided new complete dentures fabricated with balanced articulations. Patients were divided into 3 equal experimental groups: group LCRO received prostheses sub-jected to both laboratory and clinical remount procedures for occlusal cor-rection, group LRO received dentures subjected to only laboratory remount procedures, and group OOC received complete dentures for which occlusal corrections were accomplished exclu-sively by intraoral procedures when required. Routine denture placement and intaglio surface adjustments were provided. Recall examinations were performed after 48 hours and after 1 week.

The objective of the study was to identify the denture occlusal refine-ment regimen associated with opti-mal prosthesis comfort and the fewest required postinsertion appointments. At each postinsertion appointment requested by patients, examinations were accomplished, tissue irritations were identified, necessary intaglio surface adjustments were made, and patient pain/comfort was graded on a 5-point scale. Analysis for statisti-cal differences between treatment groups involved the chi-square test and Kruskal-Wallis test at a 95% con-fidence level.

Results revealed that the LCRO group required significantly fewer postinsertion adjustment appoint-ments, experienced fewer soft tissue irritations, had less pain during mas-tication, and enjoyed more mastica-tory comfort when compared to the other experimental groups. When considering postinsertion adjustment

appointments and patient comfort as indicators of treatment success, the authors concluded that, within study limitations, the combined use of lab-oratory and clinical remount proce-dures to effect occlusal refinement of complete dentures is preferred to lab-oratory remounts alone or intraoral occlusal corrections.

Temporomandibular disorders

Literature appearing in the broad subject area of temporomandibular disorders (TMDs) was again volu-minous in 2008. Of note were 2 re-view/summation articles likely to be of interest to those seeking detailed, state-of-the-art information on tem-poromandibular disorders (TMD). The first addressed the relationship between TMDs and bruxism in child-hood and adolescence.109 This review included 30 scientifically valid reports published between 1970 and 2007. Bruxism was identified as a possible causal factor, via functional man-dibular overload, in childhood TMD. Though the relationship between bruxism and TMD in young patients remains unsettled in the literature, this report provides an excellent, comprehensive, up-to-date review for interested readers.

A second article110 reviewed cur-rent understandings of the unique anatomy and physiology of the tem-poromandibular joint (TMJ) and the pathogenesis of joint degeneration. The authors then probe future inno-vations in TMJ diagnostics and thera-peutics by reviewing novel tools avail-able to the profession in the broad fields of biomedicine, imaging, and computer technology. Cone-beam computed tomography has been shown to be a dose-conservative, cost-effective, and accurate alterna-tive to more conventional 3-dimen-sional imaging modalities. Identifica-tion of biomarkers associated with TMJ diseases using synovial lavage and powerful new microarray tech-nologies is a promising biomedi-cal tool that may result in effective

therapeutic interventions. Since ge-netic factors likely have a role in TMD pronicity and severity, genotyping to identify risk holds promise for future diagnostic identification and sub-sequent preventive and therapeutic interventions. The development of high-throughput genome sequenc-ing will provide future clinicians with ready access to individual patient in-formation so that highly specific and therapeutically targeted interventions can be rendered.

Intraoral palpation of the lateral pterygoid muscle area is often in-cluded as a recommended element in the clinical examination of myo-fascial pain patients. However, ample intraoral clinical access to effectively accomplish this procedure has been questioned, and the anatomic avail-ability of the lateral pterygoid to intraoral palpation is suspect. To clarify this important diagnostic con-sideration, investigators performed a blind, controlled, clinical trial de-signed to evaluate the validity of in-traoral lateral pterygoid palpation as a diagnostic instrument.111

Using the Research Diagnostic Cri-teria for Temporomandibular Disor-ders (RDC/TMD),112 44 women clas-sified as RDC/TMD Diagnostic I were selected into the study. Thirty-three asymptomatic, age-matched women served as controls. Subjects ranged from 15 to 55 years of age. A single ex-aminer, blinded to patient allocation, performed all muscle palpations. In-traoral palpations of the lateral ptery-goid area were attempted by placing the forefinger, or the little finger, over the buccal area in the maxillary third molar region and exerting posterior, superior, and medially directed pres-sure behind the maxillary tuberocity. Patients’ indications of pain, or the absence of pain, on palpation were noted. Descriptive statistics were used to compare the groups studied. Sensitivity, specificity, and likelihood ratios were calculated for the muscle site palpations performed.

Results indicated that intraoral palpation in the lateral pterygoid area

presented an unacceptably low speci-ficity yielding an increased frequency of false-positive palpation responses. The authors pointed out the 22.73% false-positive response rate may be attributed to pain originating from oral mucosal compression, buccina-tor muscle compression, palpation of the tendonous insertion of the tem-poral muscle at the medial surface of the coronoid process, or pressure to medial pterygoid muscle fibers. The authors concluded that intraoral pal-pation in the lateral pterygoid region should be discouraged due to ana-tomic inaccessibility and a high level of false-positive responses. Within the study’s limitations, authors suggested that intraoral palpation of the lateral pterygoid area does not reach accept-able values of specificity. Therefore, caution in judging positive patient responses to this examination tech-nique is necessary.

Understanding functional biome-chanics of the temporomandibular joint is critical to managing patients affected by joint dysfunction. In healthy patients, normal movement of the condyle-disc assembly within joint spaces incurs low frictional load-ing due to lubrication derived from synovial fluid. However, in diseased tissues and under excessive loading conditions, the coefficient of friction within joint spaces may increase due to deterioration of the lubrication mechanism or reduction of synovial fluid viscosity. It has been suggested that, from a biomechanical point of view, prolonged clenching in the pres-ence of increased TMJ friction might contribute to anterior displacement of the disc within the joint space. Inves-tigators constructed a finite element (FE) model to investigate possible relationships between joint friction, prolonged clenching, and TMJ disc displacement.113

FE modeling of a glenoid fossa, ar-ticular disc, and mandibular condyle was performed using information de-rived from magnetic resonance imag-ing of a 23-year-old woman with no history of TMJ disorders or parafunc-

tional habits. The model consisted of 17,548 elements (1136 bone, 1273 disc, and 13,825 surrounding soft tissue nodes). Frictional coefficients used ranged from 0.001 to 0.1 µm, covering values previously observed in synovial joints. Joint loading was simulated with forces derived from 4 unilateral muscles (masseter, tempo-ralis, medial pterygoid, and lateral pterygoid). Clenching was simulated by simultaneous activation of all muscles at 20% of their maximum. FE analysis was accomplished during 10 minutes of clenching.

In general, results indicated that, regardless of the frictional coefficient used, the disc appeared to be loaded predominantly in the intermediate zone at the onset of clenching, with steady-state levels reached at 2 min-utes. After 10 minutes, the largest stress appeared in the central inter-mediate zone and the posterior band. Maximum stress produced in the disc (125.3 g/mm2) occurred when the frictional coefficient was increased to 0.1 µm. Upon tracking 5 distinct points in the disc for movement, it was demonstrated that all 5 points were displaced forward during the first 1 to 3 minutes of clench. Maxi-mum forward disc movement of 0.32 mm was found after 10 minutes of clench as the frictional coefficient in-creased.

The authors concluded that, based on evidence derived from this FE model of the TMJ, habitual and prolonged clenching might induce, or contribute to, anterior disc move-ment. Additionally, this forward disc movement may be accentuated by increases in the frictional coefficient within the joint space.

In 1992, the Research Diagnostic Criteria for Temporomandibular Dis-orders (RDC/TMD)112 was introduced as a standardized diagnostic instru-ment for classifying TMD patients during scientific research efforts. To be useful, all clinical measures within this instrument must be both reliable and valid. To date, the validity of the RDC/TMD examination has not been

scientifically demonstrated. Investiga-tors sought to determine the relative significance of various components of the RDC/TMD clinical examination in distinguishing healthy from diseased joints and whether these components possess predictive accuracy for distin-guishing healthy from symptomatic subjects.114

The experimental population con-sisted of 149 patients with symptom-atic temporomandibular joints (65% female, mean 34.4 years of age) and 43 symptom-free controls (75% fe-male, mean 38.5 years of age). All subjects were examined by 2 calibrat-ed examiners using RDC/TMD pro-cedures and other tests. Assessments included evaluations for joint sounds and pain, standardized muscle palpa-tions, range of mandibular motion measurements, psychosocial assess-ment, and dynamic and static com-pression of the TMJs. Bilateral joint MRIs were accomplished in both open and closed positions. Images were as-sessed in 2 diagnostic categories: disc displacement with reduction, disc displacement without reduction, or no disc displacement; and arthrosis or no arthrosis.

Sophisticated statistical manage-ment involved random forest analysis to evaluate the importance of differ-ent variables in the classification pro-cess. This statistical approach was used because it effectively covers all components of the clinical examina-tion, weighing the contribution of each to the diagnosis.

To distinguish between healthy joints and joints with disc displace-ment, forest plot analysis revealed overjet measurement, somatization, depression, opening pattern, and joint sounds during opening under TMJ compression to be important vari-ables. To distinguish between anterior disc displacement with and without reduction, the following examination variables were identified as impor-tant: facial pain, tenderness of lateral pterygoid area, overjet measurement, maximum unassisted opening, maxi-mum assisted opening, history of



31July 2009


locked jaw, joint sounds on opening, joint sounds on protrusion, and joint sounds on lateral excursions under TMJ compression. Finally, to distin-guish between arthrosis and no ar-throsis, analysis demonstrated locked jaw, joint sounds on lateral excursion to ipsilateral side, and joint sounds on protrusion to be significant. Of particular importance in distinguish-ing between all joint conditions were a history of locked jaw, maximum as-sisted opening, and maximum unas-sisted opening.

Within the limitations of this study as described by authors, the validity of clinical TMJ examination proce-dures might be enhanced by using the 16 variables of greatest importance (listed above) identified in this study.

Sleep-disordered breathing

Sleep-disordered breathing (SDB) is currently recognized as a significant disease entity in both adults and chil-dren. Obstructive sleep apnea is also recognized as a significant chronic disorder related to substantial end-or-gan morbidity, increased health care expenditures, compromised quality of life, as well as significant cardiovascu-lar, metabolic, and neurobehavioral complications. Additionally, mount-ing evidence points to an association of this relatively newly identified dis-ease with increases in mortality. The social impact of SDB can be appreci-ated in the rules requiring pilots and commercial truck drivers to disclose SDB diagnoses during state and fed-eral certification processes.115

For those interested in this topic, 2008 saw the production of 2 out-standing review publications that are both must-reads. First, the journal Proceedings of the American Thoracic So-ciety hosted a virtual symposium to thoroughly and critically review the current knowledge in sleep-disordered breathing and to provide insight and guidance into important questions that require further investigation.116 Seventeen separate but well-coordi-nated articles117-133 were written by

authorities in their subject areas and account for over 140 pages within this journal. Topics covered include epide-miology, pathophysiology, diagnosis, nonsurgical and surgical therapies, and associated complications. A sec-ond outstanding review publication on sleep apnea and cardiovascular disease resulted from an extensive col-laborative effort.134 This article pro-vides thorough background informa-tion on cardiovascular involvement in patients affected by sleep apnea. Authors also provided commentary on future directions in therapy and research. Authors cited over 400 ref-erences in this publication.

Currently, SDB in adult popula-tions has been shown to be indepen-dently associated with a number of clinically important outcomes. How-ever, child populations have not been subjected to similar scientific inquiry. Investigators evaluated the associa-tion between SDB and blood pressure in a large representative random sam-ple of children135 with mild to moder-ate SDB, to establish the apnea-hypo-pnea index in children that is clinically associated with significantly elevated blood pressure, and to determine the relative contribution of potential risk factors in this association. This report on SDB in children represents the largest published population-based sample of 5- to 12-year olds in this area of investigation.

The parents of 7312 elementary school children received question-naires previously validated to identify children at high risk for SDB. A total of 5740 questionnaires were returned (78.5% response rate). Using a stratifi-cation of grade, gender, and SDB risk, 700 children were randomly selected and subjected to physical examina-tion and 9-hour polysomnography, maintaining the representativeness of the original sample (70% response rate). Physical examinations included height, weight, waist and neck mea-surements, blood pressure, visual ex-amination of nose/throat, evaluation of respiratory function, and blood pressure measurement.

Sleep apnea and hypopnea were defined using criteria commonly ac-cepted in clinical practice. Apnea indexes (AI) and apnea-hypopnea indexes (AHI) were calculated. Indi-viduals were defined as “without SDB” if AHI<1, as “mild SDB” if 1≤AHI<5, and as “moderate SDB” if AHI≥5. Us-ing these criteria, 8 children (1.14%) were affected with moderate SDB, 175 (25%) were classified as having mild SDB, and 517 (73.86%) were without SDB. Statistical comparison of AHIs and blood pressure measure-ments revealed that blood pressure was strongly associated with AHI in this population of children.

In this study, SDB appeared to be an independent risk factor for elevat-ed blood pressure in children aged 5 to 12 years. Authors noted that at the threshold of AHI≥5, the effect on blood pressure appears to warrant therapeutic intervention for SDB. Ad-ditionally, at a threshold of AHI≥3, the critical assessment of blood pres-sure and AHI at routine follow-up vis-its seems warranted, although addi-tional research is necessary to validate this conclusion. Since high AHI in children was found to independently contribute to clinically significant el-evation in blood pressure, the authors suggested that its detection and man-agement may lead to a reduction of elevated blood pressure in children and the subsequent reduction of car-diovascular risk in these same individ-uals as adults.

Though nasal continuous posi-tive airway pressure (CPAP) remains the gold standard of treatment for obstructive sleep apnea syndrome (OSAS), compliance with this treat-ment modality is variable, and un-comfortable side effects limit ad-herence. Patients unable to tolerate CPAP therapy and patients with mild to moderate OSAS are candidates for mandibular advancement de-vice therapy. Unfortunately, there is little data on the long-term success of mandibular advancement devices. To shed light on long-term outcomes, investigators136 assessed the 10-year

compliance and therapeutic opinions of patients treated with mandibular advancement devices. The authors hypothesized that mandibular ad-vancement devices are an acceptable form of long-term treatment for pa-tients with problem snoring and mild to moderate OSAS.

One hundred and eighty patients were provided mandibular advance-ment devices in 1996. All devices were of the same design. At the outset, the severity of OSAS in this patient pop-ulation was as follows: all patients snored; 72 patients were considered normal with AHI<5; 52 had mild dis-ease (5≤AHI≤14); 34 had moderate disease (15≤AHI≤30); and 21 had severe disease (AHI>30). In 2006, questionnaires were provided to these patients to survey device wear and satisfaction, sleep quality/duration, lifestyle, weight, height, and smok-ing/alcohol habits. Seventy-two of the 180 questionnaires were returned (40% response rate, 56 males, 16 fe-males).

Results indicated that 48 patients (66%) were still wearing the mandibu-lar advancement device at the time of the survey. Of the 24 patients no longer wearing the device, 12 claimed it was very uncomfortable, 3 found it slightly uncomfortable, and no infor-mation was available on the remaining 7 patients. Data were then evaluated for associations between success and other factors, including body mass in-dex, smoking, alcohol consumption, sleep duration, and sleep quality. Sleep quality was the only factor sig-nificantly associated with successful wear of the mandibular advancement device. Side effects reported included discomfort, excessive salivation, dry mouth, loose fit, stained teeth, repo-sitioned jaw, and excessive flatulence. When asked to rate the overall suc-cess of the device, 24% of the patients stated “fair,” and 46% reported the device provided “good” success.

Based on this data, authors ac-cepted the original hypothesis that mandibular advancement devices are an acceptable form of treatment

in the long term for patients with problem snoring and mild to moder-ate OSAS. A high level of treatment success is suggested by the fact that 66% of the patients were still wear-ing their devices and 70% rated their devices as fair to good after 10 years of practical use. Unfortunately, the response rate for the present investi-gation was only 40%. Although this compares favorably to other similar studies, a substantial amount of pa-tient response data were not collected and evaluated on the important issue of continued therapeutic impact of the mandibular advancement devices. The authors concluded by stating that the mandibular advancement device appears to be an acceptable long-term solution for a significant number of patients with problem snoring and those with mild to moderate OSAS.

Currently, polysomnography serves as the gold-standard diagnos-tic test for OSAS, providing informa-tion on the severity of OSAS and the degree of sleep fragmentation. How-ever, polysomnography does not pro-vide direct information regarding the specific pathophysiology of this dis-ease. It is known that the severity of OSAS is generally correlated with the degree of collapse of the pharyngeal region at the base of the tongue. One method of ascertaining critical infor-mation on effects of the degree of pharyngeal narrowing on SDB is the application of nasopharyngoscopy using the Muller maneuver. As this approach has not been sufficiently in-vestigated and reported, investigators examined correlations between the degree and shape of pharyngeal nar-rowing at different anatomical levels during the Muller maneuver and the severity of SDB.137

Thirty-three patients (29 male, 4 female, mean age of 49 years, mean body mass index (BMI) of 23.5) with suspected SDB underwent polysom-nography. Mean AHI, supine body position AHI, and lateral body posi-tion AHI were calculated. Fiberoptic nasopharyngoscopy using the Muller maneuver was performed for each pa-

tient in the supine position with the head in a neutral position. Degree and shape of pharyngeal narrowing was evaluated at both retropalatal and retroglossal levels, while the shape of pharyngeal narrowing was evaluated at the retropalatal level.

Results indicated that the mean AHI for this patient population was 28 (range 1.1 to 74.8). Three subjects were simple snorers, 9 had mild OSAS (5≤AHI<15), 10 had moderate OSAS (15≤AHI<30), and 11 had severe OSAS (AHI≥30). A significant correla-tion was identified between the degree of retroglossal pharyngeal narrowing and total and supine AHI. Additional-ly, the degree of retropalatal pharyn-geal narrowing demonstrated signifi-cant positive correlation with lateral AHI. These findings suggest that the mechanism of airway narrowing at the retroglossal level in supine SDB patients is primarily posterior tongue movement influenced by gravitational force and/or reduced muscular activ-ity compared to normal individuals. The present study also showed that lateral narrowing at the retropalatal pharyngeal level is more significantly positively correlated with mean total AHI than anteroposterior narrowing. Although currently available informa-tion does not provide a clear rationale for the deleterious effects of lateral retropharyngeal narrowing on OSAS, the authors suggested that lateral fat deposition may have a role, even in relatively nonobese individuals.

The authors concluded that the anatomic pharyngeal level and the de-gree and character of pharyngeal nar-rowing, as observed during fiberoptic nasopharyngoscopy using the Muller maneuver, revealed significant corre-lations with AHIs calculated in differ-ent sleeping positions.

PROSTHODONTICS

A pilot study was conducted to determine the position of the incisal edges of maxillary canines and cen-tral incisors relative to the maxillary lip line in a reposed position.138 The



31July 2009


locked jaw, joint sounds on opening, joint sounds on protrusion, and joint sounds on lateral excursions under TMJ compression. Finally, to distin-guish between arthrosis and no ar-throsis, analysis demonstrated locked jaw, joint sounds on lateral excursion to ipsilateral side, and joint sounds on protrusion to be significant. Of particular importance in distinguish-ing between all joint conditions were a history of locked jaw, maximum as-sisted opening, and maximum unas-sisted opening.

Within the limitations of this study as described by authors, the validity of clinical TMJ examination proce-dures might be enhanced by using the 16 variables of greatest importance (listed above) identified in this study.

Sleep-disordered breathing

Sleep-disordered breathing (SDB) is currently recognized as a significant disease entity in both adults and chil-dren. Obstructive sleep apnea is also recognized as a significant chronic disorder related to substantial end-or-gan morbidity, increased health care expenditures, compromised quality of life, as well as significant cardiovascu-lar, metabolic, and neurobehavioral complications. Additionally, mount-ing evidence points to an association of this relatively newly identified dis-ease with increases in mortality. The social impact of SDB can be appreci-ated in the rules requiring pilots and commercial truck drivers to disclose SDB diagnoses during state and fed-eral certification processes.115

For those interested in this topic, 2008 saw the production of 2 out-standing review publications that are both must-reads. First, the journal Proceedings of the American Thoracic So-ciety hosted a virtual symposium to thoroughly and critically review the current knowledge in sleep-disordered breathing and to provide insight and guidance into important questions that require further investigation.116 Seventeen separate but well-coordi-nated articles117-133 were written by

authorities in their subject areas and account for over 140 pages within this journal. Topics covered include epide-miology, pathophysiology, diagnosis, nonsurgical and surgical therapies, and associated complications. A sec-ond outstanding review publication on sleep apnea and cardiovascular disease resulted from an extensive col-laborative effort.134 This article pro-vides thorough background informa-tion on cardiovascular involvement in patients affected by sleep apnea. Authors also provided commentary on future directions in therapy and research. Authors cited over 400 ref-erences in this publication.

Currently, SDB in adult popula-tions has been shown to be indepen-dently associated with a number of clinically important outcomes. How-ever, child populations have not been subjected to similar scientific inquiry. Investigators evaluated the associa-tion between SDB and blood pressure in a large representative random sam-ple of children135 with mild to moder-ate SDB, to establish the apnea-hypo-pnea index in children that is clinically associated with significantly elevated blood pressure, and to determine the relative contribution of potential risk factors in this association. This report on SDB in children represents the largest published population-based sample of 5- to 12-year olds in this area of investigation.

The parents of 7312 elementary school children received question-naires previously validated to identify children at high risk for SDB. A total of 5740 questionnaires were returned (78.5% response rate). Using a stratifi-cation of grade, gender, and SDB risk, 700 children were randomly selected and subjected to physical examina-tion and 9-hour polysomnography, maintaining the representativeness of the original sample (70% response rate). Physical examinations included height, weight, waist and neck mea-surements, blood pressure, visual ex-amination of nose/throat, evaluation of respiratory function, and blood pressure measurement.

Sleep apnea and hypopnea were defined using criteria commonly ac-cepted in clinical practice. Apnea indexes (AI) and apnea-hypopnea indexes (AHI) were calculated. Indi-viduals were defined as “without SDB” if AHI<1, as “mild SDB” if 1≤AHI<5, and as “moderate SDB” if AHI≥5. Us-ing these criteria, 8 children (1.14%) were affected with moderate SDB, 175 (25%) were classified as having mild SDB, and 517 (73.86%) were without SDB. Statistical comparison of AHIs and blood pressure measure-ments revealed that blood pressure was strongly associated with AHI in this population of children.

In this study, SDB appeared to be an independent risk factor for elevat-ed blood pressure in children aged 5 to 12 years. Authors noted that at the threshold of AHI≥5, the effect on blood pressure appears to warrant therapeutic intervention for SDB. Ad-ditionally, at a threshold of AHI≥3, the critical assessment of blood pres-sure and AHI at routine follow-up vis-its seems warranted, although addi-tional research is necessary to validate this conclusion. Since high AHI in children was found to independently contribute to clinically significant el-evation in blood pressure, the authors suggested that its detection and man-agement may lead to a reduction of elevated blood pressure in children and the subsequent reduction of car-diovascular risk in these same individ-uals as adults.

Though nasal continuous posi-tive airway pressure (CPAP) remains the gold standard of treatment for obstructive sleep apnea syndrome (OSAS), compliance with this treat-ment modality is variable, and un-comfortable side effects limit ad-herence. Patients unable to tolerate CPAP therapy and patients with mild to moderate OSAS are candidates for mandibular advancement de-vice therapy. Unfortunately, there is little data on the long-term success of mandibular advancement devices. To shed light on long-term outcomes, investigators136 assessed the 10-year

compliance and therapeutic opinions of patients treated with mandibular advancement devices. The authors hypothesized that mandibular ad-vancement devices are an acceptable form of long-term treatment for pa-tients with problem snoring and mild to moderate OSAS.

One hundred and eighty patients were provided mandibular advance-ment devices in 1996. All devices were of the same design. At the outset, the severity of OSAS in this patient pop-ulation was as follows: all patients snored; 72 patients were considered normal with AHI<5; 52 had mild dis-ease (5≤AHI≤14); 34 had moderate disease (15≤AHI≤30); and 21 had severe disease (AHI>30). In 2006, questionnaires were provided to these patients to survey device wear and satisfaction, sleep quality/duration, lifestyle, weight, height, and smok-ing/alcohol habits. Seventy-two of the 180 questionnaires were returned (40% response rate, 56 males, 16 fe-males).

Results indicated that 48 patients (66%) were still wearing the mandibu-lar advancement device at the time of the survey. Of the 24 patients no longer wearing the device, 12 claimed it was very uncomfortable, 3 found it slightly uncomfortable, and no infor-mation was available on the remaining 7 patients. Data were then evaluated for associations between success and other factors, including body mass in-dex, smoking, alcohol consumption, sleep duration, and sleep quality. Sleep quality was the only factor sig-nificantly associated with successful wear of the mandibular advancement device. Side effects reported included discomfort, excessive salivation, dry mouth, loose fit, stained teeth, repo-sitioned jaw, and excessive flatulence. When asked to rate the overall suc-cess of the device, 24% of the patients stated “fair,” and 46% reported the device provided “good” success.

Based on this data, authors ac-cepted the original hypothesis that mandibular advancement devices are an acceptable form of treatment

in the long term for patients with problem snoring and mild to moder-ate OSAS. A high level of treatment success is suggested by the fact that 66% of the patients were still wear-ing their devices and 70% rated their devices as fair to good after 10 years of practical use. Unfortunately, the response rate for the present investi-gation was only 40%. Although this compares favorably to other similar studies, a substantial amount of pa-tient response data were not collected and evaluated on the important issue of continued therapeutic impact of the mandibular advancement devices. The authors concluded by stating that the mandibular advancement device appears to be an acceptable long-term solution for a significant number of patients with problem snoring and those with mild to moderate OSAS.

Currently, polysomnography serves as the gold-standard diagnos-tic test for OSAS, providing informa-tion on the severity of OSAS and the degree of sleep fragmentation. How-ever, polysomnography does not pro-vide direct information regarding the specific pathophysiology of this dis-ease. It is known that the severity of OSAS is generally correlated with the degree of collapse of the pharyngeal region at the base of the tongue. One method of ascertaining critical infor-mation on effects of the degree of pharyngeal narrowing on SDB is the application of nasopharyngoscopy using the Muller maneuver. As this approach has not been sufficiently in-vestigated and reported, investigators examined correlations between the degree and shape of pharyngeal nar-rowing at different anatomical levels during the Muller maneuver and the severity of SDB.137

Thirty-three patients (29 male, 4 female, mean age of 49 years, mean body mass index (BMI) of 23.5) with suspected SDB underwent polysom-nography. Mean AHI, supine body position AHI, and lateral body posi-tion AHI were calculated. Fiberoptic nasopharyngoscopy using the Muller maneuver was performed for each pa-

tient in the supine position with the head in a neutral position. Degree and shape of pharyngeal narrowing was evaluated at both retropalatal and retroglossal levels, while the shape of pharyngeal narrowing was evaluated at the retropalatal level.

Results indicated that the mean AHI for this patient population was 28 (range 1.1 to 74.8). Three subjects were simple snorers, 9 had mild OSAS (5≤AHI<15), 10 had moderate OSAS (15≤AHI<30), and 11 had severe OSAS (AHI≥30). A significant correla-tion was identified between the degree of retroglossal pharyngeal narrowing and total and supine AHI. Additional-ly, the degree of retropalatal pharyn-geal narrowing demonstrated signifi-cant positive correlation with lateral AHI. These findings suggest that the mechanism of airway narrowing at the retroglossal level in supine SDB patients is primarily posterior tongue movement influenced by gravitational force and/or reduced muscular activ-ity compared to normal individuals. The present study also showed that lateral narrowing at the retropalatal pharyngeal level is more significantly positively correlated with mean total AHI than anteroposterior narrowing. Although currently available informa-tion does not provide a clear rationale for the deleterious effects of lateral retropharyngeal narrowing on OSAS, the authors suggested that lateral fat deposition may have a role, even in relatively nonobese individuals.

The authors concluded that the anatomic pharyngeal level and the de-gree and character of pharyngeal nar-rowing, as observed during fiberoptic nasopharyngoscopy using the Muller maneuver, revealed significant corre-lations with AHIs calculated in differ-ent sleeping positions.

PROSTHODONTICS

A pilot study was conducted to determine the position of the incisal edges of maxillary canines and cen-tral incisors relative to the maxillary lip line in a reposed position.138 The



33July 2009


proposed benefit would be for estab-lishing a proper incisal plane for eden-tulous patients. Measurement of the canine and central incisal edge display was conducted on 104 Caucasian dentate patients between the ages of 30 and 59. Exclusions were made for previous facial plastic surgery, or-thodontics modifying the incisal edge position, or moderate to severe wear of the maxillary anterior teeth. The in-vestigator did not control for aberrant lip length or maxillary anterior den-toalveloar extrusion, both of which will impact the central exposure more than the canine. The maxillary right canine and right central incisal edge displays were measured visually with a millimeter ruler. The data were sepa-rated by age and sex. Age was brack-eted into 3 groups: ages 30 to 39, 40 to 49, and 50 to 59 years. Exposure of the central incisors in repose dem-onstrated wide variation. In the 30 to 39 age group, women averaged 4.1 mm (0- to 8-mm range) and men av-eraged 3.2 mm (0- to 7-mm range). For women aged 40 to 49, the average display was 2.8 mm (-1 to +6 mm), and for men, it was 2.4 mm (-3 to +5 mm). In the 50 to 59 age group, women averaged 1.8 mm (-1 to +5 mm) and the men averaged 1.4 mm (-3 to +5) central incisor display. The canine measurements had less de-viation for each age bracket. For the 30- to 39-year olds, the women aver-aged 1 mm (-1 to +2 mm), and men averaged 0.9 mm (-1 to +2 mm). For the women aged 40 to 49, the average canine display was 0.4 mm (-1 to +2 mm), and for men it was 0.2 mm (-1 to +2 mm). Finally, in the group aged 50 to 59 years, the average for women was -0.5 mm (-2 to +1 mm), and for men, -0.9 mm (-2 to +1 mm). While it is more difficult to measure teeth that fall below the lip line in repose, the author concludes that the position of the canines is more predictable than the position of the central inci-sors. In future investigations, control over anatomic and dental variations at the midline would provide more

conclusive insight into the norms for positioning edentulous and dentate incisal edges in repose.

Luting agents

Self-etching cements are a rela-tively new category of luting agents. While the chemistry varies, they are essentially resin cements. One labo-ratory study attempted to determine whether self-etching cements pro-duce performance equal to conven-tional resin cements.139 The flexural strength, modulus of elasticity, and 24-hour pH profile of 3 self-etching luting agents in both translucent and A3 shades (RelyX Unicem (3M ESPE), Maxcem (Kerr Corp), and Embrace WetBond (Pulpdent Corp, Water-town, Mass)) were compared with 2 conventional resin cements (Re-lyX ARC (3M ESPE), Linkmax (GC America)), and 2 resin-modified glass ionomer (RMGI) cements (Fuji PLUS (GC America), RelyX Luting Plus (3M ESPE)). Flexural strength was tested on bar-shaped specimens (25 x 2 x 2 mm3) for each of the luting agents. The self-etch specimens were either autopolymerized or light polymerized for the dual-polymerized mode. The specimens were polished, measured, and stored in water for 24 hours. A 3-point-bend test was preformed in a universal testing machine at a cross-head speed of 0.75 mm/min, and the flexural strength was calculated. Modulus of elasticity was determined from the load deformation profiles generated during the 3-point-bend test. RMGIs had significantly lower flexural strength than the other luting agents. The resin cements and self-etch cements possess comparable flexural strengths within the same mode of polymerization. The excep-tion was the Embrace Wet bond au-topolymerizing mode that was simi-lar to the RMGIs. The modulus of elasticity results demonstrated that the autopolymerizing and dual-po-lymerizing RelyX Unicem (translucent and A3) and Maxcem clear dual-po-lymerizing cements had significantly

higher modulus of elasticity than the RMGIs and conventional resin ce-ments. The other self-etch cements were not significantly different than the traditional cements. The 24-hour pH change in each material was also tested. Self-etching cements began with the lowest pH and the conven-tional resins began with the highest. The self-etching pH changes over the 24-hour period varied significantly between type of resin and mode of polymerization. RelyX Unicem dis-played the most dramatic rise in pH over the first hour and had the high-est final pH. Both Maxcem and Em-brase showed little change in the acid-ity over time in the autopolymerizing mode. Embrase dual-polymerizing provided a more dramatic rise in pH. An oxygen-inhibited layer was noted with Embrase in both polymerization modes, indicating a lack of complete polymerization. The investigators concluded that, while the self-etching chemistry has significant advantages, the cements evaluated could not be considered a homogeneous group. The flexural strengths were similar, but the modulus of elasticity varied dramatically depending on the type of cement and the mode of polymeriza-tion. The results demonstrated that the pH profiles differed significantly, again with the mode of polymeriza-tion and type of cement. Prolonged acidity, especially periods of time when the acidity is below pH 3, may have an impact on pulpal health and postoperative sensitivity. All of the self-etching resins worked best when light polymerized, but the clinical effi-cacy of a dual-polymerizing self-etch-ing cement was not addressed.

Aprismatic cervical enamel has been shown to be more acid resis-tant and can negatively affect bond strengths. Another in vitro study of self-etching cements focused on the bond quality of resin to cervi-cal enamel with and without an acid pretreatment.140 Forty proximal cer-vical enamel surfaces were prepared on extracted third molars. Half of the specimens were etched for 30 seconds

with phosphoric acid, and the other specimens were not. Self-etching ce-ments (RelyX Unicem; 3M ESPE, and Multilink; Ivoclar Vivadent) were com-pared to a conventional resin cement (RelyX ARC; 3M ESPE). Composite resin specimens (Filtek Z250; 3M ESPE) were luted to the etched and unetched cervical enamel and light polymerized. The teeth were sectioned parallel to the adhesive surface, and specimens underwent microtensile testing. The results indicated that the effects of enamel etching were depen-dent on the resin cement tested. No significant difference was found for Multilink, but the etched specimens of RelyX Unicem resulted in a signifi-cant increase in bond strength. Under field-emission scanning electron mi-croscopy, the RelyX Unicem and RelyX ARC resins had significantly deeper penetration into the crystallites and enamel rods produced after etching than the Multilink, explaining the greater bond strength.

Endodontic posts

A prospective clinical trial com-pared the survival data for endodon-tically treated teeth with and without placement of a prefabricated metal post at 17-year follow-up.141 Eighty-seven patients with 98 restorations were included in the evaluation. Teeth included either did not require a crown or the patient could not af-ford the treatment, a reality of clinical practice. The investigators did not es-tablish a criteria for classifying a tooth as not requiring a crown after endo-dontics, or requiring a crown and not receiving it. These teeth were not dif-ferentiated in the data collection. The article suggests that all of the teeth had substantial dentin height. The au-thors define adequate height to mean that >75% of the circumferential den-tin was at least 1 mm thick and 1 mm above the free gingival margin. If more detailed information delineating the exact amount of clinical crown had been reported, it might be possible to know whether the long-term survival

is more dependent on the post, post filling material, or amount of remain-ing clinical crown. The post and no-post groups were determined by bal-anced randomization. The posts were metal, parallel-sided passive posts luted with Panavia cement (Kuraray Co, Ltd). At year 5, 87% of the teeth were available for evaluation. This decreased to 82% at 10 years, 67% at 15 years, and 39% at 17 years. The overall restoration survival rate was 53% ±14%, and the tooth survival rate was 79% ±11%. Teeth with posts re-quired more intervention, but not at a significant rate. Interestingly, only 1 tooth with a post failed from a root fracture. Crown placement was the most common intervention for failed restorations. Several factors weak-ened this study, including a high num-ber of operators, lack of calibration and randomization. It does, however, present interesting information on the long-term prognosis of endodon-tically treated teeth not provided with cuspal coverage.

An in vitro study was conducted on the residual dentin thickness of bifur-cated first premolars after endodon-tic treatment and post preparation.142 Extracted maxillary first premolars were divided into 2 groups, depending on the level of the bifurcation above or below the middle third of the root length. Endodontic canal preparation was performed using a K-40-size file at the apex in a step-back technique. Post preparations were completed on 13 teeth with junctions of the bifurca-tion located in the middle to coronal third. Parallel-sided drills (ParaPost, Nos. 3 and 4; Coltène/Whaledent, Inc, Cuyahoga Falls, Ohio) were used to finish the post preparation in both canals. The residual dentin thickness was measured for all teeth at 2, 4, and 6 mm apical to the CEJ. The re-sults indicated that a step-back tech-nique removes more dentin in the coronal than in the middle and api-cal regions. The opposite is true for post preparation with a parallel-sided drill, which will remove more dentin in the apical than in the middle and

coronal regions. Interestingly, the re-sidual dentin thickness (RDT) of the lingual aspect of the buccal root and buccal aspect of the lingual root were the most affected. The mean RDT of the lingual aspect of the buccal root, 6 mm below the CEJ, was 0.82-0.9 mm after root canal and post prepa-ration, making the root more suscep-tible to root fracture or perforation. The endodontic preparation reduced the wall thickness to less than 1 mm in 53% of the buccal roots and 38% of the lingual roots. After post prepara-tion, the values increased to 77% for the buccal roots and 61% for the lin-gual roots. The results suggest that, due to the unique architecture of the bifurcated maxillary first premo-lar, parallel-sided post preparation is contraindicated and unnecessary reduction of RDT may be detrimen-tal. Further study of other teeth with tapering canals should be conducted and may elicit similar findings.

An interesting push-out bond strength and sealing ability study was conducted on 5 adhesive cements routinely used for fiber post bond-ing.143 Fifty single-rooted teeth were endodontically prepared and obtu-rated. The post space was prepared and the teeth were restored with a carbon fiber post (Parapost Fiber Lux; Coltène/Whaledent, Inc). The luting agents were chosen by adhesive strat-egy and polymerization mode: Pana-via 21 (Kuraray Co, Ltd), self-etch, autopolymerizing; Clearfil Esthetic Cement (Kuraray Co, Ltd), self-etch, dual polymerizing; Variolink II (Ivoclar Vivadent), etch and rinse, dual po-lymerizing; RelyX Unicem (3M ESPE), self-adhesive, dual polymerizing; and an experimental self-adhesive cement (GC Corp), self-adhesive, dual polym-erizing. The post was luted following manufacturer’s instructions, includ-ing light polymerization of the coro-nal portion of the dual-polymerizing cements. Three 2-mm-thick speci-mens were cut from each tooth: coro-nal, middle, and apical. Each section was connected to a modified fluid-fil-tration system to measure the sealing



33July 2009


proposed benefit would be for estab-lishing a proper incisal plane for eden-tulous patients. Measurement of the canine and central incisal edge display was conducted on 104 Caucasian dentate patients between the ages of 30 and 59. Exclusions were made for previous facial plastic surgery, or-thodontics modifying the incisal edge position, or moderate to severe wear of the maxillary anterior teeth. The in-vestigator did not control for aberrant lip length or maxillary anterior den-toalveloar extrusion, both of which will impact the central exposure more than the canine. The maxillary right canine and right central incisal edge displays were measured visually with a millimeter ruler. The data were sepa-rated by age and sex. Age was brack-eted into 3 groups: ages 30 to 39, 40 to 49, and 50 to 59 years. Exposure of the central incisors in repose dem-onstrated wide variation. In the 30 to 39 age group, women averaged 4.1 mm (0- to 8-mm range) and men av-eraged 3.2 mm (0- to 7-mm range). For women aged 40 to 49, the average display was 2.8 mm (-1 to +6 mm), and for men, it was 2.4 mm (-3 to +5 mm). In the 50 to 59 age group, women averaged 1.8 mm (-1 to +5 mm) and the men averaged 1.4 mm (-3 to +5) central incisor display. The canine measurements had less de-viation for each age bracket. For the 30- to 39-year olds, the women aver-aged 1 mm (-1 to +2 mm), and men averaged 0.9 mm (-1 to +2 mm). For the women aged 40 to 49, the average canine display was 0.4 mm (-1 to +2 mm), and for men it was 0.2 mm (-1 to +2 mm). Finally, in the group aged 50 to 59 years, the average for women was -0.5 mm (-2 to +1 mm), and for men, -0.9 mm (-2 to +1 mm). While it is more difficult to measure teeth that fall below the lip line in repose, the author concludes that the position of the canines is more predictable than the position of the central inci-sors. In future investigations, control over anatomic and dental variations at the midline would provide more

conclusive insight into the norms for positioning edentulous and dentate incisal edges in repose.

Luting agents

Self-etching cements are a rela-tively new category of luting agents. While the chemistry varies, they are essentially resin cements. One labo-ratory study attempted to determine whether self-etching cements pro-duce performance equal to conven-tional resin cements.139 The flexural strength, modulus of elasticity, and 24-hour pH profile of 3 self-etching luting agents in both translucent and A3 shades (RelyX Unicem (3M ESPE), Maxcem (Kerr Corp), and Embrace WetBond (Pulpdent Corp, Water-town, Mass)) were compared with 2 conventional resin cements (Re-lyX ARC (3M ESPE), Linkmax (GC America)), and 2 resin-modified glass ionomer (RMGI) cements (Fuji PLUS (GC America), RelyX Luting Plus (3M ESPE)). Flexural strength was tested on bar-shaped specimens (25 x 2 x 2 mm3) for each of the luting agents. The self-etch specimens were either autopolymerized or light polymerized for the dual-polymerized mode. The specimens were polished, measured, and stored in water for 24 hours. A 3-point-bend test was preformed in a universal testing machine at a cross-head speed of 0.75 mm/min, and the flexural strength was calculated. Modulus of elasticity was determined from the load deformation profiles generated during the 3-point-bend test. RMGIs had significantly lower flexural strength than the other luting agents. The resin cements and self-etch cements possess comparable flexural strengths within the same mode of polymerization. The excep-tion was the Embrace Wet bond au-topolymerizing mode that was simi-lar to the RMGIs. The modulus of elasticity results demonstrated that the autopolymerizing and dual-po-lymerizing RelyX Unicem (translucent and A3) and Maxcem clear dual-po-lymerizing cements had significantly

higher modulus of elasticity than the RMGIs and conventional resin ce-ments. The other self-etch cements were not significantly different than the traditional cements. The 24-hour pH change in each material was also tested. Self-etching cements began with the lowest pH and the conven-tional resins began with the highest. The self-etching pH changes over the 24-hour period varied significantly between type of resin and mode of polymerization. RelyX Unicem dis-played the most dramatic rise in pH over the first hour and had the high-est final pH. Both Maxcem and Em-brase showed little change in the acid-ity over time in the autopolymerizing mode. Embrase dual-polymerizing provided a more dramatic rise in pH. An oxygen-inhibited layer was noted with Embrase in both polymerization modes, indicating a lack of complete polymerization. The investigators concluded that, while the self-etching chemistry has significant advantages, the cements evaluated could not be considered a homogeneous group. The flexural strengths were similar, but the modulus of elasticity varied dramatically depending on the type of cement and the mode of polymeriza-tion. The results demonstrated that the pH profiles differed significantly, again with the mode of polymeriza-tion and type of cement. Prolonged acidity, especially periods of time when the acidity is below pH 3, may have an impact on pulpal health and postoperative sensitivity. All of the self-etching resins worked best when light polymerized, but the clinical effi-cacy of a dual-polymerizing self-etch-ing cement was not addressed.

Aprismatic cervical enamel has been shown to be more acid resis-tant and can negatively affect bond strengths. Another in vitro study of self-etching cements focused on the bond quality of resin to cervi-cal enamel with and without an acid pretreatment.140 Forty proximal cer-vical enamel surfaces were prepared on extracted third molars. Half of the specimens were etched for 30 seconds

with phosphoric acid, and the other specimens were not. Self-etching ce-ments (RelyX Unicem; 3M ESPE, and Multilink; Ivoclar Vivadent) were com-pared to a conventional resin cement (RelyX ARC; 3M ESPE). Composite resin specimens (Filtek Z250; 3M ESPE) were luted to the etched and unetched cervical enamel and light polymerized. The teeth were sectioned parallel to the adhesive surface, and specimens underwent microtensile testing. The results indicated that the effects of enamel etching were depen-dent on the resin cement tested. No significant difference was found for Multilink, but the etched specimens of RelyX Unicem resulted in a signifi-cant increase in bond strength. Under field-emission scanning electron mi-croscopy, the RelyX Unicem and RelyX ARC resins had significantly deeper penetration into the crystallites and enamel rods produced after etching than the Multilink, explaining the greater bond strength.

Endodontic posts

A prospective clinical trial com-pared the survival data for endodon-tically treated teeth with and without placement of a prefabricated metal post at 17-year follow-up.141 Eighty-seven patients with 98 restorations were included in the evaluation. Teeth included either did not require a crown or the patient could not af-ford the treatment, a reality of clinical practice. The investigators did not es-tablish a criteria for classifying a tooth as not requiring a crown after endo-dontics, or requiring a crown and not receiving it. These teeth were not dif-ferentiated in the data collection. The article suggests that all of the teeth had substantial dentin height. The au-thors define adequate height to mean that >75% of the circumferential den-tin was at least 1 mm thick and 1 mm above the free gingival margin. If more detailed information delineating the exact amount of clinical crown had been reported, it might be possible to know whether the long-term survival

is more dependent on the post, post filling material, or amount of remain-ing clinical crown. The post and no-post groups were determined by bal-anced randomization. The posts were metal, parallel-sided passive posts luted with Panavia cement (Kuraray Co, Ltd). At year 5, 87% of the teeth were available for evaluation. This decreased to 82% at 10 years, 67% at 15 years, and 39% at 17 years. The overall restoration survival rate was 53% ±14%, and the tooth survival rate was 79% ±11%. Teeth with posts re-quired more intervention, but not at a significant rate. Interestingly, only 1 tooth with a post failed from a root fracture. Crown placement was the most common intervention for failed restorations. Several factors weak-ened this study, including a high num-ber of operators, lack of calibration and randomization. It does, however, present interesting information on the long-term prognosis of endodon-tically treated teeth not provided with cuspal coverage.

An in vitro study was conducted on the residual dentin thickness of bifur-cated first premolars after endodon-tic treatment and post preparation.142 Extracted maxillary first premolars were divided into 2 groups, depending on the level of the bifurcation above or below the middle third of the root length. Endodontic canal preparation was performed using a K-40-size file at the apex in a step-back technique. Post preparations were completed on 13 teeth with junctions of the bifurca-tion located in the middle to coronal third. Parallel-sided drills (ParaPost, Nos. 3 and 4; Coltène/Whaledent, Inc, Cuyahoga Falls, Ohio) were used to finish the post preparation in both canals. The residual dentin thickness was measured for all teeth at 2, 4, and 6 mm apical to the CEJ. The re-sults indicated that a step-back tech-nique removes more dentin in the coronal than in the middle and api-cal regions. The opposite is true for post preparation with a parallel-sided drill, which will remove more dentin in the apical than in the middle and

coronal regions. Interestingly, the re-sidual dentin thickness (RDT) of the lingual aspect of the buccal root and buccal aspect of the lingual root were the most affected. The mean RDT of the lingual aspect of the buccal root, 6 mm below the CEJ, was 0.82-0.9 mm after root canal and post prepa-ration, making the root more suscep-tible to root fracture or perforation. The endodontic preparation reduced the wall thickness to less than 1 mm in 53% of the buccal roots and 38% of the lingual roots. After post prepara-tion, the values increased to 77% for the buccal roots and 61% for the lin-gual roots. The results suggest that, due to the unique architecture of the bifurcated maxillary first premo-lar, parallel-sided post preparation is contraindicated and unnecessary reduction of RDT may be detrimen-tal. Further study of other teeth with tapering canals should be conducted and may elicit similar findings.

An interesting push-out bond strength and sealing ability study was conducted on 5 adhesive cements routinely used for fiber post bond-ing.143 Fifty single-rooted teeth were endodontically prepared and obtu-rated. The post space was prepared and the teeth were restored with a carbon fiber post (Parapost Fiber Lux; Coltène/Whaledent, Inc). The luting agents were chosen by adhesive strat-egy and polymerization mode: Pana-via 21 (Kuraray Co, Ltd), self-etch, autopolymerizing; Clearfil Esthetic Cement (Kuraray Co, Ltd), self-etch, dual polymerizing; Variolink II (Ivoclar Vivadent), etch and rinse, dual po-lymerizing; RelyX Unicem (3M ESPE), self-adhesive, dual polymerizing; and an experimental self-adhesive cement (GC Corp), self-adhesive, dual polym-erizing. The post was luted following manufacturer’s instructions, includ-ing light polymerization of the coro-nal portion of the dual-polymerizing cements. Three 2-mm-thick speci-mens were cut from each tooth: coro-nal, middle, and apical. Each section was connected to a modified fluid-fil-tration system to measure the sealing



35July 2009


ability at a constant hydrostatic pres-sure. After the sealing test, the speci-mens were subjected to a push-out test using a universal testing machine until the post was dislodged. The re-sults indicate that the choice of bond-ing agent has a significant impact on the push-out bond strength. The low-est bond strengths were recorded for the middle and apical portions of the root, except for RelyX Unicem. The highest bond strength was detected in the apical third. The highest bond strength was recorded for Clearfil Es-thetic Cement. It was not significantly different than Panavia 21, but was sig-nificantly different than the other ce-ments. No significant differences were found between the other cements ex-cept for the GC experimental luting agent, which was significantly lower than all cements. The luting agent also significantly affected the sealing ability. No difference was detected by region of the root. Both of the self-adhesive cements (Rely X Unicem and GC self-adhesive experimental ce-ment) had significantly more micro-leakage than any other cement tested. Overall, the results of the push-out bond strength appear to be inversely correlated to the sealing effectiveness of the cement.

Complete dentures

The association between periodon-tal pathogens and various systemic diseases is more widely known. Sev-eral studies evaluated the plaque and biofilm in dentate subjects, but rela-tively little is known about the bacteri-al flora of an edentulous patient. The assumption is that when the teeth are removed, the periodontal pathogens are no longer present. Several investi-gators tested that theory in a unique research project.144 Sixty-one subjects, edentulous for at least 1 year, wearing complete maxillary and mandibular dentures on a daily basis, were tested. Microbial specimens were obtained from 8 separate locations: tongue (dorsum, ventral, lateral), buccal mu-cosa, vestibule, hard palate, floor of

mouth, and anterior attached gingiva. The dentures were also sampled from the cameo surface, the teeth, and the junction between the cameo and inta-glio surfaces. In addition, unstimulat-ed saliva specimens were obtained for evaluation. All specimens were ana-lyzed with a checkerboard DNA-DNA hybridization to determine the levels of 41 bacterial species often found in the plaque and soft tissue biofilms in dentate subjects. The denture acrylic resin biofilm was high in Actinomyces species, V. parvula, and Streptococcus species. Interestingly, the periodon-tal pathogens A. actinomycetemcomi-tans and P. gingivalis were also present intraorally. The specimens from the dorsum of the tongue had the high-est bacterial counts, followed by the attached gingiva. The lowest counts occurred in the vestibule and buccal mucosa. The concentration of bacte-rial colonization varied between loca-tions and species. S. mitis and S. ora-lis, for example, were found in higher concentrations on soft tissue as op-posed to the denture acrylic resin or saliva. The periodontal pathogens isolated in this research project were believed to have been eliminated with the extraction of all natural teeth. They were, however, seen in signifi-cant numbers in the edentulous sub-ject. The researchers stressed an in-creased emphasis on the oral hygiene of edentulous patients to reduce the risk of systemic disease.

An in vitro examination of the di-mensional accuracy of different den-ture relining methods and materials was conducted.145 Fifty identical den-tures were fabricated on 50 casts from a stainless steel master cast. Denture bases were produced to create 1.5 mm of relief space for the reline. Five relining methods and materials were tested: laboratory heat polymerized, laboratory heat/pressure polymer-ized, laboratory autopolymerized, chairside autopolymerized, and chair-side light polymerized. The labora-tory methods and materials followed manufacturer specifications for a re-line. The chairside material was mixed

and placed under a static load of 2 kg. The dimensional change of the relined denture was determined with a repli-ca technique. A low-viscosity silicone impression material was injected in the intaglio of the denture and placed on the master cast under a 2-kg static load. The wash was removed from the denture and embedded between 2 lay-ers of heavy-viscosity vinyl polysilox-ane. Each block of silicone was sliced on the posterior palatal border, and the replicated thickness of the gap was measured. Statistically significant differences were found between the groups. The chairside autopolymeriz-ing reline showed the greatest dimen-sional accuracy, while the laboratory heat-polymerized conventional tech-nique produced the greatest error. Re-searchers noted that there appears to be a close correlation between the de-gree of heat and the amount of shrink-age during processing. As the heat is low, the degree of change is due to polymerization shrinkage alone. The chairside materials had large stan-dard deviations, probably due to the difficulty in repositioning the denture base. The authors concluded that the use of a chairside material along with a reline jig and pressure tank may pro-vide the advantage of low shrinkage with added control over placement and production of a posterior seal. The issue of the long-term poor physi-cal properties of the chairside materi-als was not addressed.

Maxillofacial prosthodontics

Obturators have traditionally been fabricated with silicone or polymethyl methacylate (PMMA). These materi-als have the inherent risk of bacterial colonization, increasing the risk of lo-cal and systemic infections. A study was conducted to compare the mi-croorganisms present on traditional and titanium obturators.146 Thirty-six patients with existing obturators, 17 titanium and 19 polymer, were evaluated. Microbial specimens were collected from the posterior surface of the obturators and the adjacent

soft tissue. The PMMA obturators were sectioned to obtain a section of acrylic resin from the interior to evaluate bacterial penetration. Mi-crobiological analysis and quantifica-tion of colony-forming units was con-ducted. The research confirmed that obturators harbor microorganisms that are different than normal flora. One hundred percent of the PMMA surfaces were colonized by abnormal bacterial species, while only 29.4% of the titanium surfaces were colonized. The tissue adjacent to PMMA obtura-tors was contaminated in 94.7% of the patients and in 47.1% of the pa-tients with titanium. Penetration of microbes was discovered in 68.4% of the PMMA acrylic resin specimens. The results showed that titanium can provide a light, accurate casting that may provide a healthier alternative to PMMA in maxillofacial prostheses. The difficulty in casting makes the use of titanium more costly, and titanium is more difficult to reline and adjust.

Color and shade matching

A clinical project focusing on matching the color of a metal ce-ramic crown to the natural dentition was conducted.147 The study com-pared the shade matching accuracy of the final crowns produced using a conventional visual shade matching technique (individual dentists using a shade guide to describe or map tooth color for the laboratory) versus a cali-brated spectrophotometer. The spec-trophotometer provides the techni-cian a color photograph of the tooth and a digital mapping color calibrat-ed to any shade guide. Metal ceramic crowns for 36 single maxillary central incisors were fabricated. Two crowns were fabricated for each subject: one with each shade mapping technique. The color match of each crown was analyzed both visually and with the spectrophotometer. Twenty-two per-cent of the crowns fabricated with the conventional method and 77.8% of the spectrophotometer crowns were deemed acceptable. The color differ-

ence between the target teeth and the crowns was significantly lower in all areas of the crown when measured with the spectrophotometer as com-pared to the visual method. The study did not report whether the differences were more related to chroma or value, but simply grouped the data into a color category. This project confirms that the technique used by clinicians of mapping color and drawing pic-tures for the laboratory is a poor sub-stitute for a photograph. The true in-fluence of the digital shade guide data cannot be distinguished in this study, since the difference in final crowns, comparing between a color-corrected photograph and a spectrophotom-eter, was not tested.

Historically, shade mapping has used the clinicians’ color perception of the tooth with respect to a shade guide. Use of spectrophotometers in shade matching can provide color communication in any shade guide. The ability of a ceramic system to cor-rectly reproduce the spectrophotom-eters’ selected shade was tested in an in vitro study.148 The VITA Omega 900 dental ceramic system (VITA Zahn-fabrik; Bad Säckingen, Germany) was used in the study since it is marketed to match the VITA Classical and VITA 3D-Master shade guides. Metal ce-ramic specimens were fabricated to match an A3 shade Classical and 2M3 shade for the 3D-Master. Specimens were prepared using 3 different lay-ering patterns to a standardized 1.3-mm thickness. The specimens were evaluated with a stand-alone clinical spectrophotometer. The analysis indi-cated that, regardless of layering pat-tern, the color match between the ce-ramic discs and the 3D-Master shade guide were significantly better than with the VITA Classical shade guide. While this study is limited to a single ceramic shade and porcelain system, color correspondence appears to be related to the shade guide chosen.

Ceramics

The veneering of an opaque zirco-

nium core has provided a new esthetic challenge to ceramists. Recently, col-ored zirconium frameworks have been introduced in an attempt to address this problem. The impact on core strength caused by alterations in the chemistry of colored zirconium and the bond strength between the veneer ceramic and the zirconia framework were evaluated in a unique labora-tory study.149 Five commercially avail-able zirconium framework materials (Cercon white and yellow (DeguDent GmbH, Hanau, Germany), Lava white and yellow (3M ESPE), and Procera Zirconia (Nobel Biocare AB, Göte-borg, Sweden)) were investigated. The ceramic cores were grouped by surface treatment before addition of the ve-neering ceramic: unaltered, airborne-particle abraded, or airborne-particle abraded and coated with a liner ma-terial. The specimens were tested for microtensile bond strength (MTBS). The analysis revealed a significant difference between the surface treat-ments and color. The airborne-parti-cle-abraded pretreatment provided an increase in the bond strength for white specimens. However, the yellow frameworks had significantly lower strength. The liner material was ben-eficial for all specimens but increased the percentage of interfacial failure compared to the airborne-particle-abraded specimens. Significant differ-ences were noted between white and colored zirconium. Researchers noted that the addition of coloring pigments to the zirconium frameworks changed the grain structure of the material. Loss of material from airborne-par-ticle abrasion is greater with colored zirconium compared to white. The re-sults indicate that this added surface roughness and sharpness increases interfacial failure. While each of the zirconia materials are fabricated dif-ferently, the impact of surface treat-ments remained relatively constant.

In an attempt to match adjacent restorations, laboratories may at-tempt to use zirconium veneering ce-ramic for porcelain laminate veneers. Veneer ceramics are bonded to tooth



35July 2009


ability at a constant hydrostatic pres-sure. After the sealing test, the speci-mens were subjected to a push-out test using a universal testing machine until the post was dislodged. The re-sults indicate that the choice of bond-ing agent has a significant impact on the push-out bond strength. The low-est bond strengths were recorded for the middle and apical portions of the root, except for RelyX Unicem. The highest bond strength was detected in the apical third. The highest bond strength was recorded for Clearfil Es-thetic Cement. It was not significantly different than Panavia 21, but was sig-nificantly different than the other ce-ments. No significant differences were found between the other cements ex-cept for the GC experimental luting agent, which was significantly lower than all cements. The luting agent also significantly affected the sealing ability. No difference was detected by region of the root. Both of the self-adhesive cements (Rely X Unicem and GC self-adhesive experimental ce-ment) had significantly more micro-leakage than any other cement tested. Overall, the results of the push-out bond strength appear to be inversely correlated to the sealing effectiveness of the cement.

Complete dentures

The association between periodon-tal pathogens and various systemic diseases is more widely known. Sev-eral studies evaluated the plaque and biofilm in dentate subjects, but rela-tively little is known about the bacteri-al flora of an edentulous patient. The assumption is that when the teeth are removed, the periodontal pathogens are no longer present. Several investi-gators tested that theory in a unique research project.144 Sixty-one subjects, edentulous for at least 1 year, wearing complete maxillary and mandibular dentures on a daily basis, were tested. Microbial specimens were obtained from 8 separate locations: tongue (dorsum, ventral, lateral), buccal mu-cosa, vestibule, hard palate, floor of

mouth, and anterior attached gingiva. The dentures were also sampled from the cameo surface, the teeth, and the junction between the cameo and inta-glio surfaces. In addition, unstimulat-ed saliva specimens were obtained for evaluation. All specimens were ana-lyzed with a checkerboard DNA-DNA hybridization to determine the levels of 41 bacterial species often found in the plaque and soft tissue biofilms in dentate subjects. The denture acrylic resin biofilm was high in Actinomyces species, V. parvula, and Streptococcus species. Interestingly, the periodon-tal pathogens A. actinomycetemcomi-tans and P. gingivalis were also present intraorally. The specimens from the dorsum of the tongue had the high-est bacterial counts, followed by the attached gingiva. The lowest counts occurred in the vestibule and buccal mucosa. The concentration of bacte-rial colonization varied between loca-tions and species. S. mitis and S. ora-lis, for example, were found in higher concentrations on soft tissue as op-posed to the denture acrylic resin or saliva. The periodontal pathogens isolated in this research project were believed to have been eliminated with the extraction of all natural teeth. They were, however, seen in signifi-cant numbers in the edentulous sub-ject. The researchers stressed an in-creased emphasis on the oral hygiene of edentulous patients to reduce the risk of systemic disease.

An in vitro examination of the di-mensional accuracy of different den-ture relining methods and materials was conducted.145 Fifty identical den-tures were fabricated on 50 casts from a stainless steel master cast. Denture bases were produced to create 1.5 mm of relief space for the reline. Five relining methods and materials were tested: laboratory heat polymerized, laboratory heat/pressure polymer-ized, laboratory autopolymerized, chairside autopolymerized, and chair-side light polymerized. The labora-tory methods and materials followed manufacturer specifications for a re-line. The chairside material was mixed

and placed under a static load of 2 kg. The dimensional change of the relined denture was determined with a repli-ca technique. A low-viscosity silicone impression material was injected in the intaglio of the denture and placed on the master cast under a 2-kg static load. The wash was removed from the denture and embedded between 2 lay-ers of heavy-viscosity vinyl polysilox-ane. Each block of silicone was sliced on the posterior palatal border, and the replicated thickness of the gap was measured. Statistically significant differences were found between the groups. The chairside autopolymeriz-ing reline showed the greatest dimen-sional accuracy, while the laboratory heat-polymerized conventional tech-nique produced the greatest error. Re-searchers noted that there appears to be a close correlation between the de-gree of heat and the amount of shrink-age during processing. As the heat is low, the degree of change is due to polymerization shrinkage alone. The chairside materials had large stan-dard deviations, probably due to the difficulty in repositioning the denture base. The authors concluded that the use of a chairside material along with a reline jig and pressure tank may pro-vide the advantage of low shrinkage with added control over placement and production of a posterior seal. The issue of the long-term poor physi-cal properties of the chairside materi-als was not addressed.

Maxillofacial prosthodontics

Obturators have traditionally been fabricated with silicone or polymethyl methacylate (PMMA). These materi-als have the inherent risk of bacterial colonization, increasing the risk of lo-cal and systemic infections. A study was conducted to compare the mi-croorganisms present on traditional and titanium obturators.146 Thirty-six patients with existing obturators, 17 titanium and 19 polymer, were evaluated. Microbial specimens were collected from the posterior surface of the obturators and the adjacent

soft tissue. The PMMA obturators were sectioned to obtain a section of acrylic resin from the interior to evaluate bacterial penetration. Mi-crobiological analysis and quantifica-tion of colony-forming units was con-ducted. The research confirmed that obturators harbor microorganisms that are different than normal flora. One hundred percent of the PMMA surfaces were colonized by abnormal bacterial species, while only 29.4% of the titanium surfaces were colonized. The tissue adjacent to PMMA obtura-tors was contaminated in 94.7% of the patients and in 47.1% of the pa-tients with titanium. Penetration of microbes was discovered in 68.4% of the PMMA acrylic resin specimens. The results showed that titanium can provide a light, accurate casting that may provide a healthier alternative to PMMA in maxillofacial prostheses. The difficulty in casting makes the use of titanium more costly, and titanium is more difficult to reline and adjust.

Color and shade matching

A clinical project focusing on matching the color of a metal ce-ramic crown to the natural dentition was conducted.147 The study com-pared the shade matching accuracy of the final crowns produced using a conventional visual shade matching technique (individual dentists using a shade guide to describe or map tooth color for the laboratory) versus a cali-brated spectrophotometer. The spec-trophotometer provides the techni-cian a color photograph of the tooth and a digital mapping color calibrat-ed to any shade guide. Metal ceramic crowns for 36 single maxillary central incisors were fabricated. Two crowns were fabricated for each subject: one with each shade mapping technique. The color match of each crown was analyzed both visually and with the spectrophotometer. Twenty-two per-cent of the crowns fabricated with the conventional method and 77.8% of the spectrophotometer crowns were deemed acceptable. The color differ-

ence between the target teeth and the crowns was significantly lower in all areas of the crown when measured with the spectrophotometer as com-pared to the visual method. The study did not report whether the differences were more related to chroma or value, but simply grouped the data into a color category. This project confirms that the technique used by clinicians of mapping color and drawing pic-tures for the laboratory is a poor sub-stitute for a photograph. The true in-fluence of the digital shade guide data cannot be distinguished in this study, since the difference in final crowns, comparing between a color-corrected photograph and a spectrophotom-eter, was not tested.

Historically, shade mapping has used the clinicians’ color perception of the tooth with respect to a shade guide. Use of spectrophotometers in shade matching can provide color communication in any shade guide. The ability of a ceramic system to cor-rectly reproduce the spectrophotom-eters’ selected shade was tested in an in vitro study.148 The VITA Omega 900 dental ceramic system (VITA Zahn-fabrik; Bad Säckingen, Germany) was used in the study since it is marketed to match the VITA Classical and VITA 3D-Master shade guides. Metal ce-ramic specimens were fabricated to match an A3 shade Classical and 2M3 shade for the 3D-Master. Specimens were prepared using 3 different lay-ering patterns to a standardized 1.3-mm thickness. The specimens were evaluated with a stand-alone clinical spectrophotometer. The analysis indi-cated that, regardless of layering pat-tern, the color match between the ce-ramic discs and the 3D-Master shade guide were significantly better than with the VITA Classical shade guide. While this study is limited to a single ceramic shade and porcelain system, color correspondence appears to be related to the shade guide chosen.

Ceramics

The veneering of an opaque zirco-

nium core has provided a new esthetic challenge to ceramists. Recently, col-ored zirconium frameworks have been introduced in an attempt to address this problem. The impact on core strength caused by alterations in the chemistry of colored zirconium and the bond strength between the veneer ceramic and the zirconia framework were evaluated in a unique labora-tory study.149 Five commercially avail-able zirconium framework materials (Cercon white and yellow (DeguDent GmbH, Hanau, Germany), Lava white and yellow (3M ESPE), and Procera Zirconia (Nobel Biocare AB, Göte-borg, Sweden)) were investigated. The ceramic cores were grouped by surface treatment before addition of the ve-neering ceramic: unaltered, airborne-particle abraded, or airborne-particle abraded and coated with a liner ma-terial. The specimens were tested for microtensile bond strength (MTBS). The analysis revealed a significant difference between the surface treat-ments and color. The airborne-parti-cle-abraded pretreatment provided an increase in the bond strength for white specimens. However, the yellow frameworks had significantly lower strength. The liner material was ben-eficial for all specimens but increased the percentage of interfacial failure compared to the airborne-particle-abraded specimens. Significant differ-ences were noted between white and colored zirconium. Researchers noted that the addition of coloring pigments to the zirconium frameworks changed the grain structure of the material. Loss of material from airborne-par-ticle abrasion is greater with colored zirconium compared to white. The re-sults indicate that this added surface roughness and sharpness increases interfacial failure. While each of the zirconia materials are fabricated dif-ferently, the impact of surface treat-ments remained relatively constant.

In an attempt to match adjacent restorations, laboratories may at-tempt to use zirconium veneering ce-ramic for porcelain laminate veneers. Veneer ceramics are bonded to tooth



37July 2009


structure with micromechanical reten-tion of the resin and an acid-etched roughened ceramic surface. An in vit-ro study of the bond strength of 3 zir-conium veneering ceramics: Cerabien CZR (Noritake, Aichi, Japan), Lava Ce-ram (3M ESPE), and Zirox (Wieland Dental Systems, Inc, Danbury, Conn), and 4 traditional veneering ceramics: Creation (Jensen Industries, North Haven, Conn), IPS d.Sign (Ivoclar Vivadent), Noritake EX-3 (Noritake), and Reflex (Wieland Dental Systems, Inc) was conducted to determine if conventional ceramic and zirconium veneering ceramic react similarly to acid etching.150 Specimens of each of the ceramics were etched with hydro-fluoric acid following manufacturers’ specifications. The etched specimens were microscopically evaluated. The investigators found a significant dif-ference in the surface roughness of all tested groups. Two of the traditional ceramics (Cerabien CZR and Reflex) produced a surface roughness signifi-cantly higher than the zirconia speci-mens. Zirox was slightly rougher than zirconium and IPS d.Sign created the same roughness as the zirconium specimens. The zirconium ceram-ics all demonstrated similar surface roughness after etching. The results showed that they produced smooth surfaces with some grooves. A silane solution was applied for 60 seconds, air dried, and then an adhesive bond-ing agent was added. The ceramic specimens were bonded to prepared enamel specimens using a light-po-lymerized resin cement. Shear load was applied in a universal testing ma-chine until failure. The average bond strengths were reported. The highest mean shear bond strength was from the traditional ceramics Cerabien CZR and Reflex, which were 50-60% greater than the weakest mean bond strength from a zirconium veneering ceramic. While the etch patterns on zirconia produced a smoother sur-face, some of the zirconium ceram-ics matched the bond strength of the weakest conventional ceramic, IPS d.Sign. The authors concluded that

the bond strength of some of the zir-conium ceramics was too weak to be indicated for use in bonded ceramics, and laboratories must choose the zir-conium veneering ceramic carefully to ensure a proper bond.

The impact of repeated firings on the value and color of a restora-tion fabricated with lithium disilicate glass ceramic (IPS e.max Press; Ivoclar Vivadent) and zirconium oxide (DC-Zirkon; DCS Dental AG, Allschwil, Switzerland) was tested.151 Thirty 4-mm discs with a core thickness of 1 mm were fabricated. An A1-colored veneer ceramic with a thickness of 0.5, 1.0, or 1.5 mm was fired to the discs. The firings were performed ei-ther 3, 5, 7, or 9 times. At each inter-val, the color and value were evalu-ated with a spectrophotometer and compared to the other specimens. The results showed that an increase in firings yielded an increase in value for both cores. As the veneering ceramic increased in thickness, the bright-ness decreased for both cores, result-ing in darker specimens. The chroma increased for the 0.5-mm IPS e.max Press specimens but not for the 1-mm specimen. At 1.5 mm, only the blue-yellow chroma increased. For the zirconium specimens, the red-green value decreased with repeated firings, except for the 1.5-mm specimens, for which it increased. The blue-yellow value increased for the 0.5-mm-thick and 1.5-mm-thick zirconium speci-mens, but there was no change in this value in the 1.0-mm-thick specimens. The mean color change for repeated firings and different ceramic thick-nesses for a zirconium framework was below the color change units rated as a match in the oral environment. However, the color change was higher for IPS e.max Press, indicating that extended firings could compromise a successful intraoral color match. In-vestigators did not provide detail on the color of the core ceramics. This is important, given that most zirconium specimens are opaque white, and lithium disilicate glass ceramic can be heat pressed in multiple shades. Fi-

nally, without a control of a fired, un- veneered core specimen, the true influ-ence of the core on the color change cannot be determined.

Removable partial dentures

Component removable partial dentures are fabricated in segments and assembled on a final cast. The possible advantage of a passive fit has always been countered by the dif-ficulty in maintaining passivity and strength when joining the units. Two studies addressed these issues. An in vitro analysis was undertaken to mea-sure distortions in cobalt-chromium frameworks after laser welding.152 A Kennedy Class III mandibular arch was reproduced in a refractory final cast from which 5 frameworks were cast. Measuring points were defined on a measuring base and the fit of the casting was evaluated with an optical microscope in 3 axes. Each casting was cut in the middle of both eden-tulous spans and reseated. The seg-ments were joined with acrylic resin (GC Pattern Resin; GC America), and a welding cast was poured against the framework. The joint was prepared and laser welded. The specimens were returned to the final cast for fi-nal optical measurements. The results indicate that the use of laser welding can maintain an accurate fit of the framework. The authors highlighted the significant increase in cost associ-ated with the laser welding procedure as compared to casting alone.

The torsional strength, ductility, and fracture behavior of titanium al-loy, commercially pure titanium, and cobalt-chromium after laser welding was compared in an interesting in vit-ro investigation.153 Fifteen dumbbell-shaped specimens of each metal were cast. The specimens were divided into 3 groups: unwelded, welded with 200V of laser voltage, and welded with 260V of laser voltage. The laser weld-ing was conducted with a Nd:YAG unit. The welded specimens were cut in half and then laser welded at the appropriate voltage. All of the speci-

mens were then tested with a multiax-is hydraulic unit until failure. The frac-tured specimens were observed under a scanning electron microscope for fracture characteristics. The results indicated that the welded joints in both titanium groups were as strong as in the unwelded group. The Co-Cr welded groups abruptly failed at the weld joint, resulting in significantly lower torsional strength compared to that of the unwelded casting. All of the titanium castings broke outside of the weld. The Co-CR castings failed within the welded joint. These failures demonstrated a brittle fracture char-acteristic under SEM.

Impression materials

Poor impression quality is a con-cern for both restorative dentists and dental laboratories. A randomized controlled clinical trial was conduct-ed on the reproduction of finish lines during clinical impression making with polyether monophase, 1-step vinyl polysiloxane (VPS), and 2-step putty-wash VPS impression materials.154 Im-pressions on 48 patients requiring a posterior single crown or short-span fixed prosthesis were evaluated for ac-curacy of the finish line reproduction. Plaque index, probing depth, bleed-ing on probing, and gingival index were recorded as independent param-eters for evaluation. The same inves-tigator made all of the impressions. A dual-cord technique was used with aluminum chloride chemical astrin-gent. Three impressions were made of each tooth with the materials used in random order for each subject. None of the impressions were repeated, re-gardless of the quality. Investigators recorded bleeding during impression making and blood in the impression. If investigators control the field to be impressed more carefully, it may be possible to determine if the choice of impression technique or sulcus con-trol is the key to providing a clinically acceptable reproduction of the finish line. Definitive casts were prepared from the impressions and the prepared

tooth and adjacent teeth digitally scanned. The finish line reproduction was the only outcome measured. The cast from the 1-stage VPS impression was chosen as the reference, and 3-D deviations from it were evaluated. The results showed that the 1-stage VPS impression is the most accurate. The monophase polyether reproduced fin-ish lines significantly more accurately than the 2-stage putty-wash VPS tech-nique. Several factors weakened this study, the greatest of which was that the 1-stage impression was chosen as the control. The study may only com-pare the results of the other materials against a 1-stage technique, and pro-vides no proof that any impression adequately reproduced the intraoral finish line. The study does, however, bring into question the accuracy of a 2-stage putty-wash technique, given the comparatively poor detail repro-duction. As expected, blood in the field or in the impression affected the accuracy.

Another project investigated the depth of reproduction with sulcus width and material mixing techniques as variables.155 Researchers created a steel master die with an adjustable artificial sulcus from reversible hy-drocolloid. The sulcus depth was a constant 2 mm. Sulcus widths tested varied: 50, 100, or 200 µm. Impres-sions with 1 vinyl polysiloxane (VPS) (Flexitime; Heraeus Kulzer), 2 poly-ether (PE) (Impregum; 3M ESPE, and P2 Polyether; Heraeus Kulzer) and 1 hybrid VPS/PE elastomer (FUS) (Fu-sion; GC Corp) were made using a single-mix or double-mix technique. The single-mix was made with the light-body or monophase pastes only. The double-mix was produced with a light-body wash and a monophase or heavy-body tray material. Repro-duction of the sulcus depth and de-tail was determined by 3-dimensional laser topography of the impressions. Analysis by a 3-way ANOVA indicated that the impression material, impres-sion technique, sulcus width, and their interactions were all significantly different. At a 200-µm width, VPS

and Impregum reproduced the total depth of the sulcus equally as well and significantly better than FUS and P2 Polyether, which were not signifi-cantly different. The impression mix techniques provided only a small sig-nificant difference between VPS and FUS. For a sulcus width of 100 µm, all of the variables were significantly different. Impregum reproduced the sulcus depth better than VPS and FUS, which were both significantly better than P2 Polyether. The depth of reproduction was also impacted by the mixing technique. A double-mix technique was better for all materi-als. Finally, at the 50-µm-wide sulci, the materials, techniques, and their interactions were significantly differ-ent. Impregum reproduced detail to a greater depth than FUS and VPS. The P2 Polyether showed the poorest reproduction. The double-mix tech-nique was again superior to either sin-gle-mix technique. All materials pro-duced poorer reproduction and more variation with smaller sulcus widths. The results demonstrated that with a suitable retraction technique that opens the sulcus to a width of 0.2 mm or greater, a clinically acceptable impression may be fabricated, irre-spective of the material or technique. The investigators concluded that the accuracy of the impressions is more dependent on the impression mate-rial and the mixing technique when there is insufficient retraction or when time delay after removal of the retrac-tion cord has caused the sulcus to col-lapse.

Fixed prosthodontics

A clinical study investigated the internal fit and marginal accuracy of zirconium 4-unit all-ceramic fixed partial denture (FPD) frameworks.156 Twenty-four posterior 4-unit FPDs were fabricated from a semisintered blank zirconia material using com-mercially available computer-aided design/computer-aided manufac-turing (CAD/CAM) methods. The frameworks were veneered with Lava



37July 2009


structure with micromechanical reten-tion of the resin and an acid-etched roughened ceramic surface. An in vit-ro study of the bond strength of 3 zir-conium veneering ceramics: Cerabien CZR (Noritake, Aichi, Japan), Lava Ce-ram (3M ESPE), and Zirox (Wieland Dental Systems, Inc, Danbury, Conn), and 4 traditional veneering ceramics: Creation (Jensen Industries, North Haven, Conn), IPS d.Sign (Ivoclar Vivadent), Noritake EX-3 (Noritake), and Reflex (Wieland Dental Systems, Inc) was conducted to determine if conventional ceramic and zirconium veneering ceramic react similarly to acid etching.150 Specimens of each of the ceramics were etched with hydro-fluoric acid following manufacturers’ specifications. The etched specimens were microscopically evaluated. The investigators found a significant dif-ference in the surface roughness of all tested groups. Two of the traditional ceramics (Cerabien CZR and Reflex) produced a surface roughness signifi-cantly higher than the zirconia speci-mens. Zirox was slightly rougher than zirconium and IPS d.Sign created the same roughness as the zirconium specimens. The zirconium ceram-ics all demonstrated similar surface roughness after etching. The results showed that they produced smooth surfaces with some grooves. A silane solution was applied for 60 seconds, air dried, and then an adhesive bond-ing agent was added. The ceramic specimens were bonded to prepared enamel specimens using a light-po-lymerized resin cement. Shear load was applied in a universal testing ma-chine until failure. The average bond strengths were reported. The highest mean shear bond strength was from the traditional ceramics Cerabien CZR and Reflex, which were 50-60% greater than the weakest mean bond strength from a zirconium veneering ceramic. While the etch patterns on zirconia produced a smoother sur-face, some of the zirconium ceram-ics matched the bond strength of the weakest conventional ceramic, IPS d.Sign. The authors concluded that

the bond strength of some of the zir-conium ceramics was too weak to be indicated for use in bonded ceramics, and laboratories must choose the zir-conium veneering ceramic carefully to ensure a proper bond.

The impact of repeated firings on the value and color of a restora-tion fabricated with lithium disilicate glass ceramic (IPS e.max Press; Ivoclar Vivadent) and zirconium oxide (DC-Zirkon; DCS Dental AG, Allschwil, Switzerland) was tested.151 Thirty 4-mm discs with a core thickness of 1 mm were fabricated. An A1-colored veneer ceramic with a thickness of 0.5, 1.0, or 1.5 mm was fired to the discs. The firings were performed ei-ther 3, 5, 7, or 9 times. At each inter-val, the color and value were evalu-ated with a spectrophotometer and compared to the other specimens. The results showed that an increase in firings yielded an increase in value for both cores. As the veneering ceramic increased in thickness, the bright-ness decreased for both cores, result-ing in darker specimens. The chroma increased for the 0.5-mm IPS e.max Press specimens but not for the 1-mm specimen. At 1.5 mm, only the blue-yellow chroma increased. For the zirconium specimens, the red-green value decreased with repeated firings, except for the 1.5-mm specimens, for which it increased. The blue-yellow value increased for the 0.5-mm-thick and 1.5-mm-thick zirconium speci-mens, but there was no change in this value in the 1.0-mm-thick specimens. The mean color change for repeated firings and different ceramic thick-nesses for a zirconium framework was below the color change units rated as a match in the oral environment. However, the color change was higher for IPS e.max Press, indicating that extended firings could compromise a successful intraoral color match. In-vestigators did not provide detail on the color of the core ceramics. This is important, given that most zirconium specimens are opaque white, and lithium disilicate glass ceramic can be heat pressed in multiple shades. Fi-

nally, without a control of a fired, un- veneered core specimen, the true influ-ence of the core on the color change cannot be determined.

Removable partial dentures

Component removable partial dentures are fabricated in segments and assembled on a final cast. The possible advantage of a passive fit has always been countered by the dif-ficulty in maintaining passivity and strength when joining the units. Two studies addressed these issues. An in vitro analysis was undertaken to mea-sure distortions in cobalt-chromium frameworks after laser welding.152 A Kennedy Class III mandibular arch was reproduced in a refractory final cast from which 5 frameworks were cast. Measuring points were defined on a measuring base and the fit of the casting was evaluated with an optical microscope in 3 axes. Each casting was cut in the middle of both eden-tulous spans and reseated. The seg-ments were joined with acrylic resin (GC Pattern Resin; GC America), and a welding cast was poured against the framework. The joint was prepared and laser welded. The specimens were returned to the final cast for fi-nal optical measurements. The results indicate that the use of laser welding can maintain an accurate fit of the framework. The authors highlighted the significant increase in cost associ-ated with the laser welding procedure as compared to casting alone.

The torsional strength, ductility, and fracture behavior of titanium al-loy, commercially pure titanium, and cobalt-chromium after laser welding was compared in an interesting in vit-ro investigation.153 Fifteen dumbbell-shaped specimens of each metal were cast. The specimens were divided into 3 groups: unwelded, welded with 200V of laser voltage, and welded with 260V of laser voltage. The laser weld-ing was conducted with a Nd:YAG unit. The welded specimens were cut in half and then laser welded at the appropriate voltage. All of the speci-

mens were then tested with a multiax-is hydraulic unit until failure. The frac-tured specimens were observed under a scanning electron microscope for fracture characteristics. The results indicated that the welded joints in both titanium groups were as strong as in the unwelded group. The Co-Cr welded groups abruptly failed at the weld joint, resulting in significantly lower torsional strength compared to that of the unwelded casting. All of the titanium castings broke outside of the weld. The Co-CR castings failed within the welded joint. These failures demonstrated a brittle fracture char-acteristic under SEM.

Impression materials

Poor impression quality is a con-cern for both restorative dentists and dental laboratories. A randomized controlled clinical trial was conduct-ed on the reproduction of finish lines during clinical impression making with polyether monophase, 1-step vinyl polysiloxane (VPS), and 2-step putty-wash VPS impression materials.154 Im-pressions on 48 patients requiring a posterior single crown or short-span fixed prosthesis were evaluated for ac-curacy of the finish line reproduction. Plaque index, probing depth, bleed-ing on probing, and gingival index were recorded as independent param-eters for evaluation. The same inves-tigator made all of the impressions. A dual-cord technique was used with aluminum chloride chemical astrin-gent. Three impressions were made of each tooth with the materials used in random order for each subject. None of the impressions were repeated, re-gardless of the quality. Investigators recorded bleeding during impression making and blood in the impression. If investigators control the field to be impressed more carefully, it may be possible to determine if the choice of impression technique or sulcus con-trol is the key to providing a clinically acceptable reproduction of the finish line. Definitive casts were prepared from the impressions and the prepared

tooth and adjacent teeth digitally scanned. The finish line reproduction was the only outcome measured. The cast from the 1-stage VPS impression was chosen as the reference, and 3-D deviations from it were evaluated. The results showed that the 1-stage VPS impression is the most accurate. The monophase polyether reproduced fin-ish lines significantly more accurately than the 2-stage putty-wash VPS tech-nique. Several factors weakened this study, the greatest of which was that the 1-stage impression was chosen as the control. The study may only com-pare the results of the other materials against a 1-stage technique, and pro-vides no proof that any impression adequately reproduced the intraoral finish line. The study does, however, bring into question the accuracy of a 2-stage putty-wash technique, given the comparatively poor detail repro-duction. As expected, blood in the field or in the impression affected the accuracy.

Another project investigated the depth of reproduction with sulcus width and material mixing techniques as variables.155 Researchers created a steel master die with an adjustable artificial sulcus from reversible hy-drocolloid. The sulcus depth was a constant 2 mm. Sulcus widths tested varied: 50, 100, or 200 µm. Impres-sions with 1 vinyl polysiloxane (VPS) (Flexitime; Heraeus Kulzer), 2 poly-ether (PE) (Impregum; 3M ESPE, and P2 Polyether; Heraeus Kulzer) and 1 hybrid VPS/PE elastomer (FUS) (Fu-sion; GC Corp) were made using a single-mix or double-mix technique. The single-mix was made with the light-body or monophase pastes only. The double-mix was produced with a light-body wash and a monophase or heavy-body tray material. Repro-duction of the sulcus depth and de-tail was determined by 3-dimensional laser topography of the impressions. Analysis by a 3-way ANOVA indicated that the impression material, impres-sion technique, sulcus width, and their interactions were all significantly different. At a 200-µm width, VPS

and Impregum reproduced the total depth of the sulcus equally as well and significantly better than FUS and P2 Polyether, which were not signifi-cantly different. The impression mix techniques provided only a small sig-nificant difference between VPS and FUS. For a sulcus width of 100 µm, all of the variables were significantly different. Impregum reproduced the sulcus depth better than VPS and FUS, which were both significantly better than P2 Polyether. The depth of reproduction was also impacted by the mixing technique. A double-mix technique was better for all materi-als. Finally, at the 50-µm-wide sulci, the materials, techniques, and their interactions were significantly differ-ent. Impregum reproduced detail to a greater depth than FUS and VPS. The P2 Polyether showed the poorest reproduction. The double-mix tech-nique was again superior to either sin-gle-mix technique. All materials pro-duced poorer reproduction and more variation with smaller sulcus widths. The results demonstrated that with a suitable retraction technique that opens the sulcus to a width of 0.2 mm or greater, a clinically acceptable impression may be fabricated, irre-spective of the material or technique. The investigators concluded that the accuracy of the impressions is more dependent on the impression mate-rial and the mixing technique when there is insufficient retraction or when time delay after removal of the retrac-tion cord has caused the sulcus to col-lapse.

Fixed prosthodontics

A clinical study investigated the internal fit and marginal accuracy of zirconium 4-unit all-ceramic fixed partial denture (FPD) frameworks.156 Twenty-four posterior 4-unit FPDs were fabricated from a semisintered blank zirconia material using com-mercially available computer-aided design/computer-aided manufac-turing (CAD/CAM) methods. The frameworks were veneered with Lava



39July 2009


Ceram (3M ESPE). After intraoral adjustment, the resultant internal space was documented by replica technique. A light-bodied silicone was applied as a disclosing medium and loaded from the occlusal with 20-N force. After removal, a heavy-bodied silicone was added to the retainers to stabilize the film in the abutment. The replicas were sectioned and cross-sections were measured at x50 mag-nification at 4 landmarks: marginal discrepancy, midaxial discrepancy, axio-occlusal transition, and centro-occlusally. The investigator random error was 8.9%, or twice the amount of other similar studies. The 4-unit FPDs demonstrated a mean mar-ginal discrepancy of 91 µm (SD ±58 µm) and a median of 77 µm. At the midaxial landmark, the mean discrep-ancy was 98 µm (SD ±45 µm) with a median of 87 µm. The mean of the axio-occlusal transition was 207 µm (SD ±215 µm) with a median of 167 µm. At the centro-occlusal landmark, a mean of 202 µm (SD ±181 µm) was measured, with a median of 170 µm. While molar and premolar abutments did not differ significantly from each other, it should be noted that molars showed greater inaccuracies than the premolars. The investigators con-cluded that the fit of zirconium 4-unit fixed partial dentures compares fa-vorably to the median fit of a 3-unit metal ceramic FPD and 3-unit zirco-nium FPDs. While this clinical study provides an evaluation of a novel use for a zirconium prosthesis, the large discrepancies in fit and significant standard deviations call into question the recommendation. Extreme values were possibly due to the larger milled framework and shrinkage that occurs in the sintering process, making the clinical reliability of fit questionable. While the zirconium framework occa-sionally meets the 100-µm marginal level of clinical acceptability, large internal gap widths and variations in the internal discrepancies may impact the stability of this all-ceramic resto-ration.

IMPLANT DENTISTRY

There were numerous articles re-lated to implant dentistry published in the peer-reviewed literature in 2008. A cursory search of PubMed referenced 1106 articles on this subject that were published in the past year. The major-ity of these publications were opinion or technique articles, clinical reports, or in vitro studies. There were numer-ous short-term (1 or 2 years) clinical studies, most of which had relatively small sample sizes and no controls. As has been the trend in recent years, a number of systematic reviews were published, some which are included in this review. While these systematic re-views often provide good information regarding specific questions related to the discipline of implant dentistry, they almost universally indicate signif-icant deficiencies in research design of available clinical trials, which limit the ability of the reviewers to form defini-tive conclusions.

One such example was a system-atic review that attempted to deter-mine the relative efficacy of various treatment modalities that have been advocated for the treatment of peri-implantitis.157 Periimplantitis is de-fined as plaque-induced progressive bone loss around osseointegrated im-plants observed on radiographs and coupled with clinical signs of infection of the periimplant soft tissues. The in-cidence of periimplantitis is generally underreported; it may be as high as 16% for machined implants in service more than 10 years and may be higher with rough-surfaced implants.

An initial search of the literature yielded 1304 possibly relevant titles; 13 of these publications were rigor-ously evaluated, and only 5 studies were deemed acceptable for the re-view. Sample size calculations were not done for any of the selected ran-domized clinical trials (RCTs) and all had relatively small sample sizes. It was concluded that the risk for bias was high for all included studies. As a result of the substantial methodologi-cal discrepancies amongst the stud-

ies, it was not feasible to conduct a meta-analysis.

The data were not sufficient to establish a gold-standard approach for the treatment of periimplantitis. The authors concluded that submu-cosal debridement alone may not be adequate for removal of the bacterial load from the surfaces of implants with periimplant pockets of 5 mm or more. Mechanical debridement coupled with the use of minocycline appeared to have an improved treat-ment outcome compared to debride-ment along with chlorhexidine in the short term. Guided bone regenera-tion or use of a bone substitute can be efficacious, but more data are needed to determine optimum regenerative techniques.

Another systematic review was conducted with the objective to iden-tify the most effective interventions for treating periimplantitis around os-seointegrated dental implants.158 The authors evaluated data from 7 clinical trials. Six of the 7 trials were consid-ered to be at high risk for bias. It was concluded that while most currently used protocols for the treatment of periimplantitis may be effective in the short term, there is little reliable evi-dence suggesting which intervention might be the most efficacious.

In implant sites with 50% or great-er bone loss, the addition of topical antibiotic therapy to mechanical deb-ridement resulted in a reduced pocket probing depth (PPD) of 0.6 mm over 4 months. Four of the evaluated trials demonstrated that mechanical debri-dement alone, which is the simplest approach, provided results that were equivalent to more complex and ex-pensive therapies. However, in all of these studies, sample sizes were small and follow-up times were short, so the conclusions need to be consid-ered with caution.

Results of implant therapy in pa-tients with a history of periodontitis have been of interest to clinicians. A systematic review was done to deter-mine the outcome of implant therapy in periodontitis-susceptible patients

compared to patients with no history of periodontal disease.159 Only trials with a follow-up of 1 year or more were considered for inclusion in the review.

It was determined that there was no statistically significant difference in the survival of implant superstruc-tures or implants in periodontitis-sus-ceptible or nonperiodontitis subjects evaluated at several different time frames. More subjects in the perio-dontitis-susceptible group developed periimplantitis than in the nonperio-dontitis group. Furthermore, the in-cidence of periimplantitis was higher in patients with aggressive periodon-titis as opposed to those with chronic periodontitis. Greater periimplant bone loss was seen in the periodonti-tis-susceptible group.

The author concluded that implant treatment in periodontitis-susceptible patients is not contraindicated. How-ever, the higher demonstrated inci-dence of periimplantitis may reduce the potential longevity of the implant treatment. When treating periodon-titis-susceptible patients, it is recom-mended that all severely compro-mised teeth be extracted some time before implant placement and that treatment for the periodontitis should be completed prior to implant place-ment.

Another systematic review was completed to determine implant out-comes in partially dentate patients who had been treated for periodontitis compared with periodontally healthy patients.160 Trials with a follow-up of 6 months or more were considered for inclusion. Results from 9 clinical trials were evaluated. Almost all stud-ies were rated at a high risk for bias.

Higher survival and success rates were recorded for nonperiodontitis subjects than for subjects previously treated for periodontitis. The non-periodontitis group also had less peri-implant bone loss and a lower inci-dence of periimplantitis. The authors suggest that all periodontal therapy be completed prior to initiating im-plant therapy and that these patients

require continuous monitoring and maintenance, but present limited data in support of those recommen-dations.

Interpretation of the data in the preceding systematic reviews is con-founded by the lack of data available on the smoking habits of the subjects in the included trials. Because smok-ing is strongly associated with perio-dontitis, implant failure, and periim-plantitis, and because there was little information on smoking patterns of the subjects, the relative roles of peri-odontitis and of smoking in the find-ings is unknown.

There continues to be consider-able interest in protocols involving immediate and early loading of dental implants. Outcomes with traditional delayed loading (2.5-6 months) have been excellent, but this approach re-sults in prolonged treatment times and frustration for many patients.

One RCT compared outcomes with wide-bodied implants in the mo-lar area that were restored with imme-diate and delayed loading.161 Fifteen implants were placed in each group. The delayed group implants were re-stored 3 to 4 months after implant placement. The immediate loading group received provisional restora-tions loaded in maximum intercuspa-tion position (MIP) with no contact in lateral or protrusive excursions within 24 hours of implant placement.

Bone levels were evaluated radio-graphically at the time of implant placement and at 1 year. Immediately loaded implants had an average loss of 0.77 mm at 1 year, while the de-layed loading group of implants had a mean bone loss of 1.2 mm after 1 year. The difference was statistically significant (P=.22) No implants were lost at 1 year in the delayed loading group, while 1 implant was lost in the early loading group.

The authors concluded that imme-diate loading of wide-bodied implants in the mandibular molar region was a viable option. Readers are cautioned that this study has a small sample size (n=15) and short time of observation

(1 year).A prospective multicenter study

evaluated outcomes with 170 1-stage smooth-surfaced mandibular im-plants restored with early loading.162 The definitive prostheses were placed within 6 weeks after implant place-ment. All implants were placed in the anterior mandible. One hundred and twenty implants in 30 patients were restored with mandibular overden-tures, and 50 implants in 10 patients were restored with fixed prostheses. Prostheses and implants were evalu-ated clinically and radiographically at 1, 3, and 5 years.

Twelve implants failed in 6 pa-tients, and the cumulative implant survival rate was 92.9% at 5 years. Three implants were mobile but func-tioning at 5 years, resulting in a cumu-lative success rate of 91%. Mean bone remodeling was less than 0.1 mm per year after the first year of loading, and the mean marginal bone level apical to the implant collar was 0.66 mm.

The authors concluded that early loading of implants in the anterior mandible was successful for the ma-jority of patients, and stable periim-plant conditions resulted. They spec-ulated that the slightly higher failure rate compared to that achieved with traditional loading protocols was due to generous inclusion criteria and the learning curve associated with a novel treatment procedure. Unfortu-nately, because the study had no con-trol group, any speculation regarding these results is merely speculation.

Immediate or early loading of den-tal implants can be recommended for implants placed in the anterior mandi-ble, but the efficacy of such protocols in the maxilla is not well documented in the long term. One RCT compared results of early and delayed loading with implant-supported complete-arch prostheses in the maxilla.163 An early-loading protocol (within 9 to 18 days of placement) was used with 16 subjects, and a delayed protocol (2.5 to 5.1 months after placement) was used with 8 subjects. Smokers were excluded from the study.



39July 2009


Ceram (3M ESPE). After intraoral adjustment, the resultant internal space was documented by replica technique. A light-bodied silicone was applied as a disclosing medium and loaded from the occlusal with 20-N force. After removal, a heavy-bodied silicone was added to the retainers to stabilize the film in the abutment. The replicas were sectioned and cross-sections were measured at x50 mag-nification at 4 landmarks: marginal discrepancy, midaxial discrepancy, axio-occlusal transition, and centro-occlusally. The investigator random error was 8.9%, or twice the amount of other similar studies. The 4-unit FPDs demonstrated a mean mar-ginal discrepancy of 91 µm (SD ±58 µm) and a median of 77 µm. At the midaxial landmark, the mean discrep-ancy was 98 µm (SD ±45 µm) with a median of 87 µm. The mean of the axio-occlusal transition was 207 µm (SD ±215 µm) with a median of 167 µm. At the centro-occlusal landmark, a mean of 202 µm (SD ±181 µm) was measured, with a median of 170 µm. While molar and premolar abutments did not differ significantly from each other, it should be noted that molars showed greater inaccuracies than the premolars. The investigators con-cluded that the fit of zirconium 4-unit fixed partial dentures compares fa-vorably to the median fit of a 3-unit metal ceramic FPD and 3-unit zirco-nium FPDs. While this clinical study provides an evaluation of a novel use for a zirconium prosthesis, the large discrepancies in fit and significant standard deviations call into question the recommendation. Extreme values were possibly due to the larger milled framework and shrinkage that occurs in the sintering process, making the clinical reliability of fit questionable. While the zirconium framework occa-sionally meets the 100-µm marginal level of clinical acceptability, large internal gap widths and variations in the internal discrepancies may impact the stability of this all-ceramic resto-ration.

IMPLANT DENTISTRY

There were numerous articles re-lated to implant dentistry published in the peer-reviewed literature in 2008. A cursory search of PubMed referenced 1106 articles on this subject that were published in the past year. The major-ity of these publications were opinion or technique articles, clinical reports, or in vitro studies. There were numer-ous short-term (1 or 2 years) clinical studies, most of which had relatively small sample sizes and no controls. As has been the trend in recent years, a number of systematic reviews were published, some which are included in this review. While these systematic re-views often provide good information regarding specific questions related to the discipline of implant dentistry, they almost universally indicate signif-icant deficiencies in research design of available clinical trials, which limit the ability of the reviewers to form defini-tive conclusions.

One such example was a system-atic review that attempted to deter-mine the relative efficacy of various treatment modalities that have been advocated for the treatment of peri-implantitis.157 Periimplantitis is de-fined as plaque-induced progressive bone loss around osseointegrated im-plants observed on radiographs and coupled with clinical signs of infection of the periimplant soft tissues. The in-cidence of periimplantitis is generally underreported; it may be as high as 16% for machined implants in service more than 10 years and may be higher with rough-surfaced implants.

An initial search of the literature yielded 1304 possibly relevant titles; 13 of these publications were rigor-ously evaluated, and only 5 studies were deemed acceptable for the re-view. Sample size calculations were not done for any of the selected ran-domized clinical trials (RCTs) and all had relatively small sample sizes. It was concluded that the risk for bias was high for all included studies. As a result of the substantial methodologi-cal discrepancies amongst the stud-

ies, it was not feasible to conduct a meta-analysis.

The data were not sufficient to establish a gold-standard approach for the treatment of periimplantitis. The authors concluded that submu-cosal debridement alone may not be adequate for removal of the bacterial load from the surfaces of implants with periimplant pockets of 5 mm or more. Mechanical debridement coupled with the use of minocycline appeared to have an improved treat-ment outcome compared to debride-ment along with chlorhexidine in the short term. Guided bone regenera-tion or use of a bone substitute can be efficacious, but more data are needed to determine optimum regenerative techniques.

Another systematic review was conducted with the objective to iden-tify the most effective interventions for treating periimplantitis around os-seointegrated dental implants.158 The authors evaluated data from 7 clinical trials. Six of the 7 trials were consid-ered to be at high risk for bias. It was concluded that while most currently used protocols for the treatment of periimplantitis may be effective in the short term, there is little reliable evi-dence suggesting which intervention might be the most efficacious.

In implant sites with 50% or great-er bone loss, the addition of topical antibiotic therapy to mechanical deb-ridement resulted in a reduced pocket probing depth (PPD) of 0.6 mm over 4 months. Four of the evaluated trials demonstrated that mechanical debri-dement alone, which is the simplest approach, provided results that were equivalent to more complex and ex-pensive therapies. However, in all of these studies, sample sizes were small and follow-up times were short, so the conclusions need to be consid-ered with caution.

Results of implant therapy in pa-tients with a history of periodontitis have been of interest to clinicians. A systematic review was done to deter-mine the outcome of implant therapy in periodontitis-susceptible patients

compared to patients with no history of periodontal disease.159 Only trials with a follow-up of 1 year or more were considered for inclusion in the review.

It was determined that there was no statistically significant difference in the survival of implant superstruc-tures or implants in periodontitis-sus-ceptible or nonperiodontitis subjects evaluated at several different time frames. More subjects in the perio-dontitis-susceptible group developed periimplantitis than in the nonperio-dontitis group. Furthermore, the in-cidence of periimplantitis was higher in patients with aggressive periodon-titis as opposed to those with chronic periodontitis. Greater periimplant bone loss was seen in the periodonti-tis-susceptible group.

The author concluded that implant treatment in periodontitis-susceptible patients is not contraindicated. How-ever, the higher demonstrated inci-dence of periimplantitis may reduce the potential longevity of the implant treatment. When treating periodon-titis-susceptible patients, it is recom-mended that all severely compro-mised teeth be extracted some time before implant placement and that treatment for the periodontitis should be completed prior to implant place-ment.

Another systematic review was completed to determine implant out-comes in partially dentate patients who had been treated for periodontitis compared with periodontally healthy patients.160 Trials with a follow-up of 6 months or more were considered for inclusion. Results from 9 clinical trials were evaluated. Almost all stud-ies were rated at a high risk for bias.

Higher survival and success rates were recorded for nonperiodontitis subjects than for subjects previously treated for periodontitis. The non-periodontitis group also had less peri-implant bone loss and a lower inci-dence of periimplantitis. The authors suggest that all periodontal therapy be completed prior to initiating im-plant therapy and that these patients

require continuous monitoring and maintenance, but present limited data in support of those recommen-dations.

Interpretation of the data in the preceding systematic reviews is con-founded by the lack of data available on the smoking habits of the subjects in the included trials. Because smok-ing is strongly associated with perio-dontitis, implant failure, and periim-plantitis, and because there was little information on smoking patterns of the subjects, the relative roles of peri-odontitis and of smoking in the find-ings is unknown.

There continues to be consider-able interest in protocols involving immediate and early loading of dental implants. Outcomes with traditional delayed loading (2.5-6 months) have been excellent, but this approach re-sults in prolonged treatment times and frustration for many patients.

One RCT compared outcomes with wide-bodied implants in the mo-lar area that were restored with imme-diate and delayed loading.161 Fifteen implants were placed in each group. The delayed group implants were re-stored 3 to 4 months after implant placement. The immediate loading group received provisional restora-tions loaded in maximum intercuspa-tion position (MIP) with no contact in lateral or protrusive excursions within 24 hours of implant placement.

Bone levels were evaluated radio-graphically at the time of implant placement and at 1 year. Immediately loaded implants had an average loss of 0.77 mm at 1 year, while the de-layed loading group of implants had a mean bone loss of 1.2 mm after 1 year. The difference was statistically significant (P=.22) No implants were lost at 1 year in the delayed loading group, while 1 implant was lost in the early loading group.

The authors concluded that imme-diate loading of wide-bodied implants in the mandibular molar region was a viable option. Readers are cautioned that this study has a small sample size (n=15) and short time of observation

(1 year).A prospective multicenter study

evaluated outcomes with 170 1-stage smooth-surfaced mandibular im-plants restored with early loading.162 The definitive prostheses were placed within 6 weeks after implant place-ment. All implants were placed in the anterior mandible. One hundred and twenty implants in 30 patients were restored with mandibular overden-tures, and 50 implants in 10 patients were restored with fixed prostheses. Prostheses and implants were evalu-ated clinically and radiographically at 1, 3, and 5 years.

Twelve implants failed in 6 pa-tients, and the cumulative implant survival rate was 92.9% at 5 years. Three implants were mobile but func-tioning at 5 years, resulting in a cumu-lative success rate of 91%. Mean bone remodeling was less than 0.1 mm per year after the first year of loading, and the mean marginal bone level apical to the implant collar was 0.66 mm.

The authors concluded that early loading of implants in the anterior mandible was successful for the ma-jority of patients, and stable periim-plant conditions resulted. They spec-ulated that the slightly higher failure rate compared to that achieved with traditional loading protocols was due to generous inclusion criteria and the learning curve associated with a novel treatment procedure. Unfortu-nately, because the study had no con-trol group, any speculation regarding these results is merely speculation.

Immediate or early loading of den-tal implants can be recommended for implants placed in the anterior mandi-ble, but the efficacy of such protocols in the maxilla is not well documented in the long term. One RCT compared results of early and delayed loading with implant-supported complete-arch prostheses in the maxilla.163 An early-loading protocol (within 9 to 18 days of placement) was used with 16 subjects, and a delayed protocol (2.5 to 5.1 months after placement) was used with 8 subjects. Smokers were excluded from the study.



41July 2009


A total of 142 implants were placed, 95 in the early loading group and 47 in the delayed loading group. Either 5 or 6 implants were used in each subject to support a complete-arch prosthesis. Subjects were recalled after 1, 3, and 5 years of loading for clinical and radiographic evaluation.

In the early loading group, 5.3% (5) of the implants were lost at 5 years. Also at 5 years, 4.3% (2) of the implants were lost in the delayed load-ing group. There were no differences in implant stability. The early load-ing group had more bone loss (0.8 mm versus 0.3 mm) than the delayed loading group. The main technical complications were tooth fractures from the acrylic resin denture base. It was concluded that this RCT showed no important differences in treatment outcome between early and delayed loading of implants in the edentulous maxilla after 5 years of function.

An interesting case-control study evaluated tooth and implant loss in refractory periodontal patients over a mean period of 13.4 years (range, 8 to 19 years).164 The control group was composed of matched age/gen-der patients from the same specialty practice.

Individuals who continue to suffer from progressive periodontal deterio-ration in spite of regular maintenance are classified as having refractory periodontal disease. Only 2.2% (27) of patients in the specialty practice conducting the study met the criteria for inclusion in the refractory group. Predictive factors for the refractory group were heavy smoking (>20 ciga-rettes/day), stress, and having a fam-ily history of periodontitis.

Each refractory subject lost a mean of 10.4 teeth (range, 4 to 16) over the term of the study. This represented 50% of the teeth present at baseline. Refractory subjects lost 0.78 teeth per year, which was 35 times greater than tooth loss in the control group.

Implants were placed in 14 of the refractory subjects, and 9 of these (64%) lost at least 1 implant. In total, 17 (25%) of the implants placed in the

refractory group were lost. Fourteen of these failed to integrate. Another 5 implants developed periimplanti-tis and 3 of these implants were lost. None of the implants placed in the control group were lost. While this case-control study includes a relative-ly small sample size, results indicate that implant therapy should be pro-vided with caution for patients diag-nosed with progressive periodontitis associated with continued tooth loss.

There continues to be consider-able interest and confusion related to any type of dental surgery in pa-tients taking bisphosphonates. There appears to be some evidence that patients taking intravenous bisphos-phonates are at higher risk of devel-oping osteonecrosis of the jaw (ONJ) after oral surgery, but a direct causal relationship has yet to be determined. One retrospective study attempted to determine outcomes of bone graft-ing and implant placement in a group of subjects taking oral bisphospho-nates.165

A group of 42 subjects who had taken oral bisphosphonate medica-tion prior to receiving implants or bone grafts were identified. The sub-jects received 100 implants and 68 bone grafts. The subjects had been taking oral bisphosphonate medica-tion from 6 months to 11 years prior to surgery, and most continued to take the medication through the fol-low-up period, which ranged from 4 months to over 7 years.

Of the 100 implants placed, 5 failed, yielding a success rate of 95%, which was comparable to success rates achieved in many studies. Three of the failures were in the posterior maxilla and 1 was in a heavy smoker. All failures occurred before functional loading. No patients showed any signs or symptoms of ONJ. All of the usual periodontal parameters were within normal limits. Although the sample size in this study is relatively small, it does lend credence to the commonly held concept that patients taking oral bisphosphonates are not at high risk for developing ONJ and that such pa-

tients can be the recipients of success-ful implant and bone graft surgery.

Another retrospective analysis of implant placement outcomes in pa-tients taking oral bisphosphonates was conducted.166 A total of 468 im-plants were placed in 115 subjects who were taking oral bisphospho-nates. Only 2 of the implants failed to integrate, yielding a success rate of 99.6%. There was no evidence of bisphosphonate-associated ONJ in any of the patients. The authors con-cluded that guidelines for treatment of dental patients receiving intrave-nous bisphosphonate treatments should be different than for patients taking the oral formulations of these medications. Given the small sample sizes in both of the last 2 studies, cli-nicians would be wise to proceed with caution when treating patients taking oral bisphosphonates and in need of implants and/or bone grafts. Clearly treatment can be accomplished suc-cessfully, but many questions remain unanswered. It is possible that the duration of bisphosphonate therapy may influence results or that there are confounding variables, such as smok-ing or concomitant prednisone ther-apy, which also may have an effect. Clearly this subject requires more investigation before clear, unambiva-lent guidelines can be suggested.

One interesting systematic review asked the question: “Does systemic prophylactic antibiotic administra-tion improve the outcome of implant therapy versus no antibiotic/placebo administration”?167 Only 2 acceptable RCTs were identified. One of these RCTs compared a protocol of 2 g of preoperative amoxicillin versus a pla-cebo (316 subjects). The other RCT compared a protocol of 2 g of amoxi-cillin preoperatively plus 500 mg of amoxicillin 4 times/day for 2 days postoperatively, versus no antibiotics (80 subjects).

The meta-analysis of the 2 tri-als demonstrated a statistically sig-nificantly higher number of subjects experiencing implant failures in the group not receiving antibiotics. There

were no differences in the other out-comes evaluated.

The authors concluded that there is some evidence that 2 g of amoxi-cillin given orally preoperatively sig-nificantly reduces failures of dental implants. It remains unclear whether postoperative antibiotics are ben-eficial, and which antibiotic might be the most effective.

Another systematic review evalu-ated the incidence of abutment screw loosening in single implant restora-tions.168 After initially identifying 1526 articles, the review was conducted us-ing 27 studies. Internal and external connection groups were examined separately. The external connection group consisted of 12 studies and 586 single implant restorations for a mean follow-up time of between 3 and 5 years. The number of complication-free single implant restorations after 3 years was 97.3%.

The internal connection group comprised 15 studies with 1113 sin-gle implant restorations for a mean follow-up time of 3 to 10 years. The percentage of complication-free sin-gle implant restorations after 3 years was 97.6%. The results between the groups were not statistically signifi-cant.

It was concluded that abutment screw loosening is a rare event in sin-gle implant restorations, regardless of the implant-abutment connection, provided that proper antirotational features and torque are used.

Given that achieving accurate de-livery of torque to implant screws is important to prevent screw loos-ening, one timely study evaluated the accuracy of 2 different types of torque drivers.169 Five new mechani-cal torque-limiting devices (MTLDs) were obtained from 6 different manu-facturers, and forces were applied to the precalibrated torque values. Three of the devices were of the friction style and the other 3 were spring loaded. The peak torque value registered by a digital torque gauge was recorded, and the procedure was repeated 50 times for each MTLD.

Statistical analysis used repeated-measures ANOVA (α=.05) to assess the accuracy of the MTLDs in deliv-ering target torque values. Both the mean absolute difference and the mean percentage deviation between measured torque values and target torque values differed significantly for the friction-style MTLDs and the spring-style MTLDs. The data revealed that the spring-style MTLDs were sig-nificantly more accurate than friction-style MTLDs in achieving their target torque values.

A systematic review was conducted to determine if there is a certain num-ber of implants necessary to retain an overdenture.170 The literature was ex-tensively searched, and, using specific inclusion and exclusion criteria for the studies, 11 studies were selected for inclusion in the review. Three of these studies concerned maxillary overden-tures and 8 involved mandibular over-dentures.

Considering the fundamental truth that no single treatment modal-ity for tooth replacement can meet all patient requirements, the review concluded that in the maxilla, patient satisfaction with implant-supported overdentures was not significantly higher than with new conventional complete dentures. Overdentures in the maxilla should only be used when anatomical or physiological condi-tions compromise the retention and stability of a conventional complete denture. The review also concluded that if an overdenture is fabricated in the maxilla, it should be implant-retained or implant-supported, and 4 implants should be placed.

In the mandible, success rates of implants and prostheses and patient satisfaction are not dependent on the number of implants used. Con-sidering economic and maintenance factors, the use of 2 implants and a connecting bar seems to be the best option for mandibular implant-re-tained overdentures.

An excellent systematic review was conducted to determine the 5-year survival rate of implant-supported

single crowns (SCs) and to determine the incidence of both biological and technical complications.171 Ultimate-ly, data from 26 clinical studies were used to conduct a meta-analysis.

Five-year survival of implants sup-porting single crowns was 96.8%, while the survival rate of single crowns supported by implants after 5 years was 94.5%. The survival rate of metal ceramic crowns at 5 years (95.4%) was significantly superior to the sur-vival rate of all-ceramic crowns, which was 91.2%.

The incidence of periimplantitis at 5 years was 9.7%, and 6.3% of im-plants had bone loss exceeding 2 mm. For other complications, implant fracture rate was 0.14%, screw or abutment loosening was 12.7%, and the incidence of ceramic or veneer fractures was 4.5%. Clearly, survival rates for both implants and implant-supported SCs were high at 5 years, but both biological and technical complications occur frequently.

A 20-year follow-up was published on a group of 48 consecutive patients treated with implants in the early 1980s.172 Nineteen of the patients had died, and 21 patients with 23 im-plant-supported prostheses could be examined clinically and radiographi-cally. All patients had been treated ad modem Brånemark with a 2-stage surgical procedure. Implant connec-tions were made 3 to 4 months after placement in the mandible and after a minimum of 6 months in the maxilla. Prostheses were fabricated with gold alloy and acrylic resin denture teeth.

A total of 123 implants (27 in the maxilla, 96 in the mandible) had been placed in these 21 patients. Only 1 implant was lost, yielding a 20-year survival rate of 99.2%. Mean bone loss at 20 years was 0.53 mm. The incidence of periimplantitis and other complications was low. These results are outstanding, but readers are cau-tioned that they may not be extrapo-lated to the abbreviated surgical and loading protocols currently used. The implants used with these patients also had machined surfaces, which may



41July 2009


A total of 142 implants were placed, 95 in the early loading group and 47 in the delayed loading group. Either 5 or 6 implants were used in each subject to support a complete-arch prosthesis. Subjects were recalled after 1, 3, and 5 years of loading for clinical and radiographic evaluation.

In the early loading group, 5.3% (5) of the implants were lost at 5 years. Also at 5 years, 4.3% (2) of the implants were lost in the delayed load-ing group. There were no differences in implant stability. The early load-ing group had more bone loss (0.8 mm versus 0.3 mm) than the delayed loading group. The main technical complications were tooth fractures from the acrylic resin denture base. It was concluded that this RCT showed no important differences in treatment outcome between early and delayed loading of implants in the edentulous maxilla after 5 years of function.

An interesting case-control study evaluated tooth and implant loss in refractory periodontal patients over a mean period of 13.4 years (range, 8 to 19 years).164 The control group was composed of matched age/gen-der patients from the same specialty practice.

Individuals who continue to suffer from progressive periodontal deterio-ration in spite of regular maintenance are classified as having refractory periodontal disease. Only 2.2% (27) of patients in the specialty practice conducting the study met the criteria for inclusion in the refractory group. Predictive factors for the refractory group were heavy smoking (>20 ciga-rettes/day), stress, and having a fam-ily history of periodontitis.

Each refractory subject lost a mean of 10.4 teeth (range, 4 to 16) over the term of the study. This represented 50% of the teeth present at baseline. Refractory subjects lost 0.78 teeth per year, which was 35 times greater than tooth loss in the control group.

Implants were placed in 14 of the refractory subjects, and 9 of these (64%) lost at least 1 implant. In total, 17 (25%) of the implants placed in the

refractory group were lost. Fourteen of these failed to integrate. Another 5 implants developed periimplanti-tis and 3 of these implants were lost. None of the implants placed in the control group were lost. While this case-control study includes a relative-ly small sample size, results indicate that implant therapy should be pro-vided with caution for patients diag-nosed with progressive periodontitis associated with continued tooth loss.

There continues to be consider-able interest and confusion related to any type of dental surgery in pa-tients taking bisphosphonates. There appears to be some evidence that patients taking intravenous bisphos-phonates are at higher risk of devel-oping osteonecrosis of the jaw (ONJ) after oral surgery, but a direct causal relationship has yet to be determined. One retrospective study attempted to determine outcomes of bone graft-ing and implant placement in a group of subjects taking oral bisphospho-nates.165

A group of 42 subjects who had taken oral bisphosphonate medica-tion prior to receiving implants or bone grafts were identified. The sub-jects received 100 implants and 68 bone grafts. The subjects had been taking oral bisphosphonate medica-tion from 6 months to 11 years prior to surgery, and most continued to take the medication through the fol-low-up period, which ranged from 4 months to over 7 years.

Of the 100 implants placed, 5 failed, yielding a success rate of 95%, which was comparable to success rates achieved in many studies. Three of the failures were in the posterior maxilla and 1 was in a heavy smoker. All failures occurred before functional loading. No patients showed any signs or symptoms of ONJ. All of the usual periodontal parameters were within normal limits. Although the sample size in this study is relatively small, it does lend credence to the commonly held concept that patients taking oral bisphosphonates are not at high risk for developing ONJ and that such pa-

tients can be the recipients of success-ful implant and bone graft surgery.

Another retrospective analysis of implant placement outcomes in pa-tients taking oral bisphosphonates was conducted.166 A total of 468 im-plants were placed in 115 subjects who were taking oral bisphospho-nates. Only 2 of the implants failed to integrate, yielding a success rate of 99.6%. There was no evidence of bisphosphonate-associated ONJ in any of the patients. The authors con-cluded that guidelines for treatment of dental patients receiving intrave-nous bisphosphonate treatments should be different than for patients taking the oral formulations of these medications. Given the small sample sizes in both of the last 2 studies, cli-nicians would be wise to proceed with caution when treating patients taking oral bisphosphonates and in need of implants and/or bone grafts. Clearly treatment can be accomplished suc-cessfully, but many questions remain unanswered. It is possible that the duration of bisphosphonate therapy may influence results or that there are confounding variables, such as smok-ing or concomitant prednisone ther-apy, which also may have an effect. Clearly this subject requires more investigation before clear, unambiva-lent guidelines can be suggested.

One interesting systematic review asked the question: “Does systemic prophylactic antibiotic administra-tion improve the outcome of implant therapy versus no antibiotic/placebo administration”?167 Only 2 acceptable RCTs were identified. One of these RCTs compared a protocol of 2 g of preoperative amoxicillin versus a pla-cebo (316 subjects). The other RCT compared a protocol of 2 g of amoxi-cillin preoperatively plus 500 mg of amoxicillin 4 times/day for 2 days postoperatively, versus no antibiotics (80 subjects).

The meta-analysis of the 2 tri-als demonstrated a statistically sig-nificantly higher number of subjects experiencing implant failures in the group not receiving antibiotics. There

were no differences in the other out-comes evaluated.

The authors concluded that there is some evidence that 2 g of amoxi-cillin given orally preoperatively sig-nificantly reduces failures of dental implants. It remains unclear whether postoperative antibiotics are ben-eficial, and which antibiotic might be the most effective.

Another systematic review evalu-ated the incidence of abutment screw loosening in single implant restora-tions.168 After initially identifying 1526 articles, the review was conducted us-ing 27 studies. Internal and external connection groups were examined separately. The external connection group consisted of 12 studies and 586 single implant restorations for a mean follow-up time of between 3 and 5 years. The number of complication-free single implant restorations after 3 years was 97.3%.

The internal connection group comprised 15 studies with 1113 sin-gle implant restorations for a mean follow-up time of 3 to 10 years. The percentage of complication-free sin-gle implant restorations after 3 years was 97.6%. The results between the groups were not statistically signifi-cant.

It was concluded that abutment screw loosening is a rare event in sin-gle implant restorations, regardless of the implant-abutment connection, provided that proper antirotational features and torque are used.

Given that achieving accurate de-livery of torque to implant screws is important to prevent screw loos-ening, one timely study evaluated the accuracy of 2 different types of torque drivers.169 Five new mechani-cal torque-limiting devices (MTLDs) were obtained from 6 different manu-facturers, and forces were applied to the precalibrated torque values. Three of the devices were of the friction style and the other 3 were spring loaded. The peak torque value registered by a digital torque gauge was recorded, and the procedure was repeated 50 times for each MTLD.

Statistical analysis used repeated-measures ANOVA (α=.05) to assess the accuracy of the MTLDs in deliv-ering target torque values. Both the mean absolute difference and the mean percentage deviation between measured torque values and target torque values differed significantly for the friction-style MTLDs and the spring-style MTLDs. The data revealed that the spring-style MTLDs were sig-nificantly more accurate than friction-style MTLDs in achieving their target torque values.

A systematic review was conducted to determine if there is a certain num-ber of implants necessary to retain an overdenture.170 The literature was ex-tensively searched, and, using specific inclusion and exclusion criteria for the studies, 11 studies were selected for inclusion in the review. Three of these studies concerned maxillary overden-tures and 8 involved mandibular over-dentures.

Considering the fundamental truth that no single treatment modal-ity for tooth replacement can meet all patient requirements, the review concluded that in the maxilla, patient satisfaction with implant-supported overdentures was not significantly higher than with new conventional complete dentures. Overdentures in the maxilla should only be used when anatomical or physiological condi-tions compromise the retention and stability of a conventional complete denture. The review also concluded that if an overdenture is fabricated in the maxilla, it should be implant-retained or implant-supported, and 4 implants should be placed.

In the mandible, success rates of implants and prostheses and patient satisfaction are not dependent on the number of implants used. Con-sidering economic and maintenance factors, the use of 2 implants and a connecting bar seems to be the best option for mandibular implant-re-tained overdentures.

An excellent systematic review was conducted to determine the 5-year survival rate of implant-supported

single crowns (SCs) and to determine the incidence of both biological and technical complications.171 Ultimate-ly, data from 26 clinical studies were used to conduct a meta-analysis.

Five-year survival of implants sup-porting single crowns was 96.8%, while the survival rate of single crowns supported by implants after 5 years was 94.5%. The survival rate of metal ceramic crowns at 5 years (95.4%) was significantly superior to the sur-vival rate of all-ceramic crowns, which was 91.2%.

The incidence of periimplantitis at 5 years was 9.7%, and 6.3% of im-plants had bone loss exceeding 2 mm. For other complications, implant fracture rate was 0.14%, screw or abutment loosening was 12.7%, and the incidence of ceramic or veneer fractures was 4.5%. Clearly, survival rates for both implants and implant-supported SCs were high at 5 years, but both biological and technical complications occur frequently.

A 20-year follow-up was published on a group of 48 consecutive patients treated with implants in the early 1980s.172 Nineteen of the patients had died, and 21 patients with 23 im-plant-supported prostheses could be examined clinically and radiographi-cally. All patients had been treated ad modem Brånemark with a 2-stage surgical procedure. Implant connec-tions were made 3 to 4 months after placement in the mandible and after a minimum of 6 months in the maxilla. Prostheses were fabricated with gold alloy and acrylic resin denture teeth.

A total of 123 implants (27 in the maxilla, 96 in the mandible) had been placed in these 21 patients. Only 1 implant was lost, yielding a 20-year survival rate of 99.2%. Mean bone loss at 20 years was 0.53 mm. The incidence of periimplantitis and other complications was low. These results are outstanding, but readers are cau-tioned that they may not be extrapo-lated to the abbreviated surgical and loading protocols currently used. The implants used with these patients also had machined surfaces, which may



43July 2009


have contributed to the low incidence of periimplantitis.

In summary, the discipline of im-plant dentistry continued to grow in 2008. In general, the results of prop-erly delivered implant therapy tend to be positive. Long-term data are begin-ning to be available. It is clear, howev-er, that the designs of most published studies tend to be less than optimal and, thus, it is difficult to definitively answer many of the important ques-tions that clinicians would like to have resolved.

REFERENCES

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2. Accorinte ML, Loguercio AD, Reis A, Costa CA. Response of human pulps capped with different self-etch adhesive systems. Clin Oral Investig 2008;12:119-27.

3. Bogen G, Kim JS, Bakland LK. Direct pulp capping with mineral trioxide aggregate: an observational study. J Am Dent Assoc 2008;139:305-15.

4. Accorinte M, Loguercio A, Reis A, Carneiro E, Grande RH, Murata SS, et al. Response of human dental pulp capped with MTA and calcium hydroxide powder. Oper Dent 2008;33:488-95.

5. Accorinte MdeL, Holland R, Reis A, Bor-toluzzi MC, Murata SS, Dezan E Jr, et al. Evaluation of mineral trioxide aggregate and calcium hydroxide cement as pulp-capping agents in human teeth. J Endod 2008;34:1-6.

6. Min KS, Park HJ, Lee SK, Park SH, Hong, CU, Kim HW, et al. Effect of mineral triox-ide aggregate on dentin bridge formation and expression of dentin sialoprotein and heme oxygenase-1 in human dental pulp. J Endod 2008;34:666-70.

7. Tuna D, Olmez A. Clinical long-term evalu-ation of MTA as a direct pulp capping ma-terial in primary teeth. International Endo J 2008;41:273-8.

8. Camilleri J. Characterization of hydration products of mineral trioxide aggregate. Int Endo J 2008;41:408-17.

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17.Chang SH, Su YC. A self-adaptive flu-idic probe for electrical caries detection. Biomed Microdevices 2008;10:447-57.

18.Iijima Y. Early detection of white spot le-sions with digital camera and remineraliza-tion therapy. Aust Dent J 2008;53:274-80.

19.Nishimura M, Oda T, Kariya N, Matsumura S, Shimono T. Using a caries activity test to predict caries risk in early childhood. J Am Dent Assoc 2008;139:63-71.

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54.Mealey BL, Rose LF. Diabetes mellitus and inflammatory periodontal diseases. Curr Opin Endocrinol Diabetes Obes 2008;15:135-41.

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58.Schropp L, Kostopoulos L, Wenzel A. Bone healing following immediate versus delayed placement of titanium implants into extraction sockets: a prospective clini-cal study. Int J Oral Maxillofac Implants 2003;18:189-99.

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71.Chambrone L, Chambrone D, Pustiglioni FE, Chambrone LA, Lima LA. Can subepi-thelial connective tissue grafts be consid-ered the gold standard procedure in the treatment of Miller Class I and II recession-type defects? J Dent 2008;36:659-71.

72.Han JS, John V, Blanchard SB, Kowolik MJ, Eckert GJ. Changes in gingival dimensions following connective tissue grafts for root coverage: comparison of two procedures. J Periodontol 2008;79:1346-54.

73.Keceli HG, Sengun D, Berberoglu A, Karabulut E. Use of platelet gel with con-nective tissue grafts for root coverage: a randomized-controlled trial. J Clin Perio-dontol 2008;35:255-62.

74.de Souza SL, Novaes AB Jr, Grisi DC, Taba M Jr, Grisi MF, de Andrade PF. Comparative clinical study of a subepithelial connective tissue graft and acellular dermal matrix graft for the treatment of gingival reces-sions: six- to 12-month changes. J Int Acad Periodontol 2008;10:87-94.

75.Papageorgakopoulos G, Greenwell H, Hill M, Vidal R, Scheetz JP. Root coverage using acellular dermal matrix and comparing a coronally positioned tunnel to a coronally positioned flap approach. J Periodontol 2008;79:1022-30.

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78.Leskinen K, Salo S, Suni J, Larmas M. Comparison of dental health in sealed and non-sealed first permanent molars: 7 years follow-up in practice-based dentistry. J Dent 2008;36:27-32.

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43July 2009


have contributed to the low incidence of periimplantitis.

In summary, the discipline of im-plant dentistry continued to grow in 2008. In general, the results of prop-erly delivered implant therapy tend to be positive. Long-term data are begin-ning to be available. It is clear, howev-er, that the designs of most published studies tend to be less than optimal and, thus, it is difficult to definitively answer many of the important ques-tions that clinicians would like to have resolved.

REFERENCES

1. Fernandes AM, Silva GA, Lopes N Jr, Napimoga M, Bernatti BB, Alves JB. Direct capping of human pulps with a dentin bonding system and calcium hydroxide: an immunohistochemical analysis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;105:385-90.

2. Accorinte ML, Loguercio AD, Reis A, Costa CA. Response of human pulps capped with different self-etch adhesive systems. Clin Oral Investig 2008;12:119-27.

3. Bogen G, Kim JS, Bakland LK. Direct pulp capping with mineral trioxide aggregate: an observational study. J Am Dent Assoc 2008;139:305-15.

4. Accorinte M, Loguercio A, Reis A, Carneiro E, Grande RH, Murata SS, et al. Response of human dental pulp capped with MTA and calcium hydroxide powder. Oper Dent 2008;33:488-95.

5. Accorinte MdeL, Holland R, Reis A, Bor-toluzzi MC, Murata SS, Dezan E Jr, et al. Evaluation of mineral trioxide aggregate and calcium hydroxide cement as pulp-capping agents in human teeth. J Endod 2008;34:1-6.

6. Min KS, Park HJ, Lee SK, Park SH, Hong, CU, Kim HW, et al. Effect of mineral triox-ide aggregate on dentin bridge formation and expression of dentin sialoprotein and heme oxygenase-1 in human dental pulp. J Endod 2008;34:666-70.

7. Tuna D, Olmez A. Clinical long-term evalu-ation of MTA as a direct pulp capping ma-terial in primary teeth. International Endo J 2008;41:273-8.

8. Camilleri J. Characterization of hydration products of mineral trioxide aggregate. Int Endo J 2008;41:408-17.

9. Blinkhorn AS,Davies RM. Caries preven-tion. A continued need worldwide. Int Dent J 1996;46:119-25.

10.Loesche WJ, Abrams J, Terpenning MS, Bretz WA, Dominguez BL, Grossman NS, et al. Dental findings in geriatric populations with diverse medical backgrounds. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1995;80:43-54.

11.Ellefsen B, Holm-Pedersen P, Morse DE, Schroll M, Andersen BB, Waldemar G. Caries prevalence in older persons with and without dementia. J Am Geriatr Soc 2008;56:59-67.

12.Kopycka-Kedzierawsk, DT, Bell CH, Billings RJ. Prevalence of dental caries in Early Head Start children as diagnosed using teleden-tistry. Pediatr Dent 2008;30:329-33.

13.Barberia E, Maroto M, Arenas M, Silva, CC. A clinical study of caries diagnosis with a laser fluorescence system. J Am Dent Assoc 2008;139:572-9.

14.Ekstrand KR, Ricketts DN, Kidd EA, Qvist V, Schou S, et al. Detection, diagnosing, monitoring and logical treatment of oc-clusal caries in relation to lesion activ-ity and severity: an in vivo examination with histological validation. Caries Res 1998;32:247-54.

15.Braga M, Nicolau J, Rodriques CR, Im-parato JC, Mendes FM. Laser fluorescence device does not perform well in detection of early caries lesions in primary teeth: an in vitro study. Oral Health Prev Dent 2008;6:165-9.

16.Bin-Shuwaish M, Yaman P, Dennison J, Nei-va G. The correlation of DIFOTI to clinical and radiographic images in Class II carious lesions. J Am Dent Assoc 2008;139:1374-81.

17.Chang SH, Su YC. A self-adaptive flu-idic probe for electrical caries detection. Biomed Microdevices 2008;10:447-57.

18.Iijima Y. Early detection of white spot le-sions with digital camera and remineraliza-tion therapy. Aust Dent J 2008;53:274-80.

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161.Schincaglia GP, Marzola R, Giocanni GF, Chiara CS, Scotti R. Replacement of man-dibular molars with single-unit restorations supported by wide-body implants: immedi-ate versus delayed loading. A randomized controlled study. Int J Oral Maxillofac Implants 2008;23:474-80.

162.Friberg B, Raghoebar GM, Grunert I, Hobkirk JA, Tepper G. A 5-year prospective multicenter study on 1-stage smooth-sur-face Branemark System implants with early loading in edentulous mandibles. Int J Oral Maxillofac Implants 2008;23:481-6.

163.Fisher K, Stenberg T, Hedin M, Sennerby L. Five-year results from a randomized, controlled trial on early and delayed loading of implants supporting full-arch prosthesis in the edentulous maxilla. Clin Oral Implants Res 2008;19:433-41.

164.Fardal Ø, Linden GJ. Tooth loss and implant outcomes in patients refractory to treatment in a periodontal practice. J Clin Periodontol 2008;35:733-8.

165.Bell BM, Bell RE. Oral bisphosphonates and dental implants: a retrospective study. J Oral Maxillifac Surg 2008;66:1022-4.

166.Grant BT, Amenedo C, Freeman K, Kraut RA. Outcomes of placing dental implants in patients taking oral bisphosphonates: a review of 115 cases. J Oral Maxillofac Surg 2008;66:223-30.

167.Esposito M, Grusovin MG, Talati M, Coulthard P, Oliver R, Worthington HV. Interventions for replacing missing teeth: antibiotics at dental implant placement to prevent complications. Cochrane Database Syst Rev 2008:CD004152.

168.Theoharidou A, Petridis HP, Tzannas K, Garefis P. Abutment screw loosening in single-implant restorations: a system-atic review. Int J Oral Maxillofac Implants 2008;23:681-90.

169.Vallee MC, Conrad HJ, Basu S, Seong WJ. Accuracy of friction-style and spring-style mechanical torque limiting devices for den-tal implants. J Prosthet Dent 2008;100:86-92.

170.Klemetti E. Is there a certain number of implants needed to retain an overdenture? J Oral Rehabil 2008;35 Suppl 1:80-4.

171.Jung RE, Pjetursson BE, Glauser R, Zembic A, Zwahlen M, Lang NP. A sys-tematic review of the 5-year survival and complication rates of implant-supported single crowns. Clin Oral Implants Res 2008;19:119-30.

172.Astrand P, Ahlqvist J, Gunne J, Nilson H. Implant treatment of patients with edentu-lous jaws: a 20-year follow-up. Clin Implant Dent Relat Res 2008;10:207-17.

Corresponding author: Dr Terence E. DonovanDepartment of Operative DentistryUniversity of North CarolinaSchool of Dentistry437 Brauer Hall, Campus Box 7450Chapel Hill, NC 27599Fax: 919-966-5660E-mail: [email protected]

Copyright © 2009 by the Editorial Council for The Journal of Prosthetic Dentistry.



45July 2009


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136.Jauhar S, Lyons MF, Banham SW, Cam-eron DA, Orchardson R. Ten-year follow-up of mandibular advancement devices for the management of snoring and sleep apnea. J Prosthet Dent 2008;99:314-21.

137.Kim HY, Bok KH, Dhong HJ, Chung SK. The correlation between pharyngeal nar-rowing and the severity of sleep-disordered breathing. Otolaryngol Head Neck Surg 2008;138:289-93.

138.Misch CE. Guidelines for maxillary incisal edge position- a pilot study: the key is the Canine. J Prosthodont 2008;17:130-4.

139. Saskalauskaite E, Tam LE, McComb D. Flexural strength, elastic modulus, and pH profile of self-etch resin luting cements. J Prosthodont 2008;17:262-8.

140. Duarte S Jr, Botta AC, Meire M, Sadan A. Microtensile bond strengths and scan-ning electron microscopic evaluation of self-adhesive and self-etch resin cements to intact and etched enamel. J Prosthet Dent 2008;100:203-10.

141. Fokkinga WA, Kreulen CM, Bronkhorst EM, Cruegers NH. Composite resin core-crown reconstructions: an up to 17-year follow-up of a controlled clinical trial. Int J Prosthodont 2008;21:109-15.

142. Pilo R, Shapenco E, Lewinstein I. Residual dentin thickness in bifurcated maxillary first premolars after root canal and post space preparation with parallel-sided drills. J Prosthet Dent 2008;99:267-73.

143. Zicari F, Couthino E, De Munck J, Poitevin A, Scotti R, Naert I, Van Meer-beek B. Bonding effectiveness and sealing ability of fiber-post bonding. Dent Mater 2008;24:967-77.

144. Sachdeo A, Haffajee AD, Socransky SS. Biofilms in the edentulous oral cavity. J Prosthodont 2008;17:348-56.

145. Kim Y, Michalakis KX, Hirayama H. Effect of relining method on dimensional ac-curacy of posterior palatal seal. An in vitro study. J Prosthodont 2008;17:211-8.

146. Depprich RA, Handschel JG, Meyer U, Meissner G. Comparison of prevalence of microorganisms on titanium and silicone/polymethyl methacrylate obturators used for rehabilitation of maxillary defects. J Prosthet Dent 2008;99:400-5.

147. DaSilva JD, Park SE, Weber HP, Ishikawa-Nagai S. Clinical performance of a newly developed spectrophotometric system on tooth color reproduction. J Prosthet Dent 2008;99:361-8.

148. Corciolani G, Vichi A, Goracci C, Ferrari M. Colour correspondence of a ceramic system in two different shade guides. J Dent 2009;37:98-101.

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152. Brudvik JS, Lee S, Croshaw SN, Reimers DL. Laser welding of removable partial denture frameworks. Int J Prosthodont 2008;21:285-91.

153. Srimaneepong V, Yoneyama T, Kobayashi E, Doi H, Hanawa T. Comparative study on torsional strength, ductility and fracture characteristics of laser-welded alpha+beta Ti-6Al-7Nb alloy, CP titanium and Co-CR alloy dental castings. Dent Mater 2008;24:839-45.

154. Luthardt RG, Walter MH, Weber A, Koch R, Rudolph H. Clinical parameters influencing the accuracy of 1- and 2-stage impressions: a randomized controlled trial. Int J Prosthodont 2008;21:322-7.

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156. Reich S, Kappe K, Teschner H, Schmitt J. Clinical fit of four-unit zirconia poste-rior fixed dental prostheses. Eur J Oral Sci 2008;116:579-84.

157.Kotsovilis S, Karoussis IK, Trianti M, Fourmousis I. Therapy of peri-implantitis: a systematic review. J Clin Periodontol 2008;35:621-9.

158.Esposito M, Grusovin MG, Kakisis I, Coulthard P, Worthington HV. Interven-tions for replacing missing teeth: treatment of perimplantitis. Cochrane Database Syst Rev 2008: CD004970.

159.Schou S. Implant treatment in periodonti-tis-susceptible patients: a systematic review. J Oral Rehabil 2008;35 Suppl 1:9-22.

160.Ong CT, Ivanovski S, Needleman IG, Retzepi M, Moles DR, Tonetti MS. System-atic review of implant outcomes in treated periodontitis subjects. J Clin Periodontol 2008;35:438-62.

161.Schincaglia GP, Marzola R, Giocanni GF, Chiara CS, Scotti R. Replacement of man-dibular molars with single-unit restorations supported by wide-body implants: immedi-ate versus delayed loading. A randomized controlled study. Int J Oral Maxillofac Implants 2008;23:474-80.

162.Friberg B, Raghoebar GM, Grunert I, Hobkirk JA, Tepper G. A 5-year prospective multicenter study on 1-stage smooth-sur-face Branemark System implants with early loading in edentulous mandibles. Int J Oral Maxillofac Implants 2008;23:481-6.

163.Fisher K, Stenberg T, Hedin M, Sennerby L. Five-year results from a randomized, controlled trial on early and delayed loading of implants supporting full-arch prosthesis in the edentulous maxilla. Clin Oral Implants Res 2008;19:433-41.

164.Fardal Ø, Linden GJ. Tooth loss and implant outcomes in patients refractory to treatment in a periodontal practice. J Clin Periodontol 2008;35:733-8.

165.Bell BM, Bell RE. Oral bisphosphonates and dental implants: a retrospective study. J Oral Maxillifac Surg 2008;66:1022-4.

166.Grant BT, Amenedo C, Freeman K, Kraut RA. Outcomes of placing dental implants in patients taking oral bisphosphonates: a review of 115 cases. J Oral Maxillofac Surg 2008;66:223-30.

167.Esposito M, Grusovin MG, Talati M, Coulthard P, Oliver R, Worthington HV. Interventions for replacing missing teeth: antibiotics at dental implant placement to prevent complications. Cochrane Database Syst Rev 2008:CD004152.

168.Theoharidou A, Petridis HP, Tzannas K, Garefis P. Abutment screw loosening in single-implant restorations: a system-atic review. Int J Oral Maxillofac Implants 2008;23:681-90.

169.Vallee MC, Conrad HJ, Basu S, Seong WJ. Accuracy of friction-style and spring-style mechanical torque limiting devices for den-tal implants. J Prosthet Dent 2008;100:86-92.

170.Klemetti E. Is there a certain number of implants needed to retain an overdenture? J Oral Rehabil 2008;35 Suppl 1:80-4.

171.Jung RE, Pjetursson BE, Glauser R, Zembic A, Zwahlen M, Lang NP. A sys-tematic review of the 5-year survival and complication rates of implant-supported single crowns. Clin Oral Implants Res 2008;19:119-30.

172.Astrand P, Ahlqvist J, Gunne J, Nilson H. Implant treatment of patients with edentu-lous jaws: a 20-year follow-up. Clin Implant Dent Relat Res 2008;10:207-17.

Corresponding author: Dr Terence E. DonovanDepartment of Operative DentistryUniversity of North CarolinaSchool of Dentistry437 Brauer Hall, Campus Box 7450Chapel Hill, NC 27599Fax: 919-966-5660E-mail: [email protected]

Copyright © 2009 by the Editorial Council for The Journal of Prosthetic Dentistry.

Documents

Annual review of selected scientific literature 1