Annual review of selected scientific literature: Report of the committee on scientific ... · 2012. 7. 11. · Donovan et al Annual review of selected scientific literature: Report

Donovan 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,b William Becker, DDS,c David R. Cagna, DMD,d Thomas J. Hilton, DDS,e James R. McKee, DDS,f and James E. Metz, DDSg

University of North Carolina, Chapel Hill, NC; University of Southern California, Los Angeles, Calif; University of Tennessee Health Science Center, Memphis, Tenn; University of Oregon Health Sciences Center, Portland, Ore

aChair, Committee on Scientific Investigation, American Academy of Restorative Dentistry (AARD); Professor and Section Head for Biomaterials, Department of Operative Dentistry, University of North Carolina at Chapel Hill.bPrivate practice, Sequim, Wash.cClinical Professor, Advanced Education in Prosthodontics, Herman Ostrow School of Dentistry, University of Southern California; private practice, Tucson, Ariz.dAssociate Dean, Professor and Director, Advanced Prosthodontics, University of Tennessee Health Science Center, College of Dentistry.eAlumni Centennial Professor in Operative Dentistry, University of Oregon Health Sciences Center.fPrivate practice, Downers Grove, Ill.gPrivate practice, Columbus, Ohio.(J Prosthet Dent 2012;108:15-50)

An enormous quantity of informa-tion related to restorative dentistry is published every year. Some of this in-formation is science based, some ap-pears to be science based but is not, and some is clearly based on anecdote, opinion, or represents marketing. All of this information may be of value; many clinicians have difficulty gaining access to much of the published infor-mation. Part of the problem with ac-cess is the sheer volume and number of publications, both peer-reviewed journals and trade publications. In addition, many studies related to re-storative dentistry are currently being published in nondental journals in-volving disciplines that have interests in common with dentistry.

The real problem, however, for most clinicians is time. Most den-tists subscribe to a few peer-reviewed journals and receive complimentary trade publications. In addition, they attend at least the minimum number of continuing education courses to maintain licensure and have access to information over the internet. How-

ever, many other variables compete for their time. Dentists, like it or not, are managing a small business, and this requires time and effort. They are also managing a team of auxiliary professionals, which can, at times, be difficult and frustrating. They are also spouses and parents, which clearly re-quires time and effort. They may serve as leaders in their communities. Most dental professionals also have person-al interests and hobbies, in which they participate. In addition to acquiring the knowledge and skills required to provide appropriate contemporary restorative dentistry for their patients, they also are required to be aware of advances in the specialties so that their patients may receive those ben-efits if indicated.

With all of these activities, most clinicians are not able to access much of the available information, nor do they have the time to critically evalu-ate the information they have. This review is conducted partially to help clinicians find pertinent studies that are relevant to their practices and also

to help critically analyze new informa-tion and the validity behind the sci-ence that produced that information. The reader is advised to read this re-view one section at a time, digest the changes that have occurred over the past year in that discipline, and then access any specific studies they may want to investigate in greater depth.

This analysis of the scientific lit-erature for the year 2011 is divided into 7 sections: (1) dental caries and cariology; (2) pulp pathology; (3) periodontics; (4) dental materials; (5) occlusion and temporomandibu-lar disorders; (6) prosthodontics; and (7) implant dentistry. Obviously, some studies may fall into 2 or more of these groups.

DENTAL CARIES AND CARIOLOGY

The understanding of dental car-ies, its processes, and its interaction in the human host continues to ad-vance albeit slowly and methodically. The breadth and granularity of this

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year’s research continues to increase, while a holistic assembly of these data in systems biology is beginning to tie sometimes seemingly disparate research together to provide a bet-ter understanding of the disease. The diversity of publications about dental caries and related topics from allied disciplines and sometimes surprising sources is also ever expanding. These data may eventually lead to better di-agnostics and preventive treatment therapies. This year’s publications were also rich in materials directly ap-plicable to the practice of dentistry with a number of outstanding reviews.

Demographics

Dental caries has consistently been associated with economic disadvantage and the education level of the mother and the individual incurring the disease. This correlation is seemingly consis-tent across international boundaries as shown this year in well performed Finn-ish and Brazilian studies.1,2

There are an increasing number of publications related to statistical design and caries evaluation indices that are important to researchers in that they provide new approaches to data analyses that have the potential to yield a better understanding of the factors influencing dental caries.3-7

The health status of individu-als and its influence on dental caries generated a series of clinically useful papers. Examples include asthma, es-sentially doubling the risk of caries in both the primary and permanent den-tition8; body mass index (BMI) with a direct association with the incidence of dental caries probably due to com-mon lifestyle factors9; HIV infection in children, which increased the preva-lence of dental caries10; and systemic sclerosis (scleroderma), which may result in limited oral opening and the potential for treatment related adver-sity, especially for those on bisphos-phonate therapy.11

North American Indigenous and Alaskan Native populations were once again noted as having serious

health concerns by both the Centers for Disease Control and the Ameri-can Academy of Pediatrics.12,13 Both groups note a high prevalence of dis-ease in these populations and suggest water fluoridation, fluoride varnishes, and earlier interventions in children. These recommendations are not new, and the disease continues unabated in these populations.

Risk Factors and Assessment

Research in risk assessment and

risk factors is designed to give the clinician or policy making entities in-formation with which they can make informed clinical decisions or pub-lic policy. The usual suspects such as sugar consumption,14,15 including sports drinks,16 and lack of fluoride were validated as risk factors in this year’s literature. Enamel defects as identified by the World Health Orga-nization (WHO) criteria17 were sig-nificantly associated with the devel-opment of caries in a cohort study of children from birth to 54 months of age.18 Defective margins and contacts (both too heavy and too light) on metal ceramic crowns are significantly associ-ated with increased caries on adjacent teeth.19 So too is the absence of space in the maxillary labial segment of pre-school children.20 The chronic use of methamphetamine and its connection to dental caries has previously been well documented. For the clinician, the other clinically relevant manifestations of chronic methamphetamine use are well reviewed.21

Prevention Research into the prevention of

dental caries followed predictable lines in 2011 with steady progress but no breakthroughs in behavioral, chemical, mechanical (sealants), or probiotic therapies. Of interest to the practicing clinician is a report on a hand-held water fluoride analysis unit that correlates highly with laboratory testing devices, allowing the optimum analysis of the patient’s water sup-

ply and titration of fluoride supple-ments.22 Chemically, fluoride in the form of silver diamine fluoride and fluoride varnish was investigated.23-25 Silver diamine fluoride research pro-vided confirmatory evidence of its ef-ficacy, while fluoride varnish (22 600 ppm applied 3 times per year) failed to reduce caries against an untreated cohort in a well conducted 3-year school-based trial.26 A systemic re-view of the chlorhexidine varnish treatment of root caries showed no conclusive evidence of benefit in pa-tients with regular professional oral prophylaxis.27

Microbiology /Biofilms The technologies being applied to

understanding the putative pathogens and their in vivo ecology in dental car-ies is quite remarkable and is yielding an ever clearer, albeit currently incom-plete, picture of the microbiology of dental caries. In the not too distant past, Streptococcus mutans (SM) was considered the primary pathogen in dental caries because of its ability to metabolize many sugars and pro-duce a hardy biofilm, and because of its acidogenic and acidoduric nature. The plentiful elution of an acid waste product is still a formidable weapon for SM in its battle for resources in its environment since many of its com-petitors cannot tolerate low pH en-vironments. Today the roles that SM and other organisms play in dental caries are being shown to be more di-verse, and the knowledge of this study of dental biofilms is still evolving.

Genotypic methods, such as 16S rRNA gene sequence analysis, have become the standard bacterial iden-tification technology, supplanting the use of phenotypic characteristics. This technology, developed in the 1980s, allows better analysis of the oral biome and gives rise to the iden-tification of a larger number of po-tential pathogens such as Scardovia wiggsiae, Veillonella parvula, Strepto-coccus cristatus, and Actinomyces ge-rensceriae in early childhood caries.28

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S. mutans glucosyltransferases (Gtfs) are increasingly seen as important in the generation of biofilms and the virulence of those biofilms. These Gtfs adsorb to enamel and synthesize glucans, which are adherent in all dimensions provid-ing adhesion for other bacteria. They also adsorb to the surface of other oral bacteria converting them to glucan pro-ducers.29 Both of these actions enhance biofilm formation and are being stud-ied as potential targets for emerging therapeutics.

Both the innate and adaptive im-mune systems were investigated as therapeutic strategies in the modula-tion of the oral biofilm. An interesting study of dendritic cells (messengers between the innate and adaptive im-mune systems) shows the compli-cations of these attempts. In vitro, dendritic cells presented antigens and initiated the proliferation of T-cells in a normal manner. In vivo, with live bacteria, this did not work.30 Antimi-crobial peptides (AMP) of the innate immune system for use against oral biofilm residents is reviewed by Bato-ni et al31 and a representative example exploration of an individual AMP is found in the work of Liu et al.32

For those who want to refresh their knowledge of the layered human im-mune system, many current resourc-es exist on the web. An examples is: http://uhaweb.hartford.edu/BUGL/immune.htm#summary A current un-derstanding is becoming imperative for understanding both periodontal diseases and dental caries.

Treatments

Treatment of dental caries can be viewed as the treatment of the le-sions produced by the disease dental caries and treatment of the disease processes themselves. Clearly over-lapping areas such as glass-ionomer restorations that elute fluoride, affect the disease process. Glass ionomer was investigated in a nonsurgical use to assess its effect on interproximal le-sions.33 The test group of initial, non-cavitated interproximal lesions was

more likely to remain stable or regress radiographically than the control group (odds ratio [OR] 6.3 at 95% confidence with a confidence interval of 1.3 to 30.9.)

The predominant nonmechanical interventions investigated in 2011 were fluoride and chlorhexidine. The systematic investigation and sug-gested research protocols of natural products are reviewed in a publica-tion by Jeon et al.34 A number of in-vestigations in 2011 on natural plant extracts, including Evening Primrose (Oenothera biennis)35 and Prune (Prunus mume) extracts showed ef-ficacy in treating dental caries.36 The mechanism of action of Evening Prim-rose appears to be a polyphenol in the extract that inhibits glucosyltrans-ferase (Gtf ) in S. mutans as reviewed above. An investigation of infiltration polymers showed that they are not ef-fective in treating cavitated lesions.37

Reviews A number of very useful reviews

involving dental caries were written in 2011. A narrowly focused review of the role of bacteria in dental caries provides a useful discussion of what is known about bacterial behaviors and adaptations to acid production in oral biofilms.38 The authors focus on the changes and adaptations in the microbial mix that occur as a re-sult of bacterially produced acids and on how these are related to the stages of the development of carious lesions. The review lacks information about the microbial biofilm formation, in-terspecies and intraspecies signaling/communications, and most other as-pects of a holistic view of the dental caries process.

Featherstone et al39 published an outstanding review of caries man-agement in prosthetic patients. This publication provides risk assessment guidance and clinical prevention and treatment advice. When combined with a review of fluoride use in adults by Gib-son et al,40 it provides a comprehensive review of the current knowledge.

A review of the benefits and risks of fluoride toothpastes in children showed that only those dentifrice formulations with greater than 1000 ppm fluoride were effective in reduc-ing caries.41 An increased benefit to increased fluoride content with only weak association to increased fluoro-sis was observed.

Dental erosion was reviewed and information provided on the bio-chemical aspects of erosion and the microscopic and macroscopic histo-pathology of the processes.42,43 An in vitro study of evolving anti-erosion products compared to conventional NaF products showed no increased benefit for the 4 anti-erosion formu-las tested.44 Finally, Simonsen and Neal provided a succinct and clini-cally relevant review of dental sealant application.45

PULP PATHOLOGY

A recommendation of many oper-ative departments is to achieve a min-imal thickness of 2 mm of combined base/liner/remaining dentin thickness between the definitive restorative ma-terial and the pulp. One of the chal-lenges for the clinician when making decisions regarding pulpal protection is attempting to ascertain the remain-ing dentin thickness (RDT). An in vitro study attempted to determine if RDT under caries could be determined from a radiograph.46 Twenty-five in-dividuals who were having a posterior tooth extracted and had a radiograph showing caries with remaining dentin thickness participated in the study. Before extraction, a periapical radio-graph was made with F-speed film. After extraction, another film radio-graph and a digital radiograph were made of the tooth. The tooth was then sectioned mesiodistally, and the caries was hand excavated until firm dentin remained, at which point the actual RDT was measured. Overall, only 25% of the radiographs dem-onstrated good agreement with the actual measurements. There was a general trend for the radiographs to



overestimate the RDT, although the films tended to show a greater over-estimation than did the digital image.

Controversy regarding what is the best pulp cap material continues. A retrospective clinical study evalu-ated the long-term success of direct pulp capping with calcium hydrox-ide.47 Over ten years, 1075 direct pulp caps performed by dental students and dentists at the dental school in Mainz, Germany were assessed. Pulp exposure was due to caries or trauma. Only teeth that had pulps assessed as being normal or as having reversible pulpitis with normal periapical radio-graphic findings were included. The exposure could be no larger than 1 mm2 and with no-to-little bleeding af-ter the exposure. Upon pulp exposure, the tooth was isolated with a rubber dam and disinfected with hydrogen peroxide until bleeding stopped and any coagulated blood was removed. The pulp was covered with soft cal-cium hydroxide (Calxyl; Otto & Co, Frankfurt, Germany) followed by hard setting calcium hydroxide (Life; Kerr Corp, Orange, Calif ). The tooth was definitively restored with a vari-ety of restorative materials, including amalgam, compomer, glass ionomer, and composite resin. Participants were followed at 3 months and an-nually thereafter. Treated teeth were evaluated by cold, percussion, pal-pation, occlusion testing, and radio-graphs. The success rates (regardless of reason for pulp exposure) by time were the following: year 1: 80.1%; year 2: 75.2%; year 3: 72.0%; year 5: 68.0%; year 6: 62.5%; year 8: 58.7%. The greatest percentage of patients requiring endodontic treatment was in the 50 to 69 year age range. There was a significant correlation with the number of surfaces of the pulp in-volved in the exposure and the out-come; as more pulp surfaces were involved, the survival rate decreased. Teeth restored with amalgam demon-strated a higher survival (84.2% after 9 years) rate than those restored with glass ionomer (51.5% after 9 years).

Tooth type, age, and gender had no significant effect on outcome.

PERIODONTOLOGY

For 2011 clinical research findings were reviewed to identify systemic conditions that may be related to periodontal health and nonsurgical periodontal therapy. Studies were also reviewed that dealt with periodontal regeneration and various methods for treating mucogingival problems.

Periodontal/Systemic Conditions and Smoking

The association between metabol-ic diseases and periodontal diseases is a continuing topic for discussion. The systemic inflammation in both metabolic syndrome (MetS) and peri-odontitis is a common denominator when associating these conditions with a higher risk of atherosclerosis.48 This study investigated whether peri-odontal therapy may reduce systemic inflammation in patients with meta-bolic syndrome and reduce cardio-vascular risk. A parallel-arm, double blind, randomized clinical trial of 1 year in participants with MetS and periodontitis was conducted. Par-ticipants were randomized to an ex-perimental treatment group (ETG) (n=82) that received plaque control and root planing plus amoxicillin and metronidazole or to a control treat-ment group (CTG) (n=83) that re-ceived plaque control instructions, supragingival scaling, and 2 placebos. Risk factors for cardiovascular disease were recorded; serum lipoprotein cholesterol, glucose, body mass index (BMI), C-reactive protein (CRP) and fibrinogen concentrations, and clini-cal periodontal parameters were as-sessed at baseline and every 3 months until 12 months after therapy. The primary and secondary outcomes were changes in CRP and fibrino-gen levels, respectively. The patients’ baseline characteristics were similar in both groups. No significant chang-es in lifestyle factors, frequency of hy-

pertension, BMI, serum lipoprotein cholesterol, and glucose levels were observed during the study period. The periodontal parameters significantly improved in both groups 3 months after therapy and remained lower than baseline up to 12 months. The improvement of periodontal status was significantly greater in the experi-mental treatment group (P<.001). A multiple linear regression analysis, controlled for gender, smoking, hy-pertension, and extent of periodon-titis, demonstrated that CRP levels decreased over time and that this re-duction was significant at 9 and 12 months in both groups. There was no difference between the groups. Fibrin-ogen levels significantly decreased in the ETG at 6 and 12 months, but not in the CTG. Periodontal inflammation either with root planing and systemic antibiotics or with plaque control and subgingival scaling was significantly reduced. It should be noted that the study groups were somewhat small, and definitive conclusions are difficult to make.

Recent epidemiological studies have shown that individuals with peri-odontitis have a significantly increased risk of developing coronary heart dis-ease.49 In addition to conventional risk factors, dyslipidemia may be as-sociated with this increased risk. The authors measured concentrations of lipids in patients with moderate to severe periodontitis before and 3, 6, and 12 months after local periodon-tal treatment. Fifty participants with periodontitis and 25 participants without periodontitis were included in the analyses. Lipoproteins were measured by using serological analy-ses. Periodontal health indicators included the plaque index, gingival bleeding index, and periodontal dis-ease status (defined by pocket depth and attachment loss). Patients were nonsurgically treated with mechanical debridement of calculus once a week for 1 month. Results showed a signifi-cant relationship between indicators of poor periodontal status and serum level lipoproteins. Periodontal ther-

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apy resulted in a significant reduc-tion of local inflammation and tissue destruction as reflected in reduced pocket depth and reduced bleeding indices. The levels of lipoproteins after therapy seemed to be lower than those reported before treatment in patients with periodontitis than in healthy pa-tients. Lipoproteins decreased signifi-cantly after treatment except for high-density lipoprotein cholesterol. This pilot study shows that periodontal disease significantly affects the serum levels of lipoproteins and suggests that successful periodontal treatment decreases serum lipid concentration. This study also suggests that lipopro-teins are possible intermediate factors that may link periodontal disease to elevated cardiovascular risk.

Another pilot study evaluated the association of severe periodontitis with pulse wave velocity (PWV), ca-rotid artery intima-medial thickness (IMT), and clinical, metabolic, and atherogenic inflammatory mark-ers in 79 participants with heterozy-gous familial hypercholesterolemia (hFH).50 All participants were free of previous vascular disease manifesta-tions. Body mass index (in kilograms per square meter), plasma lipids, glu-cose, C-reactive protein, and white blood cell counts were evaluated. After complete-mouth periodontal examinations, patients were catego-rized into the severe periodontitis group (SPG) or nonsevere periodon-titis group (NSPG). The SPG showed significantly higher values of choles-terol-year scores, triglycerides, glu-cose, PWV, IMT, and diastolic blood pressure (DBP) than the NSPG. After adjustment for traditional risk factors for atherosclerosis, only the associa-tion between severe periodontitis and DBP (odds ratio: 3.1; 95% confidence interval (CI): 1.1 to 8.5; P=.03) was confirmed. In individuals with hFH, severe periodontitis was associated with a higher DBP, which suggests that severe periodontitis itself may contribute to the increased cardiovas-cular risk profile in this population.

A number of epidemiologic stud-

ies were published that looked at the association between coronary heart disease (CHD) and periodontal dis-ease.51,52 However, debate exists about whether this association is a true rela-tionship or simply an example of an uncontrolled confounder. One retro-spective cohort study examines the relationship between periodontal dis-ease and CHD.52 Digital panoramic radiographs were used to assess al-veolar bone loss (ABL) using a Schei ruler. Participants consisted of Veter-ans Administration (VA) patients who were eligible for dental benefits and had a digital panoramic radiograph made at the VA Medical Center, Den-ver, Colorado. Information on CHD and other important clinical variables were obtained from electronic medi-cal records. The examination of the relationship between ABL and CHD revealed a significant nonlinear rela-tionship with a threshold at approxi-mately 20% bone loss with a doubling of the probability ratios of CHD com-pared to those at 7.5% bone loss. This is the first study to demonstrate a nonlinear relationship between ABL and CHD. A significant positive as-sociation between ABL and CHD was found even at low levels of bone loss between 10% and 20%.

Erectile dysfunction (ED) and chronic periodontitis (CP) may share common risk factors. There is only 1 report on the association between ED and CP.53 The purpose of this study was to find the association between vasculogenic ED and CP. A total of 70 individuals clinically diagnosed with ED were included in the study. They were given the Sexual Health In-ventory for Men Questionnaire and subjected to colored penile Doppler ultrasound. Periodontal parameters of probing depth and periodon-tal attachment level were recorded. Five participants with ED and CP were selected randomly for cardiac color Doppler to assess the integrity. Among the selected vasculogenic patients with ED, mild-to-moderate vasculogenic ED showed the highest prevalence, whereas prevalence for

CP among all vasculogenic patients with ED was highest among severe ED (81.8%). The association of CP and vasculogenic ED was correlated posi-tively but showed no statistical sig-nificance. Two of 5 participants were found to have vascular insufficiency. It can be hypothesized that an asso-ciation exists between vasculogenic ED and CP in young men. However, a large-scale study with confounder analysis and a longitudinal follow-up is warranted.

Adjunctive Periodontal Therapy

The purpose of one study was to assess the clinical benefit of metroni-dazole, amoxicillin or doxycycline ad-ministered immediately after comple-tion of full-mouth scaling, and root planing (FRP) for treatment of gener-alized aggressive periodontitis.54 Pa-tients, 18 to 40 years of age, referred to the Karadeniz Technical University department of periodontology be-tween January 2009 and September 2009 were randomly chosen for inclu-sion in the study if radiographic exam-ination showed they had ≥ 20 teeth, clinical attachment loss and a prob-ing pocket depth (PPD) ≥ 6 mm at 2 sites in ≥ 12 teeth, ≥ 3 of which were not first molars or incisors. Partici-pants were divided into 3 groups and received FRP alone, FRP combined with metronidazole and amoxicillin, or FRP combined with doxycycline. PPD, clinical attachment level, gingi-val index, gingival bleeding index, and plaque index values were measured at baseline and 2 months after treat-ment. Thirty-eight participants with untreated generalized aggressive peri-odontitis participated in the study. In all 3 groups, the periodontal index values 2 months after treatment were significantly lower than baseline val-ues (P<.05). Values for PPD and clini-cal attachment level were more im-proved in the antibiotic groups than in the FRP group and more improved in the metronidazole and amoxicillin group than in the doxycycline group (P<.05). However, no statistically



significant intergroup difference was observed in the other clinical param-eters (P>.05). Systemic use of met-ronidazole and amoxicillin or doxy-cycline was clinically superior to FRP for reducing PPDs ≥ 7 mm (P<.05). The treatment of generalized aggres-sive periodontitis with FRP alone or with FRP combined with systemic antibiotics provided significant clini-cal benefits that reduced the need for periodontal surgery. Both antibiotic treatments had more clinical benefits than FRP alone.

Periodontitis, the most common chronic inflammatory condition known to mankind, is a disease that results in the destruction of tooth supporting tissues.55 Periodontitis is initiated by a bacterial biofilm on the tooth surface below the gingival margin. Until fairly recently it was assumed that the bacteria were the primary cause of tissue destruction; however, a large body of research has revealed that it is the patient’s immune response that is actually responsible for the majority of the breakdown of tooth supporting tis-sues. Contemporary thinking sug-gests that successful, long term man-agement of chronic periodontitis may combine local mechanical and anti-microbial strategies. This approach may reduce the microbial bioburden and modulates the host’s excessive immuno-inflammatory response to the bacterial exposure, an approach known as host modulatory therapy (HMT). Based on the data from ex-tensive literature, documenting the enzymatic inhibition and related anti-inflammatory properties of the tetra-cyclines, a new drug was developed as a host modulatory agent and ap-proved for use as an adjunct to con-ventional scaling and root planing for the treatment of chronic periodontitis by the United States Food and Drug Administration (FDA). A subantimi-crobial dose of doxycycline (SDD) at 20 mg (Periostat, CollaGenex Phar-maceuticals, Newtown, Pa) has been found to be a safe and effective ad-junct when taken twice daily for at

least 3 months and up to 24 months in randomized placebo-controlled clinical trials. Periostat is currently the only FDA-approved inhibitor of the matrix metalloproteinases implicated in the plaque-induced pathologic deg-radation of connective tissue collagen of the periodontal supporting struc-tures. This review paper begins with a brief description of the disease process known as periodontitis and is followed by an extensive review of the Phase I to IV clinical trial data that established the safety and efficacy of subantimi-crobial dose doxycycline (SDD) as an adjunct to scaling and root planing for the treatment of periodontitis.

Moxifloxacin works extremely well against most putative periodontal pathogens and has been shown to kill bacteria in biofilm and host cells.56 Participants with chronic periodonti-tis were randomly assigned to receive a single subgingival application of a 0.125%, 0.4%, or 1.25% moxifloxacin gel or placebo gel immediately after full-mouth scaling and root planing (SRP). Clinical efficacy measurements were assessed in sites with baseline probing depth (PD) of ≥5.4 mm at 6 weeks and 3 months, and any adverse events were determined. In addition, putative periodontal pathogens and the resistance of subgingival bacteria against moxifloxacin were assessed. The data of 57 participants were in-cluded in the statistical analysis. In all treatment groups, the PD decreased from baseline to 3 months, with the greatest reduction seen in partici-pants treated with moxifloxacin 0.4% (1.5 ±0.6 mm; P=.023 compared to placebo), followed by participants receiving moxifloxacin 1.25% (1.2 ±0.4), moxifloxacin 0.125% (1.1 ±1.1), and placebo (1.0 ±0.6). No linear trend for PD reduction with increasing moxifloxacin concentra-tions was found. Porphyromonas gin-givalis showed the greatest reduction in prevalence among the assessed pathogens, without any significant in-tergroup differences. No correlation or systematic relationship between adverse events, including bacterial

resistance against moxifloxacin, and the investigational gels was found. In periodontal pockets with a PD of ≥5.4 mm, a single subgingival admin-istration of a 0.4% moxifloxacin gel as an adjunct to SRP may result in addi-tional PD reduction compared to SRP alone. In addition, the investigated moxifloxacin gels seem to be safe.

Systemic metronidazole and amoxicillin significantly improved the outcomes of nonsurgical debride-ment in individuals with generalized aggressive periodontitis. A study was conducted to observe whether re-treatment with adjunctive antimicro-bials would give the placebo group benefits comparable with the test group.57 Thirty-eight of 41 partici-pants from the initial 6-month trial completed the second phase retreat-ment of sites with remaining pockets of 5 mm. Participants on placebo in phase 1, received adjunctive antibiot-ics for 7 days. Clinical parameters were collected at 2 months after treatment (8 months from baseline). Participants who received antibiotics at initial therapy showed more statistically sig-nificant improvement in pocket depth reduction and a higher percentage of sites improving above clinically rele-vant thresholds than participants who received antibiotics at retreatment. In deep pockets (7 mm), the mean dif-ference was 0.9 mm (P=.003), and in moderate pockets (4 to 6 mm), it was 0.4 mm (P=.036). For pockets convert-ing from 5 mm to 4 mm, this was 83% compared with 67% (P=.041), and for pockets converting from 4 mm to 3 mm, it was 63% compared with 49% (P=.297). At 8 months, participants who had antibiotics at initial therapy showed more statistically significant benefits than those who had antibiot-ics at retreatment.

A study was designed to evaluate the clinical efficacy of subgingival ul-trasonic instrumentation irrigated with essential oils (EOs) of residual periodontal pockets.58 Sixty-four in-dividuals with chronic periodontitis were invited to participate in this ran-domized, double blind, parallel, and

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placebo-controlled clinical trial. All participants received nonsurgical peri-odontal therapy. After reevaluation (baseline), residual pockets (pocket depth ≥5 mm) received test (ultra-sonic instrumentation irrigated with EOs) or control therapy (ultrasonic instrumentation irrigated with nega-tive control). Probing pocket depth (PPD), gingival recession (R), clini-cal attachment level (CAL), bleeding on probing (BOP), and plaque were assessed at baseline and after 4, 12, and 24 weeks. Differences between groups and changes over the course of time were analyzed according to a generalized linear model. A signifi-cant reduction in PPD and BOP and a significant gain in CAL between the 2 groups (P<.001) were noted. Nev-ertheless, no differences were found between the groups at any time in the study. When only initially deep pock-ets (PPD ≥7 mm) were analyzed, a significantly greater CAL gain (P=.03) and PPD reduction (P=.01) were ob-served in the test group. The adjunc-tive use of EOs may promote signifi-cant CAL gain and PPD reduction in deep residual pockets.

A group of investigators compared the effects of systemic amoxicillin (AMX) plus metronidazole (MET) or placebos combined with anti-infec-tive mechanical debridement on the subgingival microbiota of generalized aggressive periodontitis (GAP).59 The study was a 6-month randomized, double-blinded, placebo-controlled clinical trial. Thirty-one participants received full-mouth ultrasonic de-bridement, followed by scaling and root planing with chlorhexidine rins-ing, brushing, and irrigation. During mechanical therapy, participants re-ceived systemic AMX (500 mg) plus MET (250 mg) or placebo, 3 times daily for 10 days. Subgingival samples were obtained from each participant and analyzed for their composition by checkerboard at baseline, 3 months, and 6 months post therapy. Signifi-cant differences between groups over time were determined by the General Linear Model of Repeated Measures.

High levels of periodontal patho-gens, as well as some nonperiodontal species were observed. Most of the periodontal pathogens decreased sig-nificantly over time (P<.05), whereas “nonperiodontal” bacteria tended to increase in both groups. Sites that showed attachment loss and probing depth increase exhibited higher levels of Dialister pneumosintes, Campy-lobacter rectus, Fusobacterium nec-rophorum, Prevotella tannerea, and Peptostreptococcus anaerobius than sites that improved after both thera-pies (P<.05). Systemic AMX+MET or placebos adjunctive to anti-infec-tive mechanical debridement were comparable in lowering periodontal pathogens up to 6 months after treat-ment. Species not commonly associ-ated with GAP were less affected by both therapies.

Another study investigated the impact of 2 surface debridement/decontamination (DD) methods on the clinical outcomes of combined surgical treatment of periimplanti-tis.60 Thirty-two participants suffering from advanced periimplantitis (n=38 combined suprabony and intrabony defects) were treated with flap sur-gery, granulation tissue removal, and implantoplasty at buccally and supra-crestally exposed implant parts. The intrabony aspects were randomly al-located to surface DD by using either (i) an Er:YAG laser (ERL) device, or (ii) plastic curets+cotton pellets+sterile saline (CPS). In both groups, the in-trabony component was augmented with a natural bone mineral and covered with a collagen membrane. Clinical and radiographic parameters were recorded at baseline and after 6 months of nonsubmerged healing. Two participants were lost during follow-up. At 6 months, ERL-treated sites failed to reveal higher reduc-tions in mean bleeding on probing (ERL: 47.8 ±35.5% versus CPS: 55.0 ±31.1%) and CAL values (ERL: 1.5 ±1.4 mm versus CPS: 2.2 ±1.4 mm) when compared with the CPS group. Both groups exhibited a comparable radiographic bone fill at the intrabony

defect component. The study failed to demonstrate a significant impact of the method of surface DD on the clinical outcome after the combined surgical therapy of advanced periim-plantitis lesions.

Periodontal Regeneration - Ridge Preservation

The purpose of a randomized, controlled clinical trial was to deter-mine whether residual ridge preserva-tion using an osteoinductive allograft (test) would prevent ridge resorption and promote bone maturation com-pared to extraction alone (control).61

Seventeen participants, for a total of 20 sites in need of a nonmolar extrac-tion and delayed implant placement were randomly selected to receive ei-ther ridge preservation or extraction alone. A cone beam computed tomo-graph (CBCT) was completed with a radiographic stent in place before ex-traction and 10 to 12 weeks postop-eratively for dimensional and buccal plate analyses. Bone cores were taken for micro-CT and histologic analyses. Resorption of the alveolar ridge oc-curred at all sites with no statistically significant differences found between test and control sites. A significant correlation was found between the initial buccal plate thickness and the loss of vertical ridge height. Micro-CT and histologic analyses found a mean new bone volume (BV) of 44.9% with micro-CT and 37.4% with histology in test sites, and 39% with micro-CT and 35.5% with histology in con-trol sites. The residual graft volume (RGV) was 2.4% with micro-CT and 4.5% with histology. Test and control sites lost similar amounts of alveolar ridge, with the loss of buccolingual width occurring predominately at the expense of the buccal bone. A thicker buccal plate was associated with less ridge loss in the vertical dimension. The percentage of new bone was not statistically significant between either the test or control sites, measured with either micro-CT or histologic analyses.

Treatments for mandibular second



molar (M2) periodontal defects after third molar (M3) removal in high-risk patients are a clinical dilemma for clinicians.62 One study compared the healing of periodontal intrabony de-fects at distal surfaces of mandibular M2s by using bioabsorbable and non-resorbable membranes. Eleven partic-ipants with bilateral probing depths (PDs) ≥6 mm distal to mandibular M2s and intrabony defects ≥3 mm related to the total impaction of M3s were treated with M3 extraction and covering of the surgical bone defect with a bioabsorbable collagen barrier on one side and a nonresorbable ex-panded polytetrafluoroethylene (ePT-FE) barrier contralaterally. The PD, clinical attachment level (CAL), M2 mobility, and furcation class probing were evaluated preoperatively and 3, 6, and 9 months postoperatively. In-traoral periapical radiographs were made immediately preoperatively and 3 and 9 months postoperatively. Both treatment modalities were successful. At 9 months, the mean PD reduction was 5.2 ±3.9 mm for bioabsorbable sites and 5.5 ±3.0 mm for nonresorb-able sites; the CAL gain was 5.9 ±3.3 mm and 5.5 ±3.4 mm, respectively. The outcome difference between the 2 sites for PD and CAL did not differ statistically (P>.05) at any assessment time. Bioabsorbable collagen mem-branes in the guided tissue regenera-tion treatment of intrabony defects distal to the mandibular M2 obtained the same marked PD reductions and CAL gains as nonresorbable ePTFE membranes after M3 extraction.

The purpose of a single-masked, randomized, controlled clinical trial was to compare hard and soft tissue changes after ridge preservation per-formed with (control, RPc) and with-out (test, RPe) primary soft tissue clo-sure in a split-mouth design.63 Eleven participants completed this 6-month trial. Extraction and ridge preserva-tion were performed by using a com-posite bone graft of inorganic bovine-derived hydroxyapatite matrix and cell binding peptide P-15 (ABM/P-15), demineralized freeze-dried bone al-

lograft, and a copolymer bioabsorb-able membrane. Primary wound clo-sure was achieved on the control sites (RPc), whereas test sites (RPe) left the membrane exposed. Pocket probing depth on adjacent teeth, reposition-ing of the mucogingival junction, bone width, bone fill, and postopera-tive discomfort were assessed. Bone cores were obtained for histologic examination. Intragroup analyses for both groups demonstrated sta-tistically significant mean reductions in probing depth and bone width. However, intergroup analysis did not find these parameters to be statisti-cally different at 6 months. The test group showed statistically significant mean change in bone fill (7.21 mm; P<.001). Compared to the control group, the test group showed statis-tically significant lower mean post-operative discomfort (RPc 4 versus RPe 2; P=.002). Histomorphometric analysis showed a presence of 0% to 40% of ABM/P-15 and 5% to 20% of new bone formation in both groups. A comparison of the clinical variables between the 2 groups at 6 months revealed that the mucogingival junc-tion was statistically significantly more coronally displaced in the con-trol group than in the test group, with a mean of 3.83 mm versus 1.21 mm (P=.002). Ridge preservation without flap advancement preserves more ke-ratinized tissue and causes less post-operative discomfort and swelling. Al-though ridge preservation performed with both methods results in bone width loss of approximately 27% to 30%, ridge preservation can minimize the loss of alveolar bone subsequent to tooth extraction in preparation for implant therapy.

The purpose of another study was to histologically and clinically com-pare human demineralized bone ma-trix (DBM) putty with 1 size of bone particles (SPS) to human DBM putty with 2 different sizes of bone particles (MPS) in ridge preservation after molar extractions.64 Molar tooth ex-traction and ridge preservation were performed in 20 participants for each

treatment group. Approximately 20 weeks after grafting, core biopsies were obtained during implant place-ment and analyzed with light micros-copy. Specimens were analyzed for the percentage area of vital bone, residual graft particles, and nonmineralized structures (CT). Changes in alveolar ridge dimensions were also deter-mined. The results were that 16 par-ticipants in the SPS group and 14 in the MPS group completed the study. The SPS group had a mean of 49% vi-tal bone, 8% residual graft, and 43% CT. The MPS group had 53%, 5%, and 42%, respectively. Participants in both groups lost a mean of less than 1 mm alveolar height on the buccal and lingual aspects and less than 1.5 mm of total ridge width. There were no statistically significant differences between the 2 groups for any clinical or histological parameters. The re-sults of this study suggest that adding larger bone particles to a DBM putty does not offer additional benefit in the preservation of alveolar bone af-ter the extraction of molar teeth.

Periodontal Regeneration

A systematic review was con-ducted to review the literature and to determine the clinical performance of conservative surgery (CS) for the treatment of intrabony defects (ID).65 Randomized clinical trials (RCTs) on intrabony defect (ID) treatment with 12 months of follow-up were identi-fied through electronic databases and hand-searched journals. Primary out-comes were tooth survival, clinical at-tachment (CAL) gain, probing depth (PD) reduction, and gingival reces-sion (REC) increase. Weighted means and forest plots were calculated for each outcome variable 12 months after surgery. Long-term stability was explored with RCTs of at least 24 months of follow-up. Subgroup anal-ysis was performed according to the type of flap. Twenty-seven trials re-porting 647 participants and 734 de-fects were identified. Twelve months after CS, tooth survival was 98% (In-

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terquartile range (IQ): 96.77 to 100), CAL gain 1.65 mm (95% CI: 1.37 to 1.94; P<.001), PD reduction 2.80 mm (CI: 2.43 to 3.18; P<.001), and REC increase 1.26 mm (CI: 0.94 to 1.49; P<.001). Longer follow-up showed similar findings. The CIs of CAL gain were 1.44 to 3.52 for recently intro-duced papilla preservation flaps and 1.25 mm to 1.89 mm for access flaps. The treatment of intrabony defects with CS is associated with high tooth retention and improvement of peri-odontal clinical parameters. Clinical performance may vary according to the type of surgical flap used.

The purpose of a randomized, long-term clinical trial was to com-pare clinically based and patient-based outcomes after periodontal regeneration or extraction and re-placement of hopeless teeth with chronic perio-endo lesions and/or attachment loss to or beyond the apex.66 Fifty patients presenting with generalized severe periodontitis and at least 1 hopeless tooth to be ex-tracted for periodontal reasons were entered in this study. The test treat-ment consisted of the application of a regenerative strategy to 25 hopeless teeth. The control treatment consist-ed of the extraction of the 25 hope-less teeth and their replacement with conventional or implant-supported partial fixed dental prostheses. In the control group, 14 teeth were replaced with implant-supported restorations, 8 with tooth-supported fixed pros-theses, 2 with resin-bonded prosthe-ses, and 1 was not replaced. All fixed prostheses survived the 5-year follow-up period, and 83% were free from biological complications. In the test group, 23 of the 25 regenerated teeth showed important clinical improve-ments: the 2 teeth with unsatisfactory outcomes were extracted at 1 year. The 23 successfully regenerated teeth (92%) were in good health and func-tion at the 5-year examination visit, and 84% did not develop biologi-cal complications during the recall period. All participants consistently reported comfort in function. In the

test group, the average clinical attach-ment level gains were 7.7 ±2.8 mm, the radiographic bone gain 8.5 ±3.1 mm, and the probing pocket depth (PPD) reduction 8.8 ±3 mm. Residual PPDs were 4 ±1.7 mm. Most of the regenerated teeth showed a decrease in tooth mobility. Regenerative ther-apy can be applied to hopeless teeth and has the potential to change their prognosis; it is a suitable alternative to the extraction of severely compro-mised teeth with intrabony defects at or beyond the root apex.

A 3-arm study compared the clini-cal and radiographic efficacy of the modified minimally invasive surgical technique (M-MIST) alone and com-bined with enamel matrix derivative (EMD) or EMD plus bone mineral derived xenographs (BMDX) in the treatment of isolated, interdental in-trabony defects.67 Forty-five deep, isolated, intrabony defects in 45 participants were included, accessed with the M-MIST, and randomly as-signed to 3 balanced experimental groups. The M-MIST consisted of a small buccal flap without elevation of the defect-associated papilla. Af-ter removing the granulation tissue by sharp dissection and root instru-mentation, the regenerative material was applied before obtaining primary closure with a single internal modi-fied mattress suture when indicated. Surgery was performed with the aid of an operating microscope and micro-surgical instruments. Outcomes were evaluated as pocket depth reduction, attachment level gain, radiographic bone fill, and patient-related. Primary wound closure was maintained in all treated sites with the exception of one M-MIST EMD+BMDX site. No patient reported intraoperative or postop-erative pain. Within group differences between baseline and 1 year were sta-tistically significant in the 3 groups in terms of probing pocket depth reduction, clinical attachment level (CAL) gain and bone fill (P<.001). Comparisons among the 3 groups showed no statistically significant dif-ference in any of the measured clinical

outcomes. In particular, CAL gains of 4.1 ±1.4 mm were observed in the M-MIST control group, 4.1 ±1.2 mm in the EMD group, and 3.7 ±1.3 mm in the EMD+BMDX group. The percent-age radiographic bone fill of the in-trabony component was 77% ±19% in the M-MIST control group, 71% ±18% in the EMD group, and 78% ±27% in the EMD+BMDX group. M-MIST with or without regenerative materials re-sulted in significant clinical and radio-graphic improvements. Interestingly, while this initial study did not have sufficient power to detect intergroup CAL differences of less than 0.96 mm, the observed outcomes were remark-ably similar and warrant further inves-tigations.

Enamel matrix derivative (EMD) is commonly used in periodontal therapy. The purpose of one system-atic review was to provide an updated answer to the question of whether the additional use of EMD in peri-odontal therapy is more effective than control or other regenerative proce-dures.68 A literature search in MED-LINE (PubMed) for the use of EMD in periodontal treatment was performed up to May 2010. The use of EMD in treatment of intrabony defects, furca-tions, and recession was evaluated. Only randomized controlled trials with at least 1 year of follow-up were included. The primary outcome vari-able for intrabony defects was the change in clinical attachment level, for furcations the change in horizon-tal furcation depth, and for recession complete root coverage. After screen-ing, 27 studies (20 for intrabony de-fects, 1 for furcation, and 6 for re-cession) were eligible for the review. A meta-analysis was performed for intrabony defects and recession. The treatment of intrabony defects with EMD showed a significant additional gain in clinical attachment of 1.30 mm in comparison to open flap de-bridement, EDTA, or placebo, but no significant difference in comparison to resorbable membranes was shown. The use of EMD in combination with a coronally advanced flap compared



to a coronally advanced flap alone showed significantly more complete root coverage (OR=3.5), but in com-parison to a connective tissue graft the result was not significantly dif-ferent. The use of EMD in furcations (2.6±1.8 mm) gave significantly more improvement in horizontal defect depth than resorbable membranes (1.9 ±1.4 mm). In the treatment of in-trabony defects, the use of EMD is su-perior to control treatments but only as effective as resorbable membranes. The additional use of EMD with a coronally advanced flap for recession coverage will give superior results to control but is as effective as a con-nective tissue graft. The use of EMD in furcations will give more reduction in horizontal furcation defect depth than resorbable membranes.

One study compared the clinical and radiographic outcomes of a com-bination of enamel matrix derivatives (EMD) and a synthetic bone graft (EMD/SBG) with EMD alone in wide ≥2 mm) and deep (≥4 mm) 1- wall and 2- wall intrabony defects 12 months after treatment.69 Seventy-three par-ticipants with chronic periodontitis and 1 wide ≥2 mm) and deep ≥4 mm) intrabony defect were recruited in 5 centers in Germany. During surgery, defects were randomly assigned to EMD/SBG (test) or EMD (control). Assessments at baseline after 6 and 12 months included bone sounding, attachment levels, probing pocket depths, bleeding on probing, and re-cession. Changes in defect fill were recorded radiographically. Both treat-ment modalities led to significant clini-cal improvements. In the EMD/SBG group a mean defect fill of 2.7 ±1.9 mm was calculated, and in the EMD group the defect fill was 2.8 ±1.6 mm. A mean gain in clinical attachment of 1.7 ±2.1 mm in the test group and 1.9 ±1.7 mm in the control group af-ter 1 year was observed. Radiographic analysis confirmed that deeper defects were associated with greater defect fill for both groups. The results show

comparable clinical and radiographic outcomes for both treatment mo-dalities 12 months after treatment. Mucogingival Treatment

The standard of care for increas-ing keratinized gingiva adjacent to teeth that do not require root cover-age is the free gingival graft (FGG). A pilot study indicated that the use of a living cellular construct (LCC fore-skin) could be effective in this clinical scenario.70 A pivotal, multicenter, ran-domized, within-patient, controlled, open-label trial was conducted (n=96 participants). After the removal of the mucosa and keratinized gingiva from the test site, either an LCC or FGG was applied. The primary effi-cacy endpoint was the ability of the LCC to regenerate ≥2 mm keratinized gingiva at 6 months. Secondary mea-sures were the same color and texture as the adjacent tissue, a 1 mm width of keratinized gingiva at 6 months, patient treatment preference, surgical site sensitivity at 1 week, and patient-reported pain after 3 days. Safety was assessed by reports of adverse events. At 6 months, the LCC regenerated ≥2 mm of keratinized gingiva in 95.3% of participants (81 of 85 participants; P <.001 versus a 50% predefined stan-dard). As expected, the FGG gener-ated more keratinized gingiva (4.57 ±1.0 mm) than the LCC (3.2 ±1.1 mm). The gingiva regenerated with the LCC matched the color and tex-ture of the adjacent gingiva. All par-ticipants achieved ≥1 mm keratinized gingiva with the LCC treatment by 6 months, and more participants pre-ferred treatment with the LCC than with the FGG. No difference in sen-sitivity or pain was noted between the treatments. The treatments were well tolerated, and reported adverse events were typical for this type of periodontal surgery.

The purpose of one study was to evaluate the local tolerance and ef-ficiency of 2 experimental collagen matrices to increase the width of ke-ratinized tissue.71 In 12 pigs, 2 api-

cally positioned flaps were prepared on both sides of the mandible. The denuded defect areas were randomly covered with 1 of 2 experimental por-cine-derived collagen matrices (M1; M2). The other defect area was left un-treated (control). At 1 and 6 months, clinical measurements for the width and thickness of the keratinized tissue were recorded. At 6 months, all ani-mals were sacrificed. Descriptive and semiquantitative histologic analyses were performed. For statistical analy-sis, the Kruskal-Wallis test and the McNemar test were applied. Results revealed collagen matrices integrated well into the surrounding tissue with-out any signs of inflammation. The thickness and width of the keratinized tissue increased significantly over 6 months in all the groups, resulting in slightly more favorable results for M1 (compared with M2) with respect to the thickness and for M2 (compared with M1) with respect to the width of keratinized tissue. No statistically sig-nificant differences were observed for any of the evaluated clinical and his-tologic parameters among the 3 treat-ment modalities. Within the limits of this animal study, the prototype colla-gen matrices can be safely used to in-crease the width of keratinized tissue.

An interesting randomized clinical trial compared the long-term results of subepithelial connective tissue grafts (SCTG) versus acellular der-mal matrix allografts (ADMA) in the treatment of gingival recession.72 In 16 participants with bilateral Miller Class I/II gingival recession, one side was treated with SCTG and the other side with ADMA. Clinical parameters were measured at baseline, 6 months, and 5 years postsurgery. Fifteen par-ticipants completed the study. At 6 months, all parameters showed sig-nificant improvement in ADMA and SCTG groups [complete root cover-age (CRC): 73.3% versus 26.7%, P= .027; reduction of recession depth (RD): 2.6 ±1.1 mm versus 2.2 ±1.1 mm P=.376; reduction of recession width (RW): 3.0 ±1.4 mm versus 2.4 ±1.4 mm, P=.207, respectively]. At

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5 years, significant relapses were de-tected in CRC and reduction of RD and RW in both groups with no sta-tistically significant difference (CRC: 20.0% versus 13.3%, P=1.00; RD: 1.6 ±1.2 mm versus 1.5 ±1.4 mm, P=.838; RW: 1.8 ±1.4 mm versus 1.3 ±1.5 mm, P=.367). Participants practicing horizontal toothbrush-ing showed more relapse (OR=11.2; P=.01). Compared with baseline, the gingival width (GW) did not increase in ADMA-treated sites (P=.903). Five-year results of SCTG and ADMA were similar in terms of CRC and reduc-tion of RD and RW. Both techniques showed a significant relapse associ-ated with participants returning to horizontal tooth brushing habits. The increase of GW was stable in SCTG-treated sites but reached presurgical values in ADMA-treated participants.

The objectives of another study were (1) to test the reliability of a new classification system of gingival reces-sion by using the level of interproxi-mal clinical attachment as an identifi-cation criterion and (2) to explore the predictive value of the resulting clas-sification system on the final root cov-erage outcomes.73 Participants show-ing at least 1 buccal gingival recession were recruited by 1 operator. Three recession types (RT) were identified. While class RT1 included gingival re-cession with no loss of interproximal attachment, class RT2 recession was associated with interproximal at-tachment loss less than or equal to the buccal site and class RT3 showed higher interproximal attachment loss than the buccal site. The classification was tested by 2 examiners blinded to the data collected by the other exam-iner. Intrarater and interrater agree-ment were assessed. Furthermore, the 6-month root coverage outcomes of consecutively treated gingival reces-sion were retrospectively evaluated to explore the predictive value of the proposed classification on the final recession reduction (Rec Red). The new classification system of gingi-val recession was tested in a total of 116 patients with gingival recession

(mean 3.2 ±1.2 mm) in 25 partici-pants. The intraclass correlation coef-ficient (ICC) for interrater agreement was 0.86, showing an almost perfect agreement among the examiners. The RT classification was predictive of the final Rec Red (P<.001) at the 6-month follow-up in 109 patients with treated gingival recession. The evaluation of the interproximal clinical attachment level may be used to classify gingival recession defects and to predict final root coverage outcomes.

DENTAL MATERIALS

Dental Adhesives

Much of the focus of research on adhesive systems continues to be on improving bond durability to en-hance restoration longevity. An excel-lent review paper examined factors that compromise resin-dentin bond durability, including hydrolytic deg-radation by water sorption into the adhesive interface and incomplete infiltration by resin monomers into the demineralized dentin surface.74 A factor of increasing importance to bond degradation is the release of matrix metalloproteinases (MMPs) as a result of the bonding process, which can degrade collagen fibrils in adhesive zones that are incompletely infiltrated with resin. Approaches that are being actively investigated include the use of MMP inhibitors such as chlorhexidine, benzalkonium chloride, and quaternary ammonium salts, either applied separately to the dentin surface or incorporated into the adhesive resin. An additional experimental approach is biomimetic remineralization in which portions of the adhesive zone that have been depleted of apatite during the etching process are remineralized by us-ing polyanionic analogs of acidic matrix proteins to induce the growth of apatite.

A combination in vivo and in vitro study evaluated the effect of chlorhex-idine use and biomimetic remineral-ization on the integrity of resin-dentin interfaces.75 Participants requiring premolar extractions for orthodon-

tics (age 12 to 17 years) had a total of 18 premolar pairs that received a standardized occlusal composite res-in restoration. The preparations were etched with phosphoric acid and 1 randomly assigned tooth of each pair had 2% chlorhexidine applied for 30 seconds; the control tooth had deion-ized water applied for 30 seconds. The surface was blot dried and a 2-step adhesive (Prime & Bond NT; Dentsply Intl, York, Pa) was applied, air dried, and polymerized. A microfill com-posite (Epic TMPT; Parkell Inc, Edge-wood, NY) was used to incrementally fill the preparations. Ten tooth pairs were immediately extracted and used for the in vitro aspect of the study; the other 8 tooth pairs were allowed to function for 1 year and then extract-ed. Following extraction, the tooth/restoration was sectioned to create a 1 mm thick slab that included the bonded interface. Eight tooth slabs prepared from the immediately ex-tracted chlorhexidine-treated teeth were aged in simulated body fluid for 12 months. Eight tooth slabs from the control group were placed in a rem-ineralization medium and stored for 12 months. The final 2 tooth pairs of the immediate extraction group were used for baseline analysis. After aging, all slabs were prepared and subjected to transmission electron microscopy (TEM). In vivo specimens bonded without chlorhexidine revealed exten-sive hybrid layer degradation, whereas both the in vivo and in vitro chlorhex-idine-treated specimens showed an intact hybrid layer after 12 months of function. The specimens subjected to biomimetic remineralization proto-col showed collagen remineralization in the hybrid zone. The authors con-cluded that both the use of chlorhexi-dine and biomimetic remineralization provided similar results in terms of preventing degradation of the hybrid layer, although the biomimetic remin-eralization protocol is experimental at this time.

The effect of 2% chlorhexidine on bond strength and silver nitrate up-take over 2 years when applied as an



aqueous solution or when associated with acid etchant was examined in an in vitro study.76 Forty-two extracted human third molars had their occlu-sal surface reduced to produce a flat dentin surface. Two, 2-step etch-and-rinse adhesives (Adper Single Bond 2; 3M ESPE, St Paul, Minn) ethanol-wa-ter solvents; and (Prime & Bond NT; Dentsply Intl), an acetone solvent, were used. The teeth were divided into 6 groups: 2 control groups, in which the 2 adhesives were applied after normal etching, rinsing, drying, and rewetting with water; 2 groups in which the same bonding procedure as the controls was used except the etchant contained 2% chlorhexidine; and 2 groups bonded as for the con-trol group except that rewetting was accomplished with a 2% chlorhexi-dine solution. Composite resin was polymerized onto the bonded sur-faces, stored for 24 hours, sectioned into 0.8 mm2 sticks, and randomly assigned for immediate testing or 2 year storage in distilled water before testing. Two sticks from each tooth were immersed in silver nitrate and subjected to scanning electron mi-croscope (SEM) analysis to measure silver uptake, and the remainder were used for microtensile strength test-ing. The control specimens had a significant decrease in bond strength over 2 years, while the specimens that used chlorhexidine in either the acid etchant or the rewetting solution showed no such bond strength reduc-tion. There was increased silver uptake into the hybrid zone of all groups, but the amount was significantly higher in the control groups than in the experi-mental groups. Both the silver uptake and bond strength results demon-strated the improved stability of the resin-dentin zone when chlorhexidine was used in conjunction with bond-ing procedures.

The effectiveness of chlorhexidine on resin-dentin bond stability in nor-mal and caries- affected dentin was the subject of an in vitro study.77 Ex-tracted human molars (n=120) with occlusal caries were ground down

until dentin hardness, visual exami-nation, and staining with dye deter-mined that affected dentin remained surrounded by normal dentin. The tooth roots were sectioned and at-tached to a device that simulated intrapulpal pressure. The teeth were divided into 3 groups: control, in which water was applied to the den-tin surface before the application of a 2-step self-etch adhesive (Clearfil SE; Kuraray America Inc, Houston, Tex); a second group, in which 2% chlorhexi-dine solution was applied before the adhesive; and a third group, in which 5% chlorhexidine solution was ap-plied before the adhesive. All bond-ing procedures were accomplished by using simulated intrapulpal pressure. Half of the specimens in each group were tested after 24 hours, and the other half were tested after 2 years storage in artificial saliva and under intrapulpal pressure. Double-faced adhesive tape with holes punched to isolate an area of affected dentin and an area of normal dentin was applied before bonding. Polyethylene tubes with a 0.9 mm internal diameter were used to apply resin composite to the bonded areas. The specimens were tested for microshear bond strength. There was no statistical difference among the 2-year strength speci-mens in normal dentin, although the chlorhexidine groups had numerically higher bond strength values. In af-fected dentin, the 5% chlorhexidine group had statistically higher bond strength at 2 years compared to the 2% chlorhexidine and control groups. There was a significant degradation of bond strength from 24 hours to 2 years for all groups except the 5% chlorhexidine-affected dentin group. Again, this study showed the benefi-cial effect of chlorhexidine on bond stability, although the effect was lim-ited, perhaps due to the application of chlorhexidine before dentin condi-tioning, necessitated by the use of a self-etch adhesive.

An alternative technique for en-hancing bond stability was the sub-ject of a 24 month clinical trial.78 The

effect of using a vigorous rubbing ac-tion to apply 2 different adhesives to noncarious cervical lesions (NCCLs) under both wet and dry bonding con-ditions was evaluated in this study. Forty participants received 160 resto-rations of NCCLs with moderate scle-rosis. Individuals were excluded for poor oral hygiene, severe or chronic periodontitis, or heavy bruxism. No additional tooth preparation or bev-eling was done. Two, 2-step etch-and-rinse adhesives (One-Step, Bisco Inc, Schaumburg, Ill; Adper Single Bond, 3M ESPE) were applied according to manufacturer instructions. Following acid etching, one half of the cavities were left dry after rinsing, and the other half were rewet with water. The adhesive systems were applied with vigorous rubbing. The restorations were filled and polymerized in 3 incre-ments. Two evaluators blinded to ex-perimental assignment and who were not involved in restoration placement evaluated the restorations at baseline, 6, 12, and 24 months. At the end of 24 months, no restorations exhib-ited secondary caries, nor were there any significant differences among the groups for hypersensitivity, retention (91.9% to 97.5%), or marginal adap-tation. There was no difference be-tween rewet and dry conditions for either adhesive. However, there was significantly greater marginal discol-oration in the One Step restorations at 24 months versus at baseline than in the Adper Single Bond restorations, regardless of dentin moisture. The au-thors attributed this latter result to One Step’s higher solvent content and higher hydrophilicity.

The effect of the application tech-nique on immediate and long-term bonding performance of 1-step ad-hesives was investigated in an in vi-tro study.79 The occlusal surfaces of 42 extracted human molars were reduced to create flat dentin sur-faces. Three 1-step adhesives (Adper Prompt L-Pop, 3M ESPE; Xeno III, Dentsply Intl; Clearfil S3 Bond, Ku-raray) were applied either following manufacturer instructions (control)

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or applied as per manufacturer in-structions but with the microbrush being scrubbed on the dentin surface under manual pressure (active). Af-ter adhesive application, composite resin was placed and polymerized, the teeth were sectioned into bonded sticks of approximately 0.8 mm2, and the sticks were divided for either silver nitrate uptake analysis or microtensile bond strength testing. One half of the specimens was tested immediately, and the other half was tested after 3 years storage in water. The micro-tensile bond strengths of the 3 year specimens were significantly lower than those of the immediately tested specimens. However, the active ap-plication groups showed significantly higher bond strengths at both time periods. A significant increase in sil-ver nitrate uptake was observed after 3 years of storage; however, the ac-tive application groups showed less silver nitrate uptake, particularly in the aged specimens. The authors at-tributed the higher bond strength and lower silver nitrate uptake in the ac-tive application groups to higher dis-solution of the smear layer and a re-sultant improved penetration of resin monomers into the dentin surface and to enhanced solvent evaporation.

It is well established that bonding immediately after bleaching will re-duce bond strength due to the reten-tion of released oxygen from peroxide bleaching agents. An in vitro study evaluated the amount of time 35% hydrogen peroxide is retained in den-tin after bleaching and the effect of sodium ascorbate on the removal of residual peroxide.80 Seventy recently extracted human third molars had the occlusal enamel removed, and then 4×4×2 mm dentin specimens were sectioned from the teeth and divided into 8 groups. A standardized amount of 35% hydrogen peroxide (Whiteness HP Maxx; FGM Dental Products, Jo-inville, SC, Brazil) was applied in 3 applications of 15 minutes each; the gel was then rinsed from the speci-mens. A 35% percent solution of so-dium ascorbate was added to tubes

containing the bleached dentin speci-mens, in either 1 or 2 increments of time varying from 1 minute to 60 min-utes. Colorimetric analysis was used to assess the amount of remaining peroxide. A large amount of hydrogen peroxide was released immediately af-ter bleaching. This amount increased during the first 24 hours, decreased dramatically by 48 hours, and ap-proached statistical equivalence with the control (nonbleached) specimens by 72 hours. The groups treated with a single application of sodium ascor-bate, regardless of time, did not show a reduction in the hydrogen peroxide elimination time. In contrast, all of the groups in which sodium ascorbate was applied more than once, regard-less of contact time, were statistically similar to the control group.

It is known that adhesive proce-dures are sensitive to environmen-tal factors such as relative humidity and contaminants such as saliva and blood. While the rubber dam is an effective way to counter these prob-lems, surveys have shown that few dentists routinely use rubber dams for restorative dentistry. An interesting study compared the relative humidity and intraoral temperature produced by 2 intraoral vacuum devices (Isolite i2 Dryfield Illuminator System, Isolite Systems, Santa Barbara, Calif; Coo-lex, APT Inc, Fukushima, Japan) and a rubber dam.81 Five volunteers were used for the study. Each volunteer had the relative humidity and intraoral temperature measured with a digital sensor before and after the placement of a rubber dam on a lower left first molar. The sensor was placed in the same location for all measurements. The control was measured with only an occlusion block in place. The rub-ber dam produced the lowest relative humidity after placement. While the temperature dropped in the first 3 minutes following rubber dam place-ment, by 4 minutes the temperature was the same as at baseline. The 2 intraoral vacuum devices significantly reduced the relative humidity relative to baseline but to a level that was still

significantly higher than that obtained with the rubber dam. Relative humid-ity quickly returned to normal follow-ing the removal of all of the devices. There was a significant reduction in temperature with the 2 intraoral vacuum devices that did not return to normal until they were turned off.

One of the benefits of porcelain restorations is that they can be re-paired. However, this normally re-quires the use of hydrofluoric (HF) acid for porcelain conditioning and phosphoric acid (PA) for condition-ing the enamel and dentin adjacent to the restoration. A study evaluated the effect of altering the concentra-tion of and the sequence of applying HF acid on the bond strength of com-posite resin to enamel and dentin.82 Standardized flat enamel or dentin surfaces were created on 80 extracted human third molars, which were then divided into 10 groups (5 enamel groups and 5 dentin groups). The 8 experimental groups were etched with 35% PA and either 5% or 9.5% HF; however, the order in which the etchants were applied was varied. Af-ter rinsing and drying, a 2-step etch-and-rinse adhesive (ExciTE; Ivoclar Vivadent, Amherst, NY) was applied and polymerized. The enamel and dentin control groups were treated according to manufacturer instruc-tions without HF acid etching. After bonding, composite resin was ap-plied with a 3.5 mm diameter poly-ethylene mold, polymerized, thermo-cycled, and bond strength tested in shear. The 2 control groups had sig-nificantly higher bond strength than the experimental groups. For enamel, significantly lower bond strength was obtained when HF was applied be-fore PA. The results were mixed for the dentin groups, with the specimens that were treated with PA followed by 9.5% HF demonstrating significantly higher bond strength than specimens treated with 5% HF followed by PA. HF clearly reduced the bond strength to both enamel and dentin, dem-onstrating that the clinician should avoid applying HF to adjacent tooth



structure when repairing porcelain restorations.

Composite Resin

Composite resin is an area of em-phasis in restorative dental materials research, and researchers, both in academics and employed by manu-facturers, expend considerable ef-fort on improving these materials. A comprehensive review that begins by summarizing the major components of composite resin and then explains the current state of the art from a materials perspective gives the reader a good foundation for understand-ing the ongoing research into each of these components.83 Areas of active research include finding new initiators that are more efficient, reducing col-ored by-products, and lessening reli-ance on toxic amine co-initiators. An-other area of intensive investigation is finding new monomers that can im-prove mechanical properties, reduce polymerization shrinkage and shrink-age stress, and lessen the amount of unreacted monomer that can leach out of a completed restoration. Re-cent investigations have examined incorporating an acidic functional group into the composite resin mono-mer with the intent of eliminating the separate placement of an adhesive. Much of the recent improvements in dental composite resins can be at-tributed to altering filler shape, size, nature, type, and surface modifica-tion. Research continues to consider the filler component, including novel compositions, and morphology.

A key shortcoming in dental com-posite resin is polymerization shrink-age, and research continues to focus on methods to mitigate its effect on restorations. One study compared the effect of bulk and incremental fill techniques by using composite resin with different elastic moduli on cuspal deflection.84 A standardized mesio-occlusodistal (MOD) prepara-tion was performed on 120 extracted human premolars, the enamel was etched with phosphoric acid, and a

2-step self-etch adhesive (AdheSE; Ivoclar Vivadent) was applied. The preparations were filled with one of 4 different composite resins with simi-lar volumetric polymerization shrink-age but varying elastic moduli in one of 3 techniques: bulk fill, or 2 or 3 horizontal layers with an LED polym-erization light. Cuspal deflection was measured with a custom screw and pin measuring device. The results showed that cuspal deflection was significantly greater in the bulk place-ment group than in the incremental placement groups and that the use of 2 horizontal layers induced greater cuspal deflection than did the use of 3 horizontal incremental layers. In addition, there was a significant cor-relation between the elastic moduli of the composite resins and cuspal deflection, with the stiffer composite resins demonstrating greater cuspal deflection. This study emphasized the benefit of a multilayer incremental approach to reducing the adverse ef-fects of polymerization shrinkage and shrinkage stress.

Another technique that has been reported as effective in lessening the impact of polymerization shrinkage is the use of flowable composite resin as a liner. Investigators evaluated the effect of using flowable composite resin in MOD composite resin resto-rations on cuspal deflection.85 Forty extracted human mandibular molars of similar dimension received stan-dardized MOD preparations and a 2-step etch-and-rinse adhesive (Ex-ciTE; Ivoclar Vivadent). The teeth were divided based on the use of 1 of 2 different composite resin systems (Tetric EvoCeram/Flow, Ivoclar Viva-dent; Grandio, VOCO America Inc, Briarcliff Manor, NY). Each half was further subdivided into 2 groups: one group had a flowable composite resin applied to the internal cavity line an-gles before placement of the respec-tive nanohybrid restorative composite resin, while the other group was filled entirely with the restorative compos-ite resin. Cuspal deflection was mea-sured with strain gauges. Specimens

with flowable composite resin liners demonstrated significantly greater cuspal deflection than those filled with the restorative composite resin alone, probably due to the greater res-in content and polymerization shrink-age of the flowable composite resins.

Another study evaluated the im-pact of adhesive type (etch-and-rinse versus self-etch) and restoration with or without a flowable composite resin liner on marginal and internal integ-rity.86 Eighty extracted human molars were prepared for standardized MOD cavities with the gingival margin below the cementoenamel junction (CEJ). Cavities were randomly treated with 1 of 2 etch-and-rinse adhesives (Syntac; Ivoclar Vivadent and XP Bond; Dent-sply Intl) or 1 of 3 self-etch adhesives (Xeno V; Dentsply Intl, Prompt-L-Pop; 3M ESPE, and iBond SE; Heraeus Kul-zer, South Bend, Ind). One half of all specimens was restored by filling the apical 4 mm of the preparations with a flowable composite resin (SDR; Dent-sply Intl) and the coronal 2 mm of the preparations with the manufacturer’s composite resin (Ceram.X Mono, Dentsply Intl; Tetric EvoCeram, Ivo-clar Vivadent; Filtek Supreme XT, 3M ESPE; and Venus Diamond, Heraeus Kulzer). The other half of the prepa-rations was filled with the composite resin only by using a horizontal incre-mental fill technique. Specimens were stored for 21 days at 37°C in distilled water, subjected to 100 000 cycles in a masticatory simulator and 2500 thermal cycles (5oC/55oC), examined by SEM for external marginal integrity (% gap-free margin), sectioned mesio-distally, and reexamined for internal marginal integrity. For both external enamel margins and internal dentin margins, etch-and-rinse adhesives demonstrated significantly better mar-ginal integrity than self-etch adhesives. The flowable composite resin had no effect on marginal integrity.

The effect of a flowable compos-ite resin liner compared to a resin-modified glass ionomer (RMGI) liner on microleakage in class 2 composite resin restorations was the subject of

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an in vitro study.87 Forty-eight extract-ed premolars received 2 standardized class 2 slot preparations with the gin-gival margin below the CEJ. The teeth were randomly divided into 6 groups. Half received a 2-step etch-and-rinse adhesive (Single Bond; 3M ESPE), and the other half received a 2-step self-etch adhesive (Clearfil SE; Kura-ray America Inc). One group for each adhesive received a 0.6 mm to 0.8 mm thick layer of flowable composite resin (Filtek Flow; 3M ESPE), and 1 group for each adhesive received a an RMGI lining (Fuji II LC; GC America, Alsip Ill) before the application of the adhesive. All cavities were filled with Filtek P60 composite resin (3M ESPE) by using horizontal increments. After finishing, all specimens were thermo-cycled (5oC/55oC) for 1000 cycles and immersed in methylene blue for 48 hours, sectioned, and the gingival margin graded for microleakage. The groups that received the RMGI liner had significantly lower microleakage than either the flowable composite resin or no liner groups.

The benefits of an RMGI liner for maintaining the composite resin-den-tin interface were also demonstrated in an in vitro study of class 1 compos-ite resin restorations.88 Standardized occlusal cavities were prepared in 60 extracted third molars and randomly assigned to 1 of 6 groups. Two groups received no liner; 2 groups received a 0.5 mm glass ionomer cement liner (Ketac Molar Easymix; 3M ESPE); and 2 groups received a 0.5 mm RMGI lin-er (Vitrebond; 3M ESPE). All groups were restored with a 2-step etch-and-rinse adhesive (Adper Single Bond 2; 3M ESPE) and composite resin (Filtek Z250; 3M ESPE) by using a horizon-tal incremental technique. One half of the specimens were thermocycled (5oC/55oC) for 5000 cycles and cut into 0.8 mm thick slices for microten-sile bond strength testing and confo-cal microscopic analysis. The results showed that glass ionomer did not improve the bond strength to dentin; however, the use of an RMGI liner significantly reduced the presence of

interfacial gaps after thermocycling, suggesting that the long-term quality of the adhesive interface is improved when RMGI liner is used.

A challenge in the restoration of posterior composite resin restora-tions is achieving appropriate proxi-mal contacts. An in vitro study evalu-ated the impact of 3 different matrix techniques on the proximal contact tightness of a restoration.89 To maxi-mize standardization, an MOD cavity was manufactured in 45 ivorine man-dibular right first molars that were in-dividually restored in a dental manikin with 1 of 3 fill techniques: a sectional matrix system (Palodent; Dentsply Intl) and wooden wedge were ap-plied and used to fill the mesial box, removed and a fresh matrix placed to restore the distal box, followed by an occlusal increment of composite resin; mesial and distal matrices were applied simultaneously and the tooth filled as in the first group; a circum-ferential matrix (Walser Matrices; Walser Dental GmbH) was placed and the tooth filled as for the other 2 groups. The contact tightness was evaluated with a tooth pressure meter that has been used in multiple previ-ous studies of this type. The applica-tion of 2 matrix bands simultaneously produced the tightest proximal con-tacts. The circumferential system pro-duced a mesial contact that was simi-lar to the first group but lower than the simultaneous matrix application group, whereas the distal contact was the lowest of any contact tightness in the study.

An in vivo study evaluated the proximal contact tightness of class 2 cavities restored with a sectional or circumferential matrix system.90 Eighty-five individuals in need of a 2-surface or 3-surface posterior res-toration were included in the study. After the cavity was completed, the teeth were randomly assigned to be restored by using a sectional matrix system (Palodent; Dentsply Intl) or a circumferential matrix system (Hawe Tofflemire Matrices; Kerr Corp). For a MOD cavity assigned to the sectional

matrix group, both the mesial and dis-tal surfaces received the matrix, ring, and wooden wedge at the same time. Restorations were bonded with Opti-bond FL (Kerr Corp) and Herculite composite resin (Kerr Corp) was ap-plied in a multilayer incremental tech-nique. All restorations were done by using rubber dam isolation. Proximal contact tightness was measured with the tooth pressure meter before treat-ment and immediately after restora-tion placement at 5 proximal con-tacts: both contacts of the restored tooth and an additional contact in a mesial direction in the same quadrant and corresponding contacts in the contralateral quadrant. For the 2-sur-face restorations, the use of the sec-tional matrix resulted in a significantly tighter proximal contact than did the circumferential matrix. The sectional system resulted in an increase of con-tact tightness, whereas the circumfer-ential system resulted in a decrease of contact tightness. Regarding the 3-surface restorations, the sectional matrix resulted in a slight increase in proximal contact tightness, while the circumferential system resulted in a slight decrease. The difference was not significant. The authors suggest that the result with the MOD restorations was likely due to the simultaneous ap-plication of the matrices and rings, re-sulting in a separation effect in oppo-site directions and thereby diminishing their effect at the contact area.

A study evaluating the light in-tensity of quartz-tungsten halogen (QTH) and light-emitting diode (LED) polymerization lights emphasized the importance of monitoring polymer-ization lights in dental offices.91 At 8 government dental health institutions in Saudi Arabia, 210 dental polym-erization lights were evaluated for light intensity output with a digital spectrometer. Each light was tested 3 separate times, and the tip diameter was accounted for in determining the light intensity. Any light with a read-ing below 300 mW/cm2 was consid-ered unsatisfactory. The test included 120 QTH lights and 90 LED lights.



The intensity values of the QTH lights ranged from 6 to 795 mW/cm2, and only 32.5% of the tested QTH lights achieved the minimum 300 mW/cm2 cutoff value. The intensity of the LED lights ranged from 2 to 986 mW/cm2, and only 15.6% of the LED lights were considered unacceptable. This study reflects findings in earlier polymer-ization light assessments and clearly shows that just because a unit emits light does not mean that it is ade-quately polymerizing composite resin.

Finishing and polishing composite resin restorations is a concern for clini-cians, not only to make the restoration more esthetic but also to minimize plaque adherence. An in vitro study evaluated S mutans biofilm adherence to different composite resin types sub-jected to different polishing regimens.92 Sixty 6.0 mm diameter × 3.0 mm high specimens were made with each of 3 composite resin materials: nanofilled (Filtek 350; 3M ESPE), nanohybrid (Esthet X; Dentsply Intl), and microhy-brid (Vit-l-essence; Ultradent Products Inc, South Jordan, Utah). Composite resin was placed into the mold in a single increment, covered with a My-lar strip, and polymerized. After 24 hours dark storage in distilled water for 24 hours, 20 specimens of each composite resin were submitted to 1 of 3 finishing techniques: none (con-trol); sequential finishing with Sof-Lex disks (3M ESPE); and 30 blade tung-sten carbide bur (Beaver), followed by silicon carbide brushes (Astro-brush; Ivoclar Vivadent). One half of the specimens from each group were incubated in sterile human saliva for 1 hour. All specimens were incubated with a standard suspension of S mu-tans and tested for biofilm adher-ence. The nanofilled composite resin presented the lowest level of bacterial adherence, regardless of the finish-ing technique or presence/absence of human saliva. In the presence of saliva, no difference in bacterial ad-hesion to the nanohybrid or micro-hybrid composite resins was found, regardless of the finishing technique used. The nanofilled composite res-

in showed the lowest bacterial ad-hesion to the unfinished surface. Caries Diagnosis and Prevention

Accurate caries detection contin-ues to be a problem for clinicians. A number of caries detection devices are commercially available, although the one that has attracted the most attention to date is DIAGNOdent (KaVo Dental, Charlotte, NC). A clinical study compared the diagnos-tic ability of laser fluorescence using DIAGNOdent to visual inspection in newly erupted, noncavitated molars in children with active caries.93 This study was conducted in 505 man-dibular first molars with no visible cavitation in 307 children, aged 6 to 7 years. Bitewing radiographs were made, and teeth with either dentin or enamel radiolucencies were ex-cluded from the study. The teeth were professionally cleaned with a polish-ing rubber cup and pumice before diagnostic assessment. Previously calibrated and blinded evaluators assessed each tooth. Visual examina-tion was done with the teeth wet and after air drying, and the teeth were scored by using a previously validat-ed system. Teeth in which caries was not detected either visually or radio-graphically were measured by using DIAGNOdent; the scores of the 2 ex-aminers were averaged. Interexaminer reliability was excellent. Of 322 teeth scored as sound by visual examina-tion, DIAGNOdent only scored 217 (67.4%) as sound, with the remainder scoring caries anywhere from enamel caries to deep dentin caries. Of 183 visually scored as having enamel car-ies, DIAGNOdent scored 20 (10.9%) as sound, 24.6% with enamel caries and 59% with dentin caries. Statisti-cal analysis found poor agreement between DIAGNOdent and the visual caries assessment. The lower specific-ity (higher rate of false positive diag-nosis) with DIAGNOdent compared to visual assessment could lead to overtreating sound teeth. A weakness of this study was a lack of histologic

diagnosis for the true level of caries in the teeth, although the visual scoring system used has been evaluated and found to be reliable in other studies.

An in vitro study evaluated the ability of DIAGNOdent in determin-ing the end point for carious dentin removal.94 Extracted molars with occlusal caries presumed to extend into dentin were selected. Teeth were cleaned with an air scaler and radio-graphed, and teeth without dentin caries were excluded. Fifty-six teeth were assigned to 7 different caries ex-cavation methods (tungsten carbide burs, ceramic burs, sono-abrasion, and chemomechanical using 4 differ-ent solutions), by using caries remov-al endpoints specific to the technique. After caries removal, DIAGNOdent measurements were made of the deepest point of the caries excavation site. Color stereomicroscopic images were used to correlate the staining of dentin to residual caries. The ex-cavated teeth were subjected to mi-crocomputerized tomography (micro CT) to determine the residual min-eral density; this is considered a “gold standard” for dentin caries determi-nation. The results showed that the higher DIAGNOdent readings were recorded with greater dentin staining; however, micro CT determined that stained dentin was more mineralized. The authors noted that the results in-dicate that DIAGNOdent would not be reliable in determining the end-point for caries excavation.

A procedure that is receiving more attention as a treatment for initial proximal and white spot caries le-sions is the infiltration technique. One study evaluated the impact of caries infiltration and fluoride appli-cation on white-spot appearance.95 Sixty enamel-dentin specimens were cut from bovine incisors and their col-or was measured with a spectropho-tometer. They were then subjected to demineralization to artificially pro-duce white spots, and the color was remeasured. The teeth were divided into 4 groups: control (artificial saliva storage for 8 weeks); daily immersion

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for 1 minute in 0.05% NaF solution, followed by storage in artificial saliva for 8 weeks; application of 2% NaF gel for 1 minute, followed by storage in artificial saliva for 8 weeks; and infil-tration with low viscosity resin (Icon; DMG), followed by storage in arti-ficial saliva for 8 weeks. Specimens were retested for color change after 4 and 8 weeks. The group treated with resin infiltration showed a more sig-nificant reduction in whiteness than the other 3 groups.

A systematic review of the effec-tiveness of resin-based versus glass ionomer sealants was conducted.96 The purpose was to update a sys-tematic review on the same topic in 2009. A search of English language articles was conducted by using cri-teria determined a priori, and articles were assessed for quality and risk of bias. A total of 16 trials met the cri-teria for inclusion in the review. Data were pooled and a meta-analysis con-ducted. The cumulative Relative Risk showed no statistical difference in the performance of the 2 materials in preventing caries after 5 years. How-ever, the authors noted that the risk of selection, detection, and perfor-mance bias is high and recommended that more high quality, randomized controlled clinical trials should be done to more conclusively determine whether both resin-based and glass ionomer sealants are equally effective in preventing pit and fissure caries.

Silver Amalgam

Amalgam continues to be an area of less emphasis in materials research. However, some valuable research con-tinues. One clinical study evaluated the effect of various treatment alter-natives, other than replacement, for amalgam restorations diagnosed as having 1 or more features that deviat-ed from the ideal.97 Fifty participants with 113 defective restorations were included in the study. Restorations with localized defects were assigned to one of the following treatment groups: repair (defective site repaired

with amalgam), sealing of defective margins (marginal ditching filled with resin sealant), and refinishing (excess amalgam in defective areas was re-duced/polished with carbide burs and rubber polishing points). The remain-ing restorations were either replaced or received no treatment. Restora-tions were evaluated and scored clini-cally by using modified USPHS crite-ria preoperatively, immediately after treatment, and after 1, 2, and 7 years. After 7 years, the repair group had significantly less downgrades or failures than the no treatment group. None of the other groups were significantly dif-ferent from the no treatment group. The authors noted the study showed that repair was an effective alternative to replacement for amalgam restorations exhibiting the defects addressed by the study. After 7 years, the restorations in the replacement group performed simi-larly to the other treatment groups. A shortcoming of this study is low recall after 7 years (48%) and subsequent low sample size (54 restorations).

The impact of fetal exposure to metallic mercury from maternal amal-gams was the subject of a retrospective cohort analysis.98 A cohort of children and mothers that was part of the Sey-chelles Child Development Study had been studied previously because they consumed a diet high in fish (methyl-mercury exposure) and had already un-dergone extensive neurodevelopmental testing. Researchers were able to con-struct the dental status of 587 mothers to determine the number of amalgam surfaces that were present during gesta-tion. Prenatal methylmercury exposure had been previously determined by ana-lyzing the maternal hair growing during gestation. At age 66 months, the chil-dren underwent a comprehensive bat-tery of tests to assess their neurological development. The analysis, adjusted for covariates, showed that amalgam surfaces were not statistically associ-ated with any outcome, either with or without adjustment for prenatal and postnatal methylmercury exposure.

PROSTHODONTICS

Once again, the 2011 literature yielded much clinically important in-formation in the area of prosthodon-tics for clinicians to consider. A small portion of this voluminous documen-tation will be considered here. Addi-tionally, several interesting review ar-ticles were published that may be of interest to the reader and assist in the intellectual management of an ever ex-panding body of knowledge in prosth-odontics. Although not targeted in the present effort because of limited time and space, readers may choose to investigate synopses addressing guidelines for the care and mainte-nance of complete dentures,99 guide-lines for maxillary implant therapy,100 treatment options for missing man-dibular incisors,101 caries risk assess-ment for prosthodontic patients,102 the epidemiology and etiology of denture stomatitis,103 the dimension-al stability of irreversible hydrocol-loid,104 impression materials in fixed prosthodontics,105 the evidence base for restorations of posterior bounded edentulous spaces,106 zirconia-based partial fixed dental prostheses,107 posterior ceramic inlays,108 an update on soldering technology,109 the invio-lability of the biologic width,110 aller-gic reactions in the dental office,111 research trends in prosthodontics,112 and implant dentistry in modern den-tal school curricula.113,114

Diagnostics

The use of a properly adjusted dental articulator is believed to assist in accurate diagnostic procedures and in the precise fabrication of indirect dental restorations in the laboratory. While intentional overcompensations during adjustment of the articulator’s posterior controls have been sug-gested as a means of assuring nega-tive prosthesis errors (more than ad-equate posterior eccentric occlusal clearance), careful and accurate man-agement of the articulator controls may facilitate optimal mechanical



and functional occlusal morphologic results. In an attempt to identify av-erage values for articulator settings, investigators115 used electronic pan-tography (Cadiax Compact; Whip Mix Corp, Louisville Ky) to measure 3 characteristics of condylar movement [sagittal condylar inclination (SCI), immediate mandibular lateral trans-lation (IMLT), and progressive man-dibular lateral translation (PMLT)] in 73 healthy individuals that varied with respect to horizontal and verti-cal skeletal relationships.

Data gathered from participants included profile photographs with the Frankfort plane horizontal and the teeth in maximum intercuspation and an electronic pantographic record. Three senior investigators scored each profile photograph according to horizontal (skeletal Class I, II, or III) and vertical (reduced, average, or in-creased) classifications.

Results indicated good or total agreement for sagittal (97%) and vertical (70%) skeletal patterns. Par-ticipants judged to be skeletal Class II had significantly higher SCIs than Class I (4 degrees) and Class III (7 degrees) participants, while skeletal Class I and III participants were sta-tistically similar. Participants with average vertical skeletal patterns dis-played significantly lower SCIs than those with reduced and increased ver-tical skeletal patterns. No statistically remarkable trends in the data could be identified with respect to progres-sive horizontal condylar guidance (PMLT), although clustering around the minimum of 5 degrees and maxi-mum of 15 degrees was seen. An IMLT of limited clinical impact (>0.5 mm) was recorded across all participants.

The authors concluded that during prosthodontic therapy for patients with noticeable skeletal discrepan-cies, consideration should be given to the acquisition of appropriate clinical records to facilitate the adjustment of articulator controls, thereby optimiz-ing treatment outcomes.

During this time of great emphasis by patients on dentofacial esthetics,

successful clinicians must consider so-cietal perceptions of beauty, harmony, balance, and proportion when treat-ment planning. It has been suggested that the general public considers the smile second only to the eyes when evaluating the facial features most im-portant to esthetics. But what in the smile is considered esthetically attrac-tive and who should be the final judge of dental esthetics when clinician and patient opinions diverge?

To begin to answer these im-portant questions, investigators116 searched the Internet using the key phrases “best smile” and “female ce-lebrities.” The search resulted in 50 celebrities voted by lay people to have beautiful smiles. Large, frontal view images of these individuals displaying entire faces and open smiles at pub-lic events were acquired. Images were evaluated by a single examiner with the aid of image analysis software to qualify 8 specific esthetic smile criteria.

Results indicated that 80% of the smile specimens exhibited an aver-age upper lip position (revealed 75% to 100% of maxillary anterior teeth), 62% displayed upward upper lip cur-vature (corners of mouth higher than midpoint of upper lip), and 78% had a parallel smile line (maxillary inci-sal edges parallel to lower lip curva-ture). Forty-two percent of the im-ages revealed maxillary incisal edges not touching the lower lip (34% were touching, 24% were covered). With regard to total tooth visibility, 60% displayed up to the second premolar, and 32% displayed up to the first mo-lar. In 64% of the sample the dental midline was coincident with the fa-cial midline, while 36% demonstrated a midline discrepancy. None of the frontal view images exhibited maxil-lary anterior tooth widths that abided by the golden proportion. No midline diastemas were detected.

During diagnostic and therapeutic interventions, clinicians should have a clear understanding of the esthetic expectations of patients. Often these expectations are derived from high profile individuals considered beauti-

ful by the general public. If this is true, then a beautiful smile might contain the following: exposure of the entire cervicoincisal length of the maxil-lary anterior teeth, maxillary incisal edges parallel to the lower lip, maxil-lary first molars in the esthetic zone, coincidence of the dental and facial midlines, absence of diastemas, and emphasis on the harmony of the smile composition as opposed to strict ad-herence to the golden proportions. The authors suggested that the opin-ions and perceptions of lay people re-garding beauty must be clearly under-stood in order to satisfy the esthetic desires of an increasingly demanding dental patient population.

When the prosthodontic replace-ment of some or all of the anterior maxillary teeth is required, or when substantial portions of anterior tooth structure must be restored, the cor-rect diagnosis of the appropriate out-line form of the teeth is considered critical to the esthetic success of the restorative effort. Classic dental lit-erature has been relied upon to aid in selecting the tooth form. J. Leon Williams117 suggested that the maxil-lary central incisor outline form was oval, triangular, or quadrangular and that the outline form should harmo-nize with the inverted shape of the patient’s face (Typal Form Theory or Law of Harmony). Later, John Frush and Roland Fisher118 discussed the concept of “Dentogenics,” which recommended an esthetic relation-ship between gender and the outline form of the maxillary anterior teeth. Accordingly, a feminine personality is best associated with a rounded maxil-lary incisor outline form, while a mas-culine personality is best represented by a square or angular tooth form.

To identify more scientifically credible parameters for the diagnostic selection of maxillary anterior tooth form, researchers119 have assessed differences between males and fe-males in terms of oval, triangular, and quadrangular tooth form. The experi-mental population consisted of 433 participants (mean age of 15.92 years).

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Maxillary right central incisors were photographed by using a standardized protocol, and the images were digitized and subjected to a detailed software-aided, graphical image evaluation.

Results indicated that an oval outline form was most prevalent in both genders (male = 54.93%, female = 57.73%). However, significant dif-ferences were identified with respect to the triangular and quadrangu-lar forms. The triangular form was significantly more common in men (36.15%) than in women (23.54%), while the quadrangular form was sig-nificantly more prevalent in women (18.64%) than men (8.92%).

The authors suggest that predic-tive theories of prosthetic tooth out-line form can serve, at best, as diag-nostic guidelines or selection starting points. Ultimately the prosthetic pro-vision of anterior tooth forms that dif-fer from the patient’s original incisor outline form may not compromise the esthetic outcome of the reconstruc-tion. Perhaps the esthetic preferences of the observers are more important than anticipated form-gender cor-relations. If so, careful consideration must be given to modern esthetic perceptions and the many personal, professional, social, and cultural fac-tors that temper estimations of facial-dental beauty.

Removable Prosthodontics

Denture tooth debonding during extended, high-force oral function remains a concern, particularly when involving complicated and expensive, fixed or removable implant-support-ed dental restorations. Long-term successful repair of denture tooth bonding failures are both challenging and inconvenient. Attempts to im-prove denture tooth-to-base adher-ence have focused on surface treat-ments (tooth preparation, creation of diatorics, and chemical priming), and resin chemistry manipulations.

A recent in vitro investigation120 addressed fatigue failure between highly cross-linked central incisor

denture teeth and 2 popular denture base resins, including compression-molded, heat-activated, polymethyl methacrylate (PMMA) resin and light-activated, urethane dimethylac-rylate (UDMA) resin. Experimental manipulations of the denture teeth included: (1) grinding on the tooth ridge lap, (2) grinding plus placement of a diatoric, (3) grinding plus use of a bonding agent, and (4) grinding plus diatoric plus bonding agent. The bonding agent used was a proprietary material (Eclipse Bonding Agent; Dentsply Intl). Following fabrication, all specimens were stored in water for 7 days, thermocycled (1000 cycles, 5°C to 55°C, 30 second dwell time), stored in water for an additional 28 days, and subjected to cyclic load-ing (22 N, 14 to 400 cycles, 1.5 Hz, 5 mm/minute crosshead speed, water submerged) until failure. Incisal edge loading occurred at a 135-degree an-gle to the tooth’s long axis. Fractured surfaces were assessed microscopi-cally to characterize mode of failure.

Results indicated no significant dif-ferences in mean shear bond strength for all surface treatments investigated in the PMMA group. In the UDMA group, specimens fabricated without a bonding agent were too weak to test, while specimens incorporating a bonding agent demonstrated statisti-cally similar shear bond strengths. A comparison between the PMMA and UDMA groups revealed significantly higher shear bond strengths in the UMDA group.

The authors concluded that the use of the denture tooth surface treat-ments investigated before the fabrica-tion of PMMA denture bases yields similar bond strengths, indicating no need for proprietary bonding agents. The highest shear bond strengths were seen with the UDMA denture bases when proprietary bonding agents were used. Evaluation of the mode of failure indicated mixed adhesive-cohesive fail-ure or pure cohesive failure in both the PMMA and UDMA systems.

Varying opinion exists regarding the optimal posterior occlusal con-

ditions for conventional complete dentures. Consideration should likely be given to the physiologic health of the stomatognathic system, including residual ridge dimensions, neuromus-cular coordination, and a number of other edentulous diagnostic criteria. Pressure transmission originating from occlusal loading and force dis-tributed along the denture founda-tion are thought to have a role in the health and durability of the denture supporting tissues. Occlusal form and denture tooth material may influ-ence this pressure transmission and distribution.

To investigate this concept, an in vitro study121 considered 3 denture tooth materials (acrylic resin, micro-filled composite resin, and ceramic) and 4 posterior cusp angulations (0, 20, 33, and 35 degrees). Eight pairs of maxillary and mandibular left and right first molar denture teeth were incorporated into simple single tooth denture segments (flat acrylic resin bases, 15×15 mm, 3 mm thick). Max-illary and mandibular tooth pairs were arranged into Class I occlusal relationships and introduced into a vertical test frame, and occlusal contacts were refined. A simulated 50 N occlusal impact load was used. Color-keyed, pressure sensitive sheets registered pressure transmission and distribution under the denture bases. Pressure-sensitive sheets were then digitally analyzed.

Results indicated significant in-teractions between denture tooth materials and cusp angulations with respect to average and maximum pressure transmission. In general, 0 degree teeth showed lower pressure transmission than 33 degree and 35 degree teeth for all materials evalu-ated. Authors were careful to note the dramatic deviation of their ex-perimental design from clinical real-ity. However, they believe that un-der carefully controlled conditions, smaller posterior denture tooth cusp angulations may result in less force transfer through the denture base and, therefore, may be preferred for



compromised edentulous patients. Unfortunately, the authors did not comment on the likely influence of occlusal morphology on the mastica-tory efficiency and force needed for bolus penetration. Additional studies incorporating conditions that more closely simulate clinical reality are needed to further delineate these im-portant questions.

At a time when the dental profes-sion has a great variety of nonremov-able prosthodontic options to offer patients, the cost effectiveness and therapeutic conservatism of conven-tional complete dentures and partial removable dental prostheses (PRDP) render them the therapy of choice for many. The past year’s professional lit-erature yielded a number of interest-ing articles addressing conventional PRDPs. Two of these publications ad-dressed the appropriateness of mouth preparation and prescription writing in the provision of PRDP therapy.

It remains the clinician’s responsi-bility to appropriately prepare the pa-tient to receive a PRDP and to assure that the design of the PRDP is optimal for existing conditions. Researchers122 have studied the degree to which den-tists have fulfilled these responsibili-ties by examining work authorizations and definitive casts sent to a dental laboratory for PRDP fabrication. This investigation specifically addressed the prevalence of requests for occlusal and cingulum rests in work authoriza-tions and the indications of quality rest seat preparations on accompany-ing definitive casts.

Definitive casts and work autho-rizations provided by 45 general den-tists to a single dental laboratory for PRDP framework fabrication over a 5 month time period were investigated. The best available literature was used to define criteria for ideal rest seat prepa-rations. Upon examination of available definitive casts, rest seats that fell out-side these criteria were classified as ei-ther underprepared or overprepared.

Over the time period of this study, 68 definitive casts were provided to the dental laboratory for PRDP frame-

work fabrication. Of these casts, 48% did not have work authorization, pre-scribed framework designs, or any indication of rest seat preparation on the definitive casts and so were ex-cluded from further investigation. Of the remaining 35 casts, a cumulative total of 81 rests were prescribed. Only 24 of the prescribed 81 rests had ob-vious rest seat preparations on corre-sponding definitive casts. When com-pared with the defined criteria, 18 of the 24 rest seat preparations (75%) did not satisfy the criteria. Eye open-ing examples of inadequate definitive casts, resultant PRDP frameworks, and work authorizations are illustrat-ed in the article.

Overwhelmingly conservative con-cluding remarks provided by authors suggested that mouth preparations for PRDPs and accompanying labo-ratory work authorizations are not always of adequate quality. The au-thors go on to suggest that dental pro-fessionals should aim to provide high quality dental prostheses and that em-phasis should be placed on the impor-tance of denture design in continuing dental education courses for dentists and dental laboratory technicians.

Investigators123 undertook a sec-ond investigation, surveying materi-als provided to 5 commercial dental laboratories in the Midwest related to requests for new PRDP fabrication. All submitted materials were photo-graphed upon receipt by the labo-ratory and before their return to the dentist. The photographic images doc-umented work authorizations, casts, impressions, interocclusal records, ar-ticulators when provided, completed frameworks, and completed PRDPs. A total of 573 matched images (before and after photographs) and an ad-ditional 330 unmatched images were available for data analysis.

Findings indicated that Kennedy Class I PRDPs remain the most com-mon (39% of total), followed by Class III (31%), Class II (25%), and Class IV (5%). Approximately 70% of the PRDPs produced incorporated a metal frame-work, 25% were fabricated in acrylic

resin without metal frameworks, and 5% were fabricated with flexible acrylic resin.

Approximately 42% of the available work authorizations did not contain dentist-directed PRDP design informa-tion. Based on liberal criteria for rests (extension onto either prepared rest seat, or over occlusal/incisor tooth surface, or over dental implant), 79% of PRDPs were considered to have rests; this included no flexible PRDPs and only one-third of the acrylic resin PRDPs. With respect to major connec-tors, the U-shaped major connector was most frequent in the maxilla (73%), while the lingual plate major connec-tor was most frequent in the mandible (60%). For PRDPs that did not incor-porate a metal framework, a U-shaped design was most frequently used in the maxilla (95%), and a lingual plating de-sign was most frequently used for man-dibular restorations (91%).

The authors concluded that PRDPs of all Kennedy classifications continue to be prescribed, even though dentist input into design and fabrication is minimal. The incidence of PRDPs that do not incorporate metal frameworks in this sample was 33%, higher than in previous reports. Additionally, an unfavorably high incidence of PRDPs fabricated without appropriate tooth support (20%) was identified. This re-port represents the disappointing level of professionalism brought to bear on the treatment of partial edentulism with PRDP prosthodontics.

For extension base PRDPs, the in-clusion of dental implants in edentu-lous areas may alter the rotational me-chanics on functional loading of the prosthesis. The potential for improved prosthesis support, stability and reten-tion, and short-term and long-term bi-ologic/physiologic benefit necessitates the consideration of this underused treatment option. Two researchers124 provided a retrospective investigation quantifying the posterior mandibular ridge resorption associated with Ken-nedy Class I implant-supported and implant-retained partial removable overdentures (PRODs).

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Thirty-four healthy males with edentulous maxillae and 8 remaining mandibular anterior teeth were stud-ied. Single, root-form dental implants were placed bilaterally in the first mo-lar positions by using a 2 stage surgi-cal protocol. Implant lengths ranged from 8.0 mm to 13.0 mm and implant diameters ranged from 3.6 mm to 5.0 mm. After healing, mandibular PRODs and maxillary complete dentures were provided by using a balanced, semi-anatomic occlusal scheme. Half of the participants received implant-support-ed PRODs in which extension bases di-rectly contacted the healing abutments fastened to the dental implants. The re-maining participants received implant-retained RPRODs by using a ball and gold matrix attachment system. Attach-ment components were incorporated into the RPRODs by using a direct intra-oral functional pick-up procedure. Ap-propriate maintenance was provided over a 5- year recall period.

Two panoramic radiographs, one immediately before and one 5 years af-ter prosthesis placement, were obtained for comparison. The posterior residual ridges were evaluated on panoramic radiographs by using a previously de-scribed method of proportional area measurement in terms of area index.125 This method is said to control for in-herent magnification problems in the posterior mandible on panoramic ra-diographs. Results indicated that the overall loss of edentulous ridge height associated with implant-supported PRODs was 0.15 mm (0.03 mm/yr) during the 5-year recording period. For implant-retained PRODs over the same time period, the loss of edentulous ridge height was significantly greater at 1.03 mm (0.21 mm/yr).

The authors carefully suggested that direct vertical resistance to func-tional loading provided by implant-supported PRODs may be linked to the reduced loss of edentulous ridge height in this study. However, the au-thors caution that additional clinical trials on larger, mixed-gender patient populations are needed before any definitive conclusions can be reached.

Fixed Prosthodontics

Evidence-based dentistry involves reducing available science to the best, most credible information and clini-cally applying that information during patient management. A comprehen-sive appraisal of the cumulative pro-fessional literature is challenging for private practitioners due, in part, to convoluted search strategies, compli-cated statistical techniques, and the lack of universal access to published material. With this in mind, Layton126 detailed the efforts of one clinician to use an evidence-based approach to answer a clearly defined, clinically important question that contains the 4 elements: P-Patient, I-Interven-tion, C-Comparison, O-Outcome or PICO: For a patient with biologically and structurally sound natural tooth abutments, are the survival and com-plication rates of ceramic partial fixed dental prostheses (PFDPs) compara-ble or superior to those of metal ce-ramic PFDPs?

A 6S search strategy127 was used to identify relevant clinical evidence in a timely manner. This search method involves referencing 6 layers of cumula-tive evidence: systems (decision support services), summaries (evidence-based textbooks), synopses of syntheses (de-scriptions of systematic reviews), syn-theses (systematic reviews), synopses of studies (evidence-based journal ab-stracts) and original studies.

The author’s search yielded the following: no systems or summaries; no synopses in the journal Evidence-Based Dentistry, 3 synopses in the Trip database; 3 systematic reviews in the Cochrane database; 6 system-atic reviews in MEDLINE OVID; and no systematic reviews in Embase da-tabase. Of the potential resources identified, 1 systematic review128 and 1 original prospective cohort study129 were considered valid and relevant to the PICO question posed.

Although the internal validity of the single selected systematic review was deemed compromised, it was believed that careful consideration

of results could be applied to clinical practice. Estimated event rates and 5-year outcomes (95% confidence) suggested the survival rate of metal ceramic PFDPs to be significantly higher than that of ceramic PFDPs. Ceramic PFDPs were shown to expe-rience a higher incidence of technical failure. Having good internal validity, the selected prospective cohort study demonstrated high survival rates for metal ceramic PFDPs.

The author concluded that for pa-tients with sound natural abutments, the provision of a metal ceramic PFDP is likely to have a significantly greater 5-year survival rate than a ceramic PFDP. While differences in clinically important complications remain un-clear in the current literature, studies indicate that the incidence of com-plications for metal ceramic PFDPs is lower than that for ceramic PFDPs.

The interest of the general popula-tion in improved dental esthetics and the demand for ceramic laminate ve-neers remains great. While good long-term survival rates have been demon-strated for ceramic veneers given ideal clinical conditions, questions remain regarding the clinical application of veneers in patients presenting with worn dentitions and limited natural tooth structure. When limited tooth structure exists, consideration must be given to the optimal tooth prepa-ration design and fracture resistance of the definitive restoration.

To address this clinically impor-tant question, investigators130 re-ported on an in vitro investigation involving 32 intact, nonworn, non-restored, extracted, human maxillary central incisors. Available teeth were distributed to 4 experimental groups; 2 groups of teeth without incisal wear and 2 groups with incisal wear. The incisal edges of the teeth allocated to the wear groups were reduced by 2 mm to simulate clinical incisal at-trition. The teeth in 1 of the nonwear groups received veneer preparations incorporating palatal shoulder finish lines, while teeth in the other nonwear group received palatal chamfer finish



lines. Likewise, 1 of the wear groups received palatal shoulder finish lines, and the other wear group received palatal chamfers. All preparation fin-ish lines were maintained in enamel.

Pressed ceramic veneers (IPS Em-press; Ivoclar Vivadent) of consistent overall dimensions were fabricated. Veneers were luted by using standard bonding procedures. Each specimen was positioned in a universal testing machine, loaded 1 mm apical to the incisal edge at 90 degrees to the pala-tal surface (0.05 mm/min crosshead speed) until catastrophic failure. Re-sults indicated that the highest load-to-failure was seen in the nonwear/palatal chamfer group. Load-to-fail-ure for the nonwear/palatal shoulder and the wear/palatal chamfer groups were statistically similar. The lowest load-to-failure was seen in the wear/palatal shoulder group.

The authors concluded that prep-aration design and the presence of in-cisal edge wear significantly affected the load to failure of bonded press ceramic veneers. The use of a palatal chamfer preparation significantly in-creased load to failure compared to palatal shoulder preparation for both worn and nonworn central incisors.

Severe occlusal wear is generally characterized as a complex multifac-torial, biomechanical phenomenon. The successful restoration of severely worn occlusal tooth structure requires the broad consideration of etiologic, biomechanical, chemical, clinical, and patient-related factors. Restoring advanced occlusal wear with minimal tooth preparation and additive adhe-sive techniques is certainly an attrac-tive alternative in carefully selected situations. However it is unknown which materials or processes offer the greatest opportunity for long-term re-storative success.

Ultrathin bonded posterior oc-clusal veneers may represent a viable and conservative alternative to tradi-tional occlusal coverage restorations in the management of severe occlusal wear. By using an in vitro protocol, re-searchers131 assessed the influence of

ceramic and composite resin comput-er-aided design and computer-aided manufacturing (CAD/CAM) restor-ative materials on the fatigue resis-tance of ultrathin (0.6 mm) posterior occlusal veneers.

The selective removal of occlu-sal enamel from 40 sound, freshly extracted human maxillary molars maintaining cuspal inclinations was accomplished to simulate occlusal wear. Occlusal veneer restorations were fabricated by using a CAD/CAM system (Cerec 3; Sirona Dental Sys-tems GmbH, Bensheim, Germany). All tooth specimens were fitted with a standardized occlusal overlay from the CAM database. The average thick-ness of the restorations was 0.6 mm at the central groove, a maximum of 1.3 mm at the cusp tips, and 1.0 mm at the internal cusp slopes. Ten resto-rations were milled from each of the following materials: leucite ceramic (Empress CAD; Ivoclar Vivadent), lithium disilicate ceramic (e.max CAD; Ivoclar Vivadent), composite resin (Paradigm MX100; 3M ESPE), and an experimental polyethylene fi-ber reinforced composite resin (XR material; Kerr Corp). All restorations were luted to tooth specimens by us-ing standardized bonding protocols.

Fatigue testing incorporated closed-loop, servohydraulic loading through a 7 mm diameter composite resin spheri-cal loading probe. All occlusal loads were delivered to tripod, simultaneous intercuspal contacts while submerged in water. Isometric masticatory load-ing was simulated at 5 Hz, starting with 200 N for 5000 cycles, followed by stages of 400, 600, 800, 1000, 1200, and 1400 N at a maximum of 30 000 cycles each. The number of cycles to initial failure (crack detec-tion) and the number of cycles to catastrophic failure (restoration frag-mentation) were recorded.

Results indicated that both the composite resins tested demonstrat-ed significantly increased fatigue re-sistance when compared to the ceram-ic materials tested. None of the leucite or lithium disilicate occlusal veneers

withstood all 185 000 load cycles, while 60% of the composite resin and 100% of the experimental resin veneers survived the full loading regimen.

The authors concluded that, with-in the limitation of this in vitro accel-erated fatigue study, the CAD/CAM composite resins investigated may be considered for ultrathin posterior oc-clusal veneers, even in patients with expected high functional loading. Among the ceramic materials tested, only the lithium disilicate should be used for the fabrication of this resto-ration type and should only be consid-ered when light to normal functional loading is expected. Additional in vivo testing under carefully controlled con-ditions must be carried out.

Implant Prosthodontics

The accuracy or passivity of fit of multiple-implant, screw-retained, metal frameworks has been an area of inter-est to the profession for many years. While definitive information on adverse outcomes related to inaccurate fit is lacking, concern for optimizing pros-thesis fit has been expressed, and meth-ods for achieving such outcomes have been developed and applied. To assess evidence-based, best manufacturing methods, investigators132 systematically reviewed all in vitro research on the fit of screw-retained implant frameworks fabricated by using available tech-niques and materials.

An electronic search of the profes-sional literature produced 248 arti-cles related to implant framework fit. After applying predetermined inclu-sion criteria and manually searching additional publications, 26 articles were selected for review. The hetero-geneity of experimental design, the use of different implant/abutment systems, and the varying fit assess-ment methodologies and conditions complicated the systematic review process. Fit accuracy recordings were made by using microscopic measure-ment, photogrammetric assessment, laser videography, coordinate mea-surement, and modeling techniques

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(strain gauge and photoelastic stress analyses). The fabrication methods reviewed included the conventional casting of noble and base metal alloys; connection of sectioned frameworks with soldering, cast-to, and laser weld-ing processes; electric discharge ma-chining corrective processing; CAD/CAM; and fabrication by means of the resin bonding of premachined cylin-ders to the framework body.

The results of the systematic review of in vitro studies indicate that no one implant framework fabrication meth-od or material provides absolute ac-curacy or passivity of fit. The casting of noble alloys is a predictable meth-od for producing accurately fitting frameworks without the need for ad-ditional corrective processing. How-ever, the casting of base metal alloys generally does not yield acceptable framework fit, necessitating addition-al corrective measures (laser welding or electric discharge machining). The benefits of soldering were found to be unclear and likely of historical interest given modern laser welding alterna-tives. Electric discharge machining, CAD/CAM, and bonded framework constructions have great potential to produce multiple-implant frame-works of excellent fit. To date, the CAD/CAM process provides the most consistent fit accuracy outcomes.

The authors were careful to con-clude that despite the processes available for producing accurate im-plant frameworks by using in vitro protocols, overriding clinical con-cerns must be considered. When the inherent inaccuracies of impression procedures and definitive cast fabri-cation are considered, the provision of passively fitting, multiple-implant, screw-retained prostheses becomes a far more complicated issue.

Implant-assisted dental restora-tions are often called upon to resist substantial functional and para-functional loads. To avoid technical complications (loosened, bent, or fractured screws or damage to the im-plant-abutment interface), the load-bearing capacity of the implant and

its components becomes a critical feature of the restorative system. By using an in vitro protocol, research-ers133 evaluated the static load-bear-ing capacity of 6 different implant systems, representing various im-plant-abutment connection designs.

Experimental specimens from 6 implant companies were developed. Implant-abutment connection de-signs included internal conical inter-face with hexagon index (Astra Tech Inc, Waltham, Mass); internal butt in-terface and short conical matrix with hexagon index (Bego USA, Lincoln, RI); internal butt interface with trilobe index (Camlog Industries, Basel, Swit-zerland); internal conical interface without index (Dentsply-Friadent, York, Pa); internal butt interface with hexagon index (Nobel Biocare, Zur-ich, Switzerland); and internal conical interface with octagon index (Strau-mann USA, Andover, Md). Implants were mounted in a universal testing machine at 30 degrees to the loading trajectory. The abutments were placed by using prescribed screws and torque specifications. A custom-made, hemi-spherical loading device was seated on all unmodified abutments. Load-to-failure was accomplished at a con-stant crosshead speed of 1 mm/min. The load-displacement curves were developed, and the onset of notable plastic deformation was determined. After load testing, the specimens were embedded, sectioned, and visually inspected at ×10 magnification to as-sess failure mode.

The results indicated that the im-plant-abutment load-bearing capaci-ties of Straumann, Friadent and Astra Tech were significantly lower than those for Camlog and Bego, while there was no statistical difference between Nobel Biocare and all other systems. Applied loads at the onset of plastic deformation for Straumann, Friadent and Astra Tech were signifi-cantly lower than for Camlog, while Bego and Nobel Biocare did not dif-fer significantly from other systems tested. The system-specific failure modes resulting from this static over-

load experimental approach varied widely. In general, long opposing lat-eral surfaces at the implant-abutment interface appear to be advantageous with respect to load-bearing capac-ity when compared to relatively short connection designs.

The authors made 2 important concluding statements. First, the load-bearing capacities of all systems tested were considerably higher than the expected average functional forc-es. Second, static overload testing of implant-abutment connections does not permit reliable conclusions with respect to long-term clinical mechani-cal durability or success. The perfor-mance of these constructions during in vivo functional and parafunctional loading conditions may be influenced by other factors not considered in the present protocol, including cyclic loading, variable load trajectories, screw loosening and fatigue, and pro-gressive interfacial microgap forma-tion to name only a few.

Solid documentation of the ben-efits of implant-retained and implant-supported mandibular overdentures compared with conventional mandib-ular complete dentures has appeared in the professional literature over the past 15 years. Enhanced prosthesis retention and stability are likely 2 of the more important factors contrib-uting to the success of mandibular implant overdentures. However, in-formation related to the number of implants needed and the attachment systems used to provide optimal treat-ment outcomes remains ill-defined. Investigators134 evaluated 3 differ-ent mandibular implant overdenture treatment modalities with respect to 4 treatment outcomes (prosthesis re-tention and stability, tissue response, patient satisfaction and preference, and complications) by using a prospec-tive, randomized, crossover, clinical trial design to determine statistical equiva-lence among treatment approaches.

Thirty edentulous participants (63% male; mean age 58.9 years) with at least 1 year of conventional com-plete denture experience received 4



root-form, threaded, 3.75 mm diam-eter dental implants (Brånemark, No-bel Biocare) in the anterior mandible by using a conventional 2-stage sur-gical approach. After 4 to 6 months of healing, 3 different overdenture attachment systems were developed for each participant in the trial: a 4-implant bar-clip attachment sys-tem, a 2-implant bar-clip attachment system, and a 2-implant ball-ring at-tachment system. The crossover ex-perimental design incorporated 4 observation periods (12 months per period) and 6 different patient expo-sure sequences to the 3 different over-denture attachment systems. Direct transfer clinical procedures were used to switch among attachment systems during the course of the trial. All par-ticipants were provided with new prostheses incorporating 0-degree occlusal schemes. Patients received denture adjustments and attachment maintenance as needed throughout the experimental period.

Results indicated that the 3 treat-ments were not equivalent, with re-spect to physical retention measure-ments, with the 4-implant bar-clip system demonstrating the greatest physical retention and the 2-implant bar-clip the least. Observational, criterion-based retention was judged equivalent among treatments. Both physical and criterion-based stability measurements revealed equivalence among the 3 treatments. In general, all other criterion-based evaluations (condition of prosthesis supporting tissues and periimplant tissue health) revealed equivalence, although the 2-implant ball-ring treatment tended to be more favorable than the 4-im-plant bar-clip attachment approach. No differences among treatments rela-tive to complication rates were noted. With respect to participant reported treatment preferences, 53% selected the 2-implant ball-ring attachment system, 32% preferred the 4-implant bar-clip system, while only 16% select-ed 2-implant bar-clip prostheses.

The authors concluded that re-storing 2 interforaminally placed

implants with independent ball-ring attachments and a mandibular over-denture provided equivalent or more favorable outcomes for most of the measured parameters in the present clinical trial when compared with the more costly and more compli-cated 2-implant and 4-implant bar-clip alternatives. Perhaps the most telling experimental finding was that patients expressed greater satisfac-tion with the 2-implant ball-ring ap-proach. This finding seems to suggest that the level of physical retention may not be as important to patient satisfaction and implant overdenture success as previously thought

OCCLUSION AND TEMPOROMANDIBULAR JOINT DISORDERS

The quest to understand tem-poromandibular disorders (TMDs) more clearly continued in 2011 with a number of interesting articles. The increase in temporomandibular (TM) joint imaging resulted in several stud-ies with clinical relevance. The first study investigated the association be-tween the disk position and degenera-tive bone changes of the TM joints.135 The study was conducted with 218 participants who were clinically diag-nosed with internal derangements de-fined as “an abnormal positional re-lationship of the articular disk to the mandibular condyle and the articular eminence.” The abnormal positional relationship in internal derangements is more commonly referred to as an anteriorly displaced disk. The signifi-cance of anteriorly displaced disks has been recognized in recent years because of TM joint imaging with magnetic resonance imaging (MRI) and computed tomography (CT) scanning. Condylar changes such as cortical bone erosions, marrow space alterations, and decrease in size are some of the changes that can occur with an anteriorly displaced disks.

The purpose of this study was to determine the frequency and pos-sible relationship between disk posi-

tion and TM joint degenerative bone changes. The inclusion criteria con-sidered individuals who had been clinically diagnosed with an internal derangement in at least 1 TM joint and who had not received any previ-ous treatment. Individuals younger than 16 years and older than 65 years and individuals with systemic dis-eases, removable dental prostheses, or a history of TM joint surgery were excluded. There were 179 females (82.1%) and 39 males (17.9%), and the average age was 33.4 years. The participants were imaged with both MRI and CT.

The MRI imaging was performed by using a number of different se-quences. The 2 most commonly seen sequences in TM joint imaging are the sagittal image with either T1 or pro-ton density (PD) weighting. The con-dyle, disk, and eminence can be clear-ly seen in T1 images. The PD helps identify the disk in the scan. Differ-ent sequences such as the T2 and the spectral presaturation with inversion recovery (SPIR) help evaluate the con-dition of the condylar marrow. The coronal sequences allow a different view and help create a 3-dimensional understanding of the anatomy of the TM joint. The echo gradient series was taken at closed mouth, 10 mm, 20 mm, and 40 mm of interincisal opening. This series assesses the posi-tion of the TM disk in various stages of opening to determine if the disk realigns when opening. The CT scans were taken in both closed and open mouth positions. The mouth opening was maintained by a disposable oc-clusion block.

The MRI was used to evaluate both the condition and the position of the TM disk. The disks were de-termined to be normal (DWD), disk displacement with reduction (DDR), or disk displacement without reduc-tion. (DDWR) Additionally, the MRI assessed and classified range of mo-tion as normal, reduced, or increased. Finally, the MRI was used to evaluate joint effusion in the T2 images. The CT scan determined the presence of

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degenerative bone changes in partici-pants with condylar erosion, concav-ity, flattening, osteophyte formation, osteosclerosis, or subchondral cysts. The MRI and CT scans were evaluated twice by a clinician who was blinded to previous clinical information.

The hypothesis of the study was that there is a relationship between degenerative bone changes and disk displacement without reduction in symptomatic patients with internal derangement of the temporoman-dibular joint. Of the initial 218 par-ticipants, 38 were excluded by the exclusion criteria. The remaining participants were close to the origi-nal gender mix, with 82.8% females with an average age of 35.2 years and 17.2% males with an average age of 34.4 years. The most frequent disk position observed was disk displace-ment with reduction observed in 58% of the participants and disk displace-ment without reduction observed in 36% of the participants. Of the par-ticipants in the study, 6% presented with normal TM joints after imag-ing. Degenerative bone changes were found in 112 participants (62.2%), with multiple changes found in many TM joints. The bony changes that oc-curred were, in order of frequency, flattening of the anterior surface of the condyle, surface irregularities and erosions of the articular surfaces, flattening of the articular surface of the temporal eminence, subchondral cysts, and osteophytes.

A statistically significant asso-ciation between disk displacement without reduction (DDWR) and de-generative bone changes was found in the TM joints of participants with internal derangement (P<.001), and a high probability of degenerative changes with DDWR was present in both the right and left TM joints. Sixty-eight (37.7%) of the partici-pants did not demonstrate degenera-tive bone changes on imaging, while 112 (62.3%) exhibited some signs of degenerative bone change. Fifteen par-ticipants exhibited changes in the right TM joint (8.3%), 17 exhibited changes

in the left TM joint (9.4%), and 80 (44.4%) exhibited bilateral changes. An interesting analysis of the participants with DDR demonstrated that DDR did not relate to degenerative bone chang-es in symptomatic participants.

The significance of degenerative bone changes in DDWR as opposed to the lack of bone changes in DDR resulted from the lack of any disk tis-sue between the condylar bone and the temporal eminence in both rest-ing and functional positions. Without the benefit of disk tissue to cover the bony structures, changes in cartilage and synovial tissue can occur. Adapta-tion can occur if the body can respond and repair the areas of damage. As the degenerative process exceeds the adaptation process, the changes can become clinically apparent.

When reviewing the participants who were excluded from the study, 28 of the 38 excluded participants were younger than 16 years old. This is an important issue since the incidence of structural changes in the TM joints oc-curs in patients younger than previous-ly assumed. When structural changes occur early in life, patients may bear the consequences for decades.

In reviewing the study protocol, the open mouth CT scan could have been eliminated, since information such as joint spacing gained from the open mouth CT could have been seen in the open mouth MRI. The consid-erable strength of this study was the use of both MRI and CT scanning to evaluate the structural changes that occur in TM joints with internal de-rangements. Using MRI to evaluate disk conditions and disk position in combination with CT to evaluate con-dyle conditions and condyle position allows for an accurate assessment of the TM joints and the foundation of the occlusion.

The clinical significance of struc-tural changes in the TM joint was reviewed in a study136 that evaluated the concept that bilateral TM joint disk displacements without reduction (DDWO) are determinants of hori-zontal and vertical ramus deficiencies.

The study consisted of 68 consecutive participants who were referred for TM joint pain. There were 62 women and 6 men in the group with a mean age of 35.2 years. Inclusion criteria were having a TMD diagnosis, being aged from 18 to 50 years, being of Eu-ropean origin, having all first molars, and being ambulatory and available for the study schedule. Exclusion cri-teria included acute infection or other significant diseases of the teeth, ears, eyes, nose, or throat, a debilitating physical or mental illness, the pres-ence of a collagen capsular disease, a history of traumatic orthodontic treatment, a history of rheumatoid arthritis, and congenital anomalies.

The participants underwent clini-cal and cephalometric evaluations, followed by MR imaging of the TM joints in order to determine whether bilateral DDWO is related to the cephalometric parameters of horizon-tal and vertical mandibular ramus de-ficiencies. The MR imaging was used to diagnose disk displacement and osteoarthrosis (OA) in the TM joints. The MR imaging diagnosis of OA was defined by the presence of flattening, subchondral sclerosis and surface ir-regularities and erosion of the con-dyle. The lateral cephalograms were made with the teeth in maximum intercuspation and with the Frank-fort horizontal parallel to the floor. All cephalograms were obtained by using the same radiographic machine set for a standardized exposure, and a single investigator traced all the cepha-lograms. The 3 reference points traced were articulare, gonion, and pogonion.

The analysis of the cephalometric parameters selected for horizontal mandibular and vertical ramus defi-ciencies showed a significant relation-ship between the MR imaging group with bilateral OA and the cephalo-metric variable of ramus height. Ad-ditionally, there was a significant as-sociation between the MR imaging finding of bilateral OA and the cepha-lometric parameters of mandibular body length. The results of this study raise the question whether the use of



cephalometric radiographs should to be supplemented by MR imaging when evaluating suspected structural changes in the TM joint and changes in mandibular morphology.

The study protocol could have been improved by imaging with the participants indexed in a fully seated joint position. Imaging in maximum intercuspation allows for a possible horizontal and vertical positional change in the mandibular position, which would impact the results of this study. Additionally, normal disk posi-tion was defined at the 12:00 position relative to the condyle and a 1:00 disk position may be a better normal refer-ence. The clinical significance of this study relates to the discussion that in-ternal derangements and/or OA may have a role in skeletal relapse after orthognathic surgery. Since orthog-nathic surgery is necessary in many patients who have significant hori-zontal mandibular and vertical ramus deficiencies, the use of MR imaging preoperatively during the diagnos-tic process will help determine if the deficiencies are related to structural changes in the TM joint.

A similar study137 examined par-ticipants who presented with disk displacements without reduction (DDWO) and osteoarthrosis (OA). The participants had clinical and cephalometric evaluations followed by MR imaging of the TM joints in order to determine whether bilateral DDWO and/or OA are related to the cephalometric parameters of mandib-ular backward positioning and clock-wise rotation. Fifty individuals, 44 women and 6 men with a mean age of 35.5 years and with similar exclusion and inclusion criteria as the above study, participated in this study. The angular measurements used for man-dibular backward positioning were the facial plane angle (FH to Na-Pog), the angle of convexity (Na-A-Pog), and the SNB angle. The angular measure-ments for mandibular clockwise rota-tion were the Frankfort occlusal plane angle (FH to OP) and the Frankfort mandibular plane angle (MP to FH).

The analysis of the cephalometric parameters selected for mandibular backward positioning and clockwise rotation showed a significant rela-tionship between the MRI group of bilateral DDWO and the cephalomet-ric variables of the angle of convex-ity and Frankfort mandibular plane angle. There was a significant associa-tion between the MRI finding of bi-lateral OA and the cephalometric pa-rameters of the SNB angle, Frankfort occlusal plane angle, and Frankfort mandibular plane angle. Lastly, there was a significant association between the MRI finding of bilateral DDWO and OA and the cephalometric vari-ables of the facial plane angle and Frankfort plane angle. The authors hypothesized that increasing changes in dental morphology may be relat-ed to the progressive osteoarthritic changes occurring in individuals with DDWO. This concept warrants the close attention of both general den-tists and specialists when attempting to achieve an occlusal scheme with anterior tooth contact to achieve posterior disclusion in excursive man-dibular movements.

While the previous study looked at the effect of disk displacement on the mandibular morphology, another in-teresting study138 examined the effect of disk displacement on the shape of the condyle in juvenile females. Nine-ty-six females between the ages of 9 and 20 years with clinical signs and/or symptoms of TMD, including joint sounds, limitation of opening, and mouth pain, participated in the study. The exclusion criteria included corti-cal bone abnormalities.

The MR imaging was performed with a 1.5 Telsa system with 7.5 cm TM joint bilateral surface coils. Imag-es were obtained in closed and open mouth positions. The disk position of the right and left TM joints on sagit-tal T1 weighted images was classi-fied into a normal group with no disk displacement in the closed or open mouth view, the DDW group with anterior disk displacement with re-duction, and the DDWO group with

anterior disk displacement without reduction. One radiologist who was blinded to the clinical symptoms of all participants evaluated these clas-sifications.

The condyles were examined by using MR from the horizontal and frontal plane. The horizontal plane evaluation used 8 points matching the outline of the condyle, and the entire horizontal condylar area was estimat-ed as an octagon. The frontal plane evaluation used 9 points matching the outline of the condyle, beginning at the medial pole. The 192 condyle-disk assemblies were evaluated in the 96 participants. Sixty-two (32%) of the condyles were judged as having a normal disk position. Eighty-four (44%) were diagnosed as DDWO, and 46 (24%) were diagnosed as DDW. The condylar area in a horizontal di-mension measured 111.1 mm2 in nor-mal joints, 106.7 mm2 in DDW joints, and 85.8 mm2 in DDWO joints. In the frontal perspective, with structural changes to the TM disk, the condyles decreased in size throughout the mid-point of the condyle, with the great-est decrease occurring in the DDWO joints. The hypothesis of the study, that condylar shape varies based upon disk position, was supported.

Alterations in disk position can affect normal physiology, lubrica-tion, nutrition, and joint function. The change may negatively influence the adaptive capacity of the condylar cartilage, which may alter the normal growth of the condyle in adolescence and subsequent facial development. The results of this study support the concept that disk displacements cause a smaller condyle but may be understated since patients with any cortical bone abnormalities were ex-cluded. The clinical significance of this study underscores the importance of realizing that disk displacements, es-pecially in younger patients, may be associated with facial asymmetries.

As demonstrated in these studies, disk displacements create an environ-ment where changes in the articular cartilage and synovial membrane can

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cause both pain and structural chang-es in the TM joint. A logical approach to treatment would include attempts to reduce the degenerative process. One study139 using hyaluronic acid (HA) injections in the TM joint at-tempted to identify predictors of pos-itive outcomes of arthrocenteses plus HA injections in damaged TM joints. While techniques for TM joint lavage and injections have been investigated over the last 20 years, few studies ad-dress the mechanism of action. In this study, the search for strongly signifi-cant predictors failed, and little clini-cal information was gained.

An intriguing animal study140 inves-tigated the effects of the intra-articu-lar injection of an insulin-like growth factor (IGF-1 suspended in HA on the cartilage and subchondral cancellous bone repair in osteoarthritis (OA) of the TM joints. Fifty skeletally mature (6 months old) New Zealand white rabbits were used in the study, 48 of which were anesthetized and the TM joints exposed over the zygomatico-squamosal suture. One-third of the TM disk in the anterior and lateral regions of the TM joint was resected with a scalpel. After the disk resec-tion, the articular capsule and the skin were closed independently. Two rabbits were used as normal controls, and their TM joints remained intact.

Four weeks after the induction of OA as described above, the rabbits were randomly divided into 4 groups. The first group was the OA group with OA induction only. The second group was the HA group with OA induction and a single intra-articular injection of HA. The third group was the IGF-1 group with OA induction and a single injection of IGF-1. The fourth group was the HA/IGF-1 group with OA induction and a single intra-articular injection of IGF-1 suspended in HA. Six animals from each group were sacrificed at 12 and 24 weeks after the injections.

The mandibular condyles of the sacrificed animals were dissected, fixed in 10% buffered formalin, decal-cified with 5% ethylenediamine tet-raacetic acid (EDTA), and embedded

in paraffin. For each specimen, 3 ran-domly selected sections in each joint were evaluated for the severity of OA by 2 independent blinded observers. At 12 weeks post injection, the OA group had highly irregular surfaces, and most condyles exhibited small osteophytes. After 24 weeks, the joint had a marked reduction in joint space, which may indicate a fibrous ankylo-sis between the articular surface and the condyle. The gross appearance of the condyles in the HA group and the IGF-1 group was similar to the OA group at both 12 and 24 weeks. The condyles in the HA/IAG-1 group showed round, smooth, consistent surfaces that resem-bled normal cartilage.

The key factor in this experiment was the suspension of IGF-1 in HA during the injection. While HA injec-tions can restore the properties of synovial fluid, it is not known at this time whether HA injections can mod-ify structural damage in TM joints with OA. The injection of IGF-1 alone did not improve the articular carti-lage or protect the microarchitectural properties of the subchondral cancel-lous bone. This finding is not surpris-ing since IGF-1 has a short biological life span. The combined therapy of HA and IGF-1 resulted in decreased cartilage surface lesions and nearly normal microarchitectural properties. Research in this area will continue to develop new options for treating structurally altered TM joints.

The diversity of opinion in the pro-fession is demonstrated in a position paper141 addressing TM disorders. The role of dental occlusion in TMD is discussed in detail with different studies quoted mentioning how ex-perimental occlusal contacts were added to the dentition and how, as a result, muscle hyperactivity occurred as measured by surface electromyog-raphy. The authors claim the results of these studies clearly substantiate the role of occlusion in the onset and perpetuation of TMD and a return to normal masticatory function when occlusal harmony is restored. The oc-clusal scheme advocated in this ar-

ticle is neuromuscular occlusion with isotonic contraction of relaxed mas-ticatory muscles achieved through stimulation of those muscles on a trajectory beginning at a muscularly rested mandibular position. While occlusal treatment has historically focused on decreasing masticatory muscle activity, the current challenge is for the general dentist and special-ist to understand not only how the teeth contact but also the condition and position of the TM disk and con-dyle. Understanding not only how the teeth fit but also how the joints fit will increase the ability to help patients make a more informed decision.

Sleep-Disordered Breathing

One study was done to evaluate

the influence of an oral appliance on morning headache and orofacial pain in individuals without sleep-disordered breathing.142 Twelve indi-viduals suffering from frequent morn-ing headache were recruited for this study. A custom mandibular advance-ment appliance (MAA) was fabricat-ed for each participant. Participants spent 2 nights in the sleep laboratory for habituation and gathering of base-line data, then slept 5 nights without the MAA, followed by 8 nights with the MAA in the neutral position, fol-lowed by 5 nights without the MAA, followed by 8 nights with the MAA in the 50% advanced position, and final-ly 5 nights without the MAA. Morning headache and orofacial pain intensity were assessed each morning on a 100 mm visual analog scale.

Compared to the baseline period, the use of an MAA in both the neutral and advanced position was associ-ated with a 70% reduction in morn-ing headache and a 42% reduction in orofacial pain intensity. During the washout periods, morning headache and orofacial pain intensity returned to close to baseline levels. The use of the MAA in both positions also signif-icantly reduced rhythmic masticatory muscle activity. The authors conclud-ed that the use of an MAA is associ-



ated with a significant reduction in morning headache and orofacial pain intensity. They believed that part of this reduction may be linked to the concomitant reduction in rhythmic masticatory muscle activity. Readers should be cautioned that although the results seem positive, the sample size (n=12) was low.

A randomized controlled study cephalometrically assessed the pos-sible changes in craniofacial morphol-ogy associated with the long-term use of an adjustable oral appliance with continuous positive airway pressure (CPAP) in patients treated for ob-structive sleep apnea (OSA).143 Fif-ty-one individuals were randomized to oral appliance therapy and 52 to CPAP therapy. At baseline and after follow-up (2.3 ±0.2 years), a lateral cephalogram of all patients was made in maximum intercuspation to determine relevant cephalometric variables. Both baseline and follow-up cephalograms were traced digitally, whereupon ceph-alometric variables were compared. Changes in craniofacial morphology between the oral-appliance group and the CPAP group were evaluated with a linear regression analysis.

Compared with CPAP, the long-term use of an oral appliance result-ed in small but significant (dental) changes. Mean (SD) horizontal over-lap decreased 1.0 (±1.5) mm and vertical overlap decreased 1.7 (±1.6) mm. Furthermore, a retroclination (-2.0 (±2.8) degrees) of the maxillary incisors was found as well as a pro-clination (3.7 (±5.4) degrees) of the mandibular incisors. Moreover, the lower total anterior facial height in-creased significantly to 0.8 (±1.5) mm and the total height to 0.9 (±1.4) mm. No changes in skeletal variables were found. Linear regression analysis re-vealed that the decrease in horizontal overlap was associated with the mean mandibular protrusion during follow-up (B) (deepest midline concavity on the mandibular symphysis)=-0.029, SE=0.014, P<.05).

The authors concluded that oral appliance therapy should not be

considered as a lifelong treatment and that there is a risk of craniofacial changes. Therefore, patients treated with an oral appliance need a thor-ough follow-up by a dentist or dental specialist experienced in the field of dental sleep medicine.

Another study, using data col-lected from the same participants as in the previous study, evaluated the nature and incidence of TMDs in patients receiving either appliance therapy or CPAP for the treatment of OSA.144 There were 52 partici-pants in the CPAP group and 51 in the mandibular advancement appli-ance group. Evaluations were made at 2 months, 1 year, and 2 years. At 2 months, 6% of the participants in the CPAP group had signs and symptoms of TMDs, while 24% in the appliance groups experienced TMDs. However, the TMDs were described as being mild and transient, and both the in-cidence and severity decreased over time. No participant discontinued therapy as a result of the TMDs.

Another interesting study evaluat-ed ethnicity, obesity, and craniofacial structure as risk factors for obstruc-tive sleep apnea.145 The investigators found the contribution of the risk factors of obesity and craniofacial structure differed in Asians, African-Americans, and whites. Certain cra-niofacial phenotypes may be more vulnerable to the development and severity of OSA than others as obesity increases. This may have implications in determining optimum prevention and treatment protocols for patients of specific ethnicities.

A Canadian study evaluated the apnea-hypopnea index (AHI) in com-plete denture wearers who slept with and without their dentures.146 Twen-ty-three participants completed the study, which was conducted in a sleep laboratory. The AHI was significantly increased when participants diag-nosed with mild OSA slept with their dentures than when they slept with-out them. With individuals with mod-erate to severe OSA who slept with their dentures, no significant rise in

OHA was noted. Accordingly, it may be of benefit to advise complete den-tures wearers with OSA to consider removing their dentures at night.

A provocative review article on the use of oral appliances in the manage-ment of bruxism was published in late 2010 and is included in this re-view.147 Data accumulated in many sleep laboratories have led to changes in thinking about the function of oral appliances in the management of sleep bruxism. In the past, oral appli-ances were thought to be provisional measures that would assist dentists in the analysis of so-called improper dental relationships. This often led to dental treatment, including occlusal equilibrations, orthodontics, occlusal opening, and major reconstruction, to improve these improper relation-ships. Based on data from sleep labo-ratories, the proper role for oral appli-ances is now thought to be to protect the teeth and perhaps reduce muscle activity during sleep.

IMPLANT DENTISTRY

A search of PubMed on February 20, 2012 using only the words “im-plant dentistry” for the year 2011 yielded 932 citations. When the search was repeated with the words “dental implants,” the number of ci-tations increased to 1616. In spite of this extensive research in the disci-pline, systematic reviews done to de-termine the answers to specific ques-tions almost always state that more research with better study designs is required. Sadly, many studies have small sample sizes and are underpow-ered, are not properly randomized, have a high possibility of bias, and have no control. While the knowledge base regarding clinical performance of root-form implants is growing, lit-tle of the evidence produced by clini-cal trials ranks in the top categories for evidence-based dentistry.

A number of systematic reviews and meta-analyses evaluating the ef-fect of risk factors such as smoking on implant survival and the effect of

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prosthodontic considerations such as splinting were conducted. The efficacy of using platelet-rich plasma was ex-amined as was the effect of different implant designs. The interest in the in-cidence and etiology of periimplantitis was high, and a number of studies re-lated to that topic will be reviewed.

One systematic review evaluated studies identifying patient-related risk factors for implant therapy.148 Table I in the review is an excellent summary of the discussions in the article. While the authors commented that the evi-dence base related to many of the risk factors was less than perfect, they determined there was no increased risk for failure in patients with car-diovascular disorders, diabetes, au-toimmune disorders, or osteoporosis. Failure rates in irradiated bone are 2 to 3 times greater than in nonirradi-ated bone. Patients with a history of tooth loss due to periodontitis are at higher risk for the development of pe-riimplantitis. Failure rates of implants in smokers are more than twice those in nonsmokers and are even higher when implant placement and bone augmentations are combined. The evidence does not support the notion that failure rates are higher in patients who have taken bisphosphonates, but should osteonecrosis of the jaw de-velop, the morbidity is high. Success rates are dependent on bone quality, with implants in the maxilla failing at a higher rate than in the mandible and the poorest success rates occurring in the posterior maxilla. The authors suggest that genetic factors may have a role in success/failure rates but ad-mit there is little specific evidence to support that notion.

One retrospective 5-year multi-center study specifically evaluated the influence of smoking on the survival of dental implants in 1727 partici-pants.149 Nonsmokers received 4460 implants, and smokers received 2260 implants. The implant failure rate in nonsmokers was 2.9%, and the fail-ure rate in smokers was 5.5%. Ninety per cent of the failures occurred before loading. The study is impressive because

of the number of participants and im-plants in each group, and the data cor-relate well with previous studies com-paring smokers and nonsmokers.

Another review evaluated prosth-odontic considerations designed to optimize outcomes with single-tooth implants.150 The authors used exist-ing literature to draw the following conclusions: The use of custom pro-visional restorations to sculpt periim-plant soft tissues has been described by several authors, but there are no published studies to verify efficacy. Laboratory studies support the use of transfer impression copings and inter-nal connections to improve stress dis-tribution, but there are no supportive clinical data. Both cement- and screw-retained prostheses demonstrate high success rates, but the authors prefer screw-retained prostheses for long-term retrievability. Gold, titanium, and zirconia abutments exhibit ex-cellent biologic responses, but there is insufficient evidence regarding the durability of zirconia abutments. The optimum occlusal scheme for implant supported prostheses has yet to be defined. The final conclusion was that implant-supported single crowns provide comparable service to tooth-borne PFDPs but are associated with an increased incidence of biological and technical complications.

Another systematic review evalu-ated the relative merits of splinting or not splinting implants supporting overdentures.151 Data were extracted from 12 studies of at least 3 years du-ration selected from an initial yield of 1022 titles. Survival rates for implants supporting overdentures were 95% to 100% in the mandible and 90% to 95% in the maxilla and were the same for both splinted and nonsplinted implants. Unsplinted implants with a ball and ring system required more maintenance than splinted implants with a bar and clip. The data showed no differences in periimplant hard and soft tissues between splinted and nonsplinted implants. Individu-als with bar-retained implants have greater difficulty with oral hygiene.

Evaluating subjective patient variables related to satisfaction, again no sig-nificant differences between the use of splinted and nonsplinted implants were found. The results from this systematic review would seem to indicate both ap-proaches to implant-supported over-dentures are clinically successful.

A systematic review evaluating the prosthetic outcome of cement-retained fixed restorations was pub-lished in 2011.152 Data from 32 stud-ies were used in the review. Fifteen of these studies were considered short-term studies and yielded data from implant-supported restorations in service for less than 5 years. Seven-teen studies had data from implants in service from 5 to 10 years. The prosthetic success rates in the short-term studies were between 69.8% and 100% and in the long-term studies between 56.2% and 96.7%. The most common technical complication in both groups was loss of retention. The results of this systematic review were disappointing in that no useful information was available from the included studies to provide guidelines for cement selection and/or cemen-tation protocols. Many different ce-ments were used with no rationale for use provided.

One meta-analysis reported on the effects of the use of platelet-rich plas-ma (PRP) in conjunction with implant placement and sinus bone grafting.153 The analysis used data from 8 con-trolled clinical trials with 352 sinus bone grafts in 191 participants. The use of PRP had no effect on implant survival, on either a patient or im-plant basis. Bone-to-implant contact was not significantly different whether PRP was used or not used. The use of PRP reduced healing time and in-creased early stage bone formation but had no effect on the long-term survival of the implants. The ques-tion of whether the seemingly minor benefits of using PRP in sinus lifting, justifies the additional cost was not addressed in this analysis.

Many partially edentulous pa-tients present with compromised



bone heights in the residual ridge and cannot receive implants of standard length without bony augmentation. The use of short implants has been suggested as a solution to this prob-lem. Two systematic reviews and 1 meta-analysis evaluated success/fail-ure rates with short implants.154-156 The first systematic review evaluated long-term failures with short im-plants (10 mm or less) and factors that might influence those failures.154 In total, 35 studies involving 14, 722 implants, of which 659 (4.5%) failed, were included in the review. Most of the implant failures (57.9%) were early failures and occurred before prosthe-sis connection. There was no statisti-cally significant difference between the failure rates of short implants and standard implants. Machined im-plants had a higher rate of failure in the maxilla than in the mandible and a higher rate of failure overall than implants with rough surfaces. The au-thors concluded that short implants have a similar prognosis to standard implants but that stronger evidence is needed to confirm this finding.

The second systematic review evaluated the estimated survival rate of short (<10 mm) implants placed in partially edentulous individuals.155 Twenty-nine acceptable studies were identified and results from 2611 short implants were analyzed and reported as survival rates after 2 years. The authors concluded that the data sug-gest there is fair evidence that short implants can be successfully placed in partially edentulous individuals, although longer implants (8.5 mm) had slightly higher survival rates than shorter (6.0 mm) ones. Mandibular implants had a higher survival rate than maxillary implants, and implants placed in nonsmokers survived at a higher rate than those placed in smok-ers. There were no differences in the survival rates of implants with rough ver-sus smooth implant surfaces, although these parameters were not clearly de-fined in most of the included studies.

The meta-analysis on the impact of implant length on early failure rates

used data from 54 prospective stud-ies and 19 083 implants.156 Implants were evaluated after the first year of prosthetic loading. Failure rates for short implants (<10 mm) were the same as for standard implants in the mandible. Short implants in the ante-rior maxilla had a higher failure rate than standard implants, whether the implant surfaces were machined or roughened. Again in the anterior max-illa, short implants with machined surfaces had higher failure rates than standard implants or short implants with rough surfaces. No influence of implant diameter could be seen with short implants. The authors conclud-ed that in areas with reduced alveolar bone height, the use of short implants may reduce the need for invasive bone augmentation procedures. Readers are cautioned that this analysis only evaluated implants during the first year of prosthetic loading and thus gives little information on the long-term efficacy of short implants.

One disappointing systematic re-view attempted to determine whether different implant neck configurations had an effect on preserving the mar-ginal bone level.157 The authors in-cluded 20 studies in the review and evaluated the use of microthreads, different implant diameters, modifi-cations of implant surfaces, insertion depth, use of 1-piece implants, and platform switching on marginal bone loss. Because of poor study design and the heterogeneity of the studies, no evidence was found regarding the effectiveness of any specific modifica-tion in the implant neck area in pre-serving marginal bone or preventing marginal bone loss.

Interest in the topic of periim-plantitis continues to be high, and a number of studies on that topic were published in 2011. The first study re-viewed the scientific literature to eval-uate the difference between gingivitis lesions around natural teeth and peri-implant mucositis.158 Periimplant mu-cositis is defined as the presence of in-flammation in the mucosa around an implant with no signs of supporting

bone loss. Periimplantitis is charac-terized by loss of supporting bone in addition to inflammation in the muco-sa. Based on data from both animal and human studies, the authors concluded that gingivitis and periimplant mucosi-tis are not fundamentally different from the perspective of pathogenesis. Both diseases represent a host response (in-flammation) to the bacterial challenge caused by biofilm formation. They also concluded that because periimplant mucositis represents the obvious pre-cursor to periimplantitis, as does gingi-vitis for periodontitis, treatment of mu-cositis has to be the prerequisite for the prevention of periimplantitis.

A logical extension of the ques-tion posed in the previous study was posed in another review to determine whether periimplantitis lesions are different from periodontitis lesions.159 The authors reviewed human histo-pathological studies of both peri-odontitis and periimplantitis lesions and histopathological animal studies of ligature-induced experimental pe-riimplantitis to determine similarities and differences between the 2 enti-ties. Despite the similarity of the clini-cal features and etiology of periodon-titis and periimplantitis, the authors found that critical histopathological differences exist between the 2 le-sions. The differences are both real and complex, and interested readers should review the study carefully. The differences are important when devel-oping potential treatment protocols for periimplantitis.

A short-term RCT was conducted to compare the efficacy of 2 anti-infective protocols for the treatment of periimplant mucositis.160 Since periimplant mucositis may progress to periimplantitis, determining an effective protocol for controlling or preventing its development is of con-siderable interest. Twenty-nine indi-viduals with periimplant mucositis in 4 different centers were recruited for the study. All participants received nonsurgical mechanical debridement at the implant sites and were instruct-ed to brush around the implant twice

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daily with a provided gel. The test group (n=15) received chlorhexidine gel (0.5%), while the control group (n=14) received a placebo gel. Partici-pants were asked to discontinue the use of the gel after 4 weeks. Periodon-tal parameter and microbiologic test-ing were done at baseline, 1 month, and 3 months.

Both groups demonstrated re-ductions in bleeding on probing, and probing depth at 1 month was the same as at 3 months. Only 38% of the implants had complete reduc-tion in bleeding on probing. There was no difference in these parameters or microbiologic results between the control and test groups. One result of note was that improvement in the periodontal parameters was greater with implants with supramucosal res-toration margins than in those with submucosal restorative margins.

Currently, there is no gold stan-dard protocol for the treatment of implants with periimplantitis. Several protocols have been proposed and used with varying degrees of success and failure. One prospective case-control study evaluated the stabil-ity of bone regenerative procedures by using a bone substitute with and without a membrane after 3 years.161 Thirty-eight participants with pro-gressive bone loss around an implant of 1.8 mm or more and with bleed-ing on probing after the first year of healing were recruited for the study. Nonsurgical treatment of all implants was first accomplished and judged to have failed. All participants had sur-gical regenerative treatment with a bone graft substitute (Algipore; Dent-sply Friadent, Malmo, Sweden). With the first 19 participants, the graft was covered with a resorbable membrane (Osseoquest; WL Gore & Associates Inc, Flagstaff, Ariz), and the next 19 participants were treated with the bone graft substitute alone. All par-ticipants received antibiotic therapy for 10 days following surgery and used chlorhexidine mouth rinse for 5 weeks. Participants were recalled for maintenance every 3 months and

finally evaluated after 3 years. Seven-teen participants treated with both the graft and membrane returned for the 3-year follow-up, and 15 partici-pants in the graft alone group were evaluated at 3 years. The plaque in-dex was determined at baseline and at various intervals throughout the study. Bone loss/gain was determined radiographically.

At 3 years, the mean defect fill with the bone substitute alone was 1.3 mm and 1.6 mm with the graft and membrane. The differences were not statistically significant. It is im-portant to note that the plaque index dropped dramatically after baseline and remained low throughout the study, presumably because of the ag-gressive recall and maintenance pro-tocol. While the results are encour-aging, readers must understand that the radiographic evaluation of bone levels around implants is imperfect at best, and with the methodology used in the study, it is impossible to determine whether the calcified tis-sue around the implants was actually regenerated bone or simply defect fill. The discussion section in the study should be read carefully as it clearly delineates the limitations of the study.

A systematic review evaluating the outcome of the regenerative treat-ment of periimplantitis by using bone substitutes and membranes was pub-lished in 2011.162 Data from 17 stud-ies involving 173 treated implants were analyzed. It is interesting to note that there were no randomized con-trolled clinical trials (RCTs) available for inclusion in the review. Of the 17 articles used, 3 were controlled clini-cal trials, 2 were cohort studies, 8 were case series, and 4 were single-case presentations. Many different types of implants were treated with different types of membranes and dif-ferent bone substitutes. Reevaluation periods ranged from 5 to 36 months. All studies investigated radiographic bone morphology, while few reported on bleeding on probing or probing pocket depth. Although most of the studies provided only qualitative or

semiquantitative data for bone fill, 10% of the implants showed complete bone fill, and 86% showed partial bone fill. As discussed in the previous study, this review provides no insight as to what structure actually filled the treated bony defect. The authors’ primary conclusion was that RCTs comparing guided bone regeneration treatment and noninvasive debride-ment in the treatment of implants with periimplantitis are needed.

Another review was conducted in an attempt to determine the specific microbiota associated with periim-plantitis.163 While the review is diffi-cult reading for those without specific training in microbiology, data from the 18 studies selected clearly showed that the microbiota associated with healthy implants is different and less complex than the microbiota found around implants diagnosed with peri-implantitis. The primary flora in these implants with bone loss consists of anaerobic gram-negative periodonto-pathogens. Evidence was also found indicating that certain cases of peri-implantitis are characterized by peri-ods of rapid and marked destruction compared to periodontitis and that prompt treatment is required once a diagnosis is made. The authors were unable to reach consensus regarding the optimum treatment protocol for periimplantitis but commented that the treatments proposed for periimplantitis are based on evidence gained from the treatment of periodontitis. They note that the surface of some implants facili-tates the adherence of bacterial biofilm and complicates its elimination.

A prospective RCT was conducted to compare the efficacy of the nonsur-gical treatment of periimplantitis with an airborne-particle abrasion device with oral hygiene instruction (APAD) to mechanical debridement and the local application of chlorhexidine.164 The authors claim that the nonsurgi-cal treatment of periimplantitis has generally been unpredictable and that benefits have been limited and short-term, primarily because of the difficul-ty of completely eliminating plaque



biofilms from the roughened titanium implant surfaces. This prevents the establishment of new bone-to-implant contact. This study was initiated on the hypothesis that the use of an airborne-particle abrasion device (APAD) might provide more thorough biofilm removal and hence improved efficacy over me-chanical debridement in the treatment of periimplantitis.

Thirty individuals with at least 1 implant with periimplantitis, 15 in each group, were recruited for the study. All participants received a pro-phylaxis and oral hygiene instruction for 4 weeks before treatment. In the debridement group, mechanical de-bridement was performed by using carbon curets, followed by irrigation with 0.1% chlorhexidene gluconate and the submucosal application of 1% chlorhexidene gel. In the APAD group, air abrasion was accomplished with a specially designed instrument (Air Flow Master with Perio-Flow nozzle; Electric Medical Systems (EMS), Nyon, Switzer-land) and amino-acid glycine powder (Air Flow Perio Powder, EMS). Clinical parameters were measured at baseline and 3 and 6 months.

At 6 months, both groups exhibit-ed comparable probing depth reduc-tions and limited improvements in clinical attachment levels. The APAD group had higher changes in bleeding on probing scores, and it was con-cluded that the use of the APAD might be more effective for the treatment of initial periimplantitis than mechanical debridement. Readers should accept this conclusion with caution. Sample sizes in the study were small (n=15), the time frame short (6 months), and the differences between the 2 groups small. It is important to note that no microbiologic testing was done in this study, so there is no information on actual biofilm reduction. It is also worthy of note that the study was partially funded by EMS.

Another RCT was conducted to determine the impact of 2 different methods of implant surface debride-ment and decontamination (DD) on the clinical outcome of combined

surgical therapy for periimplantitis.165 Thirty participants with advanced periimplantitis were recruited and treated with 1 of 2 different protocols for DD in combination with surgical regenerative therapy. Both groups received similar presurgical debride-ment procedures. All participants re-ceived flap surgery, granulation tissue removal, and implantoplasty of ex-posed implant parts. One group had DD with an Er:YAG laser (ERL) device (Elexxion Delos; Elexxion AG, Radolf-zell, Germany). In the other group, DD was accomplished with plastic cu-rets, followed by scrubbing with cotton pellets soaked in sterile saline, followed by irrigation with sterile saline (CPS). All defects were filled with natural bone mineral (BioOss; Geistlich, Wolhusen, Switzerland) covered with a collagen membrane (BioGide; Geistlich). Peri-odontal parameters were recorded and radiographs obtained at baseline and at 6 months.

At 6 months, both groups exhib-ited comparable radiographic bone fill, reductions in bleeding on prob-ing, and improvements in clinical at-tachment levels. The method of sur-face DD did not have an impact on the clinical outcome. These are short term results (6 months), and there is no way of determining whether the observed radiographic bone fill is actually bone or simply the graft material.

Given that the effective removal of biofilm from contaminated implant surfaces is important to the success-ful treatment of periimplantitis, a systematic review on the effect of che-motherapeutic agents on contami-nated titanium surfaces would be of interest. Such a systematic review was published in 2011.166 Unfortunately, it provided little useful information for the practicing dentist. Only 4 studies were found that addressed the issue, 3 of which were in vitro studies and the other an ex vivo investigation. The use of chlorhexidine, citric acid, and saline or water was investigated with different concentrations and techniques. Citric acid appeared to be more useful than chlorhexidine but

did not result in complete biofilm re-moval and was only as effective as sa-line or water. Clearly this is a subject that should receive thorough investi-gation in the immediate future.

Another review evaluated the role of different implant systems on the initiation and progression of periim-plant disease.167 While implants with a roughened surface have demon-strated improved bone-to-implant contact compared to implants with machined surfaces, it is possible that implants with rough surfaces may be more susceptible to periimplantitis. Limited data from human studies sug-gest that smooth implants may be less affected by periimplantitis than im-plants with rough surfaces. Data from animal studies using a spontaneous progression model of periimplantitis suggest that the progression of pe-riimplantitis is more pronounced in implants with a porous anodized sur-face. Based on the limited data avail-able, the authors concluded that there is no evidence that implant surface characteristics have a significant effect on the initiation of periimplantitis.

In summary, it is clear there was a significant amount of investiga-tive activity in the discipline of im-plant dentistry in 2011. In spite of this high volume of activity, little evidence at the top of the evidence-base hierarchy has been produced. It is clear that failure rates of implants in smokers are 2 times those of non-smokers. It seems that short implants (<10 mm) may be used predictably in the mandible and may reduce the need for bony augmentation. Clear definitions for perimucositis and pe-riimplantitis have emerged, and it does appear that the incidence of pe-riimplantitis is higher than originally thought in implants in place 10 years or more. No optimum protocol for the treatment of periimplantitis has been determined, and no technique for optimum decontamination of the implant biofilm has been developed. The role of different implant surfaces on the progression of periimplantitis requires further investigation. Indeed,

47July 2012

Donovan et al

almost all aspects of the relatively young discipline of implant dentistry require further investigation.

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

Copyright © 2012 by the Editorial Council for The Journal of Prosthetic Dentistry.

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Annual review of selected scientific literature: Report of the committee on scientific ... · 2012. 7. 11. · Donovan et al Annual review of selected scientific literature: Report