ous improvements and the undesirable changes that can occuras a consequence of incorrect occlusal contacts.

For various reasons, anterior teeth can start to migrate inolder people. In most patients, alignment of only the offend-ing anterior teeth is sought rather than comprehensive appli-ance therapy. Chapter 17 illustrates the many ways thatanterior teeth in adults can be aligned by using simple,inconspicuous appliances. The concluding chapter illustratesvarious methods of effectively retaining teeth after orthodon-tic treatment. Also debated is how long teeth should be keptin retention and whether to accept a mild relapse rather thanrecommend permanent retention.

This magnificently produced volume is essentially anatlas. The treatment procedures are superficially described.How the appliances function and are activated are shown inthe many illustrations, photographs, and legends, 2300 in all!Dr Van der Linden is to be commended on having gatheredand recorded so much valuable material over more than 30years. The author gives credit for recording the material to thephotographers and the technical assistants on his team.Readers will discover among the pages many useful and oftenunique interceptive fixed and removable devices.

Alex JacobsonAm J Orthod Dentofacial Orthop 2005;127:267-80889-5406/$30.00Copyright © 2005 by the American Association of Orthodontists.doi:10.1016/j.ajodo.2004.11.011

Orthodontic management of agenesisand other complexities: Aninterdisciplinary approach tofunctional estheticsMichael ArvystasLondon and New York: Taylor & Francis; 2003; distributed in the

US and Canada by Thieme Publishing, New York; 227 pages; $99

The author introduces this book by discussing variousconcepts of esthetics, beginning with the artistic and scientifictheories of perspective and proportion such as the GoldenProportion and the Fibonacci series, as they relate to the faceand the smile. Establishing rigid measurements and propor-tional values as characteristics of the ideal face is unnaturalbecause they do not incorporate the natural variations ofpopulation groups. Emphasized is the clinician’s need toacquire a modicum of artistic talent and good clinical judg-ment if an esthetic result is to be achieved and fitted to theneeds of each patient. In the second chapter, the author dealswith the agenesis of lateral incisors. The most commonmissing permanent teeth, excluding third molars, are secondpremolars (3.4%) and maxillary lateral incisors (2.2%). Manyauthors advocate moving maxillary canines mesially intolateral incisor positions and grinding the canines to the correctshape if necessary. Others disagree and, for functional andesthetic reasons, prefer to create adequate mesiodistal spacefor the restoration of agenesis of the lateral incisor. The

reasons for the latter approach are elaborately debated. Shownare sequential photographs of 5 magnificently treated patientsin whom either the left, right, or both lateral incisors weremissing. In each instance, space was created for the missinglateral incisor(s) and the teeth replaced with implants orprecious metal and porcelain bridges. Chapter 3 discusses theagenesis of maxillary and mandibular premolars which canoccur unilaterally or bilaterally. Orthodontic debate fluctuatesbetween extraction and nonextraction therapy, with the choiceof treatment necessitating discussion among patient, parents,and restorative dentist. Every decision should be made on acase-by-case diagnosis. The soft tissue effects of treatment,evaluation of the smile, space closure versus creation ormaintenance of space are issues to be considered in treatingthese patients. Shown are treatment sequences of 6 such patients.

Chapter 4 involves adults seeking orthodontic treatmentsthat require interdisciplinary restorative and surgical care.Shown are photographs of 2 treated patients, the first a ClassII Division 2 malocclusion with severe overbite, and the othera Class I malocclusion with minimal incisor contact andanterior open bite. The results are impressive. In “Estheticconsiderations of the long-face syndrome” (chapter 5), theauthor discusses 2 types of Class II skeletal long-face mal-occlusions—with and without a skeletal open bite; the char-acteristics of both are described. The treatment sequences of4 such patients are shown. According to the author, the mainfocus in the treatment of these patients should be the etiologicfactors; the identification of disproportionality is of para-mount importance. The final chapter describes and shows themanagement of 8 nontraditional malocclusions, each seem-ingly more complex than the other. The results achieved ineach instance are excellent. Orthodontists must expect toencounter patients in their private practices similar to these; itis comforting to see how these patients were managed by anexperienced colleague. Much can be learned by astute rea-soning and observation.

Alex JacobsonAm J Orthod Dentofacial Orthop 2005;127:2680889-5406/$30.00Copyright © 2005 by the American Association of Orthodontists.doi:10.1016/j.ajodo.2004.11.010

THESIS ABSTRACTS

Evaluation of Invisalign treatmentutilizing the American Board ofOrthodontics Objective GradingSystem for dental castsScott VincentDepartment of Orthodontics, Oregon Health & Science University,

Portland, Ore

For orthodontic treatment of certain malocclusions, In-visalign (Align Technology, Santa Clara, Calif) offers analternative to fixed appliances. The purpose of this study was

American Journal of Orthodontics and Dentofacial OrthopedicsFebruary 2005

268 Reviews and abstracts

to evaluate the treatment outcome of patients treated withInvisalign aligners by using the American Board of Orth-odontics Objective Grading System (OGS) for dental casts.The dental cast component of the OGS scores 7 categories fordiscrepancies from ideal related to tooth alignment andocclusion. Depending on the magnitude of the discrepancy,up to 2 points can be scored in each category; thus the fewerthe points scored, the more ideal the result. A total of 135patients treated with the Invisalign system and having pre-treatment and posttreatment records were identified from 7orthodontic private practices. If patients met the selectioncriteria, the dental cast component of the OGS was performedon the pretreatment and posttreatment casts. The selectioncriteria were (1) no missing teeth (other than previouspremolar extractions), (2) Invisalign treatment exclusively,and (3) available pretreatment and posttreatment models ofdiagnostic quality. Pretreatment and posttreatment OGSscores were compared, and the differences were analyzed byusing paired t tests. Results showed that, of the 135 subjects,65 (48%) met the inclusion criteria. These were evaluatedwith the OGS. For those not included in the OGS analysis, 33(24% of the 135) required fixed appliances or spring alignersto finish the treatment, 25 (19%) had poor or missing records,and 12 (9%) had missing teeth. For the 65 subjects analyzed,the mean age was 31.1 (� SD 12.5) years, the duration oftreatment was 12.5 (� 4.1) months, and the patients wore17.9 (� 7.3) maxillary and 17.7 (�6.9) mandibular Invisalignaligners. The pretreatment total OGS score (dental componentonly) was 47.0 (� 16.5), and the posttreatment OGS scorewas 36.4 (� 16.0; P � .001). Comparison of the categories inthe OGS showed that significant improvements occurred intooth alignment (pretreatment mean: 21.5 points vs posttreat-ment: 7.0 points (P � .001), buccolingual inclination (4.7 vs4.1 points, P � .001), and interproximal spaces (1.3 vs 0.0points; P � .05). On the other hand, there was a negativechange in posterior occlusal contacts (4.0 vs 10.3 points; P �

.001). The remaining categories, including marginal ridgerelationships, occlusal relationships (eg, posterior interdigita-tion), and overjet (anterior and posterior), showed no signif-icant change. Thus, for this sample treated with the Invisalignsystem, the greatest positive change as measured by the OGSpoint system was in the alignment of teeth, followed byclosure of interproximal space. An undesirable change wasfound with a decline in posterior occlusal contacts. The scorefor the latter category had a negative impact on the overallchanges as measured with the OGS method. The results of theOGS show that treatment with Invisalign aligners had adverseeffects on posterior occlusal contacts and positive effects ontooth alignment, buccolingual inclination, and interproximalspaces.

Am J Orthod Dentofacial Orthop 2005;127:268-90889-5406/$30.00Copyright © 2005 by the American Association of Orthodontists.doi:10.1016/j.ajodo.2004.07.016

The effect of bracket material onfatigue strength of the orthodontic bondC. Mark BuxtonDepartment of Orthodontics, Oregon Health & Science University,Portland, Ore

Repetitive masticatory forces can cause microfracturesand eventual breakdown of the dental materials through theprocess of fatigue. Orthodontic brackets are subjected tocyclical loading, with the forces transmitted through thebonding material attaching the brackets to the teeth. Bracketsmade of different materials will have different flexure prop-erties that can influence fatigue properties of the bond. Thepurpose of this bench-top study was to investigate the fatiguestrength of the bond with brackets made of titanium, stainlesssteel, and ceramic, and to relate the bond’s fatigue strength toits shear bond strength. The orthodontic brackets were indi-vidually bonded to extracted mandibular premolars withTransbond XT composite (Unitek, Monrovia, Calif). For eachbracket type, 24 samples were subjected to fatigue tests and 8to shear bond tests. Fatigue testing used a “staircase” meth-odology; samples of each bracket material were tested se-quentially by placing a load on the occlusal tie-wings for5000 cycles. For each bracket material, a predetermined loadbased on pilot study data was applied for the first trial. If thebracket bond failed before the end of the trial, the load wasdecreased by 5% for the next sample. If there was no failure,the load was increased by 5%. The load was recorded, and theprocess continued sequentially until all samples had beentested. For the shear bond strength, an increasing load wasapplied to the occlusal tie-wings until bond failure. Themeasurements were compared by using ANOVA and Tukeymultiple comparisons statistical tests set to P � .05. Resultsshowed that mean fatigue strengths for titanium (6.78 � SD0.53 MPa) and stainless steel brackets (5.97 � 0.37 MPa)were not significantly different; bond fatigue strength for theceramic bracket was significantly higher (9.60 � 0.44 MPa)(P � .05). The shear bond strength for the titanium bracket(8.66 � 1.37 MPa) did not differ from that of the stainlesssteel bracket (9.43 � 1.55 MPa), and was significantly higherfor the ceramic bracket (12.06 � 2.17 MPa; P � .05). Thefatigue strength of the bond for the 3 bracket types wassignificantly different from the shear bond strength (P� .02);the fatigue strength of the bond for titanium brackets was78% of the shear bond strength, 63% for stainless steelbrackets, and 80% for ceramic brackets. Results of this studyshow that, for the 3 bracket types, the bond strength waslower in fatigue testing than in shear testing. In addition, inboth fatigue and shear testing, the bond with titanium andstainless steel brackets performed comparably, whereas, withceramic brackets, the bond withstood significantly higher forces.

Am J Orthod Dentofacial Orthop 2005;127:2690889-5406/$30.00Copyright © 2005 by the American Association of Orthodontists.doi:10.1016/j.ajodo.2004.07.013

American Journal of Orthodontics and Dentofacial OrthopedicsVolume 127, Number 2

Reviews and abstracts 269