REVIEWS AND ABSTRACTS

Book reviews and article abstractsAlex Jacobson, DMD, MS, PhDBirmingham, Ala

THESIS ABSTRACTS

Influences of age, sex, and orthodon-tic treatment modality on thecorrection of Class II malocclusionsJoseph D. Hicks, DDSDepartment of Orthodontics, University of Tennessee, Memphis

The central question was whether the nature of theorthodontic correction depends on the patient’s age at the startof treatment—using chronological age as a proxy for degreeof biological maturity. As a secondary issue, we investigatedthe treatment differences among 3 common orthodontic tech-niques–Tweed edgewise, Begg lightwire, and straightwire–toidentify systematic differences in the nature of the orthodon-tic correction in adolescents. Third, we tested for male-femaledifferences in the correction because boys exhibit later, butmuch larger, facial growth vectors during adolescence. Asample of Class II Division 1 adolescents (13 to 18 years ofage) was collected (n � 155), proportionately divided bytreatment technique (edgewise, lightwire, and straightwire),and sex. A comprehensive battery of cephalometric variables(� � 65) was computer generated from tracings of thepretreatment and posttreatment cephalograms. Age differ-ences, by technique and sex, were assessed with analysis ofcovariance. Results showed significantly greater growth inadolescent boys than in girls at all ages, especially in verticaldimensions of the midface. Maximum growth occurred in theyoungest ages of 13 to 18 years, with linear decreases withincreasing age. Trivial growth was seen in boys about 15 to16 years of age and in girls after about 13 to 14 years of age.It was striking how little facial growth occurred in the typicaladolescent girl. Peripheral facial variables grew more thandeep structures because rates are cumulative across theseveral circummaxillary sutures and remodeling surfaces.Greater growth in boys works to the advantage of theorthodontist because more growth requires less molar move-ment to achieve Class I correction. Treatment differenceswere few: Begg treatment left U1 in a more upright position,probably because of incomplete root torque during stage 3.The percentage contribution of the patient’s sex plus mode oftreatment was quantified with multiple regression, and, onaverage, the patient’s age and sex accounted for 5% to 10%of the skeletodental variation; this is measurable and statisti-cally significant, but probably not apparent to the orthodontiston a case-by-case basis. But, from a research perspective,these sources of variation should be taken into account,especially when comparing studies. If it is desired to maxi-

mize growth to aid in correcting Class II malocclusions,treatment should be started very early in adolescence becausefacial growth rates slow progressively with age.

0889-5406/2002/$35.00 � 0 8/3/128215doi:10.1067/mod.2002.128215

Long-term changes in theintegumental profile following ortho-dontic treatmentDaniel Wade BradshawDepartment of Orthodontics, University of Tennessee, Memphis

Most orthodontic patients begin treatment as youngteenagers, so considerable facial growth occurs thereafter,extending at least into their twenties. The purpose of thepresent study was to document the growth, notably the changein the facial profile, from the start to the end of comprehen-sive orthodontic treatment (T1 � 13 years of age; T2 � 16years) and again at a long-term recall examination (T3 � 31years). Patients (n � 80, American whites; 57 males, 23females) all had 4-premolar extractions and were recalled anaverage of 15 years out of treatment and assessed cephalo-metrically. A Cartesian coordinate system was used to parti-tion changes in the skeletodental profile (7 variables) and theintegumental profile (10 variables) into horizontal and verti-cal components relative to Frankfort horizontal with registra-tion at sella. Because the T1 age interval often overlaps theparapubertal growth spurt, the patients grew appreciably, bothhorizontally and vertically, during treatment, but the changeswere especially obvious in boys. After treatment, facialgrowth was statistically significant in boys in all dimensions,notably vertically, but not so in girls whose growth vectorswere much smaller. Two related events occurred during andafter treatment: the supporting hard skeletodental facial tis-sues grew downward and forward, more so in boys; and thesoft-tissue thicknesses increased with age, also more so inboys. The facial profile grew differentially during earlyadulthood: the nose and the chin grew forward much morethan the upper face or the lips. The lips, particularly the upperlip, grew forward at very modest rates, especially in women.Relative to sella, the perioral landmarks of Point A andlabrale superius and inferius diminished about 0.5 mm inwomen from T2 to T3 and increased about 2 mm in men.Growth flattened the profile; the lips were more retrusive byearly adulthood because the nose and chin grew forwardmuch more. The situation was comparable in the sexesbecause, although males were larger and grew more, the

676 American Journal of Orthodontics and Dentofacial Orthopedics/December 2002

changes were proportionate in men and women. We do notknow yet the role of the premolar extractions in flattening theface—versus normal aging events. In sum, it would seem tobe more appropriate to treat adolescent patients to adolescentnorms, which take subsequent growth into account, ratherthan to adult standards.

0889-5406/2002/$35.00 � 0 8/3/128724doi:10.1067/mod.2002.128724

Long-term stability of orthodonticcases treated by an experiencedspecialist: a cast analysisTroy Alan WilliamsDepartment of Orthodontics, University of Tennessee, Memphis

Stability is an important objective of orthodontictreatment because, without it, the improvements in esthet-ics and function obtained during treatment will degradewith time. The present study evaluated the stability of anexperienced orthodontic specialist’s patients a minimum of10 years after treatment to assess the long-term conse-quences of relapse, growth, and other changes. Patientswere treated with standard edgewise Tweed mechanics inDr R. G. Alexander’s private practice in Arlington, Texas.They were treated before his use of straightwire mechan-ics. Diagnostic records of 60 patients (48 women, 12 men)were studied, all of whom had received comprehensiveorthodontic treatment. Records were taken at 3 times,corresponding to mean ages of 12, 15, and 27 years. Thepatients had Class I or Class II malocclusions, and the castswere analyzed with DentoFacial Planner software. Weregressed posttreatment change (T3 minus T2) on theorthodontic change (T2 minus T1) with linear regression.Statistical significance disclosed that the amount of changepredicts the amount of relapse, and the regression coeffi-cient tells the direction and average amount of relapse perunit of treatment change. For example, the regressioncoefficient for sagittal molar relationship was �0.2 (P �.01; r2 � 16%), meaning that 1 mm of correction of themolar relationship was followed, on average, by 0.2 mm ofrelapse back toward the pretreatment condition; this wassignificant, accounting for 16% of the postorthodonticchange. The same pattern held for overbite (b � �0.4; P �.01; r2 � 21%), overjet (b � �0.2; P � 0.01; r2 � 20%),curve of Spee (b � �0.3; P � .01; r2 � 16%), maxillarycanine width (b � �0.3; P � .01; r2 � 39%), mandibularcanine width (b � �0.3; P � .01; r2 � 24%), maxillarymolar width (b � �0.2; P � .01; r2 � 23%), andmandibular molar width (b � �0.2; P � .01; r2 � 12%).As such, orthodontic treatment—moving teeth from lessfunctional and less esthetic but stable positions to esthetic,functional but evidently less stable positions—is a signif-icant predictor of the vector of relapse, much more so thanthe patient’s age, sex, difficulty of the case, extractionpattern, treatment time, or any other variable tested.

Relapse of some variables was independent of treatmentchange, notably mandibular incisor irregularity (b ��0.05; P � .12; r2 � 4%), probably because little relapseoccurred (T1, 5.3 mm; T2, 0.1 mm; T3, 0.7 mm), much lessthan reported from graduate orthodontic clinics. We alsocompared these changes with those of another long-termstudy from the Tweed Foundation. Several minor butstatistically significant differences were seen in the natureof the relapse, including differences in overjet, intermolarwidth, and incisor irregularity. These differences disclosestylistic differences even among experienced practitionersusing the same mechanics.

0889-5406/2002/$35.00 � 0 8/3/128725doi:10.1067/mod.2002.128725

Cephalometric assessment ofVietnamese-American orthodonticpatients at pretreatment: characteristicrelationshipsDavid Gee Wong, DDSDepartment of Orthodontics, University of Tennessee, Memphis

Each orthodontic patient has unique treatment needs,but the goals of treatment ought to incorporate consider-ations of the patient’s sex, age, and racial background.Cephalometric norms have, historically, been based onpeople of European extraction, even though there is con-siderable variation in modal facial patterns among theworld’s populations. In the United States, the influx ofpeople from Vietnam, particularly after American involve-ment in their civil war, has created a need to assess thecephalometric status of this people’s craniofacial struc-tures with an eye toward obtaining race-appropriate norms.Presently, there are no published data on the cephalometricnorms of Vietnamese-Americans. In the present study, 500cephalograms of Vietnamese-American adolescents takenat the start of orthodontic treatment were analyzed. Noneof the patients had a disease condition known to affectgrowth. Outside of selecting for age at the start oftreatment (12 to 17 years) and an intact permanent denti-tion, subjects were obtained sequentially from 1 orthodon-tic specialist’s office. We traced and digitized the cepha-lograms and computer generated 63 linear and angulardimensions. Analysis showed that, compared with same-age normative data published on American white adoles-cents, these Vietnamese-Americans possess distinctive fa-cial patterns. Key differences include: (1) The Vietnameseskull is smaller overall than that of age-matched European-Americans, and this persists into late adolescence, suggest-ing it might be a life-long phenomenon. Characteristicallysmaller craniofacial dimensions can bias diagnoses thatdepend on millimetric sizes. (2) The anterior cranial base(sella-nasion) is quite short, so nasion is “displaced”dorsally; this distorts several common measurements that

American Journal of Orthodontics and Dentofacial OrthopedicsVolume 122, Number 6

Reviews and Abstracts 677