The future of orthodontics, like the destination of a sailor, is rarely visible to the naked eye. The sailor uses the sextant to get direction as we must use the sextant of past experience to see what lies ahead for us.

There is no question that today's orthodontic students are tomorrow's orthodontic profession, but they will have little control over the educational experiences they encounter. These experiences will be a function of the systems we have put in place. Today's orthodontists, by and large, are professionally happy and successful. The systems worked for us and we would naturally like to

Abstract

The amount and direction of condylar growth, glenoid fossa displacement, and “effective” temporomandibular joint (TMJ) changes (a summation of condylar growth, glenoid fossa displacement, and condylar position changes within the fossa) were analyzed in 35 Class II, Division 1 malocclusions (23 boys and 12 girls) treated with the Herbst appliance. Lateral head films in habitual occlusion and with the mouth wide open from before (T1) and after 7.5 months of Herbst treatment (T2) as well as 7.5 months (T3) and three years (T4) after treatment were evaluated. As a control group, a sample of 12 untreated male Class II, Division 1 malocclusions was used during a 7.5-month time period corresponding to the treatment period (T2-T1) of the Herbst cases. The results revealed that during the treatment period (T2-T1) condylar growth was directed posteriorly about twice the amount as in the control subjects, and the fossa was displaced in an anterior inferior direction. The effective TMJ changes showed a pattern similar to condylar growth but were more pronounced. During the first posttreatment period (T3-T2), all TMJ changes reverted. The glenoid fossa was displaced backward; the amount of condylar growth and effective TMJ changes was reduced, and the changes were more superiorly directed. During the second posttreatment period (T4-T3), all TMJ changes were considered physiological. Conclusion: During Herbst treatment, the amount and direction of TMJ changes (condylar growth, fossa displacement, and effective TMJ changes) were only temporarily affected favorably by Herbst treatment.

Abstract

The purpose of this study was to (1) describe the prevalence of mandibular incisor irregularity (II) among untreated adults in the United States and (2) evaluate the factors explaining individual differences in II. Data were derived for a random sample of 9044 individuals (49% male and 51% female; 35% Mexican American, 34% black, and 31% white) between 15 and 50 years of age collected as part of the Third National Health and Nutrition Examination Survey. Although the differences were small (0.5 mm), males had significantly greater II than did females; blacks showed less II than did whites (0.9 mm) and Mexican Americans (1.1 mm). Family income was negatively related with II. Incisor irregularity increased in a curvilinear fashion with age, with the greatest increases occurring during early adulthood. Although the number of premolars and molars (first and second) were positively related with II, the presence of third molars had a negative effect on II. Multivariate Poisson regression analyses showed that the ethnicity, the number of first and second molars, sex, and age combined to explain differences in II. Odds ratios were relatively low, indicating that these factors explained relatively small amounts of between-subject variation. We conclude that (1) approximately 50% of individuals in the United States who were 15–50 years of age have little or no II, 23% have moderate II, and 17% have severe irregularity, (2) erupted third molars are not associated with increased crowding, (3) crowding increases most during early adulthood, and (4) although individual differences in crowding are multifactorial, the primary determinants remain unidentified.

Abstract

The purpose of this study was to investigate dental arch changes that occurred during the mixed dentition in 30 normal occlusion children. Two analyses were done. The first one was at the age of early mixed dentition and the second at the age of late mixed dentition. Most width variables were greater in the males, and depth variables greater in the female subjects. A directionally larger left side of the maxilla and right side of the mandible were observed. Our findings indicate that most arch width dimensions are established in the early mixed dentition. We conclude that the period between the early and late mixed dentition is suitable for environmental factors to disrupt the ideal symmetrical developmental pattern because more growth and developmental changes occur after a relatively stabile period of deciduous dentition.

Effects of printing layer thickness and build orientation on the mechanical properties and color stability of 3D-printed clear aligners

Chengzan Wu,

Utkarsh Mangal,

Na Bai,

Hoon Kim,

Geelsu Hwang,

Jung-Yul Cha,

Kee-Joon Lee,

Jae-Sung Kwon, and

Sung-Hwan Choi