Tooth size discrepancies in Class II division 1 and Class III malocclusion requiring surgical-orthodontic or orthodontic treatment.

OBJECTIVE: To compare mean anterior (AR) and mean overall (OR) tooth size ratios, prevalence of clinically significant tooth size discrepancies (TSDs) and correlation between AR and OR in subjects with Class II division 1 and Class III malocclusion treated by surgical-orthodontic or orthodontic means. DESIGN: Retrospective, cross-sectional. SETTING: State-funded and private clinics. PARTICIPANTS: From pre-treatment cohorts of 770 surgical and 610 non-surgical subjects, Class II division 1 and Class III malocclusion groups were identified with 60 surgical and 60 non-surgical subjects, comprising 30 males and 30 females, in each. METHODS: AR and OR were calculated by landmarking digital models. Differences in AR and OR and their relationship were analysed using two-way analysis of variance (ANOVA) and a correlation coefficient, respectively. The proportions of the surgical and non-surgical groups with a TSD were assessed using logistic regression. Intra-examiner reproducibility involved re-landmarking 30 randomly selected image sets and differences in ARs and ORs were compared using a paired t-test. Random error was assessed using the intraclass correlation coefficient (ICC). Analyses were performed using SAS (SAS Institute Inc., Cary, NC, USA) at the 5% level of significance. RESULTS: There were no statistically significant differences associated with the measurement of either the mean AR (P = 0·913) or the mean OR (P = 0·874). ICC values were very high (AR = 0·95; OR = 0·90). Differences existed between both Class II and Class III surgical (AR: P<0·001; OR: P<0·001) and non-surgical groups (AR: P = 0·012; OR: P = 0·003). The AR and OR relationship was strong (correlation coefficient = 0·72). The highest percentage of clinically significant TSDs was seen in the AR of both Class II and Class III surgical groups (23·3%). CONCLUSIONS: In the cohort examined: AR and OR differed significantly for malocclusion groups. The prevalence of clinically significant TSDs did not differ significantly between surgical and non-surgical groups although the highest percentage of clinically significant TSDs was recorded for AR in Class II and Class III surgical cases. AR and OR were closely related.

The relationship between tooth size discrepancy and archform classification in orthodontic patients.

BACKGROUND: To determine the relationship between clinically significant tooth size discrepancies (TSD) and archform classification in orthodontic patients. MATERIAL AND METHODS: Eighty teeth with artificial white spot lesions were randomly divided into four groups: (A) distilled and deionized water, (B) Nd:YAG laser, (C) CPP-ACP crème, & (D) CPP-ACP plus laser. SMH was measured using Vickers diamond indenter in Vickers Hardness Number (VHN). Two samples of each group were analyzed using scanning electron microscope (SEM). The results were analyzed with the SPSS 17/win. RESULTS: Reproducibility of the classification of archform was very good (unweighted Kappa statistic of 0.83 with a 95% confidence interval of 0.73, 0.93). There was no statistically significant difference in the distribution of archform type between group 1 and group 2 for the upper (p=0.3305) or lower (p=0.6310) arches. CONCLUSIONS: The presence of a clinically significant TSD and archform classification do not appear to be related. Key words:Tooth Size, Archform, Bolton discrepancy, digital models, polynomial curve, archform classification.

Tooth size discrepancies in Irish orthodontic patients among different malocclusion groups.

OBJECTIVE: To determine the prevalence of tooth size discrepancies (TSDs) in an Irish orthodontic population among different malocclusion groups. MATERIALS AND METHODS: From 850 pretreatment sets of orthodontic models at a university clinic, 240 were selected with 30 female and 30 male sets for each malocclusion (Class I, Class II division 1, Class II division 2, and Class III). Digital models were produced, and the mesial and distal contact points were digitized to calculate overall and anterior tooth size ratios. The differences between the male and female groups and among the malocclusion groups were analyzed using two-way analysis of variance (ANOVA) (P < .05). RESULTS: A clinically significant anterior TSD (more than two standard deviations from the Bolton means) existed in 37.9% of the subjects. No differences existed in the prevalence of overall TSDs between the male and female groups (P  =  .5913) or among the malocclusion groups (P  =  .0809). For the mean anterior tooth size ratios in the male group, the values for Class III and Class II division 2 were higher than in Class II division 1, and the value for Class II division 2 was higher than in Class I (P  =  .0184). CONCLUSIONS: The prevalence of anterior tooth size discrepancies in this sample of Irish orthodontic patients was 37.9%. There were no statistically significant differences in the prevalence of mean overall TSDs with regard to malocclusion or gender. In the male group, the mean anterior tooth size ratio was higher in Class III and in Class II division 2 malocclusion than in Class II division 1 and higher in Class II division 2 malocclusion than in Class I malocclusion.