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.