To compare dental arch and alveolar widths of patients with Class III and Class II division 1 malocclusions and those with Class I ideal occlusion.
Ninety patients were classified in 3 groups of 30 (15 male and 15 female) according to molar relationship. No subjects had received orthodontic treatment, and in all patients, the primary teeth had completely exfoliated. Dental casts of the 90 subjects were made and photographed with a digital camera on a tripod. Dental cast measurements were taken with a dial caliper to the nearest 0.01 mm. All measurements of all subjects were carried out again 2 weeks later to evaluate the measurement error.
Analyses of 1-way analysis of variance demonstrated that (1) there were statistical differences in most of the measurements between the Class I and Class III groups (P>.05) and (2) the Class II division 1 group had differences from other groups (P<.05). This result suggests that transverse discrepancy in Class II division 1 and Class III patients may originate from the maxillary posterior teeth.
Maxillary intermolar widths are significantly greatest in Class III, Class I, and Class II division 1 groups, respectively.