Objective: To compare the arch width, alveolar width, and buccolingual inclination of maxillary and mandibular posterior teeth between Class II division 1 malocclusion and Class I occlusion.
Materials and methods: Forty-five subjects with Class I occlusion and 45 subjects with Class II division 1 malocclusion were selected to measure the maxillary and mandibular arch width and alveolar width of premolars and first molars with digital caliper. Buccolingual inclination of maxillary and mandibular premolars and first molars were measured with a modified universal bevel protractor.
Results: All of the posterior teeth in both groups were lingually tilted. The maxillary premolars and first molars were significantly more lingually tilted (P < .05) in Class II division 1 malocclusion than in Class I occlusion. Mandibular first premolars were significantly less lingually tilted in Class II division 1 malocclusion than in Class I occlusion. No significant difference of buccolingual inclination was found in mandibular second premolars and first molars between the two groups. No significant difference in maxillary and mandibular arch width and alveolar width was found between the two groups.
Conclusions: Buccolingual inclination rather than arch width and alveolar width plays an important role in transverse discrepancy of Class II division 1 malocclusion.