Craniofacial differences between skeletal Class II and skeletal Class I malocclusions according to vertical classification

Background The aim of this study was to determine morphological differences among Class II, division 1 (Class II, 1) subjects with different rotation models according to mandibular plane inclination and to compare these with normal subjects. Methods The study consisted of 132 subjects (99 Class II, 1 and 33 Class I control group). The Class II, 1 group included subjects who had ANB (point A-nasionpoint B) angles greater than 4 degrees with an overjet equal to or greater than 5 mm. Based on the SN/Go-Gn (cranial base anterior length/gonion-gnathion) angle, subjects were divided into three different rotation models as hypodivergent, normodivergent and hyperdivergent. Variance analysis (ANOVA) was used to assess the presence of differences between groups (p < 0.05). Results There was no statistical difference among the three groups in Class II, 1 malocclusion according to upper face height (N-ANS), total mandibular size (CdPg) and mandibular corpus size (Go-Gn) (p > 0.05). Although the ramus (Cd-Go) was significantly shorter in the Class II, 1 hyperdivergent group (p < 0.05), the hypodivergent group had similar ramus heights compared with controls. Conclusions Class II groups showed a similar increase in the ANB angle in spite of a different vertical rotation type. This study concludes that future Class II studies should divide subjects into subgroups according to hypodivergent, neutral and hyperdivergent phenotypes.