Relationship between different skeletal patterns and basal arch widths in adults with class Ⅱ division 1 malocclusion: a retrospective study

BACKGROUND: The purpose of this study was to investigate the maxillary and mandibular basal arch widths of Class Ⅱ division 1 malocclusion with different vertical skeletal patterns and the correlation between the basal arch widths and sagittal and vertical discrepancies. METHODS: A total of 80 cone-beam computed tomography (CBCT) images of Class Ⅱ division 1 malocclusion and Class I occlusion were selected. The patients were divided into low (< 22º), average (22º-28º) and high (> 28º) angles by the Frankfort mandibular plane angle (FMA). The maxillary and mandibular basal arch widths of canines to second molars were measured at the apical base. Measurements were statistically analyzed by one-way ANOVA test, followed by Tukey's post hoc test. Pearson correlation coefficients were used to calculate the correlation between the basal arch widths and subspinal nasion-suture angle (ANB) and FMA. RESULTS: Class Ⅱ division 1 malocclusion with high-angle group had narrower basal arch widths of the maxilla and mandible. The basal arch widths of both jaws showed no significant differences between Class Ⅱ division 1 malocclusion with low- and normal-angle and Class I occlusion groups. As the vertical skeletal patterns increased, the basal arch widths decreased. The discrepancy between the maxillary and mandibular basal arch widths in Class Ⅱ division 1 malocclusion and Class I occlusion groups were statistically significant on the same coronal plane. The ANB and FMA were negatively correlated with the basal arch widths. The negative correlation with the FMA was pronounced and became increasingly pronounced as the vertical skeletal patterns increased. CONCLUSIONS: The basal arches are discrepant in transverse dimensions for Class Ⅱ division 1 malocclusion with high-angle. Mismatch of the maxillary and mandibular basal arches is detected in patients presenting with Class Ⅱ division 1 malocclusion. It is more appropriate for clinicians to focus on the effect of vertically oriented anomalies on transverse oriented anomalies during orthodontic treatment planning for Class Ⅱ division 1 malocclusion.