Mandibular Arch Morphology in Normodivergent Patients With Impacted Maxillary Canines: A Case-Control Study

Introduction: The morphologic characteristics associated with maxillary canine impaction have been extensively investigated at the maxillary level, whereas the contribution of mandibular arch morphology remains less explored. The purpose of this study was to evaluate mandibular arch form in patients with impacted maxillary canines. Methods: The present study included 96 normodivergent Class I subjects aged 10–12 years, divided into three groups: patients with buccally impacted maxillary canines (n = 32), patients with palatally impacted maxillary canines (n = 32), and a control group with physiologic canine eruption (n = 32). Mandibular arch morphology was assessed using an angular morphometric analysis performed on digitally acquired mandibular models. A reference polygon was defined using the cusp tips of the mandibular canines and the distobuccal cusps of the mandibular first molars, and the sums of its anterior and posterior angles were calculated. Cephalometric variables were used to control for sagittal and vertical skeletal relationships. Multivariate and univariate statistical analyses were performed to evaluate intergroup differences. Results: Multivariate analysis of variance (MANOVA) revealed a significant overall effect of group membership on mandibular morphologic variables (p < 0.001). ArGoMe values were 123.35 ± 7.67 in the palatal impaction group, 128.59 ± 8.83 in the buccal impaction group, and 127.47 ± 6.77 in the control group; anterior angle sums were 133.41 ± 6.97, 123.68 ± 11.17, and 135.07 ± 6.65, respectively; posterior angle sums were 217.47 ± 8.24, 226.07 ± 7.32, and 225.25 ± 6.95, respectively. Significant intergroup differences were found for ArGoMe (p = 0.013; partial η2 = 0.090), anterior angle sum (p < 0.001; partial η2 = 0.264), and posterior angle sum (p < 0.001; partial η2 = 0.223), whereas no significant differences were observed for SNGoMe (p = 0.571; partial η2 = 0.012). Post hoc analyses showed that the palatal impaction group had significantly lower ArGoMe values than the buccal impaction group (p = 0.014), and significantly lower posterior angle sums than both the buccal impaction and control groups (both p < 0.001). The buccal impaction group showed significantly lower anterior angle sums than both the palatal impaction and control groups (both p < 0.001). Conclusions: Mandibular arch morphology differs between patients with impacted maxillary canines and subjects with physiologic eruption. Within the selected normodivergent sample, these differences were observed without significant intergroup differences in vertical divergence. Distinct mandibular morphologic characteristics were associated with palatal and buccal canine impaction, suggesting that mandibular arch assessment may complement conventional diagnostic evaluation in patients with impacted maxillary canines.