Three-dimensional geometric morphometric analysis of palatal morphology in patients with maxillary impacted canines: A retrospective case-control study in a French orthodontic population

Background The relationship between maxillary canine impaction and palatal morphology remains debated, as most previous studies relied on linear measurements. This study investigated three-dimensional palatal morphology in patients with and without maxillary canine impaction using geometric morphometric methods (GMM) to characterize shape variation independently of size.Methods This retrospective case-control study included 90 orthodontic patients (45 with maxillary canine impaction and 45 matched controls), with a mean age of 13.53±1.59 years. Digital maxillary casts were analyzed using 239 semi-landmarks. Multiple linear regression and Procrustes MANOVA were used to assess differences in palatal size and shape, adjusting for sex and skeletal characteristics. Post-hoc comparisons were performed to assess differences between impaction types.Results Palatal size did not differ significantly by impaction status. Canine impaction was significantly associated with palatal shape (P=0.002), whereas sex, skeletal class, vertical pattern, and interaction terms had no significant effect. Pairwise comparisons showed a significant mean shape difference only between controls and subjects with palatally impacted canines (padj=0.003), whereas buccally impacted canines did not differ significantly from controls. Compared with controls, palatally impacted cases exhibited a flatter and more elongated palate.Conclusions Maxillary canine impaction, particularly palatal impaction, is associated with three-dimensional palatal shape variation rather than differences in overall size. Palatal morphology should be considered as a whole during clinical evaluation, rather than focusing exclusively on transverse dimensions.