Are facial, maxillary arch and incisor dimensions related in patients with a unilaterally impacted palatal canine? A prospective investigation

Abstract Objective To identify and determine the relationship between facial, maxillary arch and incisor dimensions of patients presenting with a unilaterally impacted palatal canine. Methods Prospective referrals over one calendar year of patients identified with a unilaterally impacted palatal canine were compared with prospectively recruited control subjects. Canine location was determined radiographically and re-confirmed two weeks later. Facial, maxillary arch and incisor dimensions were assessed. Intra-examiner reproducibility was re-assessed using randomly selected images (20%, n = 40). General linear models were applied for inter-group comparisons incorporating Bonferroni adjustment with categorical parameters assessed using Fisher’s exact test (SAS®, Version 9.4, SAS.com). Inter-class correlation coefficients were calculated for relationships between the variables. Results Fifty-four patients (37 females; 17 males) presenting with a unilaterally impacted palatal canine [mean age 14.5 (SD 1.7) years] and 54 control subjects (37 females, 17 males) [mean age 14.3 (SD 2.2) years] were recruited. Measurement error was small for landmark data (0.58 mm), palatal depth (0.09 mm), palatal area (0.42 mm²) and Bolton ratio (0.14%). For facial, maxillary arch and tooth shape assessments, landmark error was 0.05 mm with complete agreement for classification. The mean nasal basal width was smaller in the unilaterally impacted palatal canine group compared with the control group (P < 0.0001) but face shape distribution and face ratio were similar (both P > 0.05). The mean anterior Bolton ratio was larger in the impacted canine group (P < 0.01). No differences were recorded between groups for other parameters (all P > 0.05). No positive correlations were identified between the variables. Conclusions Patients with a unilaterally impacted palatal canine had a narrower mean nasal basal width and a larger mean anterior Bolton ratio compared to a control group but the clinical significance of the differences was considered minor. Facial, maxillary arch and incisor dimensions were neither individually nor collectively correlated with a palatal canine which may lend support to a genetic aetiology.