Dentoskeletal features associated with unilateral or bilateral palatal displacement of maxillary canines.

The aim of the present study was to analyze the prevalence and distribution of palatally displaced maxillary canines (PDC) in a large orthodontic population, and to investigate the associations between PDC, craniofacial features, and other dental anomalies such as aplasia or small-sized upper lateral incisors. An initial sample of 5000 subjects was evaluated. The reference values were calculated in a control group of 1000 subjects that was extracted from the initial sample. Chi-squared tests were used for statistical comparisons. The prevalence rate of PDC was 2.4%, with a male-to-female ratio of 1:3. PDC subjects with low angle vertical relationships showed a significantly high prevalence rate (60.2%). Unilateral PDC was significantly associated with aplasia of upper lateral incisors, whereas bilateral PDC was associated with aplasia of third molars. PDC showed reciprocal significant associations with bilateral small-sized upper lateral incisors. None of the three hypotheses offered in support of the "guidance theory" in the etiology of PDC were corroborated by the findings of the present study. The occurrence of other dental anomalies concurrent with PDC, sex differences, and the bilateral expression of PDC, all confirm the genetic component in the etiology of this tooth disturbance.