Dental and occlusal features in patients with palatally displaced maxillary canines

The aim of the present study was to determine the dental and occlusal features that could contribute to the aetiology of palatally displaced canines (PDCs). The material consisted of pre-treatment dental casts of 50 patients (36 females and 14 males) with unilateral and bilateral PDCs aged 14-16 years (mean 15.6 +/- 1.6 years). These were compared with a control group of 50 treated subjects (25 males and 25 females) of the same age with normally erupted maxillary canines. The following parameters were measured on the dental casts: the mesiodistal (MD) and buccolingual (BL) width of each maxillary tooth, the maxillary interpremolar and intermolar widths, overjet and overbite, dentoalveolar arch relationship (based on incisor classification), and missing or anomalous teeth. The differences between the PDC group and controls were determined using a Student's t-test. P values less than 0.05 were considered significant. PDCs occurred most frequently in subjects with a Class I occlusion. Sixteen per cent of the PDC subjects had congenital absence or peg-shaped lateral incisors or congenital absence of the second premolar, demonstrating a clear association between palatal impaction of the maxillary canine and anomalous or congenital tooth absence. The overjet was significantly smaller in the PDC female subjects, especially in those with unilateral impaction (P < 0.05). Overbite was significantly greater in PDC male subjects compared with the controls, especially in bilateral impaction cases. There was no statistically significant difference between the groups with regard to the maxillary transverse dimensions, maxillary MD widths, or palatal height for either gender.