Dental transposition as a disorder of genetic origin.

A sample of 85 dental transpositions in 75 subjects (27 male, 48 female; mean age at diagnosis 12.25 years) involving both maxillary and mandibular arches was analysed using dental panoramic radiographs and clinical records. Transposition affected the maxillary dentition (76 per cent) more frequently than the mandibular dentition (24 per cent). Unilateral transposition accounted for 88 per cent of cases, with the maxilla being involved more commonly than the mandible. Overall, the most common transposition involved the maxillary canine and first premolar (58 per cent). Considering the jaws in isolation, the canine and first premolar were the most commonly affected teeth in the maxilla (83 per cent) whilst in the mandible, the canine and lateral incisor teeth were most commonly transposed (73 per cent). No significant difference in symmetrical distribution of the unilateral transposition sample occurred. There was evidence of associated hypodontia in 41 per cent of the sample; however, if third molars were excluded, this figure decreased to 25 per cent. Peg-shaped maxillary lateral incisors were judged to be present in 27 per cent of subjects, whilst 41 per cent had retained primary teeth; all of these, except one, were primary canines. Overall, the majority of the sample (76 per cent) demonstrated at least one of the dental anomalies under investigation. Multivariate analysis showed associations between unilateral transposition, gender, and the presence of peg-shaped maxillary lateral incisors; whilst bilateral transposition was more closely associated with gender and the presence of retained primary teeth. There was a poor association between both unilateral and bilateral transposition and hypodontia. Together, these results suggest a mutifactorial aetiology to this disorder, with both genetic and environmental factors playing an important role.