Maxillary tooth transpositions: characteristic features and accompanying dental anomalies.

Transposition is a dental anomaly manifested by a positional interchange of 2 permanent teeth. The maxillary permanent canine usually transposes with the first premolar and occasionally with the lateral incisor. The records of 65 orthodontically treated individuals with maxillary tooth transpositions (40 females and 25 males) with an age range of 9 to 25 years (mean age, 13.4 years) were studied to determine the distribution of transposition and to evaluate the accompanying dental anomalies. Thirty-six individuals (55%) had a transposition of the maxillary canines and first premolars, 27 (42%) of the canines and lateral incisors, and 2 (3%) of the central and lateral incisors. Females had 60% more transpositions than did males. Substantially more transpositions were unilateral (88%), with a moderate left side dominance (58%). All dental anomalies associated with transposition--including missing lateral incisors and second premolars, undersized lateral incisors, retained deciduous canines, impaction of permanent canines and central incisors, and severely rotated adjacent teeth--were observed on the side of the transposition. This dominance of the affected side suggested that unknown local factors may play a major role in these dental anomalies.