Maxillary incisor impaction and its relationship to canine displacement.

This study aimed to examine the eruption status of unerupted maxillary permanent canines in patients who also had an impacted central incisor. Seventy-five unilateral cases of the incisor anomaly were retrospectively examined. Using the initial panoramic films, we assessed the positions of the ipsilateral and contralateral canines and the lateral incisors and the timing (eruption progress) of the canines. The final position of the canines was evaluated from patient records and progress photographs. The data showed a significant increase in prevalence and severity of displaced canines in the ipsilateral side (41.3%) compared with the contralateral side (4.7%). Palatally displaced canines occurred in 9.5%, buccally displaced canines in 30.2%, and canine-lateral incisor transposition in 1.6% of the patients. Half of the buccally displaced canines in the ipsilateral side were pseudotransposed with the adjacent lateral incisor. The eruption timing of ipsilateral undisplaced canines was either similar or delayed, relative to the contralateral tooth, but never accelerated. The ipsilateral lateral incisor was strongly angulated because of a more distally located apex (5 mm) rather than a mesially tipped crown. The ipsilateral canine was relatively more superiorly positioned (undererupted). Patients who had trauma had a significantly higher prevalence and severity of canine displacement and more distally displaced lateral incisor apices. Initial height of incisor impaction did not influence the results. These data provide evidence of a significant environmental influence of an impacted maxillary central incisor in delaying and altering the eruption path of the ipsilateral maxillary canine.