[Three-dimensional localization and assessment of maxillary palatal impacted canines with cone-beam computed tomography].

PURPOSE: To evaluate the location of maxillary palatal impacted canines and resorption of neighboring incisors with cone-beam computed tomography (CBCT). METHODS: Twenty-two healthy adolescent patients who had received orthodontic treatments at Stomatological Hospital of Nanjing Medical University were selected and scanned by CBCT. Palatal impacted maxillary canines were reconstructed by Dolphin imaging 11.0 software. The impactions, spatial relationships and classification relative to adjacent structures and incisor resorption were assessed. RESULTS: Most of the maxillary palatal impacted canines inclinated mesially and palatally. Mesial malpositions were more significantly prevalent in Class I and IV, and the prevalence rates were 30.8% and 38.5% respectively. Mesial inclinations of the impacted canines to occlusal plane were mostly between 53.8° and 68.5°, and the distances from the impacted canines to median sagittal plane were between 5.4 and 8.4 mm. Older the patient was, further the impacted canines mesiopalatal displaced and mesial inclined. The roots of 84.6% of lateral incisors and 19.2% of central incisors contacted impacted canines; Root resorption occurred in 50% of lateral incisors and 15.4% of central incisors, which predominantly located in apical third of the lateral incisors and middle third of the central incisors. A inverse correlation was found between the resorption rates of adjacent incisors and minimum distances from impacted canines to adjacent incisors. CONCLUSIONS: CBCT allows three dimensional evaluation of impaction and spatial relationships relative to adjacent structures. In addition, 3 dimensional measurement contributes to more accurate exhibition of the adjacent root resorptions, inclinations and depths of the impacted canines, which leads to more efficient guidance of maxillary palatal impacted canines treatment.