Three-dimensional Analysis of the Impacted Maxillary Canine: Localization and Assessment of Severity

Aims & Objectives: The objective of this study is to determine the location of impacted or unerupted maxillary canines and evaluate their position and severity as they correlate to the clinical aspect of orthodontics. In addition, we propose to identify specific regions in the maxilla where impacted canines are more common, and to evaluate these methods for reliability and accuracy. Finally, we intend to introduce a 3-D classification for maxillary impacted canines. Materials & Methods: We reviewed approximately 1000 CBCT images of patients with impacted maxillary canines. From these images, 207 CBCT’s, with 314 unerupted canines were selected to be evaluated to determine the specific location, angulation and severity. The canine was classified as unerupted or impacted based on our definition of an impacted canine: when root development was complete or the contralateral canine was fully erupted. Of the 314 unerupted canines, 174 were classified as impacted. Our methods were analyzed for reliability and accuracy. Results & Discussion: Excellent inter-examiner and intra-examiner reliability for all variables except axial deviations from the midline, which exhibited good inter-examiner reliability, was observed. Measurements compared using a digital caliper and those acquired from a CBCT image on a typodont showed very high similarity. Females were reported to be affected 1.63 times more frequently than males. This frequency increased to a ratio of 1.93:1 once a canine was defined as impacted. Palatally displaced canines were observed at a rate of 38.54% compared to 40.76% for buccal displacement and 20.70% of the canines were located midalveolar. However, once a canine was defined as impacted, palatal displacement was 2.14 times more likely than a buccal position. From a coronal view, 34.08% of canines were normally positioned, 62.10% were found to be located mesial to the distal border of the lateral incisor and 45.54% were located mesial to the midline of the lateral incisor. Impacted canines had a higher percentage classified in these regions, with 78.16% located mesial to the distal border of the lateral incisor and 60.92% mesial to the midline of the lateral incisor. Canines were mesially tipped in 59.24% of the cases. However, when diagnosed as impacted 78.29% of canines were mesially angulated. Of the canines 33.44% were identified as mild, 37.58% moderate, and 28.98% severe. Additionally, as the age of a patient increased, severity was found to significantly increase. With each yearly increase in age, the chance of having a severe impaction increased by 3.2%. Conclusion: The location of all 314 impacted or unerupted maxillary canines was evaluated by position, angulation and severity as they correlate to the clinical aspect of orthodontics. Specific regions on the maxilla were identified in which impacted canines were more commonly located. Once diagnosed as impacted, females were observed to be affected 1.93 times more frequently than males. Impacted canines were palatally positioned 2.14 times more commonly than buccal displacement. From a frontal perspective, impacted canines were located mesial to the distal border of the lateral incisor in 78.16% of cases and 60.92% were located mesial to the midline of the lateral incisor. As the age of a patient increased, the chance of having a severe impaction increased by 3.2%. The methods outlined were found to be reliable and accurate. In addition, a classification for impacted maxillary canines examined by CBCT imaging was introduced