Morphological relationship analysis of impacted maxillary canines and the adjacent teeth on 3-dimensional reconstructed CT images

Objective: To examine whether there is a relationship between maxillary canine impaction and the morphologic characteristics of the maxillary dentition, especially the root of the lateral incisor. Materials and Methods: In this study, we selected only patients with unilateral maxillary canine impaction to compare the morphologic characteristics of the dentition on the impaction side and the clinically normal eruption side. The sample size was decided to be 40 based on the pilot study. To minimize bias depending on sex and location of the maxillary canine impaction, we selected equal numbers (20) of boys and girls, and equal cases (20) of buccal impaction and palatal impaction. Under the aforementioned conditions, the mean age was 13.5 ± 2.3 years. The multislice spiral computed tomography images of these 40 subjects were converted into three-dimensional (3D) reconstructed images using the OnDemand 3D program (Cybermed Co, Seoul, Korea). Then we measured the morphologic characteristics of the individual teeth on the obtained 3D teeth images. Results: Length and volume of the maxillary lateral incisor's roots were significantly smaller on the impaction side compared with the normal eruption side (P = 0.001 and P = 0.006, respectively). The width and volume of the canine's crown were significantly greater on the impaction side compared with the normal eruption side (P = 0.020 and P < .0001, respectively). Conclusion: These results might help to prove the hypothesis that the smaller-sized lateral incisor roots and greater-sized canine crowns are the influential etiologic factors in maxillary canine impaction.