Analysis of crown-root morphology in canines based on cone-beam computed tomography

To compare the morphology of the crown roots of upper and lower canines in patients with skeletal Class Ⅰ, Ⅱ, and Ⅲ malocclusions by CBCT and to provide guidance for the clinical treatment of orthodontics.

Randomly selected patients with permanent occlusal malocclusion who had undergone CBCT and X - ray skull lateral radiographs were Classified according to the ANB angle size: group Ⅰ, group Ⅱ, and group Ⅲ. Three-dimensional reconstruction was used to obtain the median sagittal section images of the right upper and lower canines. The crown root angle, crown root deflection distance, and lip tangent angle at the center of the clinical crown were used as indicators for measurement and analysis with the use of AutoCAD software.

The difference in the crown-root skew distance between different sagittal face types, including upper canines (F＝3.335, P＝0.042), lower canines (F＝3.745, P＝0.029) crown root angles and upper canines (F＝3.312, P＝0.043), and lower canines (F＝3.641, P＝0.032), was statistically significant (P < 0.05). The crown root angle of the maxillary canine in group Ⅰ was larger than that in group Ⅱ, and the deflection distance of the crown root was negative and the absolute value was lager in group Ⅰ than in group Ⅱ (P < 0.05). The deflection distance was positive and greater in group Ⅲ than in groups Ⅰ and Ⅱ (P < 0.05). There was no significant difference in the maxillary canine crown-labial tangent angle between the different sagittal facial misalignment groups (P > 0.05).

Differences in the morphology of canines were found among subjects with skeletal Class Ⅰ, Ⅱ, and Ⅲ malocclusions. The root of the upper canine in Class Ⅰ malocclusions was relatively closer to the labial side of the crown than that in Class Ⅱ malocclusions. The root of the lower canine in Class Ⅲ malocclusions was the closest to the lingual side of the crown among the three Classes.