| Objective: To evaluate the thickness of alveolar bone and crown-root angle of maxillary canines in skeletal type Ⅱ patients with different vertical skeletal types by cone-beam CT(CBCT),which provided reference for the control of canine torque in clinical treatment.Methods: 60 patients with skeletal type Ⅱ malocclusion were selected and divided into high-angle group,average-angle group and low-angle group according to the vertical skeletal type.All patients underwent CBCT scan before treatment to measure the crown-root angle and alveolar bone thickness of canines.The alveolar bone thickness were measured at the root neck,middle root and apex of canines.Statistical analysis was made to compare the differences between the three groups.Result:1 The total alveolar bone thickness and labiolingual thickness of maxillary canine region were the smallest in the high-angle group,while those in low-angle group were the largest(P<0.05).2 The thickness of labial alveolar bone of canine region in high-angle,average-angle and low-angle groups were less than those of lingual side,but the proportion in high-angle group was the smallest(P<0.05).3 The crown-root angles in high-angle group and average-angle group were negative,and the roots were inclined to the labial side,which were more obvious in high-angle group(P<0.05).The crown-root angles of maxillary canines in low-angle group were positive,and the roots were inclined to the lingual side.Conclusion:1 The thickness of the labial alveolar bone in the canine area of the skeletal class Ⅱ patients were smaller than those of the lingual side,but the proportion in high-angle group was the smallest.2 The roots of maxillary canines in skeletal type Ⅱ patients inclined gradually from lingual to labial at low-angle group,average-angle group and high-angle group.The effect of bracket torque expression on the root position of canines in different vertical skeletal types should be paid attention to in clinical treatment. |
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