前牙断根轴向快速牵引后根尖区牙槽骨骨密度变化初探

Bone density changes in the apical area after rapid orthodontic extrusion of subgingivally fractured tooth

目的探讨前牙龈下断根轴向快速牵引后根尖区牙槽骨密度随时间变化的情况。方法对12颗断面位于龈下、距龈缘2～5 mm 的前牙断根行完善根管治疗两周后,利用方丝弓矫治器沿牙长轴方向快速牵引,使断面升至龈上1.5～2.0 mm 并固定保持6个月。运用 CT Analyser 分析软件对保持后每个月拍摄的数字根尖片中断根根尖区相对骨密度进行分析。采用随机区组设计方差分析和 SNK 检验进行分析。结果牵引时间平均11 d,牵引结束时根尖间隙区相对骨密度为-39.6%,随后持续增加。每个月相对骨密度与上一个月相比,第3个月的变化(18.5%)最大,差异有统计学意义(P<0.01);其余各个月间差异均无统计学意义(P>0.05)。结论持续、适度的牙体轴向牵引力能快速稳定地移动断根,牵引后3个月内根尖区相对骨密度基本恢复正常。

Objective To evaluate the bone density changes in the apical area of subgingivally fractured tooth after rapid orthodontic extrusion. Methods Twelve fractured incisors in 11 patients extended 2-5 mm below the gingival line were selected. Two weeks after root canal therapy, the subgingival fragment was lifted up and the fracture line was brought 1.5-2.0 mm above the level of the gingival line by means of edgewise fixed appliance. After the extrusion completed, the tooth had been stabilized and held for 6 months. The CT Analyser software was used to measure the bone density changes in the apical area on radiographs once a month. Changes of relative value in bone density was quantitatively analyzed. Results The average period of extrusion was 11 days. The relative value of bone density in the apical region was -39. 6% immediately after extrusion and continuously increased afterwards. In the third month, the value（ 18.5% ） changed most rapidly （ P 〈 0. 01 ）. Conclusions Under the continuous and proper tooth axial extrusion force, the tooth moved rapidly and steadily. The bone density in the apical area approached normal value within 3 months after treatment.