微种植体支抗辅助内收上切牙后牙槽骨改建的锥形束CT研究

Evaluation of the changes of alveolar bone around the upper incisors after retraction with mini implant anchorage using cone-beam CT

目的:探索运用微种植体支抗结合高位牵引钩大量内收上颌切牙后牙槽骨的改建情况。方法:以22例青少年上颌前突拔牙矫治患者,上颌切牙内收前、内收完成后的锥形束CT(cone-beam CT,CBCT)为研究样本,应用Mimics15.0行CBCT影像三维重建,明确上颌切牙移动方式,利用Invivo5.0三维定点测量唇、腭侧牙槽骨厚度和高度变化。采用SPSS19.0软件包对测量数据进行配对t检验。结果:上颌切牙切缘与根尖均发生水平舌侧移动,但切缘的移动距离大于根尖;切缘点发生向下移动,根尖点出现明显的向上移动。上切牙腭侧牙槽骨厚度及唇腭侧总厚度在根颈1/3和根中1/3均显著减小(P<0.05),而根尖1/3显著增加(P<0.05),腭侧牙槽骨高度显著降低(P<0.05)。结论:青少年上颌前突患者微种植体支抗结合高位牵引钩可以实现受控制的倾斜移动。大量内收上颌切牙后,其腭侧牙槽骨吸收远大于唇侧增生,牙槽骨并没有完全跟随牙的移动而改建,提示正畸矫治时不宜过度内收前牙。

PURPOSE： The aim of this clinical study was to evaluate the changes of alveolar bone morphology before and after upper incisors retraction with mini implant anchorage using cone-beam CT（CBCT）. METHODS： Twenty-two young patients with dentoalveolar maxillary protrusion and extraction of 2 maxillary first premolars were evaluated with CBCT.CBCT scans were obtained before treatment and 3 months after retraction of the incisors. The movement patterns of the upper incisors were assessed with Mimics15.0. The labial and palatal alveolar plates at crest level, midroot level, and apical level for bone-thickness changes and labial and palatal vertical bone level during retraction of the maxillary anterior segments were assessed with Invivo5.0. Paired t tests were used to evaluate the changes. RESULTS： The edge of the maxillary incisor and the root apex appeared lingual movement horizontally, but the moving distance was larger than the root apex. The edge of the incisors was moved downward, and the root apex was moved upward obviously. The palatal thickness and total thickness of the alveolar bone showed significant decrease at the crest level and midroot level after retraction while the apical level showed significant increase（P〈0.05）. The palatal vertical bone level also showed great loss（P〈0.05）. CONCLUSIONS： After extensive retraction of the maxillary incisors, tilt movements are controlled with high traction hooks and microscrew implants. The decreases in palatal bone thickness are much more significant compared with the increases in labial bone thickness. Alveolar bone remodeling doesn＇t follow the movement of tooth, suggesting that the limitation of anterior teeth retraction should be taken into consideration.