上颌切牙内收前后牙根及牙槽骨的变化

Changes in root and alveolar bone before and after treatment by retracting the upper incisors

目的通过锥形束CT(CBCT)测量并分析上颌前突患者上颌切牙内收治疗前后牙根及牙槽骨的变化。方法选取2014年1月—2015年12月完成的正畸病例37例,其中男性17例,女性20例,平均14.5岁。所有患者拔除上颌双侧第一前磨牙且使用种植钉强支抗内收上颌切牙,通过头影测量获取上颌切牙内收角度、内收量及伸长量,使用New Tom NNT软件对CBCT数据进行多平面重建,调整冠状、轴向与矢状轴,选取通过切缘和根尖的牙齿长轴最长的矢状截面测量上颌切牙内收治疗前后牙根及牙槽骨的变化。结果上颌前牙内收治疗前后,中切牙内收角度为12.92°±6.43°,内收量为(5.54±2.21) mm,伸长量为(0.60±0.95) mm,牙根吸收长度为(0.81±0.46) mm,牙根吸收率为6.80%±3.60%,切牙内收治疗前后牙根长度变化具有统计学差异(P<0.05),治疗后唇侧牙槽骨高度降低量为(0.20±0.22) mm,治疗前后差异有统计学意义(P<0.05)。牙根吸收率与上颌中切牙切端的水平向位移及根尖至唇侧皮质骨的距离具有相关性;唇侧牙槽骨高度变化量与上颌切牙内收角度的相关系数为0.354,具有统计学意义(P<0.05)。结论上颌前突患者代偿性治疗后,上颌切牙产生了明显的牙根吸收,唇侧牙槽骨高度降低。牙齿移动量越大,或超出了牙槽骨的解剖限制和改建限度,容易导致牙根吸收。唇侧牙槽骨高度变化量与切牙内收角度呈负相关。

Objective Using cone beam computed tomography (CBCT)in image measurement on the patients with maxillary protrusion,the study aims to identify the changes in root and alveolar bone before and after treatment by upper incisor retraction. Methods The study was conducted on 37 patients who have received orthodontic treatment from January 2014 to December 2015.The sample comprised 17 males and 20 females,with an average age of 14.5 years.The patients underwent extraction of bimaxillary premolars and given maximum anchorage to retract the upper incisors.The adducent angle,adducent amount, and the amount of elongation of the upper incisor teeth were measured by cephalograms.The patients were scanned by NewTom VGi to obtain CBCT data before and after treatment with upper incisor retraction.Using the NewTom NNT tool,we obtained the multiple planar reconstruction and then adjusted the coronal,axial,and sagittal axis.The sagittal section of the long axis of the maxillary central incisor through the incisal edge and root apex was selected to measure the changes in the root and alveolar bone before and after incisional treatment.Results Before and after retracting the upper incisors,the adducent angle of central incisor measured 12.92°±6.43°.Adducent amount of the incisors reached (5.54±2.21)mm.Incisor extension amount totaled (0.60±0.95)mm.Root absorption length was (0.81±0.46)mm.Root absorption rate was 6.80%±3.60%.Statistical differences were observed in the changes in root length before and after incisor retraction (P<0.05).After upper incisor retraction,increasing distance from the labial side alveolar ridge to the cemento-enamel junction reached (0.20±0.22)mm.After treatment,we observed that the height of the labial-side alveolar bones decreased and showed statistical difference with the height of labialside alveolar bones before treatment (P<0.05).The results show the correlation between root absorption and horizontal displacement of maxillary center incisor and the distance from the upper incisor apex to labial cortical bone.A correlation also exists between the variable quantity of the labial-side alveolar bones and adducent angle of the upper incisor,with a correlation coefficient of 0.354.The results also show significant difference (P<0.05).Conclusion After compensatory treatment of patients with maxillary protrusion,the root length of upper incisor was absorbed remarkably.The height of the labial-side alveolar bones was reduced.A greater tooth movement or beyond the anatomical limitations and alteration limits of the alveolar bone can easily lead to root resorption.A negative correlation exists between the variable quantity of the labialside alveolar bones and adducent angle of the upper incisor.