摘要目的 利用三维有限元方法探讨J钩高位牵引辅助压低并内收上颌前牙的生物力学机制,以期为临床治疗提供参考.方法 在ANSYS 14.0软件中建立包括上颌牙列、牙周膜、直丝弓矫治器及上颌骨的三维有限元模型.模拟J钩施加1.5 N力量压低内收上前牙,A组加载于侧切牙近中,B组加载于侧切牙远中.牵引方向与矢状面保持30°不变、与(牙合)平面的角度在20°～ 60°之间,每间隔5°设置1种工况,两组共18种工况.分析上前牙位移及牙周膜应力情况.结果 随着牵引角度增大,上前牙位移趋势逐渐由舌向移动为主伴压低的顺时针旋转移动,变为整体压低、内收移动,最后变为压低伴唇向倾斜的逆时针旋转移动.在侧切牙近中以35°加载或在侧切牙远中以45°加载时,上前牙出现相对均匀一致的整体压低、内收移动,整体无旋转的趋势.结论 对于唇倾度正常的上颌前牙,J钩高位牵引加载于侧切牙近中更有利于前牙的整体压低和内收,临床上应根据个体情况和治疗目标调整牵引角度.

abstractsObjective To investigate the biomechanics of J-hook headgear in En mass intrusion and retraction of maxillary anterior teeth and provide guidance for clinical treatment.Methods A three-dimensional finite element model of maxillary teeth,periodontium,straight wire appliance and maxillary bone was established in ANSYS 14.0.En mass retraction of anterior teeth with force of 1.5 N through J-hook headgear was stimulated.Force was applied mesial to lateral incisor in group A and distal to lateral incisor in group B.The force direction was 30° to the sagittal plane and 20° to 60° to the occlusal plane.Force direction to the occlusal plane was changed every 5°and 18 cases were calculated.Displacement of upper anterior teeth and stress distribution in the periodontium were analyzed.Results As the degrees of force direction to the occlusal plane increased,the moving pattern of upper anterior teeth changed from clockwise rotation(lingual movement with intrusion) to bodily retraction and intrusion,and counter-clockwise rotation (intrusion with labial movement).With the force direction of 35° to occlusal plane applied mesial to lateral incisor or force direction of 45° to the occlusal plane applied distal to lateral incisor,bodily movement of upper anterior teeth without rotation was achieved.Conclusions Placement of J-hook mesial to lateral incisor enable orthodontists to maintain better en mass intrusion and retraction of upper anterior teeth.The direction of J-hook should be adjusted according to individual condition and treatment objective.