三维有限元分析不同工况下牵引上颌埋伏尖牙牙周应力分布

Periodontal stress distribution of maxillary impacted canine under different working conditions:analysis based on three-dimensional finite element method

背景:在正畸治疗埋伏尖牙过程中,粘接正畸附件的部位、角度、力值对牵引效果及牙周有较大影响,但目前对合适牵引部位、角度和牵引力值大小的相关研究较少。目的:通过三维有限元分析正畸矫治过程中不同牵引力作用下上颌埋伏尖牙的牙周应力分布。方法:选用1例上颌埋伏尖牙患者的锥形束CT扫描数据,建立包括埋伏尖牙、上颌骨骼及其周围支持结构在内的三维有限元模型,在埋伏尖牙唇侧切1/3、中1/3及颈1/3部位,分别施加与牙齿长轴呈60°,90°,120°角的牵引力(30,60,90 g),分析埋伏尖牙牙周膜Von Mises应力分布。结果与结论:①不同工况下埋伏尖牙的牙周应力分布基本相似:在尖牙切1/3施力时,模型中靠近颈部牙周膜Von Mises应力较小,舌面近颈部牙周膜Von Mises应力较大;在尖牙中1/3施力时,模型中靠近颈部牙周膜Von Mises应力较小,唇面近颈部牙周膜Von Mises应力较大;当在尖牙颈1/3施力时,模型中靠近牙颈部牙周膜Von Mises应力较小,唇面中部牙周膜Von Mises应力较大。②当施力部位、角度相同时,随着施加力的增加,牙周膜最大Von Mises应力呈增加趋势;当施加力大小、角度相同时,尖牙切1/3、中1/3及颈1/3部位牙周膜最大Von Mises应力呈递减趋势。在尖牙切1/3部位施加相同大小的力时,随着施力角度的增加,牙周膜最大和最小Von Mises应力均呈减少趋势;在尖牙颈1/3施加相同大小的力时,随着施力角度的增加,牙周膜最大Von Mises应力呈递增趋势。③结果显示,牵引上颌埋伏尖牙尽量在靠近牙颈部的部位粘接托槽,牵引上颌埋伏尖牙时牵引方向与牵引部位有关,牵引力一般为30-60 g之间。

BACKGROUND:During orthodontic treatment of impacted canines,the site,angle,and force value of bonded orthodontic attachments have a large impact on the traction effect as well as periodontics,but there are fewer studies related to the appropriate traction site,angle,and magnitude of traction force values.OBJECTIVE:To analysis the periodontal stress distribution of maxillary impacted canines under different traction forces during orthodontic treatment by the three-dimensional finite element method.METHODS:Cone-beam CT scan data of a patient diagnosed with a maxillary impacted canine was selected,from which a three-dimensional finite element model including the impacted canine,maxilla,and its supporting structures was created.In the three-mentioned model,traction forces(30,60,and 90 g)at angles of 60°,90°,and 120°to the long axis of the tooth were applied to the incisal 1/3,middle 1/3,and cervical 1/3 of the labial surface of the crown.Von Mises stress distribution in the periodontium of the impacted canine was analyzed.RESULTS AND CONCLUSION:(1)There was similar periodontal stress distribution of the maxillary impacted canine under different working conditions.When the force was applied in the incisal 1/3 of the canine,the Von Mises stress of the periodontium near the cervical part of the model was smaller,and the Von Mises stress of the periodontium near the cervical part of the lingual surface was larger;when the force was applied in the middle 1/3 of the canine,the Von Mises stress of the periodontium near the cervical part of the model was smaller,and the Von Mises stress of the periodontium near the cervical part of the labial surface was larger;and when the force was applied in the cervical 1/3 of the canine,the Von Mises stress of the periodontium near the cervical part of the model was smaller,and the Von Mises stress of the periodontium near the middle part of the labial surface was larger.(2)When the force was applied at the same site and angle,the maximum Von Mises stress of the periodontium tended to increase with the increase of the applied force;when the same amount of force was applied at the same angle,the maximum Von Mises stress of the periodontium at the incisal 1/3,mesial 1/3,and cervical 1/3 sites showed a decreasing trend.When the same amount of force was applied to the incisal 1/3,the maximum and minimum Von Mises stresses of the periodontium tended to decrease with the increase in the angle of the force.When the same amount of force was applied to the cervical 1/3,the maximum Von Mises stresses of the periodontium tended to increase with the increase in the angle of the force.To conclude,traction of the maxillary impacted canine should try to bond the brackets as close as possible to the cervical region.The direction of traction is associated with the site of traction.The traction force of the maxillary impacted canine is generally between 30-60 g.