Atieh Momen A, Alsabeeha Nabeel H M, Payne Alan G T, Schwass Donald R, Duncan Warwick J
Sir John Walsh Research Institute, School of Dentistry, University of Otago, Dunedin, New Zealand.
Quintessence Int. 2012 Oct;43(9):e115-26.
To use finite element analysis to investigate the influence of insertion torque on the stress distribution around an immediately placed oral implant.
Finite element software was used to model a mandibular molar extraction socket. The properties of surrounding cancellous bone and thickness of cortical bone were modified to give four 3D finite element models (I, II, III, and IV). A wide-diameter tapered oral implant was modeled and inserted into the socket. Final insertion torques of 32, 50, and 70 Ncm were applied, and the stress profile in each model was evaluated. The maximum von Mises stresses along the buccal cortical bone adjacent to the implant neck were statistically analyzed to compare the three torque values and four bone models.
At the level of the cortical bone, the greatest von Mises stress levels were generated in model IV and diminished as the bone quality increased. Significant increase in stress values at the crestal bone level was observed in all models after using 70 Ncm compared with 32 Ncm. The maximum von Mises stresses at the cancellous bone were higher in model I and reduced with lower level of bone quality (model IV).
The use of 70 Ncm or more insertion torque during placement of an immediately placed wide-diameter implant substantially increases stresses on the crestal bone. The development of a modified surgical protocol involving moderate insertion torque value (32 to 50 Ncm) may contribute to minimizing the risk of early implant failure in extraction sockets.
运用有限元分析研究即刻植入口腔种植体时植入扭矩对种植体周围应力分布的影响。
使用有限元软件对下颌磨牙拔牙窝进行建模。对周围松质骨的特性和皮质骨厚度进行修改，得到四个三维有限元模型（I、II、III和IV）。构建一个大直径锥形口腔种植体并将其植入牙槽窝。施加32、50和70 Ncm的最终植入扭矩，并评估每个模型中的应力分布。对种植体颈部相邻颊侧皮质骨上的最大von Mises应力进行统计分析，以比较三种扭矩值和四种骨模型。
在皮质骨水平，模型IV产生的von Mises应力水平最高，且随着骨质量增加而降低。与32 Ncm相比，所有模型在使用70 Ncm后牙槽嵴顶骨水平的应力值均显著增加。松质骨中的最大von Mises应力在模型I中较高，并随着骨质量水平降低（模型IV）而减小。
在即刻植入大直径种植体时使用70 Ncm或更高的植入扭矩会显著增加牙槽嵴顶骨上的应力。制定一种涉及中等植入扭矩值（32至50 Ncm）的改良手术方案可能有助于将拔牙窝早期种植体失败的风险降至最低。
