Insertion torque of immediate wide-diameter implants: a finite element analysis.

Objective: To use finite element analysis to investigate the influence of insertion torque on the stress distribution around an immediately placed oral implant.

Method And Materials: 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.

Results: 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).

Conclusion: 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.