Stresses Induced in Dental Implant Retaining Screw before Tightening
Author(s): Mohamed Tharwat Hamed*, Hisham Abdullah Mously, Abou Bakr Hosam Hashem and Ghada Hussein Naguib
Abstract
Introduction: The tightening of the retaining screw helps in the insertion of implant at the mandible of first molar. Moreover, the calculation of the external loads acting on the screw head during its tightening and release need to be devised.
Aims: The study aims to predict the fatigue life of a retaining abutment screw used in dental implant.
Material and Methods: A typical straumann implant, inserted in place of missing first mandible molar was selected. 3D finite element stress analysis tool was used to evaluate the normal occlusion between the restoration crown and the opposing maxillary tooth. The mastication force acting mutually on the two teeth was simulated during the time of the occluding phase of the chewing process.
Results and Discussion: The fatigue damage parameter experienced at contact time was 206.5 ms by the most stressed site within the retaining screw that was plotted against the magnitude of the chewing force. The fatigue damage the parameter is below the Ti-6AI 4V threshold value for chewing force greater than 809 N. Findings of the study were provided considering the two assemblies consisting of Ti-6Al-4V titanium alloy, followed by type III gold of screws with the friction coefficient of each from the overall 14 values.
Conclusion: Considering the findings of the study, it is concluded that the release of the tightening moment of the wrench resulted in generating the equivalent stress. Results further concluded that the increase in coefficient friction on all the assembly parts resulted in the expansion of the stress followed by the increase in the wrenching tightening moment.