Associating Torque to Abutment Screw Loosening Using Computer Aided Designing and Finite Element Analysis
Author(s): Shaiq Gajdhar*
Background: The dental implant abutment connection plays a very crucial role in the quality of the stress distribution, and, over the years, different designs were proposed. Most common complication after the dental implant treatment is abutment screw loosening that adversely affects the outcomes of implant rehabilitation. Therefore, this study was aimed to correlate the abutment screw loosening at four different torques and to study the stress and deflection pattern of the abutment screw using three - dimensional finite element analysis. Methods: Three dimensional computer aided designed (CAD) models were generated, which were having a detailed geometry of the implant, abutment, abutment screw, surrounding hard and the soft tissues of the mandibular jaw. The abutment screw was than torqued at 10 Ncm. One point load of 170 N was then applied 30o oblique to the long axis of implant. The abutment screw loosening was determined for each of the models at the specified load (170N and 185N) by calculating the amount of preload remaining in the abutment screw and remaining torque (T) after the load application. Results: After the load application the screw loosening was observed in all the models. A minimal screw loosening of 0.67o was observed for the models which were torqued at 10 Ncm and subjected to 175 N of Load. A maximum screw loosening in this study was 0.75o which was observed with the models that were torqued at 6 Ncm and subjected to 185 N of load; the abutment without screw tightening torque (0 Ncm) also showed a screw loosening of 0.71o. With the similar load application of 185 N as the torque of 10 Ncm applied, the abutment screw showed a screw loosening by 0.73o. Conclusions: CAD Designed models and finite element method to apply load can be an effective way to determine the abutment screw loosening. Within the limitations of the study it can be concluded that the abutment screw loosening increases with the increase in the load applied. Also there are more chances of abutment screw to be loosened with the decrease in the torque values.