Comparative Analysis of Screw Loosening in Titanium and Zirconia Implant-Supported Abutments-An In vitro Study

Background: Compare of the screw loosening in two different implant-supported abutments (titanium and zirconia) and the influ ence of repeated application of torque on the fixation screw. Methods: The torque of the titanium screw loosening was analyzed with two different implant-supported abutments: Titanium (n = 10) and Zirconia (n = 10). These screws/abutments were fixed for the test using external hex implants. A low-load robot (KUKA KR16 2) with a high precision torque sensor (Industrial Automation Technologies) and a square key were used to measure force of the reverse torque. Each screw/abutment was repeatedly tightened (TR1-TR10) on the implants with a torque of 30 Ncm. The reverse torque values were recorded in a database using Kuka System Software V5.X. The Mann - Whitney and the Wilcoxon test were also performed. Results: A statistically significant difference was not found only in the sample 3 (p = 0.05) in the comparative analysis between both materials (Ti and Zr). The mean reverse torque applied to loss the preload was 26.3 Ncm for Ti and 22.6 Ncm for Zr. The difference between the initial reverse torque (TR1) and final (TR10) was determined TR1 had an average of 24.8 Ncm (Ti) and 20.8 Ncm (Zr); TR 10 had an average of 27.4 Ncm (Ti) and 23.9 Ncm (Zr). Conclusion: The titanium abutment showed higher resistance to the loosening of the titanium screw compared to the zirconia abutment. The first preload applied tended to loosen more easily than the last torque applied in the same screw.