Effect of Preload on Different Implant Abutments in Terms of Screw Loosening

Aim: This study aimed to compare the mechanical behavior of the implant-abutment connection in cases where appropriate preloading is performed or not.Materials and Methods: A total of 54 bone-level implants with a diameter of 3.5 mm were employed in this study. Each group was further divided into subgroups, each of which was tightened manually and with a torque wrench, and a total of six groups were tested, three of them being control groups. Manual tightening was performed by the same researcher with maximum manual force and tightening with a torque wrench was performed with a value of 30 Ncm by the same researcher. Sample measurement values in which connection compliance is evaluated using micro-CT.Results: The total space volume between the screw and the implant body (single torque minimum 0.32 mm³) decreased significantly in the samples tightened for the second time (minimum 0.20 mm³). Still, no difference was observed between tightening manually or with a torque wrench a second time, except for the angled abutment group.Conclusion: Tightening a second time after preload significantly reduced the gap values, especially when using a torque wrench. Therefore, tightening the implants repeatedly using a torque wrench after preloading (retightening) plays a significant role in clinically preventing screw loosening and consequently major clinical problems such as screw fractures.