Effect of PEEK and PTFE coatings in fatigue performance of dental implant retaining screw joint: An in vitro study.

OBJECTIVES: Mechanical complications play a key role in failure of dental implants. Retaining screw loosening was one of the most commonly encountered. This study investigated the effect of PEEK and PTFE coatings on dental implant screw thread joint. METHODS: Retaining screws were coated with PEEK and PTFE in thickness of 30 mum and 60 mum. Friction coefficient and clamping force of screw thread pair were measured, single load-to-fracture (SLF) test and dynamic fatigue life (DFL) test were done to test the stability of implant thread connection. After that, screw fracture mode and erosion morphology of screw surface and implant internal thread were observed. RESULTS: The results showed that both PEEK and PTFE coatings could reduce friction coefficient, and consequently increase clamping force, especially PTFE coatings. PEEK coatings had no significant effect on fracture load, while 30 mum PTFE coating reduced fracture load. PEEK coatings also elongated fatigue life and improved the anti-loosening property under dynamic load, while 30 mum PTFE coating shortened fatigue life. Most of the screw fracture happened at the first thread of the retaining screws. The fracture-end of PEEK coated screws were loosed and could easily remove, but fracture-end of PTFE screws could not. Internal thread observation showed that both PEEK and PTFE coatings could reduce wear of implant internal thread. CONCLUSION: PEEK coatings could effectively improve the stability of implant threaded connection, and reduce wear of implant internal thread. PEEK coating may be a suitable way to prevent screw loosening.