Simulating periodontal effects in dental osseointegrated implants: Effect of an intramobile damping element on the fatigue strength of dental implants-An in vitro test method

Objective: The purpose of this study was to develop and adapt a new method for testing dental implant systems and to apply it to existing systems with and without dampers. The parameters examined were the fatigue strength of the superstructure-retaining titanium screw, the deformation of the damper, and the effect on the supporting, bone-stimulating, and embedding material. Method and materials: Ten pairs of implant specimens were prepared according to standard laboratory procedure and embedded in transparent polymethylmethacrylate (PMMA). Five pairs were provided with polyoxymethylene dampers and five with nondamping titanium connectors. Each pair was connected with a metal beam, and cyclic loads were applied with a pneumatic-driven machine at a frequency of 2 Hz. Chewing forces of 150 to 450 N were transmitted by springs individual to each specimen. For each of the 2 × 10⁵ cycles, there was a control of the retaining screw and bonding between the fixture and embedding material by registration of gap propagation in the implant-PMMA interface. Results: A significant damping effect was noticed on the implant -embedding material interface. Damping did affect the superstructure, since the retaining screws were plastically deformed. The screws were unscrewed when the applied load exceeded 300 N, while the undamped system was seemingly unaffected. Conclusion: The study method made it possible to evaluate damping effects on different levels of implant systems, while satisfying the requirements for testing in a "clinical-like" way. PMMA was comparable to bone in supporting implants during fatigue testing.