In-Vitro-Examination of Frameworks and Veneered Three-Unit Fixed-Partial-Dentures Made of Polyetheretherketone

Objectives: The aim was to evaluate the behaviour of three-unit frameworks (F) and three-unit fixed-dental-prostheses (FDP) made of polyetheretherketone (PEEK) during artificial ageing and fracture strength test.

Methods: Stone models were prepared to create identical situations for three-unit dentures. In part1 (n=5) unveneered substructures were made of polyetheretherketone (PEEK-Optima: Invibio, GB) with anatomically reduced framework design and  optimized connector dimensions. For part2 (n=8) three-unit dentures were made of similar PEEK-frameworks veneered with a mikrofilled light-/heatcuring composite material (SR Adoro: Ivoclar-Vivadent, FL). The substructures and veneered dentures were adhesively luted onto the stone models with a dual cured composite cement (Calibra: Dentsply Detrey, G).  TCML (Thermocycling and mechanical loading) was carried out with parameters simulating a period of five years of intraoral application (TC: 6000x5/55°C, 2min each cycle, distilled water; ML: 1.2x10⁶x50N, antagonistic steelball). Behaviour during TCML was recorded optically. Afterwards fracture strength of the constructions was determined in a universal-testing-machine (UTM 1446: Zwick, G) with a crosshead speed of 1mm/min. Failure determination: 10% loss of current fracture force.

Results: None of the frameworks or dentures showed decementation or damage signs during TCML.

Conclusion: Regarding 500N in posterior areas as a threshhold level for the fracture forces needed, the tested PEEK-Optima constructions showed positive results. With optimized connector areas and anatomic substructure design in vivo studies as well as further in vitro studies to optimize the veneering process  should be encouraged.