Investigation of the use of polyetereterketone material in telescopic retainers

The aim of this study is to evaluation the long-term retention values and surface wear of the Polyetheretherketone (PEEK) material in telescopic retainers in vitro. A conus angle of 2° was used, and the formation of an occlusal gap between the primary and secondary crowns with different primary crown and secondary crown materials was evaluated. Five groups were investigated; 1-Zirconia primary crownGold secondary crown (manufactured by electroforming), no occlusal gap (ZA); 2- Zirconia primary crown-PEEK secondary crown, no occlusal gap (ZP); 3-Zirconia primary crown-PEEK secondary crown, 100 µm occlusal gap (ZP100); 4-PEEK primary crown-PEEK secondary crown, no occlusal gap (PP); 5-PEEK primary crown-PEEK secondary crown, 100 µm occlusal gap (PP100). A total of 50 samples were prepared from the groups (n=10). A preload of 50 N was applied when the retention force measurements were measured initially and after 100, 500, 1000, 5000, 10,000 cycles of insertion-seperation cycles. All insertion-seperation cycles and retention force measurements were carried out in artificial saliva. A pair of primary and secondary crowns selected from each group and double crowns that were not subjected to insertion-seperation cycles were examined by Scanning Electron Microscopy (SEM) to evaluate the wear on their surface. The highest retention values were estimated in the PP100 group (36.04-35.73 N) at the beginning and after 10,000 cycles, and the lowest values were estimated in the ZA (9.05-15.06 N) group. Formation of an occlusal gap between the primary and secondary crowns increased the retention force values after 10,000 cycles for the PEEK primary crown and PEEK secondary crown material couple. After the experiments, wear was observed on PEEK primary crowns, PEEK secondary crowns and gold secondary crowns, while no wear was observed on zirconia primary crowns. The retention values in the study were higher than the clinically acceptable range of 5- 10 N values, and only the values initially obtained in the ZA and ZP100 groups were in this range. In the PP100 group, adequate and predictable retention force values were obtained throughout the period representing 10 years of clinical use. Keywords: Double crown, conus crown, polyetheretherketone (PEEK), occlusal gap, retention force, wear.