Purpose: Polyetheretherketone (PEEK), a high-strength, aesthetic, and non-allergic thermoplastic polymer, recently became a candidate for replacing metallic components in dental prosthesis. However, as PEEK is flexible, the need for retention presents a key challenge in terms of its clinical application. In this study, clasps prepared using PEEK were optimized and evaluated to provide the mechanical properties required by dentures. Methods: Seventy-two three-dimensional rod-shape models, based on four thickness/width ratios, three base widths, and six taper ratios were created. These models were analyzed using finite-element methods to determine which modified clasp arm shape provided the most appropriate mechanical properties. Three shape-optimized PEEK specimens and one standard-shape Co–Cr alloy specimen were then fabricated. Constant-displacement fatigue testing was performed to calculate load values and deformations after ten years of clinical use. Results: Shape optimization indicated a maximum stress concentration that was consistently located at the base of the specimen, a correlation between mean load values and thickness that was greater than that with the width, and a correlation between taper ratio and mean load values. Fatigue testing showed that although PEEK exhibited significantly lower average load values than the Co–Cr alloy, these were sufficient for clinical use. All specimens exhibited significant deformation during the first period of cycling; however, there was no significant difference in the deformation between the two materials after fatigue testing. Conclusions: PEEK exerts fewer stresses on abutments compared to standard-alloy clasps, provides adequate retention, and satisfy aesthetic demands, indicating that PEEK presents a promising alternative to conventional metal clasps.
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