Purpose: This study aimed to assess the fracture resistance of zirconia (Zr), reinforced polyetheretherketone (PEEK), and polyetherketoneketone (PEKK) implant abutments restored with glass-ceramic crowns after thermomechanical aging.

Materials and methods: Zr, reinforced PEEK, and PEKK titanium base abutments were divided into three groups (n = 10). CAD/CAM maxillary central incisor crowns were fabricated using monolithic lithium disilicate and luted to the abutments using resin cement. The specimens were thermomechanically aged (1.2 × 10⁶ cycles, 49 N, 5°C to 55°C). After testing fracture strength and determining fracture patterns, statistical analyses were made using the one-way analysis of variance (ANOVA) and Tukey post hoc tests (α = .05).

Results: Fracture resistance of the PEKK abutments (541.90 ± 68.49 N) was significantly lower than the Zr (780.65 ± 105.77 N) and reinforced PEEK (741.09 ± 99.84 N) abutments (P = .000). A significant discrepancy was not detected between the reinforced PEEK and Zr abutments. Failures usually formed due to crown or abutment fracture, plastic deformation of the titanium base or screw fracture in the Zr group, crown fracture or separation of the abutment-crown complex from the titanium base in the reinforced PEEK group, and abutment fracture without crown deformation in the PEKK group.

Conclusion: After thermomechanical aging, the reinforced PEEK abutments exhibited similar fracture resistance to the Zr abutments. All abutment types withstood the physiologic occlusal forces typical for the oral anterior region. Before considering them as alternative esthetic implant abutment materials, further in vitro and clinical studies are needed to determine their long-term performance.