Standardized Protocol to Evaluate the Effect of Surface Treatments, Luting Cements, And Thermocycling On PEEK–Composite Bond Strength

Polyetheretherketone (PEEK) has gained increasing attention as a biomaterial in prosthodontics; however, achieving durable adhesion to veneering composite materials remains a major challenge due to its chemically inert structure. This study presents and validates a standardized, reproducible protocol for evaluating shear bond strength (SBS) between PEEK and an indirect composite resin under different surface treatments, luting cements, and thermocycling conditions. A total of 240 PEEK discs were divided into four groups according to surface treatment: no surface treatment, sandblasting, sulfuric acid etching, and laser irradiation. Surface morphology was analyzed using atomic force microscopy. Each group was then subdivided according to the luting cement used (zinc oxide non-eugenol cement or self-adhesive resin cement; n = 30), and further subdivided into thermocycled and non-thermocycled groups (n = 15). SBS was measured using a universal testing machine, and failure modes were analyzed under a stereomicroscope. Among all experimental groups, specimens luted with self-adhesive resin cement and not subjected to thermocycling demonstrated the highest SBS values (25.134 ± 1.665 MPa), whereas specimens luted with zinc oxide non-eugenol cement and subjected to thermocycling exhibited the lowest SBS values (1.958 ± 0.345 MPa). For all surface treatment protocols, SBS values were significantly higher in specimens luted with self-adhesive resin cement compared with zinc oxide non-eugenol cement (p < 0.001). Thermocycling significantly reduced SBS values across all groups (p < 0.001). This protocol highlights critical procedural steps, including surface treatment selection and cement type, that significantly influence bonding outcomes. The standardized workflow and visual demonstration of key steps provide a reproducible framework for evaluating PEEK-composite bonding.