STATEMENT OF PROBLEM: Polyetheretherketone (PEEK) is an excellent restorative material, but its hydrophobicity and inertness prevent strong adhesion to resin cements. PURPOSE: The purpose of this in vitro study was to examine the use of diazonium reactions for priming PEEK surfaces to improve their adhesion to resin cements. MATERIAL AND METHODS: Polished PEEK specimens were exposed to 7 different treatments: airborne-particle abrasion (50 µm) (APA), diazonium priming (D), adhesive (visio-link) application (A), APA followed by A (APAA), D and A (DA), APA and D (APAD), and APA followed by D and A (APADA). Nontreated specimens served as controls (C). The surface composition, roughness (Ra), and contact angle of the specimens were examined before and after treatment using X-ray photoelectron spectroscopy (XPS), profilometry, and goniometry respectively. The tensile bond strength between the treated specimens and resin cement (Panavia SA) was evaluated with a mechanical testing machine after incubation in distilled water (24 hours, at 37 ℃). The fracture surfaces were examined by using a stereomicroscope at ×40 magnification. The Kruskal-Wallis, 1-way analysis of variance, Tukey HSD, and Fisher-Freeman-Halton tests were used for statistical analysis (α=.05). RESULTS: Surface characterization revealed that the APA treatment resulted in the highest surface concentration of oxygen and the highest contact angle (81.3 ±4.9 degree), the D treatment resulted in the highest surface concentration of nitrogen, the DA treatment resulted in the lowest roughness and contact angle (49 ±6.2 degree), and the APAD treatment resulted in the highest roughness. Tensile test results showed the lowest tensile bond strength in the control group (0.1 ±0.1 MPa) and the highest in the APADA group (13.9 ±1.6 MPa) (P<
.001). Differences were not observed among the APAA (10.8 ±0.9 MPa), DA (10.4 ±1.6 MPa), and APAD (9.8 ±1.7 MPa) treatments (P>
.05). The failures of the groups were different (P<
.05), with group C showing 100% adhesive failure and the APADA group showing 70% mixed failure. CONCLUSIONS: The surface treatment of PEEK with a diazonium primer increased the bonding strength of resin cement to PEEK.