Enhancing the bonding strength of PEEK through chemical modification with UV/ozone treatment

PURPOSE: Polyetheretherketone (PEEK), a high-performance thermoplastic polymer, has been explored as a dental material because of its excellent mechanical strength and biocompatibility. Composite resin has been reported as a viable prosthetic material when appropriate surface treatment is applied to PEEK. We evaluated the effects of ultraviolet and ozone (UV/ozone) irradiation on the bond strength of PEEK. METHODS: Eighty-six rectangular PEEK specimens were fabricated and divided into two surface-pretreatment groups: untreated (CO) and UV/ozone-treated (UV). The contact angle, surface roughness, and chemical composition were analyzed using contact angle goniometry, laser scanning microscopy, and X-ray photoelectron spectroscopy (XPS), respectively. The remaining specimens were assigned to two conditioning groups: no conditioning (NT) and primer conditioning (AD). Cylindrical specimens fabricated by Computer-Aided Design, Computer-Aided Manufacturing (CAD-CAM) composite resin blocks were bonded to the PEEK surface using resin cement. Half of the specimens in each group were subjected to 5000 thermal cycles. The shear bond strength was tested using a universal testing machine and the fracture surfaces were examined under a stereomicroscope. Statistical analyses were performed using t-tests (α = 0.05). RESULTS: UV/ozone treatment significantly reduced the contact angle, improved the surface wettability, and caused slight changes in the surface roughness. XPS analysis revealed a decrease in the C=O bonds and an increase in the C-OH bonds in the UV/ozone-treated group. The shear bond strength improved significantly, particularly in the AD group. CONCLUSIONS: UV/ozone treatment of PEEK surfaces increased the wettability and significantly improved the shear bond strength of the composite resin blocks.