Impact of laser modification on the contact angle and surface wettability of hydroxyapatite-coated PEEK implant material

Abstract

Introduction Polyetheretherketone (PEEK) is increasingly used in dental implantology because of its biomimetic properties. However, its application is limited by bio-inertness and inherent hydrophobicity, which may affect early biological interactions. PEEK surfaces are often coated with bioactive materials such as hydroxyapatite (HA), but it remains unclear how subsequent surface modification techniques such as laser treatment affect their wettability. There is still limited data on blood surface interactions in laser-treated HA/PEEK composites. This study was designed to assess and compare the blood contact angle of HA/PEEK surfaces before and after laser modification. Materials and methods Twenty-one HA-coated PEEK discs were evaluated, with each individual disc serving as the experimental unit for contact-angle assessment. Blood contact-angle measurements were obtained from each disc before laser treatment and repeated on the same disc following laser surface modification, resulting in paired observations. Hydroxyapatite (HA) nano powder was applied to the PEEK surfaces using friction stir processing (FSP). Fresh EDTA-anticoagulated whole blood obtained from a single donor was used as the test fluid. To minimize variability, blood was collected from the same donor and venipuncture site, and all measurements were performed by the same operator under standardized conditions. Following baseline contact-angle measurement, the HA/PEEK discs were treated using an Er,Cr:YSGG laser (2,790 nm, 1 W) for 4 s at a working distance of 10 mm under 5% water and 95% air spray, after which contact-angle measurements were repeated. Pre- and post-laser contact-angle measurements were compared using the Wilcoxon signed-rank test, with statistical significance set at p < 0.05. Results Pre-laser HA/PEEK surfaces exhibited lower blood contact angles than the corresponding post-laser surfaces, indicating greater wettability before laser modification. Following laser treatment, blood contact angles increased, indicating reduced wettability under the laser parameters investigated. Conclusion The observed reduction in wettability was specific to the laser parameters evaluated in this study.