Purpose: The use of computer-aided design and computer-aided manufacturing (CAD-CAM) systems has increased the need for reliable metal-free restorative materials. Poly (etheretherketone) (PEEK) shows excellent physical and mechanical properties, but its bonding protocols remain insufficiently established. Various surface treatments have been proposed to improve adhesion. This study investigated the effect of low-pressure plasma treatment on PEEK surfaces and evaluated the bond strength of a methyl methacrylate (MMA)-based adhesive applied to plasma-treated PEEK.

Methods: PEEK blocks were sectioned, sandblasted with 50 µm alumina particles, and divided into non-plasma-treated (PI[−]) and plasma-treated (PI[+]) groups. Each group was further classified by whether the adhesive was light-cured for 10 s or chemically cured. Specimens were bonded to steel rods with a dual-cure resin cement and stored in water at 37°C for 24 h. Groups were tested after either 0 or 5,000 thermal cycling (TC; 5-55°C). Tensile bond strength (TBS) was measured (n = 10), failure modes were analyzed by scanning electron microscopy, and surface wettability was evaluated by contact angle.

Results: A significant interaction between plasma and curing mode was observed (P < 0.05), whereas neither the interactions between plasma and TC nor between curing mode and TC were statistically significant (P > 0.05). Plasma treatment significantly reduced the contact angle (P < 0.05), indicating improved wettability.

Conclusion: Low-pressure plasma treatment enhanced the hydrophilicity of PEEK but did not improve bond strength. Light curing of the MMA-based adhesive significantly increased bond strength, suggesting improved bonding under light curing conditions.