Bonding performance of PEEK- and PEKK-based CAD-CAM polymers to a light-cured composite resin under different surface treatments and artificial aging conditions

This study evaluated the bonding performance of polyaryletherketone (PAEK) materials, specifically polyetheretherketone (PEEK) and polyetherketoneketone (PEKK), as potential orthodontic bracket base materials when bonded with a light-cured adhesive under different surface treatments and artificial aging conditions. Although these materials exhibit favorable mechanical properties and biocompatibility, their bonding behavior with orthodontic adhesives remains insufficiently understood. Disk-shaped specimens were fabricated from three PAEK materials (titanium dioxide–filled PEEK [VK], nanoceramic- and titanium dioxide–filled PEEK [BP], and titanium dioxide–filled PEKK [PK]) and zirconia (ZR) as a reference. All specimens were ground using silicon carbide paper and randomly assigned to one of three surface treatment protocols: airborne particle abrasion followed by primer (SBP), handheld nonthermal plasma (PL), or plasma followed by primer application (PLP). A light-cured composite resin was bonded under a standardized load to simulate orthodontic bracket base bonding. Specimens were then subjected to three aging conditions: no aging (NA), thermocycling (TC), or hydrothermal aging (HA). Surface wettability, shear bond strength (SBS), and failure modes were evaluated. Data were analyzed using multifactorial analysis of variance with Tukey post hoc tests (α = 0.05). PL significantly increased surface wettability in all materials, resulting in the lowest contact angles, whereas SBP and PLP produced relatively more hydrophobic surfaces ( p < 0.05). SBS was significantly influenced by material type, surface treatment, and aging condition ( p < 0.05). Under NA conditions, SBP and PLP yielded significantly higher SBS values compared with PL for all materials ( p < 0.05). Following TC and HA, SBS decreased in most groups; however, when conditioned with SBP or PLP protocols, PK and ZR retained significantly higher bond strengths compared with BP and VK ( p < 0.05). Adhesive failure was the predominant failure mode across all conditions, while mixed failures were mainly observed in PK and ZR under SBP and PLP treatments under NA conditions. Plasma treatment alone markedly improved surface wettability but did not yield optimal bond strength or durability. In contrast, plasma treatment followed by primer application, particularly for PK and ZR, provided superior and more stable bond strength after artificial aging. This protocol appears to be a more reliable surface conditioning strategy for bonding CAD-CAM PAEK materials with light-cured orthodontic composite resins.