Effect of different surface treatments on the shear bond strength of PAEKs to composite resin

The present study aimed to evaluate the effects of surface treatment techniques on the shear bond strength (SBS) of Polyetheretherketone (PEEK) and Polyetherketoneketone (PEKK) polymers to composite resin. Eighty-eight rectangular (7 × 7×2 mm) specimens were prepared for each polymer and randomly divided into eight groups (n = 11): untreated (Cnt); treated with non-thermal plasma (Pls); etched with 98% sulfuric acid (Sa); tribochemical silica-coated with Cojet (Tb30); tribochemical silica-coated with Rocatec Plus (Tb110); 98% sulfuric acid + plasma (Sa_Pls); Cojet + plasma (Tb30_Pls); Rocatec Plus + plasma (Tb110_Pls). One specimen from each group was randomly selected for scanning electron microscope analysis. After the bonding agent and an opaquer were applied, composite resin cylinders were built on the specimens. SBS test was performed after water storage, and data were statistically analyzed by 2-way analysis of variance and Tukey’s multiple comparison tests (α = 0.05). The failure-modes were examined. 2-way ANOVA showed that the surface treatment and its interaction between polymer type were significant on SBS values (p < 0.001). Among the PEEK groups, Group Sa (22.55 ± 2.01 MPa) showed the highest SBS value, but no significant difference was observed between Group Tb30, Group Sa_Pls, and Group Tb30_Pls (p > 0.05). Within the PEKK groups, Group Tb30_Pls (22.33 ± 1.19 MPa) showed the highest SBS value, but no significant difference was observed between Group Tb30 and Group Tb110_Pls (p > 0.05). Surface treatments with non-thermal plasma, 98% sulfuric acid and tribochemical silica-coating on PEEK and PEKK increase the bond strength with composite resin. Between the PEEK and PEKK polymers, tested surface treatment effects were significantly different except for the tribochemical silica-coating.