Effect of Adhesive System on Bond Strength of Polyetheretherketone (PEEK) and Polyetherketoneketone (PEKK)

It is uncertain whether the interchangeable use of two adhesive systems would yield comparable shear bond strength (SBS) for both Polyetheretherketone (PEEK) and Polyetherketoneketone (PEKK); investigating this was the main objective of this study. Milled PEEK (Bredent, Senden, Germany) and PEKK (Pekkton Ivory, AnaxDent, Stuttgart, Germany) blocks were prepared with standardized roughness (0.20 μm) and randomly assigned into two groups (n = 72): with and without aluminum oxide air abrasion (AquaCare Twin, Medivance Instruments, London, UK). Two adhesive systems (Visio.link, Bredent, Senden, Germany, or PEKKBond, AnaxDent, Stuttgart, Germany) were randomly applied (n = 36). Flowable gingival composite (AnaxGum Gingiva, AnaxDent, Stuttgart, Germany) was bonded, and the samples were stored in water (37 °C, 24 h). SBS was measured (MPa) and data were analyzed using three-way ANOVA, followed by Tukey’s test (α = 0.05). All main effects and interactions were significant (p < 0.05), except for polymer (p = 0.163) and the triple interaction (p = 0.601). In the PEEK group, Visiolink showed higher SBS (p < 0.001), regardless of prior air abrasion. For the PEKK group, PEKKBond significantly increased SBS values (p < 0.001) for both pre-treatment groups. Previous air abrasion only significantly increased the SBS of controls without adhesive. This study highlights the importance of material-specific adhesive selection, rather than interchangeable use, for optimal results. The bond strength of PEEK and PEKK is influenced by the adhesive system applied. Moreover, PEKK consistently demonstrated higher SBS values in comparison to PEEK, even without the need for pre-treatment or adhesive conditioning. This characteristic renders PEKK a preferred choice for the fabrication of adhesive restorations.