The effects of surface treatments on tensile bond strength of polyether-ketone-ketone (PEKK) to veneering resin.

Objectives: To test the different PEKK surface treatment methods on the tensile bond strength (TBS) of a resin composite to PEKK.

Methods: Two hundred and fifty polished PEKK specimens were fabricated, divided into 5 groups (n = 50) and underwent the following treatments: no pre-treatment (control group C), 110 µm AlO gritblasting at 2 bar for 10 s (Group Al), 98 wt% sulfuric acid etching for 60 s (Group SA), tribochemical silica-coating through air-abrasion with Rocatec Plus 110 µm at 2 bar for 10 s (Group Trib), and sulfuric acid etching and subsequent tribochemical silica-coating (Group SATrib). Ten specimens in each group were taken out for surface characterization. On the samples of Groups Trib and SATrib, a silane coupling agent was applied. Then, for all groups, veneering resin stubs (diameter: 3 mm) were bonded on the treated surfaces. Half of the specimens (n = 20) in each group were submitted to thermo-cycling for 7000 cycles between 5 °C and 55 °C. The TBS of all groups was examined using a universal testing machine. Fracture analysis was performed. For statistical analyses, one-way ANOVA (post-hoc: Bonferroni) and t-test were used at α = 0.05.

Results: Although the surface treatment methods used in this study were able to increase PEKK surface roughness, none of them showed impact on TBS between PEKK and the resin composite before thermal cycling (p > 0.05). However, after thermo-cycling, significantly higher TBS was measured for Groups Trib and SATrib (p < 0.05). Furthermore, the TBS for the SATrib group was not significantly affected by thermal cycling. Groups SA, Trib and SATrib illustrated an increase of Weibull moduli after thermocycling, but decrease was observed in Groups C and Al.

Conclusion: Despite low tensile bond strengths were found in all groups in this study, Tribochemical silica-coating through air-abrasion with Rocatec Plus on polished or sulfuric-etched PEKK surface can significantly increase the tensile bonding stability as well as durability of resin composite to PEKK.