Comparing shear bond strength of a composite to PEEK, PEKK and titanium

Abstract

Purpose This in vitro study aims to compare the shear bond strength (SBS) of veneering composite to PEEK, PEKK, and titanium, as well as their failure modes (adhesive, cohesive, mixed).

Materials and Method Specimens of milled titanium, PEEK, and PEKK (n = 105) were abraded using 600-1000 grit silicon carbide paper. The specimens underwent surface treatment using sandblasting with 110μm aluminium oxide particles. The titanium specimens were bonded with a methacryloyloxydecyl dihydrogen phosphate-based (MDP) adhesive (Plafique Universal Bond), whilst the PEEK and PEKK specimens were bonded using a methyl methacrylate-based (MMA) adhesive (PEKKbond, AnaxDent, Ardmore, USA). A composite (Gradia® Plus Heavy body paste, GC, Europe) was bonded to the prepared surface of the specimens. An Instron universal testing machine (Instron, UK) was used to assess the SBS of titanium, PEEK, and PEKK when bonded to composite. The sheared interface of all specimens was evaluated with a stereomicroscope (Nikon SMZ 1500) at 16X magnification

Results A comprehensive narrative analysis of material performance compared titanium, PEEK, and PEKK, focusing on their SBS to composite, including their failure modes. The data revealed substantial differences among the mean SBS of titanium, PEEK, and PEKK when bonded to composite. Titanium shows a high mean SBS of 28.60 MPa, with a 95% confidence interval (CI) (SD = 9.84 MPa). PEKK shows a moderate mean compressive stress of 25.80 MPa, with a 95% confidence interval (SD = 5.44 MPa). This mean value indicates that PEKK has a higher SBS to composite, closer to that of titanium. v PEEK has a lower mean SBS of 16.83 MPa, with a 95% confidence interval (SD = 5.71). This lower mean value indicates that PEEK has a lower SBS to composite compared to titanium and PEKK. A three-sample t-test revealed a difference of 3.77 MPa between titanium and PEEK (p < 0.0001), 2.87 MPa between PEKK and PEEK (p < 0.0001), and 0.90 MPa between titanium and PEKK (p = 0.1449). Titanium predominantly showed mixed failure mode, with 88.6% of failures involving mixed failures and 11.4% of adhesive failures. PEEK was more prone to adhesive failures, with 82.9% of failures occurring at the adhesive bonds. PEKK was also prone to adhesive failures, with 57.1% being adhesive and 42.9% being mixed failures.

Conclusions and Recommendations The current study's results allow for the drawing of the following conclusions within its limitations: When bonded to composite, PEKK exhibited comparable SBS to titanium. In terms of their bond to composite, both PEKK and titanium were superior to PEEK. Therefore, PEKK may serve as a viable substitute for titanium, offering both cost-effectiveness and improved aesthetic results. While titanium and PEKK exhibited comparable SBS, their failure mechanisms varied. Titanium primarily displayed mixed-type failure, with only three specimens experiencing adhesive failure, while PEKK displayed predominantly adhesive-type failure. The PEEK specimens exhibited primarily adhesive failure. None of the specimens demonstrated cohesive failure. However, additional studies considering the oral environment and ageing effects are recommended to assess the long-term success.