Effect of surface treatments on the bond strength between additively manufactured or injection-molded high-performance polymers and titanium.

Abstract

Purpose: To investigate the effect of surface treatment and fabrication techniques of high-performance polymers on their shear bond strength (SBS) to grade IV titanium.

Materials and methods: A total of 120 pre-milled titanium abutments were sectioned. Cylindrical polyetherketoneketone (PEKK) specimens (3 × 2 mm) were fused-filament fabricated (FFF) 3D-printed, and similar-sized polyetheretherketone (PEEK) specimens were either FFF 3D-printed or cut from injection-molded (INJ) rods (n = 40). The specimens were divided into 4 groups according to surface treatments (n = 10): non-thermal air plasma (Ntp), 98% sulfuric acid (SA), sandblasted by 110 µm silicate-coated alumina particles (Roc), and sandblasted by 30 µm silicate-coated alumina particles (Coj). Surface-treated polymer specimens were cemented onto bonding agent-applied titanium specimens. After 24 h of water storage at 37°C, SBS tests were performed; data were analyzed using Kruskal-Wallis and Dunn's multiple comparison tests (α = 0.05). The failure mode was classified using an optical microscope.

Results: The high-performance polymer surface was affected by both the fabrication method and the surface treatment. While the SA (18.86 ±1.46 MPa) and Coj (15.83 ±1.26 MPa) surface treatments demonstrated the highest SBS values for the INJ-PEEK polymer, the Roc (14.86-15.76 MPa) and Coj (11.78-15.92 MPa) treatments for FFF 3D-printed polymers (p < 0.05). The failure type was mostly adhesive, but the INJ-PEEK failures were mixed; no cohesive failures were observed. A very weak but significant correlation between SBS and failure type was detected.

Conclusion: The optimal surface treatment technique for a high SBS between high-performance polymers and grade IV titanium depends on the polymer fabrication technique. High bond strength was achieved when SA was used on INJ-PEEK and when silicate-coated alumina particle air abrading was applied on printed PEEK and PEKK.