Shear bond strength between veneering composite and PEEK after different surface modifications

This study aims to test the influence of different surface treatments and conditioning on the shear bond strength between polyetherketone (PEEK) and composite. Surfaces (570 plates) were used untreated, etched, air-particle abraded or activated with silica-modified alumina oxide. Surface roughness was determined after different treatments. Cylinders of composite were polymerized onto the surfaces. Eighteen different pre-treatment combinations were applied, partly combined with opaque application. Shear bond strength (SBS) was determined following ISO TR 11405. Baseline tests were performed 24 h after composite polymerization. For investigating the influence of storage and aging, the specimens were either stored in distilled water (37 A degrees C, 90 days) or thermally cycled (12,000 cycles 5 A degrees C/55 A degrees C, distilled water). Means and standard deviations were calculated (statistics: one-way ANOVA/Bonferroni (alpha = 0.05)). Surface roughness varied between 0.04 +/- 0.01 and 6.76 +/- 1.11 mu m. Only etching caused a significant (p < 0.001) increase. SBS strongly varied between 0.0 +/- 0.0 and 23.2 +/- 2.1 MPa. After thermal cycling (TC), nine of the investigated systems showed SBS higher than 5 MPa, varying from 8.8 +/- 2.7 MPa (#7) to 19.4 +/- 2.5 MPa (#4). After water storage, nine systems provided SBS higher than 5 MPa, seven even values higher than 10 MPa. Maximum SBS was 27.1 +/- 3.1 MPa (#2) and lowest value was 5.4 +/- 2.6 MPa (#4). Significant (p < 0.001) differences were found between the individual systems after 24 h, TC and after 90 days storage. For good bonding between PEEK and composite, cleaning and roughening is recommended. Surface conditioning prior to bonding seems essential. Combination with opaque revealed an increase in SBS. Successful bonding on PEEK surfaces can be achieved by surface roughening and subsequent surface activation with acetone- or phosphate-based methacrylate primers or tribochemical treatment.