Does rinsing following particle deposition methods have a negative effect on adhesion to titanium?

This study evaluated whether air blasting or rinsing particle remnants with water would impair adhesion of resin composite to metal. Commercially pure titanium plates (1 mm x 25 mm x 50 mm) were wet polished down to 1200-grit silicone carbide abrasive and ultrasonically cleaned. They were then embedded in auto-polymerizing acrylic with the bonding surfaces exposed. Specimens were randomly assigned to one of the following particle deposition protocols (N = 60, n = 10 per group): group 1: particle deposition with aluminum trioxide (50 µm Al2O3) (AL) + air blasting + silane (ESPE-Sil); group 2: particle deposition with 30 µm SiO2 (CoJet) (CSC) + air blasting + silane; group 3: particle deposition with Rocatec Pre 110 µm Al2O3+Rocatec Plus 110 µm SiO2 (LSC) + air blasting + silane. In groups 4 (AL-W), 5 (CSC-W) and 6 (LSC-W), the same protocols were used, but instead of air blasting only, particle-deposited specimen surfaces were rinsed with water and air blasted. Adhesive resin (VisioBond) was applied and resin composite (Quadrant Posterior, Cavex) was bonded using polyethylene molds and photopolymerized. The specimens were then submitted to thermocycling (6000 cycles, 5°C-55°C, dwell time: 30 s, transfer time: 5 s). Pre-test failures during thermocycling were assigned a value of 0 MPa. Failure modes were identified using an optical microscope. SEM images of particles were obtained. Bond strength data (MPa) were statistically analyzed using two-way ANOVA and Tukey's post-hoc tests (a = 0.05). Particle type significantly affected the bond results (p < 0.001). AL groups presented significantly lower results (air blasting: 4.3 ± 3.3, rinsing: 11.8 ± 6.5) compared to those of CSC (air blasting: 27.7 ± 6.6, rinsing: 30.4 ± 9.3) and LSC (air blasting: 31.4 ± 8.7, rinsing: 28.7 ± 7.0). AL groups presented 5 spontaneous debondings during thermocycling in the air-blasted group. Rinsing with water as opposed to air blasting only did not decrease the results with any of the particle types (p > 0.05). While AL groups showed exclusively adhesive failure between the resin composite and the substrate, the incidence of cohesive failures in the composite was more frequent in groups CSC and LSC after either air blasting or rinsing. SEM images of particles showed sharp morphology of the particles in AL compared to CSC and LSC. Rinsing and air blasting following particle deposition methods did not impair adhesion of resin composite to titanium. Particle deposition with silica particles provided better adhesion of resin composite to this substrate compared to the use of alumina particles.