Evaluation of multimode adhesion promoters with functional monomers without and with silica-coating for resin composite repair

Abstract

This study aimed to investigate the effect of universal primers on resin composite repair with and without silica-coating while assessing adhesion durability under various aging methods. Specimens were fabricated using multiple increments of composite resin (Clearfil Majesty Esthetic) placed into cylindrical forms (diameter: 3.2 mm, height: 4 mm) and photopolymerized. Specimens (N = 300, n = 15 per group) were randomly assigned to three groups for aging (control: fresh-dry, 6 months water storage and thermocycling ×5000 cycles, 5–55 °C). These three main groups were further randomly assigned to two groups according to the surface conditioning procedures; (a) Control: No air-abrasion, and (b) Air abrasion with silica-coating (Co-Jet, 30 µm, 5 s, 2.5 bar). All subgroups were then randomly divided into five subgroups to be treated with adhesion promoters (a) All Bond Universal: AB (Bisco), (b) Clearfil Universal Bond Quick: SKB (Kuraray), (c) Monobond Plus: MP (Ivoclar Vivadent), (d) G-Premio Bond: GP (GC), (e) Clearfil Universal Bond: CU (Kuraray). After bonding according to the manufacturer’s instructions to new composite blocks, shear bond strength tests were conducted using a Universal testing machine (1 mm/min). Obtained Data (MPa) were analyzed by 3-way ANOVA and Tukey`s post-hoc tests (alpha = 0.05). Bond strength results were significantly affected by the adhesive type (p < 0.05), silica-coating (p < 0.05), and aging (p < 0.001) but the interaction terms were not significant (p > 0.05). In non-aged groups (24 h), no significant effect on bond strength was observed using silica-coating (min; 8.41; max:12.98) but after 6 months, silica-coating increased the results for AB, GP, and CU ranging between 9.56 and 11.25 (p < 0.05) and even more after thermocycling for SKB, MP, GP, CU (10.23–13.95) (p < 0.05) compared to non-conditioned groups (6.83–10.37 for 6 months, 8.96–11.18 for thermocycling, respectively). Failure types were mainly adhesive for non-air abraded groups but exclusively cohesive after silica-coating. For immediate or short-term resin composite repairs, silica-coating may not improve adhesion but shear bond strength could be secured by this conditioning method after aging.