Influence of surface treatments on the bond strength of repaired resin composite restorative materials

Objectives: The purpose of this study was to investigate the effect of different surface treatments on the bond strength (σ) of repaired, aged resin composites (ARC). Methods: Forty blocks of Filtek Z250™ (Z2) and Filtek Supreme™ (SU) were made, stored in deionized water for 9 days, and randomly assigned to different surface treatment groups: hydrofluoric acid etching (HA), abrasion using a coarse diamond bur (AB), sandblasting with alumina particles (AO), and silica coating (SC). The average roughness (Ra) of the treated surfaces was measured with a profilometer. An adhesive system (SB-Adper Single Bond Plus™), a silane (SI) or a combination of both (SI + SB) were applied after each surface treatment. The blocks were restored with the same composite (RC) and cut to produce bars that were turned into dumbbell-shaped specimens (0.5 mm²) using a precision grinding machine. The specimens (n = 30) were tested in tension to fracture and the microtensile bond strength (σ) values were calculated (MPa). Data were analyzed using three-way ANOVA/Tukey test (α = 0.05) and Weibull statistics. Results: AO and SC produced similar Ra values, which were greater than the value produced by HA. The σ values were statistically influenced by the type of RC (p < 0.0001), by the surface treatment (p < 0.0001) and by the surface coating (p < 0.0001). Treating the surface of Z2 with SC + SB produced the greatest m value. Significance: AO and SC produced the greatest σ values, irrespective of the primer (SI, SB or SI + SB) used. Yet, the RC microstructure influenced the mean σ values, which were greater for Z2 than for SU. The HA should not be used for repairing ARC.