Bond strengths of bulk-fill resin composite repairs: effect of different surface treatment protocols in vitro

To evaluate the effect of different surface treatment protocols on the microtensile bond strength (mu TBS) of bulk-fill resin composite repairs. Thirty-five bulk-fill resin composite samples (Filtek Bulk Fill) were prepared (5x5x5 mm) and aged by thermocycling (X5000). Samples were randomly divided into five groups (n=7): a control (no treatment) and four surface treatment groups (Single Bond Universal [SBU]; phosphoric acid (37%)+SBU; Er,Cr:YSGG laser+SBU; aluminum oxide sandblasting+SBU). Filtek Ultimate Universal composite was used as a repair material. After storage for 24 h in distilled water (37 degrees C), sticks were obtained and subjected to a mu TBS test. The data (MPa) were analyzed by one-way ANOVA with a post hoc test (alpha=0.05). Failure mode was evaluated using a light microscope (10x). There were significant differences between the groups (p<0.05). The lowest bond strength values were obtained in the control group (p<0.05). No significant difference was observed between Group II (universal adhesive) and Group III (acid etch+universal adhesive) (p>0.05). The bond strength of Group II was significantly lower than that of the other surface treatment groups (p<0.05). While Group III showed significantly lower values than those of the laser treatment group (Group IV), similar values were obtained with Al2O3 sandblasting group (Group V). The highest repair bond strength was obtained in Group IV (p<0.05) which was not significantly different from the Al2O3 sandblasting group (p>0.05). The predominant failure mode was adhesive. Treatment of aged bulk-fill resin composite surfaces with laser and Al2O3 sandblasting provided higher repair bond strength values.