The effect of sandblasting on adhesion of a dual-cured resin composite to methacrylic fiber posts: microtensile bond strength and SEM evaluation

OBJECTIVES: To evaluate the influence of different surface treatments on the microtensile bond strength of a dual-cured resin composite to fiber posts. METHODS: Thirty-two glass methacrylate-based fiber posts (GC Corp.) were used in the study. Posts were divided into two groups, according to the surface pretreatment performed. Group 1: sandblasting (Rocatec-Pre, 3M ESPE). Group 2: no pretreatment. In each of the two groups posts received three types of additional "chair-side" treatments. (1) Silane application (Monobond S, Ivoclar Vivadent); (2) adhesive application (Unifil Core self-etching bond, GC); (3) no treatment was performed. A dual-cured resin composite (Unifil Core, GC) was applied on the posts to produce cylindrical specimens. Specimens were cut to obtain microtensile sticks that were loaded in tension at a cross-head speed of 0.5mm/min until failure. The morphology of the post/composite interface and the post surface morphology were evaluated under SEM. Statistical analysis was performed with two-way ANOVA and Tukey test for post hoc comparisons (p<0.05). RESULTS: Post surface pretreatment did not prove to be a significant factor in post-composite bond strength (p=0.08), whereas "chair-side" treatment modalities and the interaction between pretreatment and treatment showed a significant influence on bond strength (p<0.001). When no "chair-side" treatment was performed, bond strength was significantly higher on sandblasted posts. Additional adhesive application resulted in significantly lower bond strength on sandblasted posts. When no pretreatment was performed, silane application resulted in higher bond strength than adhesive application. CONCLUSIONS: Sandblasting may give an increase in microtensile strength to methacrylate-based glass fiber posts, eliminating the need for additional "chair-side" treatments. Reducing the number of clinical steps could contribute to simplify the clinical procedures.