Purpose: To evaluate the effect of cavity configuration on microtensile bond strengths of two resin composites for core build-up to pulpal floor dentin.
Methods: Access cavity preparation and root canal filling with gutta percha were performed on extracted human molars. Following this, the gutta percha in the pulp chamber was completely removed to expose pulpal floor dentin. The cavity walls remained as a control group (Cavity). For another group, the cavity walls were removed to create a flat surface for bonding (Flat). For the Cavity group, Clearfil SE Bond was applied to the cavity according to the manufacturer's instructions, and either a light-cured resin composite (PH, Clearfil Photo Core) or a dual-cured resin composite (DC, Clearfil DC Core), was placed in the bonded cavity. Clearfil Photo Core was placed in three increments while bulk-filling was used for Clearfil DC Core. The application of the bonding system and the composites to the flat dentin surface was the same as that for cavity. Specimens were stored in water for 1 week, then sectioned vertically into 2 or 3 slabs (0.7 mm thick) and trimmed for the microtensile bond strength (MTBS) test. The MTBSs were measured with a universal testing machine at a crosshead speed of 1.0 mm/minute.
Results: The results (mean +/- SD, MPa, n=10) of PH/Cavity, PH/Flat and DC/Flat were 21.9 +/- 3.4, 28.9 +/- 4.0, and 27.6 +/- 6.1 respectively. The MTBS could not be determined in DC/Cavity because of debonding occurred during sample preparation.