Push-out strength and SEM evaluation of resin composite bonded to internal cervical dentin

The bond strength of a resin composite used with a dual-cured dentin bonding system to internal cervical bovine dentin was evaluated using a direct or indirect placement technique. Teeth were sectioned transversely to produce 4 mm-thick specimens. The root canals were enlarged to a standardized taper, treated with a dentin bonding system, and filled with a light-cured resin composite using either direct, incremental composite placement or indirect composite placement of a pre-polymerized composite inlay. The debond stress of indirectly placed restorations using a composite inlay was 8.5 (SD +/- 2.7) MPa which was significantly greater (p < 0.0001) than the value of 5.0 (SD +/- 1.9) MPa for composite placed in a conventional, incremental manner. SEM evaluation revealed the indirect placement technique demonstrated increased resin tag density and length as compared to the direct technique. Enhanced retention of resin composite to endodontically prepared dentin treated with a dentin bonding system was obtained by using a composite inlay technique as opposed to direct, incremental buildup of the material.