An experimental single-step bonding system, RZ-II, has been developed as a resin coating material for crown preparation. The purpose of this study was to compare the dentin microtensile bond strengths (MTBSs) of RZ-II in direct and indirect use. Human molar dentin was used. The specimens were divided into three groups of n = 20 each. Group 1: RZ-II was applied to the dentin surface once or twice, and built up with a direct composite. Group 2: The dentin surface was provisionally covered and stored in water for 1 day. The provisional material was removed and an indirect composite was then bonded to the dentin surface. Group 3: RZ-II was applied to the dentin surface once or twice for
esin coating before the placement and removal of provisional material. An indirect composite was then bonded to the coated dentin. After 1 day, MTBSs were measured at a crosshead speed of 1 mm/min. The data were analyzed using one-way ANOVA and Fishers PLSD test (p < 0.05). The interface between the indirect composite and resin-coated dentin was also observed using a SEM. The MTBSs of RZ-II in Groups 1 and 3 were significantly higher than those of Group 2 (p < 0.05). The thickness of the resin-coating layer and the hybrid layer were 5 to 6 Ám and less than 1 Ám, respectively. The single-step bonding system, RZ-II, could be useful as a resin coating material for crown preparation.