The purpose of this study was to evaluate the effect of multiple application of all-in-one dentin adhesive system on microtensile bond strength to caries-affected dentin.

Twenty one extracted human molars with occlusal caries extending into mid-dentin were prepared by grinding the occlusal surface flat. The carious lesions were excavated with the aid of caries detector dye. The following adhesives were applied to caries-affected dentin according to manufacturer's directions; Scotchbond™ Multi-Purpose in SM group, Adper Prompt L-Pop™ 1 coat in LP1 group, 2 coats in LP2 group, 3 coats in LP3 group, Xeno® III 1 coat in XN1 group, 2 coats in XN2 group, and 3 coats in XN3 group. After application of the adhesives, a cylinder of resin-based composite was built up on the occlusal surface. Each tooth was sectioned vertically to obtain the 1 × 1 mm² sticks. The microtensile bond strength was determined. Each specimen was observed under SEM to examine the failure mode. Data were analyzed with one-way ANOVA.

The results of this study were as follows;

1. The microtensile bond strength values were; SM (14.38 ± 2.01 MPa), LP1 (9.15 ± 1.81 MPa), LP2 (14.08 ± 1.75 MPa), LP3 (14.06 ± 1.45 MPa), XN1 (13.65 ± 1.95 MPa), XN2 (13.98 ± 1.60 MPa), XN3 (13.88 ± 1.66 MPa). LP1 was significantly lower than the other groups in bond strength (p < 0.05). All groups except LP1 were not significantly different in bond strength (p > 0.05).

2. In LP1, there were a higher number of specimens showing adhesive failure. Most specimens of all groups except LP1 showed mixed failure.