Objective To investigate whether multiple coatings can improve the bond durability of one-step self-etching adhesive to primary dentin.Methods Twelve caries-free human primary molars were randomly divided into 2 groups. In group 1

each tooth was hemisected into 2 halves. One half was assigned to the control subgroup 1

which was bonded with a commercially available one-step self-etching adhesive according to the manufacturer’s instructions; the other half was assigned to experimental subgroup 1

in which the adhesive was applied three times before light curing. In group 2

one split half tooth was bonded with a commercially available one-step self-etching adhesive according to the manufacturer’s instructions; for the other half

three layers of adhesive were applied with each successive layer of light curing. Specimens were stored in 0.9% NaCl containing 0.02% sodium azide at 37℃ for 18 months and then were subjected to microtensile bond strength test and the fracture mode analysis. Results When the adhesive was applied three times before light curing

the bond strength of the experimental subgroup 1 was significantly higher than that of the control subgroup 1 (47.46±13.91 vs. 38.12±11.21 MPa

P0.05). Conclusion Multiple coatings can improve the bond durability of one-step self-etching adhesive to primary dentin when using the technique of light-curing after applying 3 layers of adhesive.