Purpose: To evaluate microtensile bond strength and interfacial nanoleakage expression of adhesive interfaces created by XP-Bond on human deproteinized dentin immediately after bonding and after 6 months of artificial aging. Materials and Methods: Noncarious human molars were selected, middle/deep dentin substrates were exposed, and either assigned to group 1 (XP-Bond applied on collagen-depleted dentin) or to group 2 (XP-Bond applied in accordance with manufacturers’ instructions). In group 1, the etched dentin surface was treated with 10% NaOCl for 60 s to remove the exposed demineralized organic matrix before XP-Bond application. Composite/dentin beams were obtained in accordance with the microtensile nontrimming technique and either pulled to failure after 24 h or after 6 months’ artificial aging. Data were analyzed with two-way ANOVA and Tukey’s post-hoc test (p < 0.05). Interfacial nanoleakage evaluation was performed on additional adhesive interfaces to quantify the amount of silver tracer along the interface. Results: The use of NaOCl before XP-Bond application (group 1: 18.9 ± 5.8 MPa) reduced immediate bond strength by 62% compared to controls (group 2: 49.9 ± 10.3 MPa; p < 0.5). After 6 months of artificial aging, the bond strength of groups 1 and 2 significantly decreased to 10.1 ± 2.7 MPa and 35.2 ± 8.7 MPa, resp (p < 0.05). Interfacial nanoleakage expression along XP-Bond adhesive interfaces was increased either by sodium hypochlorite or by artificial aging. Conclusion: The role of collagen fibrils is pivotal for the bonding of XP-Bond to dentin, as decreased immediate bond strength and reduced bond stability over time was found on collagen-depleted dentin.

Keywords: dental bonding systems, dentin, sodium hypochlorite, collagen, hybrid layer