Quality of the interface of primary tooth dentin bonded with antibacterial fluoride-releasing adhesive

Objective: Limited information is available on the physical properties and ultrastructure of resin-dentin interfaces created in primary teeth. The interfacial quality of sound and caries-affected primary tooth dentin bonded with an antibacterial fluoride-releasing self-etch adhesive was examined in the present study. Methods: Primary molars were bonded with Clearfil Protect Bond (Kuraray Medical). A nano-indentation tester was employed for creating indentations vertically across resin-dentin interfaces of the bonded sound and caries-affected primary dentin for determination of hardness (H) and Young's modulus (Y). Statistical analysis were performed using one-way and two-way ANOVA and Fisher's PLSD test at p < 0.05. Similar resin-dentin interfaces were examined with SEM/EDX, and with TEM using ammoniacal silver nitrate tracer for nanoleakage. Results: In both sound and caries-affected dentin, compared to the underlying dentin, significantly lower values were seen in the H and Y values of the interfacial dentin except for the H in caries-affected dentin. No significant difference between the interfacial dentin and the underlying dentin was observed in the H of caries-affected dentin and the Ca and P contents in both sound and caries-affected dentin. TEM revealed extensive interfacial nanoleakage in bonded sound dentin, while no silver deposit in bonded caries-affected dentin. However, silver deposits were observed in the porous caries-affected dentin beneath the interface. Conclusion: Within the limitation of this study, Clearfil Protect Bond cannot demonstrate evidence of remineralization, does not increase the hardness and elasticity of the interfacial dentin, and does not prevent nanoleakage along the resin-dentin interface.