Hardness, elasticity and ultrastructure of primary tooth dentin bonded with a self-reinforcing one-step self-etch adhesive

Abstract 

Objective

This study evaluated the interfacial quality of sound and caries-affected primary tooth dentin bonded with a self-reinforcing one-step self-etch adhesive.

Methods

Non-carious, sound dentin was prepared with water-cooled high-speed diamond burs. Caries-infected dentin was removed with water-cooled low-speed round steel burs and hand instrument. Dentin was bonded with Bond Force (Tokuyama Dental). A nano-indentation tester was employed for determination of hardness (H) and Young's modulus (Y) of resin–dentin interface. Similar resin–dentin interfaces were examined with a SEM/EDX, and with a TEM using ammoniacal silver nitrate tracer for nanoleakage.

Results

In the comparison of the H and Y values between the interfacial dentin and the underlying mineralized dentin, no significant difference was seen in caries-affected dentin, however, the values of the interfacial dentin were significantly lower in sound dentin. The H value of the interfacial dentin of sound dentin was significantly lower than that of caries-affected dentin with significantly higher Ca content. No significant difference was observed in the Y values of the interfacial dentin of the two substrates. For both sound and caries-affected dentin, TEM revealed silver deposits in the interfacial dentin and adhesive layer, and smear layer remained within the resin–dentin interface. However, Ca and P contents of the adhesive layer at 10μm above the dentin surface were the same as those present in the interfacial dentin.

Conclusions

Both for sound teeth and caries teeth, Bond Force does not prevent the nanoleakage along the resin–dentin interface.

Keywords: Hardness, Young's modulus, Ultrastructure, Caries-affected dentin, Sound dentin, Primary tooth dentin, One-step self-etch adhesive, Self-reinforcing adhesive