A newly designed all-in-one bonding system“ MTB-200”, which aims to improve the polymerization rate and the
water resistance of the bonding layer to achieve stable, durable bonding, was produced experimentally.
In this study, we observed the resin/tooth interface under FE-SEM and TEM to evaluate the bonding efficacy
of this system. We prepared bonded specimens in a routine technique before argon ion beam etching for FE-SEM, and non-demineralized ultrathin sections for TEM. SEM showed that a tight interfacial junction was obtained without any gap between the intact enamel, intact dentin, or caries-affected dentin and the MTB-200 system. In the superficial dentin layer, a hybrid layer of about 0.2 μm in thickness was observed, but in the case of the caries-affected dentin layer, the hybrid layer was not clearly observed. TEM showed that some parts of apatite crystals remained within the decalcified dentin layer. These findings suggested that MTB-200 could obtain good bonding efficacy to the tooth substances due to the mechanism at the nano-level, called“ nano-interaction zone”, rather than the hybrid layer.
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