Analysis of acid resistance of root surface and development of novel resin systems for prevention of root surface caries

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In this research project, the acid resistance of root surface was examined by determining the critical pH for demineralization, and the effectiveness of novel resin-coating system for prevention of root surface caries was investigated by in vitro studies. The following results were obtained.1) By demineralization tests using acid buffer, the cementum was found to be demineralized at pH over 5.5. Approximately 43% of the specimens showed demineralization at pH 6.3, and approximately 29% at pH 6.5 and 6.8. The cementum was more vulnerable to acid compared with enamel, and the pH value at which demineralization of cementum starts was 6.8.2) The single-step adhesives with strong etching aggressiveness demonstrated integrity of the bonding interfaces to root dentin immediately and 24 h after restoration, while the mild adhesives showed de-bonding immediately after restoration. Strong systems were advantageous to produce stable bonding to root dentin from the early stage.3) Commercial single … More -step self-etching adhesives demonstrated coating with small thickness and limited effects to prevent the root surface from demineralization, although they showed good bonding ability with cementum. The commercial root dentin sealer was effective to prevent demineralization on the root surface, but its bonding ability was poor compared with adhesives.4) The experimental resin-coating system, consisting of a self-etching primer and a multi-functional methacrylate, could prevent root surfaces from acid demineralization by producing an integral hybridization with cementum and a moderately thick surface-coating. The experimental system also showed excellent durability against tooth brushing wear.These results indicate that the vulnerability of cementum to acid is high and the preventive measures against demineralization should be conducted at the earliest occasion after exposure of the root surface. The experimental system proved to be a promising material for application on root surface to protect from demineralization. Less