Polymeric adhesion to dentin: contrasting substrates.

Clinical research has shown that resin dentin adhesive materials often fail prematurely despite encouraging laboratory-derived data. Current adhesives are reported to react with dentin surfaces by chemical and/or micro-mechanical mechanisms. The ionic bonding to calcium and the covalent coupling to collagen are representative chemical strategies employed today. Recent findings suggest that the mechanical interlocking of resins into open dentinal tubules may play an even more important role with present adhesive systems. Dentin surfaces, such as cervical abrasions, undergo changes in the oral cavity and dentinal tubules may become partially or completely obturated by the growth of peritubular dentin or by the precipitation of mineral salts within the tubules. The resulting sclerotic dentin may be less receptive to current dentin adhesives. An examination of clinically aged dentin surface types revealed extreme variability in tubular morphology. The more sclerotic dentin presented, the less effective was dentin conditioning and resin adaptation. Early correlations with ongoing clinical trials appear to substantiate this finding with the greatest failure of restorations occurring in more sclerotic lesions.