Chemical profile of adhesive/caries-affected dentin interfaces using Raman microspectroscopy

In clinical practice, dentists must frequently bond adhesives to caries‐affected dentin substrates, but the bond that characteristically forms with these substrates does not provide the durability necessary for long‐term clinical function. The purpose of this study was to characterize and compare the interfacial chemistry of adhesive with caries‐affected and noncarious dentin using micro‐Raman spectroscopy. The results indicated that the differences in the Raman spectra between noncarious and caries‐affected dentin could not be accounted for by simple decreased mineralization. Both the structure of collagen and mineral in the caries‐affected dentin has been altered by the caries process. The differences in structure and composition not only interfered with acid‐etching process but also subsequent resin monomer penetration. It was shown that the interface between the adhesive and caries‐affected dentin was wider and more complicated than that of the adhesive and noncarious dentin. As a result of adhesive phase separation, a structurally integrated hybrid layer did not form at the interface with either caries‐affected or noncarious dentin. Using chemical imaging techniques, this study provides the direct evidence of adhesive phase separation at the interface with caries‐affected dentin. Although our group previously reported adhesive phase separation at the interface with noncarious dentin, the chemistry of caries‐affected dentin leads to greater variability and a more highly irregular composition along the length and breadth of the interface. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res 2007