MOLECULAR DYNAMICS AT THE DENTIN/ADHESIVE INTERFACE

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The goal of dentin bonding is twofold, i.e. to extract the mineral phase without damaging the collagen and impregnate the voids left by the mineral with adhesive resin. If this ideal were achieved, the collagen fibers of demineralized dentin would be enclosed in resin and thus, protected from the hydrolytic action of oral or dentinal fluids. There is substantial evidence to indicate that this objective is not achieved and researchers disagree on what techniques should be used to accomplish the ideal dentin/adhesive bond. To date, the dentin/adhesive bond has primarily been studied using morphologic analysis in conjunction with bond strength measurement. Although these analyses have enhanced our understanding, numerous questions about the chemistry of the dentin/adhesive interface are unanswered. Raman spectroscopy is a light scattering technique that provides a "fingerprint" for the molecular species present within a sample. When this technique is combined with a microscope, compound- specific molecules can be detected at a lateral spatial resolution of approximately 1mum. Although background fluorescence has traditionally limited the use of Raman spectroscopy, work done in this laboratory has recently shown that interference from fluorescence can be avoided by using a red excitation source. Using micro-Raman spectroscopy and a Kr+ laser a chemical map of the dentin/hybrid/adhesive interface has been constructed. The overall hypothesis of this project is that a pre- treatment regimen which provides complete resin encapsulation of the collagen in the demineralized zone will result in durable dentin/ adhesive bonds. The optimum pre-treatment regimen can be determined using complementary chemical, morphologic, and mechanical data. The specific aims of this study are: test the hypothesis that dentin prepared with self etching primers will resist collagen collapse and that adhesive resin can penetrate dentin treated in this manner; test the hypothesis that adhesive resin completely encapsulates collagen fibrils exposed after treatment of the dentin with self etching primers; test the hypothesis that self-etching primers provide superior resin penetration and encapsulation of exposed collagen in comparison to etched dentin treated with stabilizing solvents, specifically acetone and HEMA; test the hypothesis that self-etching primers provide stronger dentin/adhesive bonds in comparison to etched dentin treated with stabilizing solvents; test the hypothesis that in comparison to etched dentin treated with stabilizing solvents self-etching primers provide dentin/adhesive bonds that are stable upon exposure to aqueous environments.