DENTIN ADHESIVES--MOLECULAR MODELING

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DESCRIPTION (Adapted from investigator's Abstract): Adhesion to dentin was a difficult problem in dentistry for many years, but there appears to be a consensus that a new generation of dentin adhesive formulations, developed in recent years, constitute a breakthrough in adhesive dentistry involving dentin. Etching or conditioning of dentin is the first step in most of these new adhesive approaches. During conditioning the etched outermost regions may be completely demineralized exposing the collagen structure while some underlying structures below these layers are partially demineralized creating a collagen rich surface. On bonding, the primers in the adhesive formulations interact with this demineralized structure creating a so called hybrid layer. It is generally believed that the hybrid layer is responsible for high bond strength at the cavity-restoration interface and reduced microleakage as well as postoperative sensitivity. There is, however, no clear understanding of the nature of the bonding forces at the interface. In fact, while some authors report identification of chemical bonds through selected spectroscopic techniques, others have found no such clear evidence for chemical bonding. It has been suggested by a number of authors that the hydrophilic monomer formulations used in the adhesive primers seek out dentinal water resulting in effective wetting and infiltration of the demineralized dentin surface and creation of micromechanical bonding through encapsulation of exposed collagen fibrils and impregnation of the underlying partially demineralized dentin surface. Such micromechanical bonding may involve van der Waals forces, electrostatic forces, secondary bonds such as hydrogen bonding. Such forces between ligand molecules and protein macromolecules are treated through a well established method of molecular modeling. In this research, such an approach is proposed to characterize the interactions between primer molecules and the collagen structure of dentin. Energy refined ligand and selected polypeptide and protein molecules will be built by computer aided modeling techniques and they will be thoroughly characterized and optimized. Interactions between ligand molecules and favored receptor sites on polypeptide and protein molecules will be evaluated by indirect and direct techniques of molecular modeling. Interaction parameters obtained by such analysis will be compared with the in vitro bond strength and microleakage data available in the literature. the Principal Investigator expects to show the types of forces and interactions responsible for effective bonding and sealing at the dentin-restoration interface.