Out of 290 million dental restorations placed/year in the U.S., 200 million are replacements for failedrestorations. This emphasis on replacement therapy is expected to grow as the public's concern regardingmercury and dental amalgam forces dentists to select alternative materials, e.g. composite. Moderate to largecomposite restorations have higher failure rates, more recurrent caries and increased frequency ofreplacement. The reduced clinical lifetime of moderate to large class II composite restorations can beparticularly detrimental for our patients because removal of these restorations can lead to extensive loss ofsound tooth structure with the concomitant need for enlarged, more complex restorations and eventually totaltooth loss. Under in vivo conditions the adhesive/dentin (a/d) bond can be the first defense against substancesthat penetrate and undermine the composite restoration. Our recent in situ characterization of the molecularstructure and micro-mechanics of the a/d interface indicated a serious limitation, i.e. physical separation ofadhesive upon mixing with water in the demineralized dentin. The critical dimethacrylate (BisGMA), thecomponent contributing the most to the crosslinked adhesive, infiltrated a fraction of the wet, demineralizeddentin. In this revised competitive renewal application, we propose to build upon our results to develop a water-compatible adhesive by addressing the next chemical 'Achilles heel' of the a/d bond, i.e. ester linkages in themethacrylate matrix. The overall hypothesis is that in the presence of moist clinically relevant dentinsubstrates, methacrylate-based adhesives formulated to be water-compatible and esterase-resistant willprovide enhanced interfacial structural integrity and increased durability. Our goal is to elucidate howalterations in the chemistry will lead, under clinically relevant conditions, to predictable changes in dentinadhesive material properties (structure, interfacial behavior, mechanical properties and durability) and tooptimize features for in situ a/d bond formation based on kinetics, biocompatibility and modeling of interfacialdamage.
The specific aims are: 1) to design and synthesize the most promising esterase-resistant, water-compatible methacrylate-based adhesives using an iterative combinatorial optimization/synthesis approach; 2)to evaluate and test the physicochemical, mechanical and structural properties of the esterase-resistant, water-compatible methacrylate-based adhesives at the interface with such clinically relevant substrates as caries-freeand -affected dentin; 3) to evaluate the bond strengths between dentin and esterase-resistant, water-compatible methacrylate-based adhesives so that specific and quantifiable relationships between molecularstructure and dentin bonding can be established. Project narrativeOut of 290 million dental restorations placed annually in the United States, 200 million are replacements forfailed restorations 1 and this emphasis on replacement therapy is expected to grow as the public's concernabout mercury release from dental amalgam forces dentists to select alternative materials, e.g. compositeresin. Under in vivo conditions the adhesive/dentin bond can be the first defense against substances thatpenetrate and undermine the composite restoration. If we are successful at completing the goals outlined inthis project the direct benefits to the patient will be: 1) a substantial reduction in those components of theadhesive system that degrade releasing unreacted components and 2) development of adhesive systems thatare compatible with the wet oral environment and thus, more resistant to premature degradation whichundermines composite restorations.
Showing the most recent 10 out of 58 publications
