The scientific objective of this proposal is to employ new surface/interface chemistries/functionalities induced by non-thermal plasmas for robust and durable dentin adhesion, thus significantly extending the longevity of resin-based tooth restorations. The proposed research stems from the critical challenge long facing restorative dentistry: dental restorations based on composite resins have a prohibitively high failure rate. One primary reason for the premature failure is the lack of a tight and long-lasting adhesion between the composite resin and the underline dentin. The inability of the current state-of-the-art bonding techniques to form a tight resin/dentin adhesion is due to three major factors. First, the bonding between resin and dentin collagen, which relies on the infiltration and subsequent entanglement of adhesive resins with exposed collagen fibrils, is poor. The micromechanical interlocking mechanism is intrinsically problematic as insufficient penetration, incomplete polymerization and solvent/water swelling all prohibit the formation of a tight adhesion. Second, the stability and quality of the dentin substrates is often poor. When the foundation to which composite resins adhere is itself shaky, achieving long-lasting restoration is not just challenging, but impossible. Third, the strength and quality of infiltrated resin polymers is usually poor due chiefly to the incomplete polymerization of current adhesives under oral environment. In this proposal, multifunctional non-thermal plasmas with judiciously engineered chemistries will be utilized to simultaneously address all three critical issues. Such a novel and multifunctional plasma technique has the following unique features/functions: 1) sterilize the area of cavity, eliminating residual caries-causing microorganisms; 2) enable direct fluoride delivery to dentin substrates to inhibit demineralization/bacterial attack, thus reduce recurrent caries and improve dentin substrate stability; 3) provide controllable plasma chemistries to tailor the surface energy in-situ and on-demand for enhanced adhesive penetration into exposed collagen fibrils; 4) participate in network polymerization and crosslinking reactions in resin matrix, consequently increase the monomer/polymer conversion and crosslinking density of the resin matrix and thus producing a more cohesive and degradation-resistant resin matrix; 5) improve the stability of the dentin substrates against biodegradation through enhanced resin protection; 6) yield a chemical/covalent bonding between adhesive resins and collagen fibrils, thus enhancing the adhesive/dentin bond strength. Various characterization techniques will be utilized to thoroughly elucidate the plasma treatment effects on the dentin and adhesive surface/interface. The goal is not only to confirm that the design principles and the engineered plasma technology/chemistries work, but also gain deep understanding into how and why they do.
Replacement of failed restorations accounts for nearly 75% of all operative dentistry. This translates to 200 million replacements for failed restorations annually in the US. The breakdown has been linked to the failure of our current techniques to develop a durable adhesion to dentin. If we are successful at completing the goals outlined in this project the direct benefits will be more durable dental restorations, increased quality of life and decreased costs to the patient in terms of both time and money.
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