Smart Self-Sterilizing Dental Composites for Class V Restorations

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Summary Dental caries continues to be a public health issue, especially more evident in underserved populations throughout the U.S. Unfortunately, especially with an ageing population, hundreds of thousands of resin composite restorations are replaced each year due to recurring decay and fracture. According to a number of cohort studies, the average life-span of this type of restoration is 7 years or less, depending on the caries risk level of the patient and on the complexity of the restorative procedure. Class V lesions, carious or non-carious in nature, are particularly challenging to restore due to the location of the margins (often in dentin/cementum), the complexity of load distribution in this area of the tooth and the tendency for greater biofilm accumulation near cervical areas. This proposal represents an effort to develop novel pH- responsive, self-sterilizing methacrylamide composites capable of overcoming the aforementioned difficulties and increasing service life of class V restorations, thus saving millions of dollars annually and the unnecessary loss of additional tooth structure. The proposed approach will improve the longevity of class V restorations by: 1. Designing monomers, based on biocompatible carboxybetaine (CB) chemistry, that are capable of responding to acidic challenges in the oral environment and performing the dual function of antifouling surfaces (at neutral pH) and bactericidal surfaces (at low pH). 2.Utilizing polymerizable functionalities that depart from the water/esterase-labile methacrylates. Methacrylamides are well known for their resistance to degradation by hydrolysis, and the systems proposed here will also be stable to enzymatic attack (through the use of tertiary methacrylamides). 3. Incorporating toughening additives, based on pre-polymerized thiourethanes, which not only reduce the concentration of polymerizable functionalities (thus reducing shrinkage), but can also delay polymer gelation (thus reducing stress). In addition, the oligomer will be functionalized to work as a carrier of the CB moiety. 4. Promoting self-adhesive, ionic/covalent interaction between the substrate and the adhesive layer, in addition to the already existing micro-mechanical interlocking. This will allow for the use of less aggressive (if any) acid etching of the substrate, decreasing activation of deleterious MMPs.