Abstract
ABSTRACTHydrolytic and enzymatic degradation of resin adhesives over time has been mainly attributed to secondary caries formation of methacrylate-based tooth-colored resin-based composite restorations. Ability of resin adhesive monomers to infiltrate into demineralized dentin forming stiff polymer matrix and potentially bonding to tooth structure is also a crucial property. The only commercially available antibacterial monomer, 12-methacryloyloxydodecyl pyridinium bromide (MDPB), is a quaternary ammonium methacrylate. This methacrylate monomer undergoes hydrolytic degradation, and could not bond to tooth structure. In this study, a new hydrolytic resistant monomer HMTAF was synthesized. It is methacrylamide-based monomer that, unlike methacrylate, is highly resistant to hydrolysis. Its molecular structure has particular functional groups; quaternary ammonium fluoride salt with potential antibacterial fluoride-releasing activity, hydroxyl and amide group with hydrogen bonding potential to dentin collagen. Hydroxyl group also increases monomer hydrophilicity for better penetration into water-saturated dentin and sufficient resin-dentin bond. The synthesized HMTAF and its polymer showed no hydrolytic degradation in acidic environment, while MDPB and its polymer were partially decomposed under this challenge. The conversion of monomer HMTAF to polymer was illustrated by FT-IR. The results indicated that HMTAF is highly resistant to hydrolysis, polymerizable and non-cytotoxic to Vero cell lines. It is a potential monomer to be incorporated into resin adhesives for improving hydrolytic and enzymatic resistance.
Highlights
Tooth-colored resin-based composite has been increasingly used in clinical practice due to esthetic concerns and the phase down of amalgam because of its toxicity
Three-step etch-andrinse adhesive system remains the gold standard for bonding resin-based composite restorative materials to tooth structure [3]
Resin adhesive monomer HMTAF was synthesized in 7 steps as shown in Scheme 2
Summary
Tooth-colored resin-based composite has been increasingly used in clinical practice due to esthetic concerns and the phase down of amalgam because of its toxicity. This material becomes defective and requires replacement nearly twice as often as amalgam [1,2]. Three-step etch-andrinse adhesive system remains the gold standard for bonding resin-based composite restorative materials to tooth structure [3]. Monomers in a bonding are copolymerized with monomers in a primer providing micromechanical lock to the tooth structure before placing a resin composite [4]. Monomers in primers should be relatively hydrophilic for efficient infiltration into watersaturated dentin and able to bond to hydroxyapatite or collagen in dentin. Monomers in a bonding should be relatively hydrophobic and have cross-linking potential for strong and durable bond to tooth structure
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