Dental Resin System With Low Shrinkage And Modification By Antimicrobial Nanoparticles

The microleakage between tooth interface and resin restoration is caused by volumetric shrinkage of conventional dental restorative resin system in the process of light-cure polymerization. The polymerization microleakage and non-antibacterial resin lead to the secondary caries. Modified hyperbranched polyester has the potential to reduce the volumetric shrinkage because of its three-dimensional structure of single molecule. Expanding monomers can also be used in dental restorative resin system because its ring-opening polymerization produce volumetric expansion. The nano-diamond which is often used as filler has many functional groups. It can possess both good hardness and antibacterial capability when it is modified by quaternary ammonium salt. These monomers were added into resin to assess performances.Hyperbranched polyester(GHBP 3) modified with 7 double bonds and 6 propyls and 3,9-diethyl-3,9-bis(allyloxymethyl)-1,5,7,11-tetraoxa-spiro[5,5]-undecane(BAOM), a kind of expanding monomers, were synthesized. Products were characterized by FT-IR and 1H NMR. The degree of branching of HBP was determined by 13C NMR. Then the mixture of BAOM and epoxy 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane-carboxylate (EE) at mass ratio 1:1 (BAOM-EE), GHBP3 and Bis-GMA were mixed in different ratio and cured by visible light. Double bond conversion, polymerization shrinkage, hydrophilicity and water absorption were tested. The hydrophilicity and water absorption were both within appropriate range. According to double bond conversion and polymerization shrinkage,30%BAOM-EE, 25%GHBP3,45% Bis-GMA was chosen as the best addition ratio.Antibacterial nano-diamond, ND-Q6PF6, was synthesized with nano-diamond(ND), (3-bromopropyl)-trimethoxysilane, polyvinyl pyridine, bromohexane and KPF6 as raw materil. The resultant NP was characterized with FT-IR and 1H NMR. The antibacterial capability (minimum inhibitory concentration MIC and the minimum bactericidal concentration MBC) against E.coli and S.aureus was tested. The results indicated that the MIC value and the MBC value of ND-Q6PF6 to the E.coli were 62.5μg/mL and 125μg/mL, and that to S.aureus were 62.5μg/mL and 125μg/mL. The results showed that modified ND have good antibacterial capability against both two bacteria. ND-Q6PF6 was added into restorative resin system in best addition ratio, and double bond conversion, polymerization shrinkage, hydrophilicity, antibacterial capability and dispersion ability in resin flake were investigated. The results indicated that the restorative resin flake had low shrinkage and good antibacterial capability when the ratio of ND-Q6PF6 is below 1%.