Study On The Multifunctional Dental Light-curing Resin Composites Containing NMgO-BAG

Objective:The volume shrinkage and shrinkage stresses predispose to the formation of microcracks between teeth and restorations.Bacteria in the oral cavity are prone to accumulate on the surface of the resin composite material to produce acid.Besides,micro-fissures between teeth and restorations as a channel for bacteria to invade deeper into the tooth tissue,which eventually leads to secondary caries.In this study,different ratios of magnesium oxide nanoparticles（nMgO）and biologically active glass（BAG）will be introduced to resin composite.The effects of the addition nMgO and BAG on antimicrobial properties,remineralizing ability,mechanical properties,and physicochemical properties of the resin composite will be investigated.Method:In this research,bisphenol A-glycidyl bis（methacrylate）（Bis-GMA）,diethylene glycol bis（methacrylate）（TEGDMA）,camphorquinone（CQ）,and dimethylaminoethyl methacrylate（DMAEMA）were used as resin matrix.Silanized silica（SiO₂）and barium borosilicate glass（BSG）were used as inorganic reinforced fillers.nMgO and BAG were used as inorganic functional fillers.The resin matrix and the photoinitiator system were mixed well and then mixed with different fillers to make up a novel light-curing resin composite.The resin was divided into three main groups according to the total mass fraction of nMgO and BAG of 5%,10%,and 15%.Within each group,the experimental resin was subdivided into three groups according to the different mass fractions of nMgO（0%,2.5%,5%）,for a total of nine experimental resin groups.The resistance of the experimental resins to Streptococcus mutans（S.mutans）was evaluated using colony counting（CFU）,metabolic activity analysis（MTT）,and live/dead bacterial fluorescent staining assays.A model of human dentin demineralization was prepared and immersed with the various groups of experimental resin in simulated body fluid（SBF）for 21 d.The ability of each experimental resin group to remineralize demineralized dentin pieces was evaluated by scanning electron microscopy（SEM）and X-ray energy dispersive spectroscopy（EDS）.The Vickers hardness,compressive strength,flexural strength,and depth of cure for the experimental resin were tested by a universal testing machine and a Vickers hardness tester.The contact angle analyzer and pH meter were used to evaluate the hydrophilicity and alkaline ability in aqueous solutions of the experimental resin.Finally,the water sorption and solubility of the experimental resins were tested.Results:1.Compared to the resin composite with only nMgO or BAG,the resin composite containing nMgO-BAG was significantly more resistant to S.mutans.And the antibacterial effect of the experimental resin was positively correlated with the amount of nMgO and BAG added.2.Mineral deposits started to appear on the surface of demineralized dentin in the experimental resin group containing 10 wt%BAG.The surface of the demineralized dentin of the 15F-M_2.5B_12.5and 15F-M₀B₁₅groups was covered with sheets of hydroxyapatite.Besides,the dentin tubules were almost completely closed.The calcium to phosphorus ratios were all greater than 1.67,indicating that both the two groups had good remineralization performance.The results of the remineralization experiments show that the remineralization capacity of the experimental resins is closely related to the amount of BAG added.3.The incorporation of nMgO and BAG did not affect the compressive strength of resin composites.However,the Vickers hardness and flexural strength of resin composites decreased with increasing BAG addition.4.The depth of cure and water sorption values of resin composites tended to increase with increasing nMgO and BAG fillers.The water contact angle of group 15F-M_2.5B_12.5was（50±2）°,which exhibited the best hydrophilicity.The pH of the aqueous solutions of all the experimental resins reached a maximum value at 24 h,then decreased and became relatively stable.It is suggested that the antimicrobial and remineralization capacity of the experimental resins may be closely related to hydrophilicity and pH factors.Conclusion:The combined application of nMgO and BAG allows the composite resin to be multifunctional.The 15F-M_2.5B_12.5group has the best performance.The new multifunctional resin composite is expected to reduce bacterial infection and promote early remineralization of caries,which provides the theoretical basis for the research on multifunctional resins.