Design,Synthesis And Research Of Novel Low Shrinkage Dental Resin Composites

Objective.Bisphenol A epoxy acrylate resin(Bis-EAR),Glycidyl methacrylate resin(GMA)were used as dental resin monomers,and A novel self-synthesized expanding monomer 3,9-dihydroxymethyl-3,9-diethyl-1,5,7,11-tetraoxacyclohexane(5,5)undecane was added to synthesize novel low-shrinkage dental resin composites,and its related properties were studied.Methods.1.The expanding monomer(DDTU)was synthesized by ourselves,and the molecular structure of the product was characterized by FTIR,1H NMR and mass spectrometry.According to the different initiator components,it was divided into three experimental groups:one,two and three initiators.The curing depth of Bis-EAR/GMA was detected under different initiator concentrations,and the initiator system was determined.2.Six experimental groups of 0%,5%,10%,15%,20%and 25%DDTU contents were set,and bisphenol A diglycidyl methacrylate(Bis-GMA)and Triethylene glycol dimethacrylate(TEGDMA)were used as the control group.The volume shrinkage rate after curing was detected by capillary method(n=8)o The resin specimens with the specification of 25mm×2mm×2mm(n=8)were prepared and the bending strength was tested by the universal testing machine after a constant temperature(37℃)water bath for 24h.According to the test results of volume shrinkage and bending strength,the optimal addition amount of DDTU was determined and characterized by FTIR and 1H NMR,and the double bond conversion rate was calculated.3.Bis-EAR/GMA/DDTU was used as the resin matrix,and a certain amount of inorganic fillers were added to synthesize the novel low shrinkage dental resin composites.Bis-GMA/TEGDMA as the matrix of self-synthesized resin composites and commercial Tetric N-ceram nano-ceramic resin composites were used as the control to test the volume shrinkage rate,shrinkage stress and mechanical properties.One-way analysis of variance(ANOVA)and Tukey’s post hoc comparison test(SPSS,version19.0)were used for statistical analysis of the experimental results,and the test level was set as α=0.05.Results.1.The synthetic product was white solid powder with a yield of 86.4%,and the characterization results were consistent with the DDTU formula;The curing depth of the unary and binary initiator groups was 0mm,while the curing depth of the ternary initiator group gradually increased with the increase of the content.When the content was 7wt%and 9wt%,the curing depth was>2mm,with no statistical difference(P>0.05).2.Compared with Bis-GMA/TEGDMA in the control group,the volume shrinkage rate of Bis-EAR/GMA was smaller(P<0.05),and the volume shrinkage rate of resin matrix gradually decreased with the increase of DDTU content(P<0.05).There was no significant difference between Bis-EAR/GMA bending strength and that of the control group(P>0.05).When the DDTU content in Bis-EAR/GMA was<15wt%,there was no significant change in bending strength(P>0.05);When DDTU content was>15wt%,bending strength gradually decreased(P<0.05).Therefore,the optimal addition of DDTU was determined to be 15wt%,and the double bond conversion rate of resin matrix was 74.1%,higher than that of the control group(P<0.05).3.The volume shrinkage rate and polymerization shrinkage stress of the novel low shrinkage dental resin composites were lower than that of the control group(P<0.05),which were 3.04%and 3.16MPa,respectively.Compared with the control group,there was no statistical difference in the elastic modulus(P>0.05),while the indexes such as compression strength,radial tensile strength and surface hardness were slightly lower(P<0.05),which were within the acceptable range reported in the literature.Conclusions.1.DDTU was successfully synthesized and the ternary initiator system with a content of 7wt%was determined.2.Add DDTU with mass fraction of 15%to Bis-EAR/GMA,the resin matrix has lower volume shrinkage(P<0.05),good bending strength and double bond conversion.3.New dental resin composites with low volume shrinkage and shrinkage stress was synthesized,which laid a foundation for further research and application of low volume shrinkage resin composites.