The Influence Of Different Initiator On The Properties Of Biphenyl Dental Resin

Dental composite resins composed of organic resin matrix,initiator system and inorganic filler is a kind of filling material which is widely used in oral cavity,and bisphenol A-glycidyl methacrylate(Bis-GMA)is used as resin matrix monomer of the dental composite resins filling material is the preferred material for tooth defect filling treatment.Because of the good bonding properties of dental composite resins filling material,it can retain more tooth tissue and meet the aesthetic requirements of patients;but it is used in the oral environment after a period of time there will be a variety of problems,the most serious of which is the tooth tissue secondary caries and filling materials wears broken,mainly due to the polymerization shrinkage of filling materials and its tissue mechanical properties do not match,so the researchers continue to research new materials to replace the current resin[1-2],the development of composite resin with low shrinkage and high mechanical properties has become a hotspot.The modification of the widely used resin monomer Bis-GMA and the synthesis of new resin monomer or modifying the existing resin are one of the research directions.In our preliminary work,a new type of acrylic dental dental matrix monomer-3,3 ’,5,5’-tetramethyl biphenyl biphenol type epoxy acrylate(TMBPEA)was already synthesized.The biphenyl structure improves the rigidity of the polymers and reduces the spatial conformational change during the polymerization process.In this study,Bis-GMA monomer was used as the control group.It was found that the polymerization shrinkage of the resin matrix system with TMBPEA monomer as matrix was small and the flexural strength was high,but there was no significant difference in the degree of conversion.The degree of conversion is closely related to the performance of the resin material.The materials with high degree of conversion has high crosslinking density,the internal structure is more compact,can improve the mechanical properties,and the material is not easy to change color,at the same time will improve the hardness,wear resistance and biosecurity.The degree of conversion factors: monomer,initiator,curing mode and time,in these three factors the type and content of initiator is essential,and the initiator can directly convert the resin from the viscous liquid system to the solid state under the light of the appropriate light wave,and the rate and degree of the transformation are directly related to the initiator,in this study,a new initiator PPD was introduced to investigate the effect of different initiators on the double bond conversion of resin matrix copolymer with TMBPEA as monomer,the purpose is to improve the double bond conversion rate of the system by the new initiator and further improve the mechanical properties of materials.Experimental method: The monomer(TMBPEA),diluent(diethylene glycol triethylene glycol ester TEGDMA),initiator and co-initiator were mixed to form a resin matrix system,the ratio of monomer to diluent in the copolymer was 7: 3,initiator and co-initiator ratio of 1: 1;According to the initiator of different composition and proportion of group: PPD group with 1% PPD as initiator;PPD + CQ group: According to CQ: PPD mass ratio 1: 1 as the initiator;The control group consisted of 1% CQ as the initiator.The degree of conversion,polymerization shrinkage and mechanical properties of the three groups were measured respectively(refer to dental industry standard).Results: The polymerization conversion and mechanical properties of PPD group were better than that of CQ group,and PPD + CQ group composite resin system had better polymerization conversion,polymerization shrinkage and mechanical properties than CQ system.PPD + CQ group composite resin system was compared with PPD,although the mechanical properties were not very different,but the polymerization conversion,polymerization shrinkage performance were better than the PPD system(p <0.05).Conclusion: PPD is an ideal initiator,the combination of PPD and CQ can improve the double bond conversion rate of resin matrix system,and further improve the performance of resin,has a good clinical application prospects.