Study On Preparation And Properties Of Low Shrinkage Stress Methacrylate-based Dental Restorative Materials

Methacrylate-based dental resin composites have been widely used in dental restorative treatment because of their superior aesthetic qualities,good mechanical properties and excellent bonding properties.Bis-GMA has been widely used as base monomer in commercial dental resin composites.Bis-GMA has a high viscosity,so it needs to add reactive diluent,such as TEGDMA,to reduce the viscosity of resin system.However,the addition of TEGDMA leads to increase of polymerization shrinkage and shrinkage stress.In order to reduce the polymerization shrinkage and shrinkage stress of dental resin composites,a urethane dimethacrylate monomer TMA with rigid sctructure and two novel methacrylate terminated oligomers PPMAs with different chain lengths were designed and synthesized in this thesis.TMA was used as resin matrix and PPMAs were used as reactive diluent in dental resin composites,respectively.All the results of this study were listed as below:?1?A urethane dimethacrylate monomer TMA with rigid sctructure was synthesized using isophorone diisocyanate?IPDI?,Tricyclo?5.2.1.O2,7?decan-4,8-dimethanol?TDDM?and2-hydroxyethyl methacrylate?HEMA?as raw materials.Its structure was confirmed by FT-IR and ¹H-NMR sprctra.?2?TMA was used to replace commercial urethane dimethacrylate monomer UDMA as based resin matrix gradually to prepare UDMA/TMA resin system.The results showed that,with the increasing of TMA content,the viscosity,water sorpotion?WS?,water solubility?SL?,flexural strength?FS?,and flexural modulus?FM?of UDMA/TMA resin system increased gradually,while double bond conversion?DC?and polymerization shrinkage decreased gradually.Compared with the UDMA control and Bis-GMA control resin system,with a certain amount of TMA,TMA containing resin systems could have lower polymerization shrinkage,higher DC and higher FS,although the viscosity and WS of the resin systems would be increased.?3?TMA containing resin systems were used as dental resin matrix and mixed with inorganic filler BaAlSiO₂ in the same fraction to prepare dental resin composites.The results showed that,with the increasing of TMA content,the polymerization shrinkage and shrinkage stress of TMA containing resin composites decreased gradually.Compared with UDMA/BaAlSiO₂ control and Bis-GMA/BaAlSiO₂ control resin composites,with a certain amount of TMA,TMA containing resin composites could have lower polymerization shrinkage,shrinkage stress and higher FM.Therefore,TMA has potential to be used in commercial dental resin composites as a substitute for Bis-GMA and UDMA.?4?Two novel methacrylate terminated oligomers PPMAs with flexible long alkoxy chain were synthesized by the reaction between polypropylenglycol diglycidyl ether?PPDE?with different number-average molecular weight?Mn=380 and 640?and methacrylic acid?MA?,respectively.Their structures were confirmed by FT-IR and ¹H-NMR spectra.?5?PPMA were used to replace TEGDMA partially as reactive diluent in Bis-GMA/TEGDMA?50/50 wt%/wt%? resin system to prepare PPMA containing resin systems.The results showed that,compared with B/T resin system,PPMA containing resin systems had higher viscosity,slower polymerization rate,lower DC and polymerization shrinkage,higher WS and SL,lower FM and FS,and similar fracture of energy.With the increase of PPMA content,the viscosity,WS,and SL of resin system increased gradually,while DC polymerization shrinkage,FS,and FM decreased gradually.Compared the resin system with different PPMAs at the same mass fraction in resin matrix,640PPMA containing resin system had lower viscosity,FS and FM,but higher WS and SL.?6?DR-380-10,DR-380-20,DR-640-10 and DR-640-20 resin systems were used as dental resin matrix and mixed with inorganic filler BaAlSiO₂ in same fraction to prepare novel dental resin composites.The Tg,heterogeneity,polymerization shrinkage and shrinkage stress of resin composites with high content of PPMA were lower,but the effect of PPMA on other properties was not obvious.Compared the dental resin composites with different PPMA at the same mass fraction in resin matrix,640PPMA containing resin composites had lower polymerization rate,DC,polymerization shrinkage and shrinkage stress,but higher WS and SL.With a certain amount of PPMA,PPMA containing resin composites could keep good mechanical properties as well as have lower polymerization shrinkage and shrinkage stress,but WS and SL of them would be higher.Therefore,PPMA can used to partially replace TEGDMA as reactive diluent to reduce polymerization shrinkage and shrinkage stress of dental resin composites.