Synthesis And Properties Of A Novel Dental Resin Monomer

Dental composite resins based on bisphenol A-glycidyl methacrylate (Bis-GMA)are widely used in clinic due to its outstanding aesthetic effect，convenient clinicalmanipulation and excellent adhesion quality. However, there still exist somedisadvantages such as polymerization shrinkage and relatively low mechanicalresistance compared to natural teeth. These drawbacks may cause potential failure byleading to secondary caries and the wear or fracture of the materials，which limit theapplication of the resin. Hence, much of recent research on resin-based dentalmaterials focused on these challenges and significant progresses were made such assynthesis of new monomer or modifying the existing resin. However, there is no idealsolution.The research aimed to synthesize an novel acrylate resin monomer with biphenylstructure which is characterized by the large rigidity and small conformationalchanges during the procedure of polymerization. The resin formulation made of thenovel acrylate matrix and diluents was cured with visible light, with the attempt ofreducing polymerization shrinkage and improving the mechanical properties.In our preliminary work,3,3′,5,5′-tetramethyl biphenyl diglycidyl ether epoxymonomer (TMBP) was already synthesized. It was proved to be a monomer with greatstability, thermal properties and mechanical qualities. TMBP performed better thanBisphenol A epoxy resin. In this work we made it react with acrylic acid to generate3,3′,5,5′-tetramethyl biphenyl epoxy acrylate(TMBPEA). In this way we introducedthe rigid structure into the resin monomer. Then the monomer was mixed with thediluents triethylene glycol dimethacrylate (TEGDMA) and the photoinitiatorcamphorquinone (CQ) to form the resin formulation. Degree of conversion,polymerization shrinkage, contact angle, water sorption, solubility, flexural strength,flexural modulus and microhardness of TMBPEA/TEGDMA based resin weremeasured to evaluate whether it could be used as an alternative of dentalresin.Bis-GMA/TEGDMA based resin was used as the control group. In this work, the structure of TMBPEA was successfully confirmed by fouriertransform infred spectroscopy(FTIR) and nuclear magnetic resonancespectroscope(1H-NMR). Degree of conversion of each formulation was measured bythe FTIR spectroscopy, showing that there was no significant difference between thetwo systems (P>0.05). Polymerization shrinkage was determined by density change ofresin before and after curing. The results illustrated that the shrinkage of TMBPEA/TEGDMA based system was reduced by18%when compared with Bis-GMA/TEGDMA system. TMBPEA/TEGDMA had the same contact angle and watersolubility with Bis-GMA/TEGDMA (P>0.05), but higher water sorption.(P <0.05).The mechanical teats were conducted by universal testing machine and microhardnesstester. The two systems had the same microhardness (P>0.05),but the flexuralstrength and modulus were significantly bigger in TMBPEA based resin.To conclude, TMBPEA could possibly be a promising alternative for dentalcomposite resins as the resin matrix with the advantages of lower shrinkage but bettermechanical properties.