Study On Water Absorption, Solubility And Monomer Release Of Six Kinds Of Light-curing Composite Resins

Due to its excellent physical and chemical properties,aesthetic effects of simulation,and ease of operation,light-curing composite resins are widely used in the field of stomatology.The widely used resin matrix system is a methacrylate matrix system.The commonly used matrix monomers are bisphenol A diglycidyl methacrylate（Bis-GMA）,triethylene glycol dimethacrylate（TEGDMA）,urethane dimethacrylate（UDMA）.After long-term exposure to saliva,water,and food in the oral cavity,the composite resins undergo water absorption,dissolution,and monomer release.When the composite resin is polymerized,some of the monomers still fail to polymerize and become residual monomers.Residual monomers can be released under saliva immersion,and the polymerized resin components can also degrade under the action of oral saliva,food microorganisms,enzymes and chewing abrasion.Bis-GMA is softer and easily penetrated by water or other solvents,which allowing the polymer network to swell,eventually resulting in the long term release of residual monomers.Certain substances released by the composite resins can cause oral mucosal allergic diseases,and are also cytotoxic,genetically toxic,or can damage the reproductive system.Long-term degradation of the material and monomer release will reduce the physical and chemical properties of the resin,and ultimately affect the clinical repair effect.In this experiment,the water absorption value,solubility value,degree of conversion and monomer release amount of several commonly used light-curing composite resins in clinic were measured,the influencing factors were discussed,and the relationship between the light-curing composite resins and the composition of the material and the immersing solvent was clarified.The water absorption and solubility values of six kinds of composite resins,including Filtek^TM Z250（Z250）,Filtek^TM Z350 XT（Z350）,Aelite LS Posterior（ALS）,CLEARFIL MAJESTY Posterior（CMP）,Neofil Nano（NN）,and Tetric N-Ceram（TNC）,were measured after immersing in water and 75%ethanol/water solution.Fourier transform infrared spectrometer was used to test the degree of conversion.The concentrations of eluted Bis-GMA and TEGDMA were tested by high performance liquid chromatography/mass spectrometry afterthe specimens were immersed in 75%ethanol/water solution for different time（24h,7 d,1 month,and 3 months）.Experimental results showed that the water absorption values of six kinds of composite resins were in ascending order of ALS<CMP<TNC≈Z250<NN<Z350（P<0.05）,and the solubility values were Z350<NN≈ALS≈CMP≈Z250<TNC（P<0.05）when immersed in water.When immersed in 75%ethanol solution,the water absorption and solubility values of the resins were higher than those of resins soaked in water.The water absorption values were as follows:ALS≈CMP<Z250<NN<TNC≈Z350（P<0.05）,and the solubility values from small to large are Z250<CMP≈Z350<TNC≈ALS≈NN（P<0.05）.The degree of conversion from small to large is NN<Z250<Z350<TNC<ALS≈CMP.The release amounts of Bis-GMA were increased slowly with the prolongation of time（P<0.05）,while the values of ALS and CMP at 3 months were decreased（P<0.05）;the descending order of Bis-GMA release amounts at 3 months was NN>TNC>Z250>Z350>ALS>CMP（P<0.05）.The released TEGDMA was not found in NN and TNC.The release amounts of TEGDMA of the other four resins were increased slowly with the prolongation of time（P<0.05）,and the release amount of CMP at 3months was decreased（P<0.05）;the order of amount at 3 months was ALS>CMP>Z250>Z350（P<0.05）.The results revealed that the water absorption values,solubility values,degree of conversion and monomer release amounts of different composite resins are different,and they are related to their organic matrix compositions and the immersing solvent.