Analysis Hydrolysis Degradation Components Of Resin Monomers Used Commonly In Dental Materials

With the development of the resin matrix, inorganic fillers and initiator system, resin-based dental materials have been widely used in dentistry. However. due to incompletely polymerization of materials, the residual monomers were wound into the polymer. Under the influence of water and enzyme in the oral environment, degradation of the resin matrix can happen because of the breakage of covalent bonds. Degradation products and residual monomers not only can elute into the surrounding, but also lead to certain potential hazards for the patients.The resin matrix, as an important part of resin-based dental composites, play a major part in the mechanical properties of materials. The structural integrity of the polymer has changed owing to elution and degradation of residual monomers and result in the failure of repair. As present, the main methods of qualitative and quantitative analysis and identification of chemical structure of degradation products are chromatography/mass spectrometry. So. in the experiment, qualitative analysis of Bis-GMA and TEGDMA was accomplished by using HPLC and MS and identifiantion of chemical structure of degradation products by using HPLC-MS. The experiment; provided the theoretical basis and some experimental data to the identification of chemical structure of degradation product.Objectives:To analysis the elution of residual monomers and identify of chemical structure of hydrolysis degradation components of monomers after the neat matrix resins aged in deionized water. Methods:First, Samples preparation of the neat matrix resins according to the3:1wt: wt ratio of Bis-GMA:TEGDMA=3:1(wt%) and0.6wt%CQ and1.2wt%DMAEMA. Before curing,0.7ml neat resin matrix paste was taken about onto the surface of potassium bromide salt and recorded infrared spectrum; after curing,1.5mg-2.0mg power of grinded the neat matrix resins were mixed with potassium bromide power, compressing to the shape of slice and recorded infrared spectrum. The functional groups of benzene (1607cm-1) was selected as the reference and conducted quantitative analysis the change relative concentrations of C=C double (1640cm-1) before and after curing. The data was processed by Origin7.5and calculated the degree of conversion according to the formula. Secondly, after resins discs were immersed in deionized water and aged for24h at37℃, aging liquid was removed according to predefine point-in-times:1h,3h,6h and24h and used ethyl acetate extraction, spin evaporate, finally confirmed hydrolysis degradation products of the neat matrix resins by the high performance liquid (HPLC)/mass spectrometry (MS).Results: The conversion degree of the neat matrix resins is60.1±3.8%. The result was measured using HPLC and MS that Bis-GMA and TEGDMA of the residual monomers were released from the polymer into deionized water. The ester bonds of Bis-GMA were hydrolyzed to form Bis-GMA-2MA and Bis-GMA-2MA and TEGDMA to form TEGDMA-MA and TEGDMA-2MA. Conclutions:After the neat matrix resins composite aged for24h in37℃constant temperature of deionized water, the ester bonds of resin monomers were broken and the degradation products and residual monomers were released into the surrounding environment.