Preparation And Property Of Epoxy/SiO₂ Dental Composite Resin Materials

Since 1960s, as a cosmetic restoration of composite resin materials, compositeresins, because of its simple, natural color fidelity, excellent physical and chemicalproperties, meet to doctors and patients in clinical dental cosmetic restorationrequirements greatly. Composite resin has gradually replaced the traditional dentalamalgam, and applied to fill after teeth, indirect veneers and crown bridge repair dueto its strong plasticity. Currently, composite resin has become a concerned researchareas of dental materials for the excellent performance of both inorganic particlesand resin matrix.Epoxy resin, an important polymer resin and the same as other polymers, hasgood mechanical properties and easy to cure and so on. E-type epoxy resinmolecular structure has the hydroxyl, ether group and very lively epoxy. Bothhydroxyl and ether have highly polarity, and make epoxy molecules haveintermolecular forces with adjacent to the interface, which will form chemical bondbetween epoxy and adjacent to the interface. Epoxy resin is a thermoplastic linearstructure polymer, and epoxy developed into three-dimensional network structureafter added curing agent, becoming a undissolved and unmelted thermosettingmaterials. E-44 epoxy resin is a heat cured resin, which is lack of curing slowly,resulting some difficult in clinical applications in dental composite. Spherical SiO₂nanoparticles, which have good biocompatibility and large surface area, are theaggregative trend because of the small sizes, large specific surface characteristics, sousually not easily dispersed and other shortcomings for the composite resin asinorganic fillers. In this paper, E-44 epoxy resin was compounded with nano-SiO₂,and heat curing resin E-44 was modified to achieve the E-44 light-cured. In addition,we deal with the surface of nano-SiO₂, geting better mechanical properties ofcomposite resins.The main results of this paper is as follows:First, selected epoxy resin E-44 and PMMA in various ratios, cured at 50℃and prepared epoxy/PMMA composited resin, the effect of the mechanical strengthand water absorption and solubility by PMMA content in composite resin were discussed. It showed that bending strength and modulus decreased with increasingPMMA content, water uptake was also significantly reduced. And selected theeasy-to-perfusion viscosity epoxy/PMMA = 80/20 (wt%) of the resin matrix phaseadded with different content of nano-SiO₂, using ultrasound to make nano-particlesuniformly dispersed SiO₂ matrix phase, the same, cured at 50℃and preparedepoxy/PMMA/SiO₂ thermal curing dental composite resin. SEM of composite resinstructure and surface morphology analysis showed that with 4% nano-SiO₂composite resin particles dispersed more evenly. X-ray diffraction analysis showedthat, diffraction peak of SiO₂ nanoparticles in composite were shifted to the smallangle than the pure nanoparticles, this may be due to SiO₂ spherical structure andchain structure of epoxy resin to form covalent bonds and hydrogen bonding. Themechanical properties of composite resin affected by different SiO₂ content, and theeffecet of water absorption and solubility were also disscussed. When the content ofnano-SiO₂ particles reach 4%, the flexural strength and flexural modulus reachedmaximum, while the water uptake sustain the value of 30-40μg/mm³ and solubilitywere less than 7.5μg/mm³ with the amount of nano-SiO₂, which are in line withinternational standards, the requirements of dental composite resin.Second, epoxy resin E-44, which was modified by the urethane acrylate, couldbe cured by ultraviolet light. The infrared spectra illustrate that the urethane acrylategrafted onto the epoxy resin E-44 successfully, so the modified E-44 achieved UVcuring. The reactive diluent TEGDMA and modified E-44 were mixed, then, added4% mass fraction of nano-SiO₂ and 0.05% of photoinitiator benzoin double ether inultrasonic and dark environment, so as to prepared epoxy resin/SiO₂ UV-curabledental composite materials under ultraviolet light. And using different test methodsof composite structure and properties of materials characterization, transmissionelectron microscopy (TEM) and scanning electron microscopy (SEM) analysisshowed good dispersion of nano SiO₂ to the resin matrix. In addition, the mechanicalstrength and hardness of composite resin were also tested and analyzed, The resultsshow that show that the composite resin has great flexural strength and flexuralmodulus, and the vickers hardness value reached VHN = 85.39. Third, the silane coupling agent KH-570 was chose to modify the surface ofSiO₂ particles and obtained grafted SiO₂ nanoparticles with KH-570. It wascharacterized by infrared spectra, which show that KH-570 was grafted onto thesurface of nano-SiO₂ particles successfully. The modified SiO₂ nanoparticles wereused to prepare the dental composite resin epoxy resin/modified nano-SiO₂ dentalcomposite materials, which were tested a series of characterization. The resultsshowed that the modified nano-SiO₂ particles as the filler combined with resinmatrix tightly, while the mechanical strength of composite resin has also beengreatly improved.