Preparation Of Nano-SiO₂ Microsphere、Fiber And Research Of Their Influence On The Properties Of Dental Resin

Composite resin system used in dental filling material have the advantages of the ability to match the color of natural tooth, excellent wear resistance, smooth finishing, ease of application, ease of manipulation compared with traditional dental restorative materials.However, the resin monomers cause volumetric shrinkage, the edge of micro-leakage and secondary caries. And they have poor hardness, mechanical properties compared with traditional dental restorative materials. These disadvantages have limited its clinical application. Therefore,it is essential for clinical practice to study the mechanical properties of dental resin. In many of the filling materials, SiO2 has good performance as reinforcing filler, and different morphology, structure and content of the SiO2 filler will affect the mechanical properties of the composite resin. Therefore, this paper focuses on the microsphere and fiber structure of SiO2 as dental resin fillers, the research and conclusions are as follows:Firstly, silica microspheres were prepared by sol-gel method, tetraethyl orthosilicate(TEOS) as silica source, ammonia(NH3.H2O) as catalyst, alcohol as solvent.Nano-silica(SiO2) was modified using γ-methacryloxypropyltrimethoxysilane(KH-570).Effect of different solvents、reaction temperatures and ways of adding TEOS on morphology and particle size were studied. Experimental results revealed that the uniformity, particle size of SiO2 varied with the solvent, the particle size of the microspheres became larger and its distribution became wider with the growth of the carbon chain of solvent, and the best solvent was ethanol. The microsphere size decreased with the increase of the hydrolysis temperature, the better hydrolysis temperatures were 30℃ and 60℃. Step method of adding TEOS was more conducive to prepare SiO2. Nano-silica was modified using silicane coupling agent KH-570, its average particle diameter decreased to 450 nm, and its heat resistance was improved.Secondly, sol-gel method was combined with electrospinning technique to prepare silica fiber under different voltages and receiving distances. Polyvinylpyrrolidone(PVP), TEOS,ethanol(CH3CH2OH), deionized water(H2O) were respectively used as template, silica source, solvent and catalytic agent. Scanning electron microscopy(SEM), X-ray diffraction(XRD), Energy dispersive X-Ray spectroscopy(EDS), FTIR spectra were used to characterize silica fibers. The results revealed that PVP template had been calcined fromsilica fiber; higher voltage and the longer receving distance contributed to better microscopy,uniform diameter, smooth surface of silica fiber, and the best electrospinning voltage was 25 kV,the receiving distance was 18 cm.Finally, the effects of different content of SiO2 microspheres and fiber on resin matrix were studied. The results revealed that the intensity of the composite resin was related with the amount of filler, and the mechanical properties had the tendency of increasing with the increase of SiO2 content. The properties of dental composite filled with SiO2 microspheres and fibers were better than filled with separate SiO2 microspheres or fibers. When the ratio of silica approached 45%, the mechanical properties reached maximum, the best performance of composite resin was SiO2 microspheres and fibers filler, flexural strength was 125.27 MPa, compression strength was 210.34 MPa, microhardness was 108.81 HV,conversion was 76.3%, volume shrinkage was 6.38%, and the reasons of this phenomenon were analyzed.