| Low shrinkage and high wear resistance are the goals of dental light-cured resin composite. For this purpose, using nanofillers, improving the interface bonding with resin matrix, and increasing volume fraction of nanofillers are important means to improve the performance of dental resin composite. The nanofillers were surface modified using a variety of techniques, which is current research frontier in the dental resin composite field both in theory and application.In this paper, based on the principle of interface compatibility, three novel nanofillers were designed and fabricated, then a variety of methods of analysis and testing were used to characterize the structure and properties of these nanofillers. The light-cured resin matrix was combined with these nanofillers respectively or together. The effects of additive amount and proportion of both nanofillers and microfillers on performances of dental resin composite were also evaluated. Meanwhile in order to overcome the shortcomings of traditional thermo-cured dental resin composite reinforced by continuous glass fiber, light-cured resin composites were fabricated and their performances were also characterized. The main innovation points of this paper were as follows:Via atomic transfer radical polymerization (ATRP), PMMA was grafted onto the surface of SiO2nanoparticles successfully. Products of each reaction stages were verified by FTIR, XPS and TGA. By changing the reaction parameters, such as reaction time and ratio of feeding, the grafting rate and average molecular weight of PMMA can be controlled. TEM and particle size analysis results showed that, when the reaction time of ATRP was7min, SiO2-PMMA in acetone could monodisperse evenly, without any agglomeration. Compared with the SiO2-KH570 (modified by traditional coupling agent), SiO2-PMMA dispersed better in the light-cured resin matrix. Even if the amount was up to15%, they still dispersed homogeneously while SiO2-KH570appeared obvious agglomerations with additive amount of5%. With the same additive amount, SiO2-PMMA and micron SiO2could synergistically enhance and toughen the resin composite more effective than SiO2-KH570. SiO2-PMMA and micron SiO2acted as if a continuous phase in the matrix and SiO2-PMMA evenly packed around the the micron SiO2fillers, filling the gaps between micro SiO2fillers; while SiO2-KH570agglomerated to form a "nanofiller phase", a clear boundary between them and micron SiO2were observed; Flexural modulus of dental resin composite reinforced synergistically by SiO2-PMMA and micron SiO2increased by31.5%than that of dental resin composite reinforced by SiO2-KH570and micron SiO2; the DMTA results showed that a better interface bonding between SiO2-PMMA and light-cured resin matrix were formed.Tested results of dental resin composite for the scale-up samples, reinforced synergistically by SiO2-PMMA and micron SiO2, were as follows:filler content≥75wt%; flexural strength≥117.4MPa; elastic modulus≥6.3GPa; volume shrinkage rate≤2.2%; biocompatibility in compliance with YY/T0268standards.Techniques combined coaxial electrospinning and frozen high-speed shearing was used to prepared chopped PAN-PMMA nanofibers; TEM results showed that the average diameter of shell and kernel layers were327±62nm and298±59nm respectively. Frozen high-speed technology has no effect on the retention of core-shell structure, after15min’s high-speed shearing, the average length of chopped PAN-PMMA nanofibers were12.8±1.1μm. Compared with the chopped PAN nanofibers, chopped PAN-PMMA core-shell nanofibers could uniformly dispersed in the light-cured resin matrix with additive amount of7.5%; while for the chopped PAN nanofibers with addtive of only2%, the phenomenon of pull-out appeared. With the same7.5%additive amount, the flexural strength, flexural modulus and fracture toughness of composite reinforced by chopped PAN-PMMA nanofibers increased by17.8%,13.9%and62.5%respectively, than those of pure resin matrix. However, flexural strength, flexural modulus and fracture toughness for chopped PAN nanofibers reinforced composite were lower than that of pure resin matrix; DMTA results showed that better interfacial adhesion between PAN-PMMA nanofiber and light cured resin matrix existed.The ladder-like polysiloxane were prepared through KH570hydrolysis and condensation method, FTIR and XRD results proved the existence of the trapezoidal structure; molecular weight of ladder-like polysiloxane can be controlled by controlling the reaction parameters such as hydrolysis time and temperature, when hydrolysis time were8h and12h, the average molecular weight of trapezoidal polysiloxane were14756Da and21673Da respectively. Two-dimensional electrspun PLGA nanofiber membrane had obvious grid structure, which was essential for the stability maintenance of the membrane during degradation process. So when the two-dimensional nanofibers membrane were chosed as reinforced fillers for dental composite, grid membrane was a better choice than both non-woven membrane and parallel membrane.Equipment was designed and developed for production of prepreg composed of continuous glass fiber and light-cured resin matrix. The scale-up samples have entered clinical trials. Surface treatment of continuous glass fiber with PMMA solution in acetone, could improve interfacial bonding with light-cured resin matrix. After glass fibers were treated by5%PMMA solution in acetone, flexural strength of the composite (546.3MPa) increased29.6%and flexural modulus (9.1GPa) increased30%. When the volume content of glass fibers was increased from51.7%to61.7%, flexural modulus, fracture toughness and the maximum loading capacity were increased by27%,34%and15%respectively.Performances of scale-up samples of light-cured prepreg reinforced by continuous glass fibers were tested and results were as follows: flexural strength≥646.1MPa, elastic modulus≥24.8GPa, interfacial bond strength≥29.2MPa and biocompatibility in compliance with YY/T0268standards. |
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