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In this study, we examined the effect of the transmitted amount of visible light through a resin composite on the curing depth and polymerization conversion. Transmitted amount of visible light was strongly dependent on the magnitude of refractive index difference that existed between the resin and silica filler. More specifically, the differences arose from the type of base monomer used. The transmitted amount of visible light exhibited a good correlation with the curing depth and Knoop hardness ratio of the bottom surface against the top surface of the resin composite. To improve the polymerization conversion of the cavity floor, it is important to reduce the refractive index difference that exists between the base resin and silica filler.

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Water is required to ionize acid resin monomers for demineralization of tooth substrates. We tested the null hypothesis that altering the water concentration in two-step self-etching primers has no effect on their aggressiveness and bonding efficacy to dentin. Five experimental self-etching primers were prepared with resin-water-ethanol volume ratios of 9-0-1, 8-1-1, 7-2-1, 5-4-1, and 3-6-1. They were applied to smear-layer-covered dentin, followed by a bonding resin and composite build-ups for microtensile bond testing and TEM examination of tracer penetration. Increasing water concentration from 0-60 vol% improved acidic monomer ionization that was manifested as increasing hybrid layer thickness. However, significantly higher bond strength was observed in the 7-2-1 group, with minimal nanoleakage in the corresponding hybrid layer. When self-etching primers are formulated, a balance must be achieved to provide sufficient water for adequate ionization of the acidic monomers, without lowering the resin concentration too much, to optimize their bonding efficacy to dentin.

This study evaluated the different amounts of 3-methacryloxypropyltrimethoxysilane (MPS) coated alumina fi ller particles on fl exural strength and wear resistance of alumina reinforced polymethyl methacrylate (PMMA) denture base. Ten mass% of alumina fi ller silanized with 0, 0.1, 0.2, or 0.4 mass% of MPS was blended with PMMA. PMMA without alumina particles served as control. Specimens were prepared for fl exural strength and wear resistance tests (n=10). Flexural strength was determined using a 3-point bending test and volume loss was measured by in-vitro 2-body wear-testing. The results were analyzed by One-way ANOVA and Tamhane's test (α=0.05). Flexural strength ranged from 95.1-117.8 MPa, while volume loss ranged from 0.038-0.160 mm 3 . Statistical analysis indicated the 0.1 mass% MPS silanized group had signifi cantly higher fl exural strength and lower volume loss than the control group. Adding alumina fi ller silanized with 0.1 mass% MPS resulted in an improvement of the fl exural strength and wear resistance of PMMA.

synopsisThe mechanisms of hydrolysis and condensation of a silane coupling agent, y-methacryloxypropyltrimetoxysilane (y-MpTs) were investigated by the me of both 13C and ?3i nuclear magnetic resonance ( N m ) spectroscopies. The NMR peaks of the hydrolyzed monomer and condensed polymer were asaigned readily. The rate of hydrolysis and condensation of y-MPTS was dependent on water content. On the basis of the time-dependent behavior of these peaks, the mechamam . of hydrolysis and condensation were clear.

Multi-purpose bonding performance of three kinds of newly synthesized phosphonic acid monomers was investigated. Methacryloxyalkyl or acryloxyalkyl phosphonoacetates of 6-MHPA, 6-AHPA, 10-MDPA were synthesized in 42.8-51.9％ yields with a light yellow viscous liquid, and identified as new compounds by 1 H NMR, IR, and elemental analysis. Conventional adhesive monomers, namely VBPA, 4-META, and 4-AETA, and CEBA-p-TSMo-t-BPMA initiator were also used. Seven experimental composite-type adhesive resins comprising these six kinds of adhesive monomers and None (control) with the initiator were prepared. Tensile bond strengths of adhesive resins to unetched ground enamel and dentin, ground porcelain, and sandblasted Ni-Cr alloy were measured at a crosshead speed of 1.0 mm/min. Results showed that except with VBPA, there were no significant differences among 6-MHPA, 6-AHPA, 10-MDPA, 4-AETA, and 4-META in bonding performance to the adherends (p<0.01). It was found that the new phosphonic acid monomers provided good multipurpose adhesion to all adherends tested.

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