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The purpose of this investigation was to examine the effect of filler particle size and shape as well as filler content on light transmittance characteristics and color of experimental composite resins. A mixture of 30 mol％ Bis-GMA and 70 mol％ TEGDMA was prepared as a base monomer and to which a photoinitiator (camphorquinone) and a co-initiator (N,Ndimethylaminoethyl methacrylate) were added. Four different irregular-and spherical-shaped filler types with an average particle size of 1.9-11.1 μm were added to the mixture in three different filler contents of 20, 30, and 40 vol％. Light transmittance characteristics including light diffusion characteristics of the materials were evaluated. Color values and color differences among filler contents of the materials were also determined. Materials containing smaller and irregular-shaped fillers showed higher light transmittance and diffusion angle distribution with a sharper peak, as compared with those containing larger and spherical-shape fillers. It was also found that there was a significant correlation between the specific surface area of fillers and the color difference of the materials containing the fillers.Our results indicated that the shape of filler particles, as well as particle size and filler content, significantly affected the light transmittance characteristics-including light diffusion characteristics-and color of composite resins.

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The purpose of this study was to investigate effects of various visible light photoinitiators on the polymerization efficiency and color of the light-activated resins. Four photoinitiators, including camphorquinone, phenylpropanedione, monoacrylphosphine oxide (TPO), and bisacrylphosphine oxide (Ir819), were used. Each photoinitiator was dissolved in a Bis-GMA and TEGDMA monomer mixture. Materials were polymerized using dental quartz-tungsten halogen lamp (QTH), plasma-ark lamp and blue LED light-curing units, and a custom-made violet LED light unit. The degree of monomer conversion and CIE L*a*b* color values of the resins were measured using a FTIR and spectral transmittance meter. The degree of monomer conversions of TPO-and Ir819-containing resins polymerized with the violet-LED unit were higher than camphorquinone-containing resin polymerized with the QTH light-curing unit. The lowest color values were observed for the TPO-containing resin.Our results indicate that the TPO photoinitiator and the violet-LED light unit may provide a useful and improved photopolymerization system for dental light-activated resins.

No abstract

The polymethylmethacrylate (PMMA) resins containing c-methacryloxypropyltrimethoxysilane (c-MPS) of 0, 2, 4, 6, 10, 15, 20 and 30 mo1%, added to methylmethacrylate, were prepared using a monomer-polymer technique and stored in air or water at 37 % 0AE5°C for 28 days. The flexural strength and flexural modulus of the PMMA resins containing c-MPS of 20 and 30 mo1% were significantly smaller than those containing 2-6 mo1% and the same statements were true for the adhesive strength to porcelain tooth. However, its value of adhesive strength to Co-Cr alloy was remarkably less than to porcelain tooth. By contrast, there was no significant difference among the Knoop hardness of the PMMA resins examined. On the other hand, the thermal expansion had an increasing tendency with an increase of a c-MPS content. The dynamic shear modulus within a temperature measured (20-140°C) decreased s1ightly as the c-MPS content of the PMMA resins increased, and the peak temperature of mechanical loss tangent also tended to decrease. These results indicated that the PMMA resin containing c-MPS of 6 mol% was the best composition from the standpoint of an excellent adhesive strength against porcelain, although its water absorption was 1AE9 times that of PMMA.

The bactericidal efficacy of 1.00-4.50% glycine-type amphoteric surfactant (Gly) was evaluated by measuring its microorganism removal rate in denture plaque. Physical and mechanical properties such as surface roughness, color difference, and bending strength of two different denture base resins were determined before and after cleaning in Gly solutions, a commercial denture cleaner, and tap water. The microorganism removal rates of all the Gly solutions were higher than those of a commercial enzymatic denture cleaner (Polident) (p>0.05). The removal rate of Candida spp. by Polident was not significantly different from the removal rate using water. Changes in the surface roughness and color difference among the specimens were slight. There were no significant differences in the bending strengths of the two resins for all concentrations of Gly solution (p>0.05). These results suggested that glycine-type amphoteric surfactant solution may be effective as a denture cleaner in conjunction with an ultrasonic cleaning device.

Because viscosity of gel moisturizers increases as weight decreases, selecting gel moisturizers with a minimal change in weight and viscosity would be preferable in the case of a long-time application and severe dry mouth.