To estimate the biocompatibility of polyacrylic acid as a dental material, the cytotoxicity and induction of inflammatory cytokines production, such as interleukin-1α and β, interleukin-6 and tumor necrosis factor α, by polyacrylic acids in human pulp fibroblasts were studied. Polyacrylic acids at concentrations below 0.1mass% did not influence human pulp fibroblasts cell growth. At concentrations at 0.2mass%, the cytotoxicity of polyacrylic acids clearly increased with increasing amounts of polyacrylic acid. When human pulp fibroblasts were treated by 0.1mass% polyacrylic acid, an increase in interleukin-6 was detected.

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We inverstigated the effects of immersion disinfection of both hydrophobic and hydrophilic vinyl silicone impressions on the reproducibility of stone models. Impressions were immersed in 2% glutaraldehyde solution for 30 minutes or 24 hours, and 1% sodium hypochlorite solution for 15 minutes or 24 hours. Hydrophobic vinyl silicone impressions were not affected on the reproducibility of stone models by immersion disinfection, and proved stable in long-term immersion disinfection. However, immersion disinfection of hydrophilic vinyl silicone impressions caused dimensional changes in the stone models. Those changes varied depending on the kind of disinfectant and duration of immersion time. Therefore, it was indicated that attention should be paid during the immersion disinfection of hydrophilic vinyl silicone impressions.

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Methacrylate bearing a spiro orthocarbonate (CMA) was synthesized and the polymerization heat of the mixtures with ethyleneglycol dimethacrylate (1G) during heat- and photopolymerizations was measured using a differential scanning calorimeter (DSC). 1) The polymers consist of CMA and 1G obtained by both heat- and photo-polymerizations with BPO, AIBN and CQ/t-amine. 2) CMA/1G comonomer has a greater photo-reactivity to visible light and on the photo-polymerization, the mixture of CMA/1G with CQ/amine showed a higher polymerization heat than that in a heat-polymerization at 70℃. 3) CMA promotes a polymerization of the mixture with 1G under heat curing.

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To develop an acrylic resin with reduced residual monomer, the effects of monomer and polymer components in resins on residual monomer were examined using methyl methacrylate (MMA) and ethyl methacrylate (EMA) monomers and fluoropolymer, homopolymers of MMA and EMA as well as their copolymer. Residual monomer in MMA-based light-curing type resin decreased with the increase in the amount of fluoropolymer added. This was supposed to be correlated with lower glass transition temperature or lower molecular weight of the polymer formed by polymerization of MMA during curing. The use of EMA instead of the usual MMA monomer resulted in significant decrease in residual monomer and improved the handling property. A resin composed of EMA and mixture of homopolymer of MMA and EMA appears worth further evaluation as a relining material or denture base material with improved safety and handling property.

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Bending test and fracture toughness test of nine commercial composite resins were performed in water at 5〜55℃ to evaluate the effect of temperature when testing the mechanical properties of composite resins. Proportional limit, bending strength, and elastic modulus at bending test decreased with increases in testing temperature. However, plastic deformation during bending test increased with increases in testing temperature. The value of fracture toughness showed a high peak at 25〜37℃, then decreased at 55℃. In addition, the critical energy release rate increased significantly with the increase in temperature. These results indicated the testing temperature influenced fracture behavior of composites and the brittle manner of composites at a low temperature influenced fracture significantly more than elastic manner at high temperature.

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Compatibility between impression materials (agar and alginate) and model stones (dental and high strength dental) used for the combined agar-alginate technique was investigated, measuring detail reproduction and surface roughness of dental stone models made by each combination. Our experimental results were as follows: In combination with agar and model stones, 4 of 24 sets of dental stones and nothing of 30 sets of high strength dental stones were evaluated as the best rank of both detail reproductions and surface roughness. On the other hand, in the case of alginate and model stones, it was given to 10 of 20 sets of dental stones and 2 of 25 sets of high strength dental stones. Accordingly, the compatibility between dental stones and both impression materials was better than of high strength dental stones, and the combination of alginate with model stones showed a preferable compatibility.

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This study evaluated the cytotoxicity of QTX using fibroblasts derived from human dental pulp. The materials used in this study were QTX, CQ, DMAEMA, LB primer, and 3% QTX contained LB primer. Cytotoxicity assessed with MTT assay and observation of cellular form. DMAEMA showed less cytotoxicity than QTX or CQ. The cell viability of specimens treated with QTX was no less than that of those treated with CQ, and LB primer with QTX showed cytotoxicity level similar to that of the LB primer without QTX. The ratio of spherical cells in CQ was almost same as that of those in QTX. These results support the safety of adding QTX to dentin primers or bonding agents.

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