Down's syndrome is a chromosome abnormality that occurs with high frequency. Recently, the average life expectancy of these patients is increasing because of advances in nursing care for handicapped people. Therefore, the necessity to consider the cytotoxicity levels of dental materials for the Down's syndrome patient will increase. It is possible that the toxicity of various dental materials to Down's syndrome cells differs from that to normal human cells, but there is no basis for determining the appropriate materials for these patients. Therefore, the cytotoxicity levels of root canal filling materials, pulp capping agents, and root canal remedial agents were compared between fibroblast-like Down's syndrome cells (Detroit 539) and normal human cells (HUG-F) - Cell viability was measured by the standard monolayer culture and three-dimensional culture with a Type 1 collagen gel matrix. As a result, the Detroit 539 cell line showed a weak cytotoxic response to most materials compared with that shown by the HUG-F cell line, and the difference in the cell proliferation degree for both cells was considered. Both IC₅₀ (50% inhibiting concentration) of the standard monolayer culture method and the cell viability on three dimensional culture showed a remarkable correlation between the two cell lines. Therefore, the utility of cytotoxicity testing using the Detroit 539 cell line is suggested.

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To improve the water resistance of the polysiloxane layer at the silica/resin interface, a mixture of 3-methacryloyloxypropyltrimethoxysilane (3-MPS) and novel silane coupling agent (MAnbF, n=5, 7, 9, 11) with a hydrophobic fluoroalkyl and a methacryloyl group, such as 3- { [1' - (perfluoro-5-methylhexyl) methyl-2' - (methacryloyloxy)] ethoxy} propyltrimethoxysilane (MA 7 bF) were used. The concentration of each silane solution was adjusted with ethanol at 2 mass%, at various weight ratios of MAnbF 10, 20, 30, 50, 70, or 100% to 3-MPS. The tensile bond strength of the resin composites and the contact angles of a resin monomer mixture (50% Bis-GMA, 50% TEGDMA) to glass plates modified with each silane were measured. MA 5 bF formed a coupling layer with high bond strength and water resistance at the silica/ resin interface at all concentrations studied and MA 7 bF, MA 9 bF and MA 11 bF formed these at concentrations within 10〜30%.

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This study investigated the material design for controlling the orthodontic force of fiber-reinforced plastic (FRP) wires consisting of CaO-P₂O₅-SiO₂-Al₂O₃ (CPSA) glass fibers and poly-methyl-methacrylate matrix. The dependence of elastic modulus and orthodontic force on the diameter of FRP wires and the diameter or volume fraction of CPSA glass fibers were measured by a three-point flexural test. The changes in elastic properties, moreover, were examined for immersion in artificial saliva for 30 days. The results revealed that the FRP wire possessing the required orthodontic force (P) could be obtained from the relation of P 8.6×10¹¹D⁴ (0.68 V_f+3.14), where D=diameter of FRP wires, V_f=volume fraction of CPSA glass fibers in FRP wires.

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To prevent casting defects such as small nodules caused by air bubbles, a gypsum-bonded cristobalite investment material incorporating the surfactant agent becomes available on the market. The present study investigated the contact angle and sticking behavior to paraffin wax plates and the fluidity of this investment material and compared those characteristics to other gypsum-bonded cristobalite investment materials. The material containing the surfactant demonstrated lower contact angle and improved sticking behavior to the paraffin wax plate when compared to those of other conventional materials however, there were no remarkable differences in fluidity among the materials tested. The results suggested that, using the investment material containing the surfactant agent, an intimate contact of the investment mixture with the wax pattern could be obtained without applying the wetting agent on the pattern.

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First, methods of accessing to ISO International Standards developed by ISO/TC 106 and obtaining the information on ISO Standards development and Technical Committee ISO/TC 106, Dentistry, over the Internet are explained. Secondly, recent information is given regarding those ISO Standards, such as the development of “horizontal” standards, the revised standard for composite resin, the revised standard for elastomeric impression materials, preventive measures against infectious diseases and revision of the standard for dental vocabulary.

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