The Japanese Society for Dental Materials and Devices(JSDMD)has started to provide Internet access to the database of literature on dental materials and devices(DENTMATE). The DENTMATE has been developed by the JSDMD with the cooperation of the members from 1986. For this new project, the retrieval system by Japanese Web database was constructed on the Internet, and is available free through our homepage site. This paper describes the guide to the retrieval system on the Japanese Web site. This retrieval system on the Web allows many users to obtain important biographical information on dental materials and devices.

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To improve the water resistance of polysiloxane at the silica-resin interface, a mixture of 3-methacryloyloxypropyltrimethoxysilane(3-MPS)and 1H, 1H, 2H, 2H-nonafluorohexyl-trimethoxysilane(4F)was used. The concentration of each silane solution was adjusted with ethanol at 2 mass%, at the ratio of 4F/3-MPS=1/4. A resin composite was adhered to the modified glass plate, and stored in deionized water up to 720 days or subjected to thermal stress for 10, 000 cycles. The tensile bond strength of the composite to the glass plate treated with 4F/3-MPS showed no significant change after immersion in water or the thermal cycling. The contact angles of resin monomer, a mixture of 50% Bis-GMA and 50% TEGDMA, to the glass plate treated with 4F/3-MPS were significantly lower than with 3-MPS alone. Therefore, the silane mixture of 3-MPS and hydrophobic 4F formed a coupling layer with a high bond strength and high water resistance ability at the silica-resin interface.

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We evaluated the surface roughness of dental stone models immersed in disinfectant solutions with 2% glutaraldehyde and 0.1% sodium hypochlorite containing 1〜5% sodium chloride, aluminum sulfate, potassium chloride and citric acid for the purpose of decreasing their surface roughness. The surface roughness(Ra₇₅)of specimens was measured after one hour immersion in disinfectant solutions. Test results indicated the following:While the surface roughness of dental stone models immersed in 2% glutaraldehyde and 0.1% sodium hypochlorite containing 1〜5% aluminum sulfate decreased, those containing sodium chloride, potassium chloride and citric acid increased. Accordingly, it is appropriate to use sulfates as additives in 2% glutaraldehyde and 0.1% sodium hypochlorite to decrease the surface roughness of dental stone models.

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To improve the bond strength and durability against hydrolysis of the silica-resin interface, a novel silane coupling agent containing a hydrophobic fluoroalkyl chain and a methacryloyl group such as 3-[(2'-methacryloyloxy)-1'-(1H, 1H-(4-trifluoromethyl)octafluoropentyl)ethoxy]propyltrimethoxysilane(MA5bF)and 3-[(2'-methacryloyloxy)-1'-(1H, 1H-(8-trifluoromethyl)hexadecafluorononyl)ethoxy]propyltrimethoxysilane(MA9bF)was synthesized. The tensile bond strength of the resin composite and the contact angles of a resin monomer mixture(50%Bis-GMA, 50%TEGDMA)to glass plates modified with MA5bF and MA9bF were investigated, and compared with those modified with 3-methacryloyloxypro-pyltrimethoxysilane(3-MPS)and the silane mixture of 1H, 1H, 2H, 2H-nonafluorohexyltri-methoxysilane(4F)/3-MPS. The tensile bond strength of the resin composite to the glass plate treated with MA5bF was nearly equivalent to that of 3-MPS. On the other hand, the strength of MA9bF was extremely low because there was no affinity to the glass plates. The contact angles of the resin monomer to the glass plates treated with the 4F/3-MPS and MA5bF were significantly low compared with that of 3-MPS, but that of MA9bF was significantly higher.

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The purpose of this study was to investigate the action of bisphenol A(BPA), which was suspected of an endocrine disruptor, in dental resins. The composition of four polyacid modified resin composites(compomers)and four resin composites, and the elution of BPA from their cured materials to acetonitrile and distilled water were examined using HPLC. No Bis-DMA monomer was found in any product. In the acetonitrile extraction of the samples cured for 3 days, BPA was detected in the eluted components of two resin composites containing Bis-GMA monomer, in 151 and 178 ng/g of composite. However, BPA was not detected for one compomer and one composite containing Bis-MPEPP monomer or the three compomers and one composite that did not contain Bis-GMA or Bis-MPEPP monomers. In the distilled water extraction of the samples cured for 3 days, BPA was not detected in any product due to the markedly small elution of BPA.

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Experimental magnetically attractive composite resins for denture attachment were fabricated. A spherical SUS446 stainless steel powder under 20 μm in size was used as a filler. The filler was treated with various concentrations of silane(γMPTS). The effects of the silane treatment were evaluated by measuring the flexural strength of the composites. The optimum concentration of γMPTS was 1.2〜2.0g per 100g filler. However, the flexural strength was still under 70 MPa, and the amount of eluted metals from the composite was over 20 μg/cm² after 7 days immersion in 1% lactic acid solution. When the filler was rinsed in HCl solution before silane treatment, the flexural strength of the composite increased over 70 MPa and the amount of eluted metals was significantly reduced to below 1 μg/cm². The attraction force to a magnet of the composite was about 40% those of the commercially available keeper.

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A method for calculating the stress distribution in the periodontal ligament under various orthodontic conditions was presented using the stiffness matrix proposed in our previous paper. In this method, the tooth-bracket element was used as an element of a finite element method. Considering the deformation of orthodontic wire and the tooth movement, the orthodontic forces and the reaction forces were calculated. The calculating method was shown for a case where the lower canine, the lower first premolar and the lower second premolar were used as anchorage and the lower second molar produced a tipping movement. By an elastic spring with a helical loop, the second molar was subjected to a moment and an elongation force and tipped in the distal direction. As the connection between the anchorage teeth was stiff, the distributed forces to the anchorage teeth became uniform. These results were reasonable mechanically the reaction force and the stress distribution in periodontal ligament could be calculated by the proposed method.

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A fatigue test was carried out on heat-treated dental Ag-Pd-Cu-Au(12mass%Au)alloys in air. The effect of microstructure on fatigue characteristics was investigated. In the water quenched alloys, the fatigue strength increased with increasing solutionizing temperature in the low-cycle fatigue region. While the fatigue strength decreased with increasing solutionizing temperature in the high-cycle fatigue region. In aged alloys, the fatigue strength increased due to precipitation strengthening caused by the precipitation of the β phase in the low-cycle fatigue region, while the fatigue strength markedly decreased due to the precipitated β phase, which led to a fracture site in the high-cycle fatigue regions. The fatigue strength of the alloy with a large volume fraction of the α₁ phase was excellent due to the work hardening of α₁ phase in the high-cycle fatigue region. However, the volume fraction of the β phase should be taken into account in order to improve the absolute value of fatigue strength.

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The purpose of this study was to evaluate the contribution of the new bracket design to the clinical application of esthetic fiber reinforced plastic orthodontic wires(FRP wire). Then, R 0 type only with an extended slot base and R 05, R 1 and R 2 with curvature, 0.5, 1.0 and 2.0 mm radius respectively, at the base were examined for the ability to avoid the shear force exerted by ligatures. The results of the cantilever breaking test showed that the limit of deflection of the FRP wire improved and that the larger radius was more effective. In the cantilever hysteresis test, FRP wires showed adequate elastic recovery, especially in the test with wires immersed in water. It was also clarified from ligated bending test that good elastic recovery and high load-retention could be obtained. From the results of this study, we suggest that the improved brackets would be useful in the clinical application of our FRP wires.

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