To improve the bond strength and durability against hydrolysis of the silica-resin interface, novel silane coupling agents containing a hydrophobic phenyl group such as 3-(n-methacryloyloxyphenyl) propyltrimethoxysilane (n=2, 4 ; o-MBS, p-MBS) and 3-(3-methoxy-4-methacryloyloxyphenyl) propyltrimethoxysilane (M-p-MBS) were synthesized. The tensile bond strength of the composite resin, and the contact angles of a monomer mixture (50%Bis-GMA, 50%TEGDMA) to glass plates modified with o-MBS, p-MBS and M-p-MBS, were investigated, and compared with those modified with 3-methacryloyloxypropyltrimethoxysilane (3-MPS). The tensile bond strength of the composite resin to the glass plate treated with p-MBS and M-p-MBS was nearly equivalent to that of 3-MPS, and was not significantly decreased by water immersion for 1 year or thermal stress. On the other hand, the strength of o-MBS was extremely low due to lack of affinity to the glass plates. The contact angles of the monomer to the glass plates treated with the p-MBS and M-p-MBS were significantly low compared with that of 3-MPS, but that of o-MBS was significantly high. From these results, p-MBS and M-p-MBS formed a coupling layer with bond strength and water resistance ability at the silica/resin interface.

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In this study, material evaluations of porcelain for pure titanium [Duceratin (DU) and Titanium porcelain (TP) ] and the conventional porcelain for gold alloy [Vintage halo (VH)] were made on the basis of lifetime predicted, using the SPT (Strength-probability-time) diagram drawn from the results of the dynamic fatigue test, in which the biaxial tensile strength and the time to fail at the three cross-head speeds were measured by the ring on ring test in distilled water at room temperature. Weibull modulus m of the porcelain for pure titanium was smaller compared to conventional porcelain. In particular, m of DU dropped markedly with a decrease in cross head speed. The fatigue parameters n calculated from the dynamic fatigue test were 13.2±0.2 in DU, 20.4±0.1 in TP and 29.9±0.4 in VH. From the SPT diagram drawn from n, the biaxial tensile strength and the time to fail, the static stresses which would assure 10 years durability with a survival probability of more than 90% were estimated to be less than 2.6MPa in DU, 4.2MPa in TP and 8.4MPa in VH. These results suggested that the fatigue resistance of porcelain for pure titanium was inferior to the traditional-model porcelain for gold alloy, and therefore, the fatigue factors must be considered in clinical use.

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The study examined the effect of thermal degradation on the mechanical strengths of resin composite materials for core build-up. Six different resin composites for core build-up were tested. The specimens were immersed in deionized water at 37℃ for 28 days (Control) or were subjected to continuous water flow at 90℃ for 28 days in the Soxhlet extraction apparatus to accelerate degradation (Td). Flexural strength and compressive strength of the specimens were determined. Significant (p<0.05) decreases in flexural strength values were found in chemical- and light-cured materials after Td ; however dual-cured materials did not show significant decrease in flexural strength. There were no significant differences in the compressive strength values among all materials tested after Td (p>0.05). Flexural strength of resin composites for core build-up, excluding dual-cured materials, was notability influenced by thermal degradation using hot water immersion.

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This study examined the effect of hot water immersion on the mechanical properties of fluoride-releasing restorative materials. Three different polyacid modified resin composites (PMRC) [Dyract AP, Reactmer, and Xeno CF] and two different light-cured glass-ionomers [Fuji II LC EM (LC) and Vitremer (VT)] were examined. The specimens were immersed in deionized water at 37℃ for 28-days or were subjected to continuous hot water (90℃) flow for 28-days in the Soxhlet extraction apparatus to accelerate degradation. The diametral tensile strength of each specimen was determined. Thermal degradation by continuous hot water flow for 28-days did not significantly reduce the strength of PMRC or VT. There was a significant decrease in the strength of LC by thermal degradation. The structural integrity of all fluoride-releasing restorative materials was deteriorated due to thermal degradation by a continuous hot water flow over 28-days. However, this structural deterioration did not notably reduce the diametral tensile strength of the materials except for LC.

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In this study, we examined the electrochemical corrosion behavior and dissolution test of gold alloy (PGA), silver-palladium-copper-gold alloy (S12), cobalt-chromium alloy (CoCr) and commercially pure titanium (TI) in various gargle solutions. The results indicated that all alloys had excellent corrosion resistance in Listerin®, Neosterin green®, and ConCool F solutions. In Isojin® solution, PGA and S12 were corroded by iodine, and dissolution of metals and deposition of corrosion products occurred. In fluoride-containing saline solution, TI was corroded by fluoride. In conclusion, we found that the corrosion resistance of PGA and S12 decreased in iodine, and that of TI decreased in fluoride.

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In the present study, the formation of calcium phosphate crystals was investigated in order to apply the thin film produced by the molecular precursor method as dental implant material. After the application of the precursor solution firing at 600℃ formed a crystalline carbonate-containing hydroxyapatite film on the titanium substrate. The greater amount of formation of calcium phosphate crystals was observed on the titanium coated with carbonate-containing hydroxyapatite thin film compared with non-coated titanium after 1 day immersion in Hanks' balanced salt solution. After 7 days and 14 days immersion, the phosphate was carbonate-containing hydroxyapatite, which was aligned in C axis in thin film X-ray diffraction and Fourier transform infrared spectrum. In conclusion, it is expected that the carbonate-containing hydroxyapatite thin film, produced by molecular precursor methods, will have excellent bone compatibility.

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The Japanese Society for Dental Materials and Devices (JSDMD) has constructed a database of literature on dental materials and devices since 1986. Additionally, from 2000 a retrieval system using freely-accessible Web database has been published on the Internet. In this paper, the current status of the database is reported, and the access log of the Web database is analyzed. It now includes over 9,100 citations for 54 Japanese journals and over 18,000 citations for 68 European journals. For the Japanese and English Web pages there have been 7,478 and 1,030 page views, respectively, up to now. Highly frequent terms cited as keywords of the database were extracted. They rank in order "bond strength", "titanium" and "composite resin" for Japanese journals cited, and "bond strength", "composite resin" and "SEM" for European journals cited.

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