To improve the colors and mechanical properties of Au-Pt-Ag-Cu system alloys for porcelain-metal restorations, 10 kinds of experimental mother alloys were prepared. Three wt% of Ga or Sn was subsequently added to these mother alloys, and the effects of the composition and additional elements were investigated. Comparing colors before and after degassing, although the mother alloys containing Cu turned black after degassing, the addition of Ga improved these color changes. The presence of Cu increased the staining of porcelains, however colors of porcelains baked on mother alloys were different from those baked on alloys containing additives, especially the addition of Ga caused preferable changes. Hardness (HV) increased with the increase of Cu content and increased more rapidly with the addition of Ga or Sn. The coefficients of thermal expansion of mother alloys during the cooling process were affected by Pt and Cu contents, and the coefficients of alloys containing additives were also affected by Pt content.

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We evaluated the effects of cooling shrinkage and reheating of vinyl sillicone rubber impressions taken with a resin tray on the reproducibility of stone models.
The impressions were reheated before the pouring of plaster by incubating the impressions in water at an oral temperature for 5 minutes.
The models were prepared using the two types of epoxy resin mold (cylindrical, simulated full crown preparation with adjacent teeth). The dimensional changes of the stone models were measured by a three-dimensional measuring system.
The stone models showed less dimensionl change due to cooling shrinkage of impressions.
The reheating of impressions taken with a resin tray did not improve the reproducibility of stone models.

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Mechanical properties and structure of fired specimens of low-fusing porcelains for multi-purpose gold alloys (MPGA)recently developed were evaluated in comparison with those of conventional porcelain for metal-ceramic restorations. Three kinds of commercial low-fusing porcelains for MPGA with a firing temperature of 780〜845℃ were examined compared to a conventional commercial porcelain with a firing temperature of 960℃. Mechanical properties such as Vickers hardness, fracture toughness, and flexural strength and surface analyses such as X-ray diffraction analysis, SEM observation, and EPMA were evaluated on the fired specimens. Mechanical properties and fired structure of low-fusing porcelains for MPGA were influenced by a firing schedule fixed on the selected muffle. Mechanical properties of low-fusing porcelains for MPGA differed in the products which were influenced by the composition and structure of powder and fired block. Mechanical properties of some low-fusing porcelains for MPGA were similar or inferior to those of conventional porcelain.

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This study investigated the role of N-AAsp on the adhesion to dentin. The electric dissociation exponent (pKa) of two carboxyl groups in N-AAsp and pH change on the dentin surface treated with N-AAsp were measured. We also tried to identify the reaction products of hydroxyapatite and N-AAsp, because particle-like react products were observed on the treated dentin.
The pKa of the carboxyl group was 3.67 at the main chain of N-AAsp and 4.19 at the side chain. The pH value on the dentin surface treated with N-AAsp increased slowly with time from 4.1 at 1-minute to 4.9 at 5-minute. N-AAsp formed the corresponding salt with hydroxyapatite. These results suggested that react products of hydroxyapatite and N-AAsp were left in the decalcified dentin layer affecting dentin adhesion.

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Water sorption behavior in 5 groups of ceramic liners (A: rock wool type, B: ceramic fiber low temperature type, C: ceramic fiber standard type, D: ceramic fiber low temperature-standard type, and E: kaolin type) in a casting ring after filling with investment slurry in vacuo was evaluated. The filling weight and working time of investment slurry in casting rings lined with various liners were measured. The δV (increase in the volume of slurry compared with the absence of water sorption by the liner) was 0.96〜2.85 cm³ for 15 liners and 3 asbestos ribbons.
The δV/volume of vacant space ratio was 77〜106% for 15 liners and 3 asbestos ribbons. When the investment slurry filled in the casting ring in vacuo, the volume of transferred water to the liner from investment slurry could be represented by the volume of vacant space of the liner. The working time was 703〜964 s for the liners in Group A, 746〜919 s in Group B, 831〜879 s in Group C, 653〜835 s in Group D, 794s in Group E, and 789〜854 s in 3 asbestos ribbons. Without liners, working time was 836 s. The effective water-powder ratio in slurry, which was calibrated from the working time, was unreasonable for evaluating of water sorption behavior of a great many liners.

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