著者

伊藤 明彦 郭 明毅 劉 嘉東 細川 隆司 永富 勝広 村上 繁樹 内田 康也 帆鷲 郷一 内山 長司

出版者

九州歯科学会

雑誌

九州歯科学会雑誌 (ISSN:03686833)

巻号頁・発行日

vol.43, no.2, pp.351-359, 1989-04-25 (Released:2017-12-21)

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In this study, we investigated the effects of the marginal surface configurations of different crown systems on the periodontal tissues. The morphology of the marginal surface of the crowns was examined by using a light- and a scanning electron microscope. In addition, biocompatibility of the materials used for crown margins was also examined by a subcutaneous implantation. The results were as follows : 1. The margins of the Ag-Pd-Au alloy full cast crowns fabricated by a conventional method were sharp and wavy with irregularities. 2. The modified method in which the margins of the Ag-Pd-Au alloy full cast crowns were rounded slightly with silicone rubber wheels was effective to make the margins smooth and round. 3. The glazed porcelain jacket crowns with metal foil copings produced sharp marginal openings because of the occurrence of a microfracture in a glass state of the ceramics. 4. The conventional ceramo-metal crowns displayed the irregularities of the surface adjacent to the boundary between metal collar and porcelain. One of the reason of this observation might be the exposure of a opaque porcelain of the crowns. 5. In the collarless ceramo-metal crowns, the marginal line configulations were totally rounded. 6. The DICOR crowns exhibited the smoothest marginal surfaces and the slightly rounded margins. 7. In the study of subcutaneous implantation, the porcelain (VMK 68) and the castable ceramic (DICOR) showed better histopathological findings than the gold alloy metal.

著者

楪 雅行 佐藤 義輝 内田 康也 田島 清司

出版者

九州歯科学会

雑誌

九州齒科學會雜誌 : Kyushu-Shika-Gakkai-zasshi (ISSN:03686833)

巻号頁・発行日

vol.39, no.6, pp.862-869, 1985-12-25

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The widely used dental Ag-Pd-Au alloy is frequently melted with a gas-air blowtorch, and cast by a centrifugal casting machine. In this case, the timing of casting the molten alloy is generally determined by means of the observation of its appearance at melting. There are few reports on the temperature of the molten alloy at casting. Therefore, the casting temperature of Ag-Pd-Au alloy melted with a gas-air blowtorch was measured, as well as the heating time until the start of castig. This study was scheduled to examine the effects of remelting, flux addition, and operator's experience in casting. Six operators, three well and three poorly experienced, were selected. The casting temperatures adopted by the three well experienced operators tended to rise gradually as the repetition times of melting increased. The difference between the casting temperatures at the first and the 10th melting without flux ranged from 10 to 15℃. On the other hand, the casting temperatures adopted by two poorly experienced operators of the three tended to fluctuate sharply, and no rising tendencies were observed in the casting temperatures. Flux addition in due course of heating the alloy reduced the difference between the maximum and the minimum casting temperature. The rise in casting temperature was suppressed by flux addition in the repeated melting by the well experienced operator group, resulting in about only 5℃ rise from the first to the 10th melting. The time required for heating the alloy from the liquidus to the casting temperature was nearly constant in the case of the well experienced operator group, but in the case of the poorly experienced one it fluctuated sharply, irrespective of flux utilization. Consequently, it may be said that the operator's experience and/or skill are inevitably necessary for casting Ag-Pd-Au alloy by judging the casting temperature from the appearance of the molten alloy.