合着用セメントの保持力に関する基礎的研究
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概要
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It has been mentioned that the retention of restoration obtained by the luting cement is principally due not to its adhesive characteristics but the mechanical interlocking with restoration and prepared cavity. The purpose of the present investigation is to examine the physical and mechanical properties of cements that have close relationships to the retention of inlay, such as compressive and tensile strength, knoop hardness number, disintegration and thermal expansion. The materials tested were zinc phosphate, carboxylate, resin and glass ionomer cement. Each cement was mixed on a glass slab according to the powder-liquid proportion recommended by the manufacturer and allowed to set in the mould. The physical and mechanical properties of the cements were markedly influenced by the difference of atmosphere after their setting. When the specimens were desicated in test tube for 14 days at 37℃ glass ionomer cement (Fuji, Type 1) showed the highest compressive strength (2, 500kg/cm^2). However, when it was placed in the atmosphere of 100% relative humidity, there was a marked decrease in compressive strength probably because of water absorption or dissolution of cement. The compressive strength was as low as 1, 500 kg/cm^2 under this condition. Such a decrease was also observed in tensile strength and knoop hardness number of all cements tested. In addition, the retention force of inlay may also be affected with differences in thermal expansion of tooth, metal and cement. Therefore, it is necessary to choose the cements that have thermal expansion closely matched with those of tooth and metal luted, in order to avoid the stresses at the interface. In this investigation, glass ionomer cement (Fuji, Type 1) and zinc phosphate cement (Elite) had the desirable thermal characteristics and so showed the superior retention of the inlay in the adhesion test.
- 九州歯科学会の論文
- 1981-05-25
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