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In this study, the adhesive strength of three commercial polycarboxylate cements to ten types of dental casting alloys, such as gold, palladium, silver, indium, copper, nickel, chromium, and human enamel and dentine were measured and compared with that of a conventional zinc phosphate cement. The 8.0㎜×3.0㎜ cylindrical alloy specimens were made by castion. The enamel specimens were prepared from the labial surface of human upper incisor, and the dentine specimens were prepared from the occlusal surface of the human molar respectively. Sound extracted human teeth, which had been kept in a fresh condition since extraction, were mounted in a wax box with a cold-curing acrylic resin to expose the flattened area. The mounted teeth was then placed in a Specimen Cutter (Technical) and were cut down under a water spray, and then the flat area on the all specimens were ground by hand with 400 and 600 grit wet silicone carbide paper. Two such specimens were then cemented together face-to-face with freshly mixed cement, and moderate finger pressure was applied to squeeze the cement to a thin and uniform film. All cemented specimens were then kept in a thermostatic humidor cabinet regulated at 23±2℃. And more than 95 per cent relative humidity and tested after 24 hours and 1 week. Link chain was attached to each alloy specimen to reduce the rigidity of the jig assembly, and then all the specimens were mounted in the grips of the Instron Universal Testing Machine, and a tensile load was delivered to the adhering surface at a cross head speed of 0.20㎜/min. The loads to which the specimens were subjected were recorded on a chart moving at 0.50㎜/min. The adhesive strength was determined by measuring the load when the specimen separated from the cement block and by dividing the load by the area. The test was performed in a room at 23±2℃. And 50±10 per cent relative humidity. A minimum of five specimens were tested each material and those which deviated more than 15 per cent from the mean were discarded and new specimens prepared. From the experiments, the following results were obtained. 1. It was found that the adhesive strength of the polycarboxylate cement to all alloys tested was considerably greater than that of the zinc phosphate cement. 2. The adhesive strength of the polycarboxylate cements was superior to the nonprecious alloys, such as the copper, indium, nickel and chromium alloys, but it was inferior to the precious gold, silver and palladium alloys. 3. Surface treatment of the alloy was found to be an important factor in achieving adhesion. It appears that a polycarboxylate cement will adhere better to a smooth surface than to a rough one. This contrasts with zinc phosphate cements, where a rough helps mechanical interlocking. 4. The adhesion of the polycarboxylate cement with enamel was found superior to its adhesion with dentine.
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