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Retention of magnetic keepers in cast noble metal alloy
E.H.N. POW1, K.H.C. CHAN1, H.W.K. LUK1, A.P.L.H. DIAS2, and A.S. MCMILLAN3, 1University of Hong Kong, China, 2Dental Health Services of Victoria, Australia, 3University of Hong Kong, Hong Kong | Objectives: This in vitro study investigated the effect of burn-out temperature on the retention of a Magfit EX keeper in cast gold alloy dowel and the thickness of the oxide layer at the keeper-alloy interface. Methods: One-hundred-and-five Magfit EX keepers were cast with gold alloy at three different burnout temperatures: 500°C, 600°C, 700°C. Sixty samples were tested in an Instron universal testing machine (UTM) until catastrophic tensile failure; forty-five samples were sectioned and the interface evaluated under a scanning electron microscope (SEM). Results: Retention of the keepers was significantly higher at lower burnout temperatures (p<.05). The retention of the keepers became unpredictable and immediate failures were observed at a burnout temperature of 700°C. Oxide formation at the keeper-alloy interface was significantly less at lower burnout temperatures (p<.05). Conclusion: High burn-out temperature for casting Magfit keepers with type IV gold alloy may lead to early loss of the keepers. The burnout temperature is recommended to be set at 500°C. | Seq #113 - Properties of Metallic Restorations and Appliances 3:30 PM-4:45 PM, Thursday, July 3, 2008 Metro Toronto Convention Centre Exhibit Hall D-E |
Back to the Dental Materials 7: Metal-based Materials Program
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