Introduction: The most commonly used restorations in fixed prosthetics are metal-porcelain restorations made of stellite alloys, which include cobalt-chromium alloy. In order to save money, dental laboratories often use used alloy that has already been casted. Purpose: Three samples containing different proportion of six times casted alloy had been made. Observation of thickness and effects in the oxide layer had been made and microanalysis of chemical composition of the alloy had been determinated. Methods: The method used in theoretical part is descriptive method and it covers literature discussed in the thesis. Online databases Dikul, Science Direct, PubMed, Google Schoolar and COBISS have been searched for the keywords cobalt-chrome alloy, metal-porcelain bond, oxide layer and dental porcelain. Literature published in last ten years have been selected. The practical part involves the production of samples in dental laboratory. The research part is based on analysis of the results of linear electron microscopy. Results: Results show that the addition of casted alloy in samples reduces mass fraction of Cr, Mo and W and increases mass fraction of Co. It affercts the type and amount of oxides formed on surface. The elements Co, Cr, Mo, Si, Al and O are present in oxide layer. A smaller amount of casted alloys in the sample produce a thinner oxide layer, and a grater amount of casted alloy produce thick oxide layer. In samples containing casted alloy several interruptions of oxide layer are noticeable. Discussion and conclusion: It was found that the addition of casted alloy to cobalt-chromium dental restorations affects composition of the alloy, changes mass fracture of elements and thus affects mehanical properties of the alloy, its corrosion resistance and the formation of oxides, which bond to porcelain. It causes non ideal oxide layer and reduces the suitability of the alloy for the metal-porcelain technique. Adding a casted alloy to prosthetic restorations can cause disintegration of metal-porcelain bond which can lead to fracture and damage of metal-porcelain restoration.
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