Introduction: Metal-porcelain restorations are the most used restorations and represent the standard in reconstructive and esthetic dentistry. In the thesis, we made and described the production of seven individually made metal-porcelain coatings with particular emphasis on casting faults. In dental laboratories, we deal with the melting on daily basis. Therefore, a comparison between the new and the used alloy was made to check whether and how re-melting affects the bond strength between the alloy and the porcelain mass. Purpose: The purpose is to present the process of manufacturing individual metal-porcelain coatings, to analyze possible errors in the use of multiple molten alloys, to investigate the adverse effects of Co-Cr alloy re-melting on the contact surface microstructure, and to bond strength between the alloy and the porcelain mass. Methods: The theoretical part is based on the review of literature in scientific and peer-reviewed journals and books. Literature was searched in COBISS, Google Scholar, and DiKul, as well as in MEDLINE and PubMed. The literature used is in Slovene and English and not older than 10 years. In the experimental part, metal-porcelain test pieces were made to analyze the bond strength between the metal frame and the porcelain mass to characterize the microstructure of the contact surface. The practical part is based on the analysis of the results obtained during test pieces production, characterization of mechanical properties, and microstructure. Results: The results illustrate the making of metal-porcelain test pieces for the analysis of bond strengths between the metal frame and porcelain mass and characterization of the microstructure of the contact surface. The test pieces were made with stereolithographica printing. They were loaded into three cuvettes and cast with Co-Cr alloys and melted once, three times, and six times. The analysis of the microstructure of a multi-molten Co-Cr alloy was performed. Sinter porcelain was sintered on the test pieces and a shear test of the bond strength between the metal frame and the porcelain mass was analyzed. The microstructure of the contact surface was analyzed using a light microscope. Discussion and conclusion: In the analysis of the microstructure, in multiple molten alloys, a thinning of the oxide layer is observed, reducing the oxides crucial for the corresponding chemical-mechanical bond. The aim of the shear test was to determine the shear strengths of the bond between molten alloy or the metal frames and porcelain mass. Alloy melting strongly influences the composition and strength of the bond between the alloy and the porcelain mass, which is crucial for a quality prosthetic restoration.
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