Influence of quantity of recasting on change of physicomechanical properties of native base dental alloys for manufacturing metal-ceramic dental prosthesis

The main structural materials forfixed dental prostheses remain base alloys that veneer ceramic coatings. Dental technicians are increasingly using in their work the gates, which, according to some authors, can strongly modify the preset manufacturer physico-mechanical properties and cytotoxicity of alloys. For scientific substantiation of the maximum permissible number remelts we have investigated the changes in physical-mechanical properties (coefficient of thermal linear expansion (CTLE), the yield strength in bending, hardness) and chemical composition of the samples domestic base dental alloys for the manufacture of metal-ceramic dental prostheses. It was found that the addition of gates in cobalt-chrome alloy (CChA) Viteri-leads to an increase in strength, and in the case of nickelchromium alloy (NChA) Viteri-N increase in strength was observed only in the second group using 50% of the gates of the total mass of the molded product. When using 100% remelting Viteri-N, it was observed a decrease of the strength indicators below the original data. The analysis of the research results CTLE allows to judge about the fact that adding gates in the case of both alloys leads to a decrease of the coefficient of thermal linear expansion, and, consequently, to increase the tangential tension strains and can cause breaks, passing radially outward. Thus, there is a risk of late chipping of ceramic coating. Multiple remelting ofprefabricated CChA, NChA leads to the frenzy of the components that play the role of scavengers and modifiers (Mn, Si, Ta, Nb). Worth noting is the increase in the carbon content in the alloy CChA and NChA. So if CChA he plays the role of a modifier and increases the hardness, the content in NChA him about 0.4% simply unacceptable. The increase in carbon 0.1% can increase the hardness to 50 units Vickers, which may impair further mechanical treatment in the dental laboratory.

metal-ceramic dental prostheses, base alloys, casting, quantity of recasting