Effect of recasting on the thickness of metal-ceramic interface of nickel-chromium and cobalt-chromium alloys

Abstract

Introduction/Aim. This research was done to establish recasting effects of nickel-chromium and cobalt-chromium alloys on the thickness of their metal-ceramic interface in making fixed partial dentures. Metal-ceramic interface determines their functional integrity and prevents damages on ceramics during mastication. Investigation of metal-ceramic samples is supposed to show if base metal alloys for metalceramics are successfully recycled without any risk of reduction of metal-ceramic interface thickness. Methods. The research was performed as an experimental study. Per six metal-ceramic samples of nickel-chromium alloy (Wiron99) and cobalt-chromium alloy (Wirobond C) were made each. Alloy residues were recycled through twelve casting generations with the addition of 50% of new alloy on the occasion of every recasting. Analysis Energy Dispersive X-ray (EDX) (Oxford Instruments) and Scanning Electon Microscop (SEM) analysis (JEOL) were used to determine thickness of metal-ceramic interface together with PC Software for quantification of visual information's (KVI POPOVAC). Results. Results of this research introduced significant differences between thickness of metal-ceramic interface in every examined recycle generation. Recasting had negative effect on thickness of metal-ceramic interface of the examined alloys. This research showed almost linear reduction of elastic modulus up to the 12th generation of recycling. Conclusion. Recasting of nickel-chromium and cobaltchromium alloys is not recommended because of reduced thickness of metal-ceramic interface of these alloys. Instead of recycling, the alloy residues should be returned to the manufacturers.Uvod/Cilj. Ovo istrazivanje sprovedeno je sa ciljem da se utvrdi uticaj ponovnog livenja nikl-hrom i kobalt-hrom legura na debljinu njihovog metal-keramickog medjuspoja u izradi fiksnih zubnih nadoknada. Metal-keramicki medjuspoj odredjuje njihov funkcijski integritet i sprecava ostecenje keramike u toku mastikacije. Ispitivanjem metalkeramickih uzoraka treba pokazati da li se bazicne legure za metal-keramiku mogu uspesno reciklirati bez rizika od smanjenja debljine njihovog metal-keramickog medjuspoja. Metode. Istrazivanje je obavljeno kao eksperimentna studija. Izradjeno je po sest metal-keramickih uzoraka legure nikl-hrom (Wiron99) i legure kobalt-hrom (Wirobond C). Ostaci legure su reciklirani kroz dvanaest generacija livenja uz dodatak 50% nove legure prilikom svakog ponovnog livenja. Za odredjivanje debljine metal-keramickog medjuspoja koriscena je Energy Dispersive X-ray (EDX) analiza (Oxford Instruments) i skening elektronska mikroskopija (JEOL) zajedno sa kompjuterskim programom za kvantifikaciju vizuelnih informacija (KVI POPOVAC). Rezultati. Rezultati ovog ispitivanja ukazali su na znacajne razlike izmedju debljine metal-keramickog medjuspoja u svakoj ispitivanoj generaciji recikliranja. Ponovno livenje negativno se odrazilo na debljinu metal-keramickog medjuspoja ispitivanih legura. Istrazivanjem je utvrdjeno skoro linearno smanjenje modula elasticnosti do dvanaeste generacije recikliranja. Zakljucak. Ponovno livenje legura nikl-hrom i kobalt-hrom ne moze se preporuciti zbog smanjenja debljine metal-keramickog medjuspoja ovih legura. Umesto recikliranja legura, preporucuje se vracanje ostataka legure proizvodjacima.