The influence of the purity of cobalt-chrome alloy on metal-porcelain bond

Uvod: Najpogosteje uporabljene konstrukcije v fiksni protetiki so kovinsko-porcelanske konstrukcije iz stelitnih zlitin, kamor spada tudi kobalt-kromova zlitina. V želji po prihranku se v zobotehničnih laboratorijih pri izdelavi konstrukcij zlitinam pogosto dodaja že uporabljena in pretaljena zlitina. Namen: izdelali smo vzorce kobalt-kromovih kovinsko-porcelanskih konstrukcij z različnimi deleži šestkrat pretaljene zlitine v vzorcu. Preučevali smo vez med zlitino in porcelanom. Želeli smo ugotoviti, ali prisotnost pretaljene zlitine vpliva na tvorbo oksidne plasti med porcelanom in kobalt-kromovo zlitino. Prav tako smo želeli preveriti, ali se kemijska sestava vzorcev spreminja glede na količino dodane pretaljene zlitine. Metode dela: Uporabljena metoda teoretičnega dela je bila deskriptivna metoda in je obsegala literaturo, obravnavano v diplomskem delu. V spletnih bazah Dikul, Science Direct, PubMed, Google Schoolar ter COBISS smo iskali ključne besede kobalt-kromova zlitina, kovinsko-porcelanska vez, oksidna plast in dentalni porcelan. Izbrali smo literaturo izdano v zadnjih desetih letih. Praktični del je obsegal izdelavo vzorcev v zobnem laboratoriju. Raziskovalni del je temeljil na analizi rezultatov elektronskega mikroskopiranja vezi med kobalt-kromovo zlitino ter porcelanom. Rezultati: Iz rezultatov je razvidno, da dodajanje pretaljene zlitine v vzorce manjša masne deleže Cr, Mo in W ter veča delež Co. Sprememba kemijske sestave zlitine vpliva na vrsto in količino oksidov, ki se tvorijo na površini. V oksidni plasti so prisotni elementi Co, Cr, M, Si, Al in O. Manjši delež pretaljene zlitine v vzorcu povzroča tanjšo oksidno plast, večji delež pretaljene zlitine v vzorcu pa zelo debelo oksidno plast. V vzorcih, ki vsebujejo pretaljeno zlitino je opaznih več prekinitev oksidne plasti. Razprava in zaključek: Ugotovljeno je bilo, da uporaba pretaljene zlitine v kobalt-kromovih zobnoprotetičnih konstrukcijah sorazmerno z dodano količino vpliva na kemijsko sestavo zlitine, spreminja deleže komponent in s tem vpliva na mehanske lastnosti zlitine, njeno korozijsko odpornost in tvorbo oksidov, ki se vežejo s porcelanom. Povzroča neprimerno oksidno plast in s tem zmanjšuje primernost zlitine za kovinsko-porcelansko tehniko. Uporaba pretaljene zlitine v protetičnih konstrukcijah lahko vodi do porušitve kovinsko-porcelanske vezi in posledično do pok, krušenja in poškodb zobnih nadomestkov.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