The effect of recasting on biological properties of Ni-Cr dental alloy

Abstract

Introduction Increases in market prices of gold over the last 20 years have led to expansion of basic dental alloys, which, primarily due to their good mechanical properties and acceptable prices, have found their place in everyday dental practice. However, within the procedure of making dental prosthetic restorations, the alloys are melted and cast, which leads to changes in their physical, mechanical and biological properties. Objective The objective of the study was to test biocompatibility of a Ni-Cr dental alloy (WIRON 99) depending on the number of melting and casting processes. Methods The working method included the testing of cytotoxicity of the alloy obtained by casting after one, after four, and after eight successive processes of melting. Cytotoxicity of samples was tested by means of a 24-hour and a three-day cytotoxicity test, done on L929 fibroblasts. Results A repeatedly melted and cast alloy shows a reduced biocompatibility and causes specific responses of the tissues in the surrounding area. Since the cytotoxic effect is more significant in the extended contact with the culture cells, a three-day cytotoxicity test showed discrete changes which were the indicator of cell growth inhibition in the cell culture. Conclusion The obtained results confirm the working hypothesis that repeated alloy melting and casting will decrease biocompatibility of dental alloys and will lead to specific responses of the tissue in the surrounding area.

Uvod Porast cene zlata na svetskom tržištu u poslednjih 20 godina doveo je do ekspanzije baznih dentalnih legura, koje su pre svega zbog dobrih mehaničkih svojstava i pristupačnih cena našle primenu u svakodnevnoj stomatološkoj praksi. U proceduri izrade protetskih radova legure se tope i izlivaju, što dovodi do promena njihovih fizičko-mehaničkih i bioloških svojstava. Cilj rada Cilj rada bio je ispitivanje biokompatibilnosti jedne Ni-Cr legure (WIRON 99) u zavisnosti od broja topljenja i livenja. Metode rada U radu je ispitivana citotoksičnost legure dobijene izlivanjem posle jednog topljenja, posle četiri i posle osam uzastopnih topljenja. Citotoksičnost uzoraka je ispitivana pomoću 24-časovnog i trodnevnog testa citotoksičnosti na L929 fibroblastima. Rezultati Više puta topljena i livena legura pokazala je smanjenu biokompatibilnost, dovodeći do specifičnih odgovora tkiva u neposrednom okruženju. Budući da je citotoksični efekat izraženiji u produženom kontaktu sa ćelijama iz kulture, trodnevni test citotoksičnosti je pokazao diskretne promene koje su pokazatelj inhibicije rasta ćelija u kulturi. Zaključak Dobijeni rezultati potvrđuju radnu hipotezu da više puta ponavljana topljenja i li venja legura smanjuju biokompatibilnost dentalnih legura i dovode do specifičnih odgovora tkiva u neposrednom okruženju.