The effect of repeated casting on the biocompatibility of a dental gold alloy

Abstract

Although highly noble Au alloys have been considered as biocompatible dental materials, little is known about whether recasting affects their biocompatibility. The aim of this work was to study the effect of repeated casting procedures on the microstructure and biocompatibilty of a noble Au dental alloy. The prepared samples of one- four- and eight times melted/cast Dentor S were used to study primary cutaneous irritation and sensibilization on experimental animals. The extract of the alloy prepared by conditioning the Dentor S samples in a cell culture medium was used to study the cytotoxicity on L929 cells. The elemental composition and surface changes of the alloy were examined by Energy Dispersive X-ray (EDX) analysis and optical microscopy, respectively. Our results showed that repeated casting decreased the biocompatibility of Dentor S, manifested as decreased metabolic and proliferative activities of L929 cells and that the effect correlated with the number of melting/casting procedures. However, neither sample of Dentor S caused irritation and sensibilization on experimental animals. EDX showed that recasting slightly increased the content of Au and Cu and slightly decreased the content of Pt, Pd and Zn. These changes correlated with the observations by optical microscopy. In conclusion, our results show that repeated casting of noble Au alloy changes its microstructure and decreases the biocompatibilty, suggesting that this procedure should be avoided in dental practice.

Visoko plemenite legure su biokompatibilni materijali, ali je malo poznato da li ponovljena livenja legura utiču na njihovu biokompatibilnost. Cilj ovog rada je bio da se utvrdi efekat ponovljenog topljenja i livenja na mikrostrukturu i biokompatibilnost visoko plemenitih dentalnih legura zlata. Pripremjena je serija uzoraka od jednom, četiri i osam puta topljene i livene Dentor S legure za ispitivanje primarne iritacije kože i senzibilizacije na eksperimentalnim životinjama, kao i in vitro ispitivanje citotoksičnosti na L929 ćelijama. Hemijski sastav i promena površine legure ispitivana je EDX analizom i optičkim mikroskopom. Naši rezultati su ukazali da ponavljana livenja smanjuju biokompatibilnost Dentor S legure, koja se manifestuje smanjenjem metabolitičke i proliferativne aktivnosti L929 ćelija i da je efekat u korelaciji s brojem topljenja i livenja. Ni jedan uzorak Dentor S legure ne uzrokuje iritaciju i senzibilizaciju eksperimentalnih životinja. EDX analiza dokazuje da ponovna livenja blago povećavaju procenat Au i Cu i blago smanjuju procenat Pt, Pd i Zn. Ove promene su u korelaciji sa zapažanjima na optičkom mikroskopu. Autori zaključuju da ponovljena livenja visoko plemenitih legura zlata menjaju mikrostrukturu i smanjuju biokompatibilnost i preporučuju da se ova procedura izbegava u svakodnevnoj praksi.