Release of cobalt from cobalt chromium alloy constructions in the oral cavity of man

In vitro element release and biological aspects of base-metal alloys for metal-ceramic applications

Objective: The aims of this study were to investigate the release of element from, and the biological response in vitro to, cobalt–chromium alloys and other base–metal alloys used for the fabrication of metal-ceramic restorations.

Material and methods: Eighteen different alloys were investigated. Nine cobalt–chromium alloys, three nickel–chromium alloys, two cobalt–chromium–iron alloys, one palladium–silver alloy, one high-noble gold alloy, titanium grade II and one type III copper–aluminium alloy. Pure copper served as positive control. The specimens were prepared according to the ISO standards for biological and corrosion testing. Passive leaching of elements was measured by using Inductively Coupled Plasma – Mass Spectrometry (ICP-MS) after incubation in cell culture media, MEM, for 3 days. Corrosion testing was carried out in 0.9% sodium chloride (NaCl) and 1% lactic acid for 7 days, and the element release was measured by Inductively Coupled Plasma – Optical Emission Spectroscopy (ICP-OES). The biological response from the extract solutions was measured though MTT cytotoxicity testing and the Hen's egg test-chorio-allantoic membrane (HET-CAM) technique for irritationt.

Results: The corrosion test showed similar element release from base-metal alloys compared to noble alloys such as gold. Apart from the high-copper alloy, all alloys expressed low element release in the immersion test, no cytotoxic effect in the MTT test, and were rated non-irritant in the HET-CAM test.

Conclusions: Minimal biological response was observed for all the alloys tested, with the exception of the high-copper alloy.

Metal content of saliva of patients with and without metal restorations

Many in vitro studies have confirmed the corrosion of dental alloys. However, in vivo corrosion studies, for example, recording of the release of metal ions into saliva, are scarce, and data on the repeatability of the metal content measurements of saliva are lacking. The present study examined the metal content of saliva of patients with and without metal restorations and assessed the repeatability of these data. The composition of each patient's oral cast alloys was analyzed using the energy-dispersive X-ray analysis of metal biopsy specimens and was compared to the metals found in saliva. Saliva analysis was performed using atomic absorption spectroscopy. Chemical analysis comprised the metals Ag, Au, Co, Cr, Cu, Fe, Ga, In, Ni, Pd, Pt, Sn, and Zn. The metals Ag, Cr, Cu, Fe, Ni, and Zn were found in saliva of patients without metal restorations, but these data showed statistically significant differences in the metal content between consecutively performed samples per patient. The metals Ag, Au, Cr, Cu, Fe, Ni, and Zn were identified in saliva of patients with metal restorations being higher in concentration than in control patients. In 77% of the cases at least one metal of the restoration was found in the patient's saliva. However, the metal content showed statistically significant differences between replicate samples of the same patient taken at different times. The metal content of saliva is affected among other things by intraoral metal restorations, but present data do not support the idea that it is a reliable indicator for the systemic exposure to metals released from dental alloys.