Cobalt-chromium alloys in dentistry: An evaluation of metal ion release

Metal ions released into the oral cavity from dental prosthesis alloys may damage the cellular metabolism or proliferation and cause hypersensitivity or allergies. The oral cavity environment is particularly prone to corrosion due to saliva, microorganisms, and pH variations.

The purpose of this in vitro study was to evaluate the ion release of chromium, cobalt, and iron from the Co-Cr alloys used for traditionally cast and computer-aided design/computer-aided manufacturing dental devices after interaction with oral bacteria and different pH conditions.

All specimens were prepared from currently available alloys, polished, and immersed in 3 different pH media (artificial saliva [pH 2.3] and 6.5% and 0.9% saline solution [pH 7.1]). Specimens were also incubated in the presence of the bacterium Eikenella corrodens. Solutions were analyzed with an atomic absorption spectrometer after 15 and 30 days in the chemical corrosion test and 30 days in the biocorrosion test to detect ions released in different solutions. An ANOVA test was used to evaluate statistically significant differences among the percentages of metal corrosion ion release values.

The greatest amount of element release was seen after 30 days: 4.964 ppm of casting alloy, 2.642 ppm of milling alloy, and 2.351 ppm of laser metal sintering.

With the exception of casting alloy under acidic conditions, no significant differences were found, even after exposure to bacteria.