Corrosion potential in artificial saliva and possible genotoxic and cytotoxic damage in buccal epithelial cells of patients who underwent Ni-Cr based porcelain-fused-to-metal fixed dental prostheses

Abstract

Nickel–chromium(Ni–Cr) based alloys account for the majority of the porcelain-fused-to-metal fixed dental prostheses(PFM-FDPs) on account of their superior properties despite both nickel and chromium being known as human carcinogens. Understanding the genotoxicity and the cytotoxicity alongside the characteristics of corrosion behavior of the alloy is vital for understanding their biocompatibility. This study has evaluated whether the Ni-Cr based alloys corroded in artificial saliva by analyzing alloy decomposition at different pH levels and immersion durations(7, 14, 21, and 28 days) using inductively coupled plasma-optic emission spectrophotometry(ICP-OES). The principal aim of the study was to determine the possible genotoxicity and cytotoxicity using micronucleus(MN) and other nuclear anomaly frequencies [nuclear bud(NBUD), binucleated(BNC), condensed chromatin(CC), karyorrhectic(KhC), pyknotic(PC) and karyolytic(KC) cells] and various cytome parameters [basal cells(BC), differentiated cells(DF)] with the buccal epithelial cell(BEC) micronucleus cytome assay(BMCyt). This test was administered at 1 pre- and 3 post-treatment time points to 40 patients who underwent installation of PFM-FDPs made of Ni-Cr based alloy. Furthermore, at the final post-treatment time point, saliva cotinine levels were measured with salivary cotinine quantitative enzyme immunoassay(EIA) kit and information obtained by questionnaire prior to the first pre-treatment time point was confirmed. The highest greatest release of Ni and Cr ions were seen at pH 2.3. MN and micronucleated cell frequencies, and BNC cell frequencies were significantly elevated at post-treatment time points(p < 0.03). BC, CC, KhC, PC and KC cell frequencies however were not significantly different between pre-and post-treatment time points(p > 0.05). MN frequency was significantly lower in non-smokers than in current and former smokers(p < 0.001) at the pre-treatment time point. There was no significant correlation between the unit number of PFM-FDPs and MN frequencies. Our results revealed that Ni-Cr based alloys are prone to corrosion and that PFM-FDPs fabricated with Ni-Cr based alloys may induce genotoxic effects rather than cytotoxic effect.