Genotoxic Effects of Silver Amalgam and Composite Restorations: Micronuclei-Based Cohort and Case-Control Study in Oral Exfoliated Cells

Assessment of Cytotoxic and Genotoxic Effect of Modern Dental Materials in vivo

Objectives

The aim of the study was to assess the biocompatibility of modern composite and amalgam dental fillings.

Material and Methods

The research was conducted on 150 healthy patients between the ages of 10 and 20 who had amalgam and composite fillings between 6 and 12 months. Under in vivo conditions, a swab of buccal cells near the fillings was taken, and the cytotoxic and genotoxic impact of composite and amalgam fillings on these cells was analyzed using the extended micronucleus test (cytomeassay).

Results

The results showed statistically significant differences between the groups of subjects with amalgam and composite fillings and subjects without fillings for the following parameters: number of micronuclei (p=0.006), number of buds (p<0.001), number of binuclear cells (p<0.001), number of nucleoplasmic bridges (p<0.001).The number of micronuclei was statistically significantly higher in the group of subjects with amalgam and composite fillings compared to the group without fillings. The results for nuclear buds, for the number of binuclear cells and the number of nucleoplasmic bridges showed that the group with amalgam fillings had a statistically significantly higher number of these changes compared to other groups.The results of the analysis of the relationship between the parameters of the micronucleus test and the number of amalgam and composite surfaces did not show statistically significant values. Parameters indicating cell cytotoxicity were not statistically significantly elevated in subjects with fillings. The results of the analysis of the influence of the patients' lifestyle on the results of the micronucleus test showed statistically significant results for certain predictors (diagnostic X-ray radiation, coffee consumption, consumption of cooked, dried meat and baked food).

Conclusion

Based on the results, it can be concluded that the buccal cells of subjects with amalgam fillings showed the highest degree of genotoxic changes, followed by those with composite fillings and the least buccal cells of patients without fillings.

Genotoxicity of Mercury and Its Derivatives Demonstrated In Vitro and In Vivo in Human Populations Studies. Systematic Review

Beside partial coverage in three reviews so far (1994, 2009, 2019), there is no review on genotoxic studies dealing with mercury (Hg) and human exposure using the most usual genotoxic assays: sister chromatid exchanges (SCE), chromosomal aberrations (CA), cytochalasin B blocked micronucleus assay (CBMN), and single-cell gel electrophoresis (SCGE or alkaline comet assay). Fifty years from the first Hg genotoxicity study and with the Minamata Convention in force, the genotoxic potential of Hg and its derivatives is still controversial. Considering these antecedents, we present this first systematic literature overview of genotoxic studies dealing with Hg and human exposure that used the standard genotoxic assays. To date, there is not sufficient evidence for Hg human carcinogen classification, so the new data collections can be of great help. A review was made of the studies available (those published before the end of October 2021 on PubMed or Web of Science in English or Spanish language) in the scientific literature dealing with genotoxic assays and human sample exposure ex vivo, in vivo, and in vitro. Results from a total of 66 articles selected are presented. Organic (o)Hg compounds were more toxic than inorganic and/or elemental ones, without ruling out that all represent a risk. The most studied inorganic (i)Hg compounds in populations exposed accidentally, occupationally, or iatrogenically, and/or in human cells, were Hg chloride and Hg nitrate and of the organic compounds, were methylmercury, thimerosal, methylmercury chloride, phenylmercuric acetate, and methylmercury hydroxide.