Association between dental amalgam fillings and multiple sclerosis: A systematic review and meta-analysis

Introduction: Mercury is a neurotoxic element that is released from dental amalgam restorations. Since circumstantial evidence exists that the pathology of multiple sclerosis (MS) disease might be in part caused or exacerbated by inorganic mercury, we conducted a systematic review and meta-analysis using a comprehensive search strategy. Methods: Data bases (PubMed, Google scholar, Cochrane, Embase, Scopus, Ovid, Proquest, and Web of Science) were searched systematically to find the relationship between dental amalgam and MS. Studies were screened according to a pre-defined protocol. The quality of the articles was evaluated by two individuals. The titles and abstracts of the articles were organized and duplicate articles were discovered with the help of Endnote X5 resource management software. Finally, 6 articles were included in the meta-analysis. Random effect model was chosen to conduct the meta-analysis. Results: Pooled mean difference of restoration numbers between two groups was 0.58 (95% CI: 0.33-0.83, P value<0.001) with greater numbers in MS patients. The pooled OR was 1.02 (95% CI, 0.86-1021, P=0.81), which was slightly higher for those with amalgam so they were more likely to develop MS. This slight increase in risk was not statistically significant. Conclusion: Although those who underwent a large number of amalgam fillings were at higher risk for MS, the difference between the two groups of patients and controls was statistically insignificant. It seems that the number of amalgam fillings can be an influential factor in the possibility of developing MS.