Longitudinal analysis of the association between removal of dental amalgam, urine mercury and 14 self-reported health symptoms

Abstract

BackgroundMercury vapor poses a known health risk with no clearly established safe level of exposure. Consequently there is debate over whether the level of prolonged exposure to mercury vapor from dental amalgam fillings, combining approximately 50% mercury with other metals, is sufficiently high to represent a risk to health. The objective of our study is to determine if mercury exposure from amalgam fillings is associated with risk of adverse health effects.MethodsIn a large longitudinal non-blind sample of participants from a preventative health program in Calgary, Canada we compared number of amalgam fillings, urine mercury measures and changes in 14 self-reported health symptoms, proposed to be mercury dependent sub-clinical measures of mental and physical health. The likelihood of change over one year in a sample of persons who had their fillings removed was compared to a sample of persons who had not had their fillings removed. We use non-parametric statistical tests to determine if differences in urine mercury were statistically significant between sample groups. Logistic regression models were used to estimate the likelihood of observing symptom improvement or worsening in the sample groups.ResultsAt baseline, individuals with dental amalgam fillings have double the measured urine mercury compared to a control group of persons who have never had amalgam fillings. Removal of amalgam fillings decreases measured urine mercury to levels in persons without amalgam fillings. Although urine mercury levels in our sample are considered by Health Canada to be too low to pose health risks, removal of amalgam fillings reduced the likelihood of self-reported symptom deterioration and increased the likelihood of symptom improvement in comparison to people who retained their amalgam fillings.ConclusionsOur findings suggest that mercury exposure from amalgam fillings adversely impact health and therefore are a health risk. The use of safer alternative materials for dental fillings should be encouraged to avoid the increased risk of health deterioration associated with unnecessary exposure to mercury.Electronic supplementary materialThe online version of this article (doi:10.1186/1476-069X-13-95) contains supplementary material, which is available to authorized users.

Removal of dental amalgam restorations in patients with health complaints attributed to amalgam: A prospective cohort study

“…Since neither blinding nor placebo control was used, the observed reduction of the intensity of general health complaints can be interpreted as an effect from both specific and non-specific treatment effects. A reduction of health complaints is in agreement with data from previous controlled studies 22,23,26,30 and studies without comparison groups. 28,31 In cross-sectional studies of large cohorts, people with many amalgam fillings did not have more symptoms or diagnosed diseases than people with few fillings.…”

How unexplained health complaints were attributed to dental amalgam

“…Different explanations, including patients' expectations , psychosocial treatment effects , elimination of worry , spontaneous recovery , and the natural course of the complaints , were suggested for the reported improvements in health. However, not all of the reported reductions were statistically significant, and the complaints that were statistically reduced varied from study to study (not described in Table 1, see for instance Zwicker et al, 2014). In the randomized controlled trial , clinically relevant reductions of health complaints were found for all interventions, including the one without amalgam removal.…”

“…The practitioners also provided an extensive list of complaints likely to be reported by amalgam patients . When investigating health complaints attributed to dental amalgam, some studies have relied on, and expanded on, questionnaires regarding common health complaints, such as the Giessener Symptom Complaints Checklist , whereas other studies have used self-constructed questionnaires with health complaints that the researchers, based on the existing research literature and their own clinical experience, believe are core symptoms reported by patients with health complaints attributed to dental amalgam Zwicker, Dutton, & Emery, 2014).…”

“…In the studies that included measures of mercury, significant reductions of mercury were found after amalgam removal Stenman & Grans, 1997;Zwicker et al, 2014). In one of the studies (Zwicker et al, 2014), a significant reduction of mercury was also found in the non-removal group. The authors suggested this could have been due to all participants being offered detoxification supplements.…”

An in vitro appraisal of properties of dental amalgam using commercially available and ayurvedically recycled mercury: Recycle and reuse

“…The conclusion was deducted on the basis of results that removal of amalgam fillings reduced the self-reported symptom deterioration and increased the possibility of symptom improvement in comparison to people who retained their amalgam fillings. [ 6 ] In contrast, Nicolae et al . opined that mean urinary mercury concentrations in Canadian population are significantly lower than the values considered to pose any risks for health.…”