Community Dent Oral Epidemiol. 2010 Apr;38(2):180-9.
Predictors of treatment outcomes after removal of amalgam fillings: associations between subjective symptoms, psychometric variables and mercury levels.
Weidenhammer W, Bornschein S, Zilker T, Eyer F, Melchart D, Hausteiner C.
Source: Centre for Complementary Medicine Research, Internal Medicine II, Technical University Munich, Munich, Germany.
Objective: This analysis aimed to study predictors of different treatment outcomes and associations between subjective symptoms, psychometric variables and mercury levels in patients who subjectively attributed their health problems to dental amalgam.
Material and methods: A secondary and retrospective analysis of data of a recently published randomized clinical trial was performed. Seventy-eight patients [44% female, mean (SD) age 35 (6) years, randomly assigned to either amalgam removal or a health promotion program] were included into statistical analysis. Prior to intervention and 12 months later, questionnaires for assessing symptoms, psychological distress and health status were presented, and mercury levels in blood and urine were determined.
Results: The patients' personality profile at study onset was characterized by slightly reduced extraversion and slightly elevated emotional instability. Overall, subjective symptoms decreased slightly and there were no statistically significant differences in the decrease of symptoms after intervention between both groups. Decrease of mercury levels after intervention was closely associated with removal of amalgam fillings (rmult = 0.64 in regression analysis). Statistically significant correlations could be found between mercury levels and subjective symptoms with respect to baseline (r = 0.29–0.39) and to changes after intervention (r = 0.24–0.42), but not for psychological distress (r = 0.05–0.25) and health related quality of life (r = )0.03–0.18). Prediction of symptom improvement after intervention was poor (rmult = 0.44). Conclusions: Results contribute some new aspects to the inconsistent findings in the literature with respect to associations between symptoms and subtoxic mercury levels. More emphasis should be placed on exploring individual vulnerability for amalgam sensitivity.
Because of concerns about considerable environmental risks, the United Nations environment program is currently discussing a world-wide ban of mercury (1, 2). Therefore, and in light of running out natural mercury deposits, a sustained reduction of amalgam use is expected in oral health care. provision across the European Union – even if in some EU member states the use of amalgam has increased slightly in the past years (1). But as millions of people still live with amalgam fillings, the question of possible health impairment attributed of dental amalgam will not lose its relevance for many years. Population-based prevalence of subjective amalgam-related health concerns is roughly estimated to range between 6 (Zilker T, Bornschein S, unpublished in-house report) and 22% (3) but reliable data are scarce.
Whether mercury released from amalgam restorations could be a causal factor for subjective health problems and also for organically defined chronic diseases has been a matter of discussion for many years. Several reviews come to the conclusion that there is no convincing evidence of any adverse health effects attributable to dental amalgam with the exception of the rare contact sensitization with a positive patch test (4–6). Accordingly, a report recently published by a scientific committee on behalf of the DG SANCO⁄ European Commission comes to the conclusion that there is no scientific evidence for risks of adverse systemic health effects and that the current use of amalgam does not pose a risk of systemic disease (7).
On the other hand, many population-based studies, especially cross-sectional ones, on possible health effects of mercury have methodological limitations (such as an inadequate longitudinal exposure assessment and negative confounding by better access to dental care in higher socioeconomic groups). Therefore, several reviewers state a research deficit, and call for better designed studies, particularly for investigation of neurodegenerative diseases and effects on infants and children (5, 8).
It is widely accepted that there is a correlation between the number of amalgam fillings and (usually subtoxic) mercury levels in blood and urine (6, 9), suggesting systemic distribution, but not necessarily systemic action. Most clinical studies suggest that there is no association between mercury levels and physical and psychological symptoms in amalgam bearers or between number of fillings and number or intensity of symptoms and complaints (10–12).
As a consequence 'amalgam intolerance' is mostly viewed as a psychosomatic rather than toxicogenic problem (13). However, longitudinal studies on the relationship between mercury burden and symptoms are sparse (14). It is only known that subjective symptom burden decreases after amalgam removal (15–17). A number of studies involved personality inventories to analyze relations between personality factors and subjective amalgam intolerance – with inconsistent findings. While some found indications of specific personality traits in amalgam patients (18–21) others failed to show any relationship or differences compared with controls (22–24).
In a recently published randomized trial, we compared the effectiveness of different treatment regimens in patients who suspected their health complaints to be caused by dental amalgam, and showed that a health promotion program and amalgam removal both had positive effects on symptoms (25). Here, we present a secondary analysis of our data examining the patients' personality, searching for outcome predictors with respect to subjective symptom burden, and analyzing associations between symptom scores and mercury levels both using a cross-sectional approach and looking at changes after removal of amalgam.
Although the results presented shed some new light on the nature of associations between mercury load, subjective symptom load and well-being, the existing picture of inconsistent scientific findings is supported. We demonstrated that the clinical features of subjective amalgam sensitivity, physical symptoms and psychological distress, can be reduced by very different therapeutic approaches.
But the data also revealed that amalgam sensitive individuals are quite heterogeneous with respect to treatment effects and that there may be a true association between symptoms and mercury levels in subgroups. Therefore, the question of 'amalgam sensitivity' should concentrate more on individual vulnerability, either in the form of biological (e.g. genetic) or psychosocial (e.g. personality, experiences, health beliefs and concerns) predispositions (32–34).
The heterogenous group of 'amalgam sensitive' subjects may require fundamentally different treatment approaches, with a subgroup of patients actually benefitting from amalgam removal and others needing psychosocial support instead of further (iatrogenic) 'somatization' of their complaints. Larger sample sizes as well as qualitative research methods would be helpful tools to answer this question (35).