Myth #4: Mercury from dental amalgam fillings causes a variety of symptoms of “amalgam illness.”

Michael J. Wahl, D.D.S.
November 1, 2002

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Amalgam — Resurrection and Redemption Part 2:

The Medical Mythology of Anti-Amalgam

Michael J. Wahl, D.D.S.

Myth #4: Mercury from dental amalgam fillings causes
a variety of symptoms of “amalgam illness.”

Fact #4: The available scientific evidence does not support the myth
that mercury from dental amalgam causes “amalgam illness.”

Anti-amalgamists often assert that a multitude of conditions, sometimes collectively called “amalgam illness,” are caused or worsened by the presence of amalgam fillings and that removing amalgam fillings (and replacing them with nonamalgam fillings) leads to dramatic health improvements. In a 1990 survey of 86 patients who had all their amalgam fillings removed, Siblerud stated that patients reported dramatic improvements in various symptoms after amalgam removal [1]. Some of the 132 symptoms listed were related to cardiovascular, endocrine, hematological, and central nervous system disorders although there was no medical examination of any patients reported. Of the total 1815 symptoms between the 86 patients, Siblerud reported “nearly 70% of them were improved or eliminated after amalgam removal.” Fully 80% of patients reported feeling better and 58% reported “an increase in happiness and peace of mind.” Although there was no control group in this study, the author concluded that even if amalgam removal worked only as a placebo, the fact was that patients got better; and he called for a ban on the use of amalgam fillings until further information was available.

Similar dramatic improvements have been noted in other reports [2-4] Lichtenberg surveyed a group of 120 patients with up to 32 various symptoms of amalgam illness. After removing all amalgams and replacing them with composite filling materials, there were dramatic improvements in symptoms [2]. “On average, 88% of the symptoms specified in this investigation either disappear or improve.” As is typical of such reports, there is no information on preoperative or postoperative mercury levels in any patients, or on the presence or absence or number of amalgam fillings, age, or gender of the patients in the “control group.” There is no report on any attempt to match the control group with the study group for age, gender, presence or number of amalgam fillings, or smoking habits. No medical examinations were reported preoperatively or postoperatively for any patients.

Meso-2,3-dimercaptosuccinic acid (DMSA) is an effective metal chelating agent that enhances excretion of mercury in exposed patients. It has been used effectively to treat people exposed to toxic levels of mercury [5]. Two placebo-controlled, double-blind studies on patients with symptoms of “amalgam illness” showed increased urinary mercury excretion levels in patients taking DMSA but failed to correlate this with improvement of symptoms [6,7]. Any improvements of symptoms were no better than that of the placebo.

In well-controlled studies, researchers have been unable to document a scientific basis for “amalgam illness.” The “placebo effect” causes actual and measurable physical changes in many patients. As a result, one of the best ways to test a drug is to compare its efficacy with a placebo in studies where both the patients and investigators are blinded to the identity of the placebo versus the tested drug. In a review article of clinical trials of medications for cardiac patients, Packer observed that after three months of treatment with placebos, many cardiac patients had a reduction in symptoms, increased cardiac output, decreased pulmonary wedge pressure, and increased exercise tolerance [8]. Packer emphasized that in clinical practice, doctors should try to increase the “placebo effect” for better quality of life for patients, but in research, investigators should try to minimize the “placebo effect” to ensure that any drug tested is better than the placebo.

In a 1998 study of 4787 people, investigators could find no relationship between presence or intensity of clinical symptoms of various medical problems in patients with and without amalgam fillings [9]. They also found no significant correlation between the number of surfaces of amalgam fillings and the intensity of symptoms. It is interesting to note that these investigators have been among the leading anti-amalgamists in Germany. In a 1989 study of women hospital workers, 35 subjects with symptoms of fatigue were compared with 30 controls without symptoms of fatigue matched for age and smoking habits [10]. There was no statistical difference in the number of amalgam surfaces between the cases and the referents, and the authors concluded that factors other than mercury from dental amalgam must explain the symptoms of fatigue.

Ahlqwist et al studied 1462 Swedish women over a 20-year period and could find no relationship between the number of amalgam fillings and the incidence of myocardial infarction, stroke, diabetes, cancer, and overall mortality [11]. Women with few amalgams actually had an increased incidence of myocardial infarction, stroke, diabetes and early death when compared with women with a large number of amalgam fillings although this inverse relationship disappeared after taking into account number of teeth and socioeconomic group.

In a similar study of 1024 women asked 30 specific questions about different symptoms and complaints (e.g., dizziness, eye complaints, headache, general fatigue, chest pain, joint complaints, irritability), Ahlqwist et al. could find no correlation between the number of amalgam fillings and the number of symptoms or complaints [12]. In fact, women with a high number of amalgam fillings actually had fewer symptoms than women with few amalgam fillings (although this usually disappeared after taking into account the number of teeth as a background variable). There were fewer symptoms of abdominal pain and poor appetite in the group with many amalgam fillings even after taking into account number of teeth and socioeconomic status.

A double-blind, placebo-controlled study of 39 subjects with self-reported “amalgam disease” was conducted by Strömberg et al in 1999 [13]. Over a 2-year period, the subjects periodically inhaled either air or mercury vapor. Both the investigators and the subjects were blinded to whether it was air or mercury vapor being administered. There was no significant difference in the number of reactions to air or mercury vapor in the study population as a whole and in 37 of the 39 subjects (95%). Two individual subjects had significantly more reactions to mercury vapor than to air. The authors concluded that short-term exposure to mercury vapor does not exacerbate symptoms in most of the population suffering from “amalgam disease” although a small percentage of these patients may be sensitive to mercury vapor. This would be consistent with the small percentage of patients who have a bona fide allergy to mercury.

Bratel et al compared 50 consecutive patients self-referred for “amalgam illness” with age-, sex-, and geographically-matched controls [14,15]. The mercury levels in the blood, urine, and hair were similar in the study and the control group. The oral health and the number of surfaces of amalgam in the study group were similar to those of the control group. There was no correlation between the severity of symptoms and the level of mercury. The authors concluded that mercury from dental amalgam was not the likely cause of the health complaints of the study group, but rather “the symptoms were part of a broad spectrum of mental disorders.”

Molin et al compared a group of patients with subjective symptoms of “oral galvanism” (dry, burning mouth, mouth pain, and/or metallic taste) to a group of controls [16]. Although there was a correlation of plasma levels of Hg with the number of surfaces of amalgam fillings in all the patients, there were no differences in the levels of plasma-selenium, erythrocyte glutathione-peroxidase, and numerous other blood parameters between the patients and the controls.

Herrström and Högstedt studied 142 women and 76 men with self-diagnosed “oral galvanism” and found no cases of mercury intoxication. Instead, 42.7% of the patients had a mental disorder, including generalized anxiety disorder or panic disorder. Amalgam removal was recommended to some patients, mainly for psychologic reasons (but none improved), but also for oral conditions. They concluded, “The clinical conditions behind the concept of oral galvanism seem to be explicable in terms of general medicine, and no generalized toxic effect of amalgam fillings need be suspected.” [17]


  1. Siblerud RL. Health effects after dental amalgam removal. J Orthomol Med 1990;5:95-106.
  2. Lichtenberg H. Elimination of symptoms by removal of dental amalgam from mercury poisoned patients, as compared with a control group of average patients. J Orthomol Med 1993;8:145-8.
  3. Zamm AV. Removal of dental mercury: often an effective treatment for the very sensitive patient. J Orthomol Med 1990;5:138-42.
  4. Kidd RF. Results of dental amalgam removal and mercury detoxification using DMPS and neural therapy. Altern Ther 2000;6(4):49-55.
  5. Ding G-S, Liang Y-Y. Antidotal effects of dimercaptosuccinic acid. J Appl Toxicol 1991;11:7-14.
  6. Grandjean P, Guldager B, Larsen IB. Placebo response in environmental disease: chelation therapy of patients with symptoms attributed to amalgam fillings. J Occup Environ Med 1997;39:707-14.
  7. Sandborgh Englund G, Dahlqvist R, Lindelöf B. DMSA administration to patients with alleged mercury poisoning from dental amalgams: a placebo-controlled study. J Dent Res 1994;73:620-8.
  8. Packer M. The placebo effect in heart failure. Am Heart J 1990;120:1579-82.
  9. Melchart D, Wühr E, Weidenhammer W, Kremers L. A multicenter survey of amalgam fillings and subjective complaints in non-selected patients in the dental practice. Eur J Oral Sci 1998;106:770-7.
  10. Michel I, Norbäck D, Edling C. An epidemiologic study of the relation between symptoms of fatigue, dental amalgam and other factors. Swed Dent J 1989;13:33-8.
  11. Ahlqwist M, Bengtsson C, Lapidus L. Number of amalgam fillings in relation to cardiovascular disease, diabetes, cancer and early death in Swedish women. Comm Dent Oral Epidemiol 1993;21:40-4.
  12. Ahlqwist M, Bengtsson C, Furunes B, et al. Number of amalgam tooth fillings in relation to subjectively experienced symptoms in a study of Swedish women. Comm Dent Oral Epidemiol 1988;16:227-31.
  13. Strömberg R, Langworth S, Söderman E. Mercury inductions in persons with subjective symptoms alleged to dental amalgam fillings. Eur J Oral Sci 1999;107:208-14.
  14. Bratel J, Haraldson T, Meding B, et al. Potential side effects of dental amalgam restorations. (I). An oral and medical investigation. Eur J Oral Sci 1997;105:234-43.
  15. Bratel J, Haraldson T, Ottosson J-O. Potential side effects of dental amalgam restorations. (II). No relation between mercury levels in the body and mental disorders. Eur J Oral Sci 1997;105:244-50.
  16. Molin M, Marklund S, Bergman B, et al. Plasma-selenium, glutathione peroxidase in erythrocytes and mercury in plasma in patients allegedly subject to oral galvanism. Scand J Dent Res 1987;95:328-34.
  17. Herrström P, Högstedt B. Clinical study of oral galvanism: no evidence of toxic mercury exposure but anxiety disorder an important background factor. Scand J Dent Res 1993;101:232-7.

Dr. Wahl practices dentistry in Wilmington, Delaware. This article was originally published in Quintessence International 32:696-710, 2001, and is reproduced here with the kind permission permission of Quintessence Publishing Co. The author thanks Drs. J. Rodway Mackert, Ivar A. Mjör, and Fred Eichmiller for reading the manuscript and offering several helpful suggestions.

Part 1:
Intro |||
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2 |||
3 |||
4, 5, 6, 7 |||
8, 9 |||
10, Conclusion

Part 2:
Intro |||
1 |||
2 |||
3 |||
4 |||
5 |||
6 |||
7 |||
8 |||
9 |||
10, Conclusion

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