Any material used in dentistry may provoke an individual local or systemic reaction, including an allergic response to its use. Due to the high toxicity of mercury, in so-called alternative dentistry, the removal of amalgam fillings is often recommended. ‘Amalgam sanitations’ often are a major component of the treatment portfolios of practitioners of this so-called alternative dentistry.
While amalgam fillings have excellent material properties, such as high marginal stability, quick processing, reliable hardening even in moist environments, good longevity under moist and warm conditions, they also have one property that is highly problematic in the long term: they are prone to corrosion. Old amalgam fillings will corrode after years and decades, without exception. The resulting oxidation products not only modify the metal microstructure, but they also change the spatial dimensions of the amalgam fillings. In dental materials science, this process is known as mercuroscopic expansion. 
The “German Amalgam Trial (GAT)”, large scale, 12-year study, tried to determine the mercury exposure from amalgam fillings in more detail. The study initially surveyed 6744 patients regarding their complaints. In a subset of the study population (n=27), the mercury burden of those with amalgam fillings to those without amalgam fillings was compared using serum and urine samples.[19,20] Inorganic mercury levels in blood and urine correlated in a highly significant manner with the presence of amalgam fillings. In patients with amalgam fillings, serum levels of mercury were increased 3.5 fold, urine levels were even more elevated and 4 times as high as those of patients without amalgam fillings.  Unfortunately, the GAT study did not examine the degree of corrosion present in the fillings, nor did it investigate mercury levels in tissues.
While the GAT study’s cytotoxic examinations showed no harmful effects at the cellular level, and found that low-dose effects consisted merely of “reduced adaptability of the cells post-amalgam exposure,”  entirely different cellular reactions may be observed when corrosion factors are taken into account. Under these conditions, Ursula Teichmann described a clearly cytotoxic reaction: “Corroded amalgams were shown to be clearly more toxic than non-corroded amalgams. Only in non-corroded amalgams a dependence of toxicity on the copper content of the samples was found.”  (Quote translated from German). While these cytotoxic effects were observed in vitro, they correspond perfectly to long-term observations from dental clinical practice. These observations show no softening of the dentin substance underneath old, corroded amalgam fillings, because the strong cytotoxic effect no bacteria will grow at the amalgam/dentin interface. Teichmann’s testing methods have become a standard of dental materials research. 
A review of various studies measuring the release of mercury vapors in the oral cavity showed an up to 15-fold increase after subjects had chewed gum.  The lungs will absorb 80% of the mercury vapors found in tidal air, and mercury vapor is considered to be most relevant in terms of its toxicological effects. The highest release rates of mercury vapor are observed during the placing and the removal of amalgam fillings. 
Within the moist and warm environment of the oral cavity, metal oxides will form due to gradual oxidation processes on any amalgam surface, both at the interface of the filling and the oral cavity, and at the interface of filling and dentin substance. It has been shown that ions diffuse into the dentin at the filling/dentin interface, and that they pass on into deeper tissue layers. 
Metal oxides also form at the occlusal surfaces of amalgam fillings, and these may successively erode, pass on to the digestive tract, and eventually may be metabolized. Oxidation processes not only release ions of copper (Cu2+), zinc (Zn2+), and tin (Sn2+), but also mercury ions (Hg2+). Problematic are in particular the mercury ions (Hg2+) from mercury salts that were formed by oxidation processes. These ions may displace the body’s own calcium ions (Ca2+) as central ions in chelate complexing agents. Due to their proven high neurotoxicity, mercury-containing substances should, therefore, be banned from everyday use. The Minamata Convention on Mercury triggered an EU-wide ban, effective July 1st, 2018, on the use of amalgam fillings in the treatment of children, adolescents, pregnant and nursing women.
Practitioners of so-called alternative dentistry routinely offer their patients homeopathic “detoxification treatments.” These are entirely useless because they do not contain any pharmacologically active substances that would be required for the removal of toxic substances. At best, they may have a placebo effect.
Effective procedures for the removal of heavy metals from the body do exist, however. They have been adapted from intensive medicine settings where they are used for the treatment of acute poisoning in emergencies. These procedures are referred to as chelation therapies and rely on substances such as 2,3-dimercaptopropane-1-sulfonate (DMPS). Chelation therapies have a high risk of side effects, and, therefore, are not recommended for alternative medicine detoxification procedures in case of suspected low-dose, chronic heavy metal poisoning. There are no scientifically proven methods for heavy metal removal in the chronic, low-dose range. 
Due to its major side effects, in scientifically based medicine, DMPS is only used to treat acute poisoning. Complexing agents cannot distinguish between vital minerals and harmful heavy metals. When chelation therapy is applied indifferently, it may, therefore, cause mineral imbalances and mineral deficiencies. In view of the long-term risks of mercury-containing dental fillings, and given the availability of other materials, it makes sense to strictly avoid amalgam in dental fillings. Despite the availability of alternative materials, and of effective preventive measures, dental amalgam continues to be used at a rate of on average 75 tons per year in the European Union. [26,27]
If amalgam use in dentistry is to be avoided in the future, massively more tooth decay prevention measures will be necessary in order to achieve a population-wide preservation of teeth. In children diagnosed with an increased susceptibility to dental decay, immediate therapeutic and preventive measures are needed, including a change in dietary habits. In Scandinavian countries that banned amalgam use many years ago, measures such as these have become everyday standards. If, on the other hand, the ban of amalgam in the EU is not accompanied by individualized, targeted, and effective prevention measures, we may be faced with similar dramatic developments and massive dental impairments, including their systemic medical and psychosocial consequences, as we have seen in patients from Russia. 
Summary and Conclusion
The procedures touted by practitioners of so-called alternative dentistry are unnecessary. This is because they are either not effective (e.g., homeopathic ‘removal’ of mercury), or because they have no relevant significance (e.g., the Prognos® measuring device for determining mercury exposure, or the LTT for material testing, or so-called dental projections as diagnostic tools for general medical conditions), or because they have a worrisome risk-benefit ratio (e.g., the use of DMPS to treat suspected chronic mercury exposure from amalgam, or bone trimming for suspected residual osteitis). It is a chastening thought that these ‘complementary’ dental procedures, while completely irrelevant, have become established in dental practice, and that by now three professional societies have formed in this field in Germany alone. In addition, insurance business models focusing on this market have emerged because so far no regulatory mechanisms in the field of continued medical education have been established to address this situation. As a result, an increasing number of unregulated courses is being offered. It seems paradoxical that the perpetuating demand is such that even state dental medical boards can no longer resist it and have begun offering classes of dubious nature in order to not miss out on this obviously booming market.
In order to preserve high quality standards in dental medicine, it seems imperative and essential to establish suitable regulatory and supervisory mechanisms. This would be surprisingly easy to achieve: Regulatory bodies might appoint continuing medical education representatives tasked with evaluating the methods to be taught. They should have no difficulty determining whether these methods are based in sound science or rather in a belief system that will not hold up to scientific scrutiny. Should continuing dental medical education remain unregulated, however, the quality of dental care will certainly be negatively affected. [28,29]
Ulrike Walter-Lipow, Bremen, Germany, provided the English translation of the first version of this manuscript.
Conflicts of Interest
The author declares no conflicts of interest with regard to this paper.
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