Dott. Giorgio Tessore
Assistant Professor in Restorative Dentistry- University of Turin

Are silver amalgam restorations bad for patient’s health?

Silver amalgam is the most widely used material by dentists all over the world for posterior tooth restoration. It has been estimated that every year 500,000,000 silver restorations are done on a worldwide basis, and 200,000,000 in the US only.

Silver amalgam is a metal alloy of silver, tin, copper, palladium, indium and a liquid component, mercury (Hg).

When these metals are mixed together, an easily condensable and mouldable plastic material is formed, which hardens completely within two hours. In Dentistry, the amalgam has been successfully used for more than a century as a restoration material for tooth decay. During the last twenty years, its quality has greatly improved, thanks to a lower amount of mercury and to the addition of new components which can reduce its corrosion in the oral cavity.

Unquestioned meritsof this material include: optimal marginal sealing; easy handling; long duration; established clinical experience; low final cost of the restoration.

Defects include: a very different color from that of teeth, hence the popular term of "lead filling"; the need to make retentive -and to a certain extenct destructive- cavity preparations, since the amalgam is not able to bind itself to the tooth structure; and, eventually, the potential toxicity of Hg.

Whether amalgam is hazardous for patients’ health is a question almost as old as the material itself, and has led to the growth of a vast scientific literature on the subject. The risk for patients and health

The risk for patients and health workers essentially depends on the possibility of Hg inhalation and ingestion in the course of either execution or removal of a restoration: during these manoeuvres, the patient may be effectively protected by a rubber barrier, the dam , which isolates teeth from the rest of the mouth.

It has been demonstrated that Hg, once bound to the other metals, is stable, and is released in the oral cavity from the restoration in an absolutely negligible amount.

In a study published in 1995, a German group of researchers developed a new technique for measuring the amount of Hg vapours in the oral cavity and in the saliva. They showed that the amount of Hg released from a tooth filling is not dangerous. Similar conclusions have been recently (1997) reached by researchers from the University of Göteborg.

The average daily intake of Hg from food in the European population amounts to 5-10 µg, while up to 5 µg of Hg can be released from a filling. The sum of both figures is far lower than that established by the World Health Organization as the maximum daily acceptable value, which corresponds to 30-40 µg.

In two creditable studies, Ivanovic (1989) and Wirz (1992) showed that blood and urinary Hg levels in patients who have multiple amalgam restorations are not higher than the levels of individuals who do not have amalgam restorations. It is worth considering that people living on islands or coastal zones (Japan, Sweden, etc.) have much higher blood and urinary Hg levels than people living in continental areas, regardless of having or not amalgam fillings.

Following introduction in the body, Hg can produce nervous and renal toxicity. In 1966, Basch hypothesized that the amalgam might cause multiple sclerosis. Although no scientific evidence for such effect has been presented, and in spite of the many patients who have been fooled, this hypothesis is still brought around as proof of toxicity. The Italian Association for Multiple Sclerosis has taken a stand by inviting its affiliates not to credit false hopes of ameliorating their symptoms by having their fillings removed.

Chronic Hg poisoning in individuals who have been professionally exposed to Hg powder or vapours may cause a multisymptom disorder characterized by depression, anxiety, irritability, tiredness, memory loss, difficulty in concentration and tremors.

Particularly in Scandinavian countries, Germany, the US and more recently in Italy, news reports have appeared on the media concerning the amalgam risk. These news have no scientific ground and are based on old reports which have been subsequently denied by more careful and sophisticated analyses. The diffusion of such false alarmism has been favoured by the so-called "alternative" medicine, by ecologists, by bad information and possibly by the industry itself, which appears to favour the diffusion of alternative materials since they are more expensive and more profitable than amalgam.

People, patients and even health care managers have been the object of such misleading campaign, which makes a scandal out of this argument, is a temptation to press and TV media and opens the doors to pseudo-experts who are completely unknown to the scientific community.

In Germany, Dr. Daunderer has appeared several times on TV and his arguments over the poisoning effects of amalgam fillings have been often reported by the press, thereby causing a lot of dismay and uncertainty among readers. His conclusions have been carefully evaluated by researchers and toxicologists from the University of Erlangen, who found them to be totally untrue since they had been based on wrong and even dishonest methodologies (Schiele and Kroncke 1989).

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