C20 Discuss the potential toxicological problems related to the presence of mercury in dental amalgams and identify the group of patients who are most susceptible to the adverse effects of mercury exposure.
During the 70th and the 80th, researchers discovered that mercury vapor was released from amalgam restorations during chewing. These findings came at a time when environmentalist groups grew stronger, caries declined, dental schools closed, and new materials were introduced on the market as so called "amalgam substitutes." At the same time, patients also became more interested in esthetic (white) restorations rather than the dark looking amalgams. All these factors; true concern for health and the environment, personal interests (job security and esthetic look), profit (expansion of a market that should decline due to a decrease in disease), etc., increased the pressure to remove amalgam as a restorative material despite the fact that this material has been used in dentistry and served the public well for almost 200 years without any proven health problems. Debate books, like the one shown below, were sold in health stores, and sometimes the debate lost proportions. Many of the anti-amalgamists suggested the removal of amalgams and that the amalgams should be replaced with materials with substantially shorter longevity. One must question the anti-amalgamists motives, because, based on existing knowledge, we know that more people have died during the last 10 years because of traffic accidents associated with the increased number of dental visits caused by the need to replace inferior dental materials than the number of patients who have died due to amalgam restorations since their introduction almost 200 years ago.
Today we can conclude that the biggest potential hazard with dental amalgam is the inhalation of mercury vapor. For example, clinical studies have shown that metallic mercury being swallowed by accident during amalgam placement is not absorbed to any greater extent by the intestinal tract.. However, almost all inhaled mercury vapor passes through lung tissues and is via the blood transported to certain target organs. The key target organs are the brain, the kidneys and the liver. Most potential harm occurs in the brain and the kidneys. In the brain, the mercury can cause neurological changes. In the kidneys, mercury can damage tubular tissue and cause kidney failure.
From the late 70th to the early 90th it was shown that mercury vapor is released from amalgam restorations (see figure below). These findings caused major concern and triggered the above mentioned amalgam debate, which has resulted in a substantial decline in the use of amalgam. However, during this debate it was also shown that the amount of mercury being released from dental amalgams was only 1-2% of the threshold level at that time. In other words, individuals working for example within the alkali industry can be exposed for 50-100 times more mercury than they receive from their amalgam fillings. In other words, it is rather obvious that the benefits of dental amalgams far outweigh the risks.
Despite the above findings, it important to emphasize that the real threat regarding amalgam exposure is for the dentist and his/her personnel. In most dental clinics, amalgam is used. It is particularly during removal and placement of amalgams as the mercury level in the work environment is high. In addition, if amalgam instruments are not well cleaned, mercury can be released to the working environment during sterilization. In other words, the dental personnel should handle dental amalgam and mercury with care.
To make sure that the mercury level is not too high in the dental office, mercury vapor detectors can be used. Different detectors exist. Some of the most cost-efficient ones can be purchased from the Environmental Division of 3M. These detectors remind about the detectors used by personnel working with x-rays. Instead of using a film to detect x-rays, the mercury detector consists of a gold foil that absorbs mercury. After a certain time of usage, the detector with the gold foil is sent to 3M for mercury analysis.
