DENTAL AMALGAM AND MERCURY CONTROL

1. INTRODUCTION 


DENTAL AMALGAM
Dental amalgam is the most widely used restorative material in the history of dentistry. It was introduced in Europe in 1819 by Bell, becoming widespread in 1826 and reaching the United States in 1830.

Refined its characteristics spread widely worldwide especially after the improvements in its composition and protocolization introduced by J. D. Black.

It is characterized by its easy manipulation, low cost, and predictability. Nevertheless, because it has Mercury in its composition, it has been questioned by different authors and its restriction has been suggested by organisms, institutions, and authorities of different countries, even reaching its prohibition in three of them for environmental reasons.

2. MERCURY AND AMALGAM  


Mercury is not essential for biological processes, but in the face of exposure and contamination, it can accumulate in living tissues, causing toxicity by precipitating proteins synthesized by the cell, particularly neurons, and inhibiting sulfhydryl groups of essential enzymes.

Mercury in amalgams is found as elemental (or metallic) and as inorganic mercury and is potentially less toxic than the so-called organic mercury of the diethyl, phenyl and methylmercury types. The elemental mercury contained in the amalgam due to intrabuccal corrosion is released as elemental mercury and as inorganic mercury.

Organic compounds such as methylmercury are soluble in lipids, are highly diffusible through membranes, and biotransform slowly into inorganic mercury. Maximum concentration levels or thresholds are handled in ambient air. Between 10 and 20 nanograms of mercury per cubic metre of air (ng/m³) have been detected in urban air.

The normal total mercury content in the body is between 1 and 13 milligrams, 10% is methylmercury.

The average urinary mercury concentration in the U.S. is 0.72 mcg/l and the average blood concentration is 0.34 mcg/l. Higher values are found in Europe.

Average urinary concentrations increase in relation to the number of dental amalgam surfaces. While the average blood concentrations increase with the consumption of fish.
With respect to simultaneous exposure: inorganic Hg amalgam, organic Hg food, there is evidence that the determination of the level of inorganic mercury in plasma and erythrocytes is the indicator of the absorption of mercury from amalgam and that the determination of total mercury in blood includes 47 % organic mercury (even in populations with low fish intake).

Inorganic mercury is excreted by intestinal and renal routes (50% and 50%). Organic mercury via the gut. This is why there is a strong correlation between the concentration of mercury in urine and the amalgam surface and therefore urine mercury concentrations are applied as a measure of exposure to mercury from amalgams.

WHO tolerable intake figure: 0.23 mcg/day/kg body weight (if it weighs 65 kg it is 15 mcg/day). In the case that the mercury absorbed by a person with 7 amalgams was only inorganic (without considering that of the diet) the WHO figure is well above that of the mercury that comes from the amalgam.

Other values for mercury vapor EPA 0.3 mg/m. ATSDR Minimum Risk Level 0.2 mg/m.

Although there are still conflicting positions in the literature, the most consolidated position is that amalgams would not offer concentrations that would reliably cause relevant physical or environmental harm. Different organisms advise discouraging their use (UNEP 2007, Global Mercury Alliance) as an efficient mercury control measure but with a gradual withdrawal of their supply and dental use. The FDI in 2009 and the ADA in 2010 also accompany this position, based especially on their impact on the environmental control of Mercury.

It should be noted that this proactive attitude towards biotolerance must be maintained for all materials including the most modern dental materials (acrylates, BIS-GMA, resins), those for medical use such as vaccines and antiseptics, lighting, agro-industry etc.

A factor that complicates the thematic approach is the risk of lobbying, at all levels, of multinational companies seeking to impose in the market materials of higher cost and that mean greater business profit but with the consequent economic loss for countries and populations.

. 3 AMALGAM AS A RESTORATIVE MATERIAL 


The amalgam has a cost/benefit ratio widely proven for its reliability and duration, since without requiring high specialization for its installation it is successfully handled by generalists, with highly predictable results (even equal or superior to some more modern techniques). This underpins what has been pointed out by different international organizations (WHO, FDI, ADA), where the suppression for underdeveloped countries or vulnerable populations would cause public health problems when strategies with characteristics adaptable to the context are lost.

Due to its lower need for replacement and specific cost (human and material), amalgam can be 1.5 to 3 times cheaper than resins or similar. Countries that replace them will therefore require a large additional economic effort. Rich countries (United States and Germany), whose insurance companies valued the possibility of removing existing amalgams to replace them with more modern materials, have gone back on their aspirations given the very high derivatives and understanding that the benefits achieved do not comply with the statements. Indeed, in addition to the fact that the deleterious condition of the material has not been demonstrated, the removal entails unnecessary volatilization of mercury and a new and massive instance of waste control.

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