Dr Andrew Chan Kieng Hock

Consultant Oral Surgeon Private Dental Practice Klang, Selangor.

The debate over the safety of amalgam fillings has been going on for decades and has caused much confusion and anxiety among consumers. The presence of mercury in amalgam has often been blamed for ill-health by some misinformed groups or parties with personal interest in this matter, in particular manufacturers of tooth-coloured dental materials. Dr Andrew Chan Kieng Hock discusses objectively the toxic effects of mercury as an element and presents a holistic view on the safety aspect of amalgam in dentistry.

WHAT IS MERCURY?

Mercury is a naturally existing element in the environment. It is highly lipid-soluble and easily infiltrates nerve cells in our body. In high quantity, mercury can cause neurotoxicity (damage to the brain and nerves) and nephrotoxicity (damage to the kidneys). The World Health Organization (WHO) recommends that mercury is safe when the intake is less than 0.47 micrograms (µg) per kilogram body weight in a day.

There are three primary types of mercury:

• Elemental mercury, which is found in the air as vapour and dental amalgam
• Inorganic mercury compounds, for example mercuric chloride, mercuric acetate and mercury sulphide
• Organic mercury compounds such as methylmercury.

Methylmercury is the most toxic mercury element and is found mostly in big fishes such as tuna, shark and swordfish. It is mainly absorbed through our gut when we eat those types of fish. Most of the mercury that we ingest is through our food.

Each person’s body processes these different forms of mercury differently with different levels of tolerance. Exposure to mercury can be an occupational hazard for people working with the element eg, factory workers in the manufacture of thermometers as well as dental health providers. However with good work practice in handling and proper disposal, mercury poses negligible health hazard to people.

 In fact, numerous scientific studies have shown that dentists and  their dental surgery assistants did not demonstrate any ill-effects clinically to their neurological, reproductive system and psychological functions. Ironically, further evidence have shown that children born to dentists have lower prenatal death and birth defects than the general population.

THE USE OF DENTAL AMALGAM

Historically, dental amalgam has been used as the main dental filling material for tooth cavities for more than 150 years. It has a good safety record compared to the newer tooth-coloured dental fillings, which consist of composite resin and glass ionomer cement. Amalgam is a suitable material for use in most situations especially in large cavities on the rear molars, decay below the gum margins or in areas that are difficult to keep dry. It is a very durable, easy to handle and relatively cheap treatment option for the general population.

It is my concern that due to misguided fears about the safety of amalgam, coupled with the more expensive filling options, this may cause ordinary people to forego essential dental care. To state that amalgam is somehow responsible for diseases such as neurological disorders, autism, Alzheimer’s disease, dementia and other chronic diseases is far-fetched. It is true that amalgam contains mercury, but when mixed with metals such as silver, copper, tin and zinc, they form a stable alloy for filling tooth decay. This mixture rapidly hardens into a solid and stable material in the cavity.

DENTAL AMALGAM IS GENERALLY SAFE

An analogy is drawn between sodium and chlorine, both of which are hazardous in their pure form. But, when combined, they form ordinary table salt! As far as I know, there has been no call for consumers to stop using table salt due to the hazardous nature of the individual elements of sodium and chlorine.

So it is with the mercury element in dental amalgam, which forms an inert compound after reacting with other metals. It is true that vigorous chewing and grinding can release minute amounts of mercury vapour from dental amalgam fillings, which are only 1 to 27 µg per day with an average of 5 µg per day (depending on the number and size of fillings) according to a WHO report in 2003. But there is no evidence for this extremely negligible quantity adversely affecting the health of patients.

The recognised safe limit for blood level of mercury is about 35 milligrams per litre in an adult. Nonetheless, some countries, such as Sweden, Norway, Denmark, Germany and Japan restricted the usage of amalgam on expecting and breastfeeding mothers due to political pressure from the public and also due to their high consumption of fish.

The US Food and Drug Administration (FDA) does not recommend removal of old and functional amalgam from teeth with air-rotor, for fear of releasing traces of mercury vapour into the lungs, if adequate water- cooling and aspiration are not used. Removing sound amalgam fillings will also result in unnecessary loss of healthy tooth structure and the procedure is quite expensive as well. However, individuals who are allergic or sensitive to mercury or any of the metals in dental amalgam are advised to replace them with alternative materials. Deciding on which type of filling material to use is best made between the patient and the dentist, after taking into consideration certain specific factors.

Recently, the American Dental Association (ADA) published a statement which conclude that “there is insufficient evidence to justify claims that mercury from dental amalgam has an adverse effect on the health of patients”. This is a strong statement by a dental body in a country with a highly litigious culture.

The only disadvantages of this material are its unsightly grey-metallic hue and its inability to bond directly to tooth structures like the tooth-coloured materials.

In conclusion, in spite of the mercury element, there is no doubt dental amalgam is a very safe, useful, durable and affordable filling material for the general population. HTDr Andrew Chan Kieng Hock

Consultant Oral Surgeon Private Dental Practice Klang, Selangor.

The debate over the safety of amalgam fillings has been going on for decades and has caused much confusion and anxiety among consumers. The presence of mercury in amalgam has often been blamed for ill-health by some misinformed groups or parties with personal interest in this matter, in particular manufacturers of tooth-coloured dental materials. Dr Andrew Chan Kieng Hock discusses objectively the toxic effects of mercury as an element and presents a holistic view on the safety aspect of amalgam in dentistry.

WHAT IS MERCURY?

Mercury is a naturally existing element in the environment. It is highly lipid-soluble and easily infiltrates nerve cells in our body. In high quantity, mercury can cause neurotoxicity (damage to the brain and nerves) and nephrotoxicity (damage to the kidneys). The World Health Organization (WHO) recommends that mercury is safe when the intake is less than 0.47 micrograms (µg) per kilogram body weight in a day.

There are three primary types of mercury:

• Elemental mercury, which is found in the air as vapour and dental amalgam
• Inorganic mercury compounds, for example mercuric chloride, mercuric acetate and mercury sulphide
• Organic mercury compounds such as methylmercury.

Methylmercury is the most toxic mercury element and is found mostly in big fishes such as tuna, shark and swordfish. It is mainly absorbed through our gut when we eat those types of fish. Most of the mercury that we ingest is through our food.

Each person’s body processes these different forms of mercury differently with different levels of tolerance. Exposure to mercury can be an occupational hazard for people working with the element eg, factory workers in the manufacture of thermometers as well as dental health providers. However with good work practice in handling and proper disposal, mercury poses negligible health hazard to people.

 In fact, numerous scientific studies have shown that dentists and  their dental surgery assistants did not demonstrate any ill-effects clinically to their neurological, reproductive system and psychological functions. Ironically, further evidence have shown that children born to dentists have lower prenatal death and birth defects than the general population.

THE USE OF DENTAL AMALGAM

Historically, dental amalgam has been used as the main dental filling material for tooth cavities for more than 150 years. It has a good safety record compared to the newer tooth-coloured dental fillings, which consist of composite resin and glass ionomer cement. Amalgam is a suitable material for use in most situations especially in large cavities on the rear molars, decay below the gum margins or in areas that are difficult to keep dry. It is a very durable, easy to handle and relatively cheap treatment option for the general population.

It is my concern that due to misguided fears about the safety of amalgam, coupled with the more expensive filling options, this may cause ordinary people to forego essential dental care. To state that amalgam is somehow responsible for diseases such as neurological disorders, autism, Alzheimer’s disease, dementia and other chronic diseases is far-fetched. It is true that amalgam contains mercury, but when mixed with metals such as silver, copper, tin and zinc, they form a stable alloy for filling tooth decay. This mixture rapidly hardens into a solid and stable material in the cavity.

DENTAL AMALGAM IS GENERALLY SAFE

An analogy is drawn between sodium and chlorine, both of which are hazardous in their pure form. But, when combined, they form ordinary table salt! As far as I know, there has been no call for consumers to stop using table salt due to the hazardous nature of the individual elements of sodium and chlorine.

So it is with the mercury element in dental amalgam, which forms an inert compound after reacting with other metals. It is true that vigorous chewing and grinding can release minute amounts of mercury vapour from dental amalgam fillings, which are only 1 to 27 µg per day with an average of 5 µg per day (depending on the number and size of fillings) according to a WHO report in 2003. But there is no evidence for this extremely negligible quantity adversely affecting the health of patients.

The recognised safe limit for blood level of mercury is about 35 milligrams per litre in an adult. Nonetheless, some countries, such as Sweden, Norway, Denmark, Germany and Japan restricted the usage of amalgam on expecting and breastfeeding mothers due to political pressure from the public and also due to their high consumption of fish.

The US Food and Drug Administration (FDA) does not recommend removal of old and functional amalgam from teeth with air-rotor, for fear of releasing traces of mercury vapour into the lungs, if adequate water- cooling and aspiration are not used. Removing sound amalgam fillings will also result in unnecessary loss of healthy tooth structure and the procedure is quite expensive as well. However, individuals who are allergic or sensitive to mercury or any of the metals in dental amalgam are advised to replace them with alternative materials. Deciding on which type of filling material to use is best made between the patient and the dentist, after taking into consideration certain specific factors.

Recently, the American Dental Association (ADA) published a statement which conclude that “there is insufficient evidence to justify claims that mercury from dental amalgam has an adverse effect on the health of patients”. This is a strong statement by a dental body in a country with a highly litigious culture.

The only disadvantages of this material are its unsightly grey-metallic hue and its inability to bond directly to tooth structures like the tooth-coloured materials.

In conclusion, in spite of the mercury element, there is no doubt dental amalgam is a very safe, useful, durable and affordable filling material for the general population. HT