Singapore to limit mercury use in tooth fillings despite WHO call for phase-out by 2034
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Dentists in Singapore still use mercury as a tooth filling judiciously, as some cases still need amalgam fillings.
PHOTO: ISTOCKPHOTO
- Singapore dentists will reduce, but not eliminate, mercury in fillings, aligning with WHO's 2034 phase-out goal but ensuring appropriate care continues.
- Amalgam is ideal for deep cavities that are hard to keep dry, as it's durable and cost-effective, but alternatives like composite resin are preferred for aesthetics.
- Studies show low mercury exposure from fillings, about 0.2 to 0.4 microgram a day per amalgam-filled tooth, and no significant health differences versus composite fillings.
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SINGAPORE – Dentists in Singapore will gradually reduce the use of mercury in tooth fillings, but will not entirely end its use.
While tooth-coloured materials – such as composite resin, porcelain (ceramic) and glass ionomer – are the first-line option in most situations, several dentists told The Straits Times that mercury-based tooth amalgams, a common filling material used for more than 175 years, are still ideal for deep cavities where keeping the tooth dry is difficult.
These dental amalgams, which comprise 50 per cent mercury, are less sensitive to moisture during placement, they said.
In November, the World Health Organization (WHO) called for a phase-out of mercury-based dental amalgams in tooth fillings by 2034
It lists mercury as one of the top 10 chemicals of major public health concerns, calling it “toxic to human health”.
Phasing out the use of mercury-based dental amalgams in tooth fillings is also a way to protect the environment from mercury emissions.
The Singapore Dental Association (SDA) said that while the Republic’s dental community is aligned with the global direction, it is reducing the use of dental amalgam while ensuring that patients continue to receive safe, effective and appropriate care.
Amalgam is still in use today, but only in a small number of cases where it remains clinically indicated.
Dr Alethea Foong, a prosthodontics consultant with the department of restorative dentistry at the National Dental Centre Singapore, said that material selection for tooth fillings is usually based on clinical scenarios, such as the location of the tooth, cavity size, caries risk and patient’s needs.
“Amalgam is (used) to restore large, load-bearing back teeth, where durability and longevity are prioritised over aesthetics. It is also preferred in situations where moisture control is difficult, in patients with high caries risk or poor oral hygiene, and when cost-effectiveness and reduced chair time are important considerations,” she said.
Resin-based composite is the most widely used alternative to amalgam, especially for back teeth, due to superior aesthetics and adequate mechanical properties.
“However, composites are associated with a higher risk of restoration failure and secondary caries compared with amalgam. They require strict moisture control and have higher technique sensitivity,” Dr Foong said.
The choice between mercury-based amalgam and alternative tooth filling materials ultimately depends on the dentist’s evaluation of the patient’s oral condition and the suitability of dental amalgam for the specific case.
For instance, if a patient has teeth subjected to a strong biting force, a stronger material such as dental amalgam could be beneficial.
But this choice would also consider whether the patient has allergies to other filling materials or any existing health conditions, according to the SDA.
While existing dental amalgam fillings in the general population, including older patients, are considered stable and durable when properly maintained, there is no local data on the number of people with amalgam fillings, said a spokesman for the Faculty of Dentistry at the National University of Singapore (NUS).
He explained that dental amalgams emit small amounts of mercury as vapour, which is unlikely to cause any major health issues.
Mercury vapour and ions from tooth fillings are released primarily through the continuous evaporation of mercury from the surface, as well as through corrosion and mechanical wear caused by chewing, tooth brushing and consumption of hot foods or beverages.
A check with the SDA found that small amounts of mercury vapour may also be released during the placement, polishing or removal of amalgam fillings. This observation aligns with extensive international reviews by regulatory and public health agencies, which confirm that exposure levels from intact restorations are generally low and below established safety thresholds for the general population.
Dr Foong said: “It is estimated that daily mercury vapour exposure from amalgam fillings is about 0.2 to 0.4 micrograms a day per amalgam-filled tooth surface, or 0.5 to 1 microgram a day per amalgam-filled tooth.”
The amount is not even visible to the naked eye and is equivalent to a speck of dust.
Citing large randomised trials in children and epidemiological studies in adults, she noted that no statistically significant differences were observed in neuropsychological function, IQ or kidney outcomes over five years between individuals with amalgam and those with composite restorations, despite higher urinary mercury levels in the amalgam groups.
“The amount of mercury released would be directly proportional to the number and surface area of amalgam restorations present, in particular amalgams on the biting surfaces of teeth (which come into contact when patients grind their teeth),” she said.
“This level of exposure would remain well below occupational exposure thresholds associated with clinical toxicity, which is 20 to 50 micrograms per litre (of) urinary mercury.”
