SINGAPORE – Dentists in Singapore will gradually reduce the use of mercury in tooth fillings, but not completely end its use.
While tooth-colored materials – such as composite resin, porcelain (ceramic) and glass ionomer – is the first choice in most cases, many dentists told The Straits Times that mercury-based dental amalgams, a common sealing material used for more than 175 years, are still ideal for deep cavities where it is difficult to keep the tooth dry.
These dental amalgams, which contain 50 percent mercury, are less sensitive to moisture during placement, they said.
In Novemberthe World Health Organization (WHO) requested a
phasing out mercury-based dental amalgams in dental fillings by 2034
a move that will change dentistry worldwide.
It ranks mercury as one of the top 10 chemicals of major public health concern, 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 as the Republic’s dental community aligns 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 used today, but only in a small number of cases where it remains clinically indicated.
Dr Alethea Foong, consultant prosthodontist in the department of restorative dentistry at the National Dental Center Singapore, said the choice of material for dental fillings is usually based on clinical scenarios such as tooth position, cavity size, caries risk and patient needs.
“Amalgam (is) used to restore large, load-bearing posterior teeth where durability and longevity take precedence over esthetics. 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,” he said.
Resin-based composite is the most widely used alternative to amalgam, especially for posterior teeth, due to its superior aesthetics and adequate mechanical properties.
“However, composite materials are associated with a higher risk of restoration failure and secondary caries compared to amalgam. They require strict moisture control and have a higher technique sensitivity,” Dr Foong said.
The choice between mercury-based amalgam and alternative tooth filling materials ultimately depends on the dentist’s assessment of the patient’s oral condition and the suitability of the dental amalgam for the particular case.
For example, if a patient has teeth that are subjected to strong bite force, a stronger material such as dental amalgam could be beneficial.
But this option will also consider whether the patient has allergies to other fillers or any existing health conditions, according to the SDA.
While existing dental amalgam fillings in the general population, including elderly patients, are considered stable and durable when properly maintained, there is no local data on the number of people with amalgam fillings, said a National University of Singapore (NUS) School of Dentistry spokesperson.
He explained that dental amalgams emit small amounts of mercury as vapor, which is unlikely to cause serious health problems.
Mercury vapor and ions from dental fillings are released primarily through the continuous evaporation of mercury from the surface, as well as through erosion and mechanical wear caused by chewing, brushing, and consuming hot foods or drinks.
An audit with the SDA found that small amounts of mercury vapor may also be released when amalgam fillings are placed, polished or removed. This observation is consistent 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 limits for the general population.
Dr Foong said: “It is estimated that the daily exposure to mercury vapor from amalgam fillings is about 0.2 to 0.4 micrograms per day per amalgam-filled tooth surface, or 0.5 to 1 microgram per day per amalgam-filled tooth.”
THE quantity is not even visible to the naked eye and is equivalent to a speck of dust.
Citing large randomized trials in children and epidemiological studies in adults, she noted that no statistically significant differences in neuropsychological functioning were observed, IQ or renal outcomes over five years between those with amalgam and those with composite restorations, despite higher urinary mercury levels in the amalgam groups.
“The amount of mercury released will be directly proportional to the number and surface area of amalgam restorations present, particularly amalgams on the biting surfaces of the teeth (which come into contact when patients grind their teeth),” he said.
“This level of exposure would remain well below the occupational exposure limits associated with clinical toxicity, which is 20 to 50 micrograms per liter of urine mercury.”
