What the Scientific Evidence Actually Says
Concerns about the safety of dental fillings occasionally appear online and in media discussions. Some sources suggest that materials used to repair teeth could release harmful chemicals into the body and potentially contribute to diseases such as cancer.
The topic usually focuses on two types of dental materials:
Silver amalgam fillings, which contain mercury as part of a metal alloy
Composite (tooth-coloured) fillings, which contain resin compounds used in modern restorative dentistry
Because these materials are used in millions of dental treatments worldwide every year, they have been extensively studied by researchers and public health organisations.
The reassuring conclusion from decades of research is that there is no reliable scientific evidence linking dental fillings with cancer.
However, understanding where these concerns come from — and what research has actually found — helps patients make informed decisions about their oral health.
Why Questions About Dental Materials Exist
Any material placed inside the human body must meet strict standards for safety, durability, and biological compatibility. Dental restorations remain in the mouth for years, sometimes decades, so it is natural that scientists closely examine how these materials interact with the body.
Two substances are often mentioned when discussing dental fillings:
Mercury, which is present in dental amalgam fillings, and Bisphenol-A (BPA), a chemical sometimes associated with plastic resins.
Both mercury and BPA have been studied extensively in toxicology research because high levels of exposure in industrial or environmental settings can affect human health.
However, exposure from dental materials occurs in very different forms and at extremely low levels compared with industrial or environmental exposure. For this reason, regulatory authorities and dental organisations regularly review scientific evidence to determine whether these materials remain safe for clinical use.
Amalgam Dental Fillings
Dental amalgam has been used for more than 150 years and remains one of the most thoroughly researched restorative materials in dentistry.
Amalgam is not pure mercury. Instead, it is a stable alloy created by combining mercury with metals such as silver, tin, and copper. When mixed together, these metals form a durable compound capable of withstanding the strong forces generated during chewing.
Historically, amalgam fillings became popular because they were extremely durable and relatively inexpensive. Many amalgam restorations placed decades ago are still functioning today.
The presence of mercury in the alloy has led researchers to study whether amalgam fillings could release mercury and potentially affect human health.
Do Amalgam Fillings Release Mercury?
Scientific studies show that dental amalgam restorations can release very small amounts of mercury vapour, particularly when chewing or grinding teeth.
However, the amount released is extremely low and remains far below levels known to cause health problems.
Public health organisations and professional dental bodies have repeatedly reviewed the available evidence. The American Dental Association states that no properly designed scientific study has demonstrated that dental amalgam causes long-term health effects or disease. (ADA)
Similarly, the Australian Dental Association maintains a policy on amalgam safety that reflects the current scientific consensus.
https://ada.org.au/policy-statement-6-18-dental-amalgam (Australian Dental Association)
These reviews examine large epidemiological studies investigating whether amalgam exposure could contribute to neurological disease, kidney problems, autoimmune disorders, or cancer.
Across decades of research, no causal relationship has been demonstrated.
Amalgam Fillings and Cancer Risk
Cancer risk is one of the most common concerns raised by patients.
Large population studies evaluating people with amalgam restorations have not found higher rates of cancers such as brain tumours, lung cancer, or breast cancer compared with individuals without amalgam fillings.
The long history of amalgam use across many countries provides strong epidemiological data. If amalgam significantly increased cancer risk, this association would likely have appeared in population health research over the past century.
For this reason, scientific organisations and dental regulatory bodies continue to consider amalgam a safe and effective restorative material for most patients.
Should Amalgam Fillings Be Removed?
Because concerns about mercury sometimes arise online, some patients wonder whether old amalgam fillings should be removed.
Dental organisations generally advise against replacing amalgam fillings that are still healthy and functioning. The American Dental Association notes that removing restorations solely to replace them with another material is unwarranted if they are clinically sound. (ADA)
Removing a filling unnecessarily may involve removing additional tooth structure and can weaken the tooth. Dentists usually recommend replacement only when there is a clear clinical reason, such as fracture, leakage, or new decay around the restoration.
Composite (Tooth-Coloured) Dental Fillings
In modern dentistry, composite resin fillings are commonly used as an alternative to amalgam.
Composite restorations are made from a mixture of resin and microscopic ceramic or glass particles. These materials bond directly to tooth structure, allowing dentists to restore teeth while preserving more natural enamel and dentine.
They are also widely preferred for aesthetic reasons because the material can be matched to the natural colour of the tooth.
Concerns about composite fillings generally relate to a compound known as Bisphenol-A (BPA).
BPA and Dental Materials
BPA is a chemical used in the manufacturing of certain plastics and resins. Because BPA can interact with hormone receptors at high exposure levels, it has been studied extensively in environmental health research.
However, the situation in dentistry is different.
According to the American Dental Association, BPA itself is not used as a direct ingredient in dental restorative materials, although related compounds may be used in resin formulations.
https://www.ada.org/resources/ada-library/oral-health-topics/bisphenol-a (ADA)
Similarly, the FDI World Dental Federation states that BPA is not a component intentionally used in dental materials used for fillings and related procedures. (PMC)
Composite resins typically use compounds such as Bis-GMA, which are structurally related to BPA but behave differently once polymerised in the restoration.
Do Composite Fillings Release BPA?
Some studies have detected very small amounts of BPA-related compounds shortly after composite restorations are placed.
Research shows that trace BPA levels can be detected in saliva immediately after dental treatment but usually decline rapidly over time, often returning to baseline levels within days. (PMC)
Importantly, the quantities measured in these studies are extremely small. Reviews of dental materials report that the amount of BPA released from dental resins is far below typical daily exposure from other environmental sources. (JSciMed Central)
Because of this, major health agencies have not recommended avoiding dental restorations due to BPA exposure.
Composite Fillings and Cancer
Scientific research has not demonstrated a link between composite dental materials and cancer.
While laboratory studies continue to examine chemical release from restorative materials, the exposure levels measured in clinical studies are extremely small and short-lived.
Dental materials must also pass strict regulatory approval before they are used in patient care. In Australia, the Therapeutic Goods Administration (TGA) regulates dental materials to ensure they meet safety and quality standards.
Why Modern Dentistry Uses Different Materials
The choice of filling material depends on many factors, including the size and location of the cavity, bite forces, aesthetics, and long-term durability.
Amalgam remains known for its durability in high-stress areas, while composite materials offer excellent aesthetics and allow more conservative tooth preparation.
For dentists, the most important priority is not simply the material used but restoring the tooth in a way that preserves structure and protects long-term oral health.
Preventing the Need for Fillings
Although questions about filling materials often receive attention online, the most effective strategy for protecting oral health is preventing cavities in the first place.
Tooth decay develops when bacteria in dental plaque produce acids that weaken enamel. Over time this process creates cavities that require restorative treatment.
Good preventive care significantly reduces the likelihood of needing fillings. Brushing with fluoride toothpaste, cleaning between teeth, limiting frequent sugar intake, and attending regular dental examinations all help maintain healthy teeth and gums.
Early diagnosis also allows dentists to detect decay at a stage when treatment can be more conservative.
The Bottom Line
Decades of scientific research have evaluated the safety of dental restorative materials.
Current evidence indicates that neither amalgam fillings nor composite fillings are associated with an increased risk of cancer. Amalgam restorations release only very small amounts of mercury, while composite materials may release trace BPA-related compounds at levels far below those associated with health risks.
For most patients, dental fillings remain a safe and effective way to restore teeth damaged by decay or fracture.
If You Have Questions About Your Fillings
If you are concerned about existing dental fillings or would like to discuss restorative options, a professional dental assessment is the best place to start.
At ArtSmiles in Southport on the Gold Coast, our team focuses on evidence-based dentistry and modern restorative techniques designed to preserve natural tooth structure while delivering long-term stability and aesthetics.
You can book a consultation with our team here:
https://artsmiles.com.au/book-online/
Frequently Asked Questions About Dental Fillings and Cancer
Do mercury dental fillings cause cancer?
No credible scientific evidence shows that mercury dental fillings cause cancer.
Dental amalgam has been studied for more than 150 years and remains one of the most researched materials in dentistry. Reviews conducted by organisations such as the American Dental Association and the World Health Organization have concluded that the amount of mercury released from amalgam fillings is extremely small and not associated with cancer or systemic disease.
Research involving large populations has not demonstrated increased cancer risk in people with amalgam restorations.
Are amalgam fillings safe?
Yes, dental amalgam fillings are considered safe for the vast majority of patients.
Amalgam is a stable alloy made by combining mercury with silver, tin, copper, and other metals. When these metals react together, they form a hardened restorative material capable of withstanding chewing forces for many years.
Health authorities including the Australian Dental Association continue to recognise dental amalgam as a safe and effective material for restoring teeth.
Should I remove my amalgam fillings because of mercury?
In most cases, dentists do not recommend removing amalgam fillings solely because they contain mercury.
If a filling is intact and functioning properly, removing it may involve unnecessary drilling and removal of healthy tooth structure. Dental organisations generally recommend replacing amalgam restorations only when there is a clinical reason, such as fracture, leakage, or decay around the filling.
Do composite fillings contain BPA?
Composite dental fillings do not intentionally contain Bisphenol-A (BPA).
Some dental resin materials use compounds related to BPA during manufacturing, and extremely small trace amounts may occasionally be detected after placement of a filling. Studies show that these levels drop quickly and are far below typical exposure levels from other environmental sources.
Professional dental organisations consider composite fillings safe for routine clinical use.
Can composite fillings cause cancer?
There is no scientific evidence linking composite dental fillings with cancer.
Research investigating the release of BPA-related compounds from dental materials has shown that exposure levels are extremely low and temporary. These levels are considered biologically insignificant and far below thresholds associated with health effects.
Composite restorations remain widely used in modern dentistry because they provide strong bonding and natural aesthetics.
Are white fillings safer than silver fillings?
Both amalgam and composite fillings are considered safe.
The choice between materials is usually based on factors such as the location of the cavity, chewing forces, durability requirements, and aesthetic preferences. Composite fillings are more commonly used today because they match the natural colour of teeth and allow more conservative treatment.
Your dentist will recommend the most appropriate material based on your specific clinical situation.
How long do dental fillings last?
The lifespan of a dental filling depends on several factors, including the size of the restoration, the location in the mouth, and the patient’s oral hygiene.
Amalgam fillings often last 10–20 years or longer, while composite fillings commonly last 7–15 years depending on wear and bite forces. Regular dental examinations help detect early signs of wear so restorations can be repaired or replaced when necessary.