Silver amalgam has a long track record and, in some studies, outlasts tooth-coloured composite in back teeth. Composite looks like tooth, bonds to it and lets the dentist keep more of the healthy structure. That is the real trade-off, and for most fillings placed today it tips towards composite. Amalgam is also on its way out: from 2034 its manufacture, import and export will be banned under a global agreement on mercury.
If you already have silver fillings, none of this means they need to come out. The sections below explain why.
A global phase-out with an environmental reason
In November 2025, the parties to the Minamata Convention on Mercury agreed at their sixth meeting to end the use of dental amalgam by 2034. The Australian Dental Association reports that the final decision still allows amalgam to be used where it is considered necessary for a particular patient, and describes the change as a step to cut mercury released into the environment, not a response to a health risk from fillings already in people's mouths. The ADA's position is that amalgam remains a safe restorative material for the general population and that there is no evidence supporting routine removal of existing fillings, apart from allergy or a specific medical need.
What each material actually is
Composite resin is a mix of plastic resin and fine glass or ceramic particles. It is placed in layers, shaped, and hardened with a blue curing light. Because it is bonded to the enamel and dentine with an adhesive, it does not need undercuts to hold it in, so the cavity can be kept to the size of the decay.
Amalgam is an alloy of mercury with silver, tin and copper. It is packed into the cavity while soft and sets hard. It does not stick to the tooth, so the dentist shapes the cavity to lock it in mechanically. That often means removing some sound tooth as well as the decay. Its strengths are durability and tolerance of a slightly damp working field, which is why it served back teeth for well over a century.
What the evidence says about how long they last
The best summary is a Cochrane review by Worthington and colleagues, updated in 2021. Pooling two trials of back-tooth fillings in children, it found low-certainty evidence that composite fillings failed almost twice as often as amalgam, mainly because new decay formed at the edges. Fracture rates were similar. The authors also noted that composite materials have improved considerably since those trials were run, and that the choice should be made together by dentist and patient.
In practice, how long any filling lasts depends a great deal on its size, where it is, how well it was placed, your bite and your decay risk. A small composite on a low-load surface in a person with good home care can last many years. A very large filling of either material in a heavily loaded molar is more likely to crack or leak, and an inlay, onlay or crown may be the better option there.
Side by side
| Composite (white) | Amalgam (silver) | |
|---|---|---|
| Colour | Matched to the tooth | Silver grey, can darken with time |
| How it stays in | Bonded with an adhesive | Mechanical retention |
| Sound tooth removed | Usually less | Usually more |
| Placement | Needs a dry field, more time and care | More forgiving of moisture |
| Longevity in back teeth (Cochrane 2021) | Higher failure rate in older trials, mostly from edge decay | Lower failure rate |
| Mercury | None | Yes, bound in the alloy |
| Future availability | Standard material | Being phased out by 2034 |
Leave sound silver fillings alone
Drilling out an intact amalgam removes more tooth every time, because the new cavity has to be slightly larger than the old filling. Each replacement also adds wear and risk to the tooth over a lifetime. For those reasons, replacement is usually advised only when there is a clinical reason:
- decay under or around the edge of the filling
- a crack in the filling or the tooth next to it
- a filling that has worn down, broken or is leaking
- a confirmed allergy, which is uncommon
Changing a visible silver filling to a white one for looks is a reasonable choice, but it is cosmetic, and it is worth weighing against the tooth that will be lost. Your dentist can check each filling and use X-rays where needed to see what is happening underneath. Our separate post on amalgam safety goes into the mercury question in more depth.
Where white fillings sit with bonding and other options
A composite filling repairs a cavity. Composite bonding uses the same family of materials to change the shape or colour of a tooth that may have no decay at all, such as closing a small gap or covering a chip. Our post on bonding versus fillings explains the difference, and the composite bonding page describes that service.
Cost and health fund cover
Fees depend on how many surfaces of the tooth are involved and how large the filling is. For typical Australian market ranges, see our filling cost guide, and for how extras cover works, our post on health insurance and dental. The cheapest filling is the one you never need, so the habits in our decay prevention guide are worth a look.
Common questions
Can I choose amalgam if I want it?
Until the phase-out takes effect, amalgam can still be used where it is clinically appropriate. Discuss it with your dentist, who can explain whether it suits that particular tooth.
Is the mercury in my fillings harming me?
Health and dental authorities, including the Australian Dental Association, regard amalgam as safe for the general population. The Cochrane review found no consistent or clinically important differences in health outcomes between children with amalgam and those with composite fillings, although that evidence is of very low certainty.
Will a white filling stain?
Composite can pick up some surface staining over time, especially at the edges, from coffee, tea or smoking. Polishing at a check-up can often freshen it.
How can I make any filling last longer?
Brush twice a day with fluoride toothpaste, clean between teeth daily, limit sugary snacks and drinks between meals, and keep up regular check-ups so small problems at the edge of a filling are found early.
If you have a filling that needs attention or want your existing fillings checked, you can book a check-up at Lumi Dental in Melrose Park. After your examination you will usually receive a written treatment plan, often by email, and current offers are on our deals page.
Sources
- Worthington HV and colleagues. Direct composite resin fillings versus amalgam fillings for permanent posterior teeth. Cochrane Database of Systematic Reviews, 2021. PubMed 34387873
- Australian Dental Association. Mercury amalgam global phase-out date set for 2034. November 2025.
