Answers
Should I replace my old silver fillings?
Not always. An old filling that is sealed, symptom-free and not cracking is usually best left alone. Replacement is warranted when there is decay underneath, a fracture, a failing margin, or the tooth is flexing under load.
Why is replacing a filling not automatically a good idea?
Because every replacement makes the cavity bigger.
To remove an old filling you have to cut it out, and the bur inevitably takes some tooth structure with it. The new filling is therefore always larger than the old one. Do that three or four times over a lifetime and a modest filling becomes a tooth with thin walls, then a crown, then sometimes a root canal.
This is the restorative cycle, and it is the single strongest argument against replacing fillings that are not actually failing. A filling that has been in place for twenty years and is still sealed has demonstrated something useful: that it works.
So the question is never "how old is this filling". It is "is this filling failing, or is the tooth around it failing".
What are the actual signs a filling needs replacing?
Some are things you may notice. Most are found on examination or radiograph, which is why intervals between check-ups matter more here than they seem to.
Decay underneath or at the edge of a filling is the clearest indication. Bacteria enter through a gap at the margin and undermine the tooth from within, often with no symptoms at all until it is substantial.
Fracture matters as much as decay. A crack in the filling itself, a chipped or missing cusp beside it, or a filling that moves under pressure all indicate that the restoration is no longer supporting the tooth. Sensitivity to cold or sweetness that is new, pain on biting or on release, food packing repeatedly between two teeth, or a rough edge you can catch with a fingernail are worth reporting.
- Decay visible at the margin or on a radiograph beneath the filling
- A visible crack in the filling or in the tooth wall beside it
- A cusp that has chipped, or a wall that looks thin and unsupported
- A margin that catches a probe or floss, or that has opened into a ditch
- New sensitivity to cold, heat or sweetness in that tooth
- Pain on biting, or a sharp pain when you release a bite
- Food consistently packing between that tooth and its neighbour
- A filling that has been repaired or added to several times
Discolouration around an amalgam filling is not, on its own, a sign of failure. Amalgam stains the surrounding tooth grey over time without the tooth being decayed. It looks alarming and often means nothing.
My filling is large but not broken — should I act pre-emptively?
This is the genuinely difficult case, and the answer is a judgement rather than a rule.
A very large filling in a back tooth with thin remaining walls is at real risk of the tooth fracturing around it. If it does fracture, the break often runs below the gum, and what would have been a straightforward restoration becomes a crown, a root canal, or an extraction.
Against that, replacing it now costs tooth structure and money for a problem that may not arrive for years, or ever. The reasonable approach is proportionate: assess how much sound structure actually remains, whether the patient grinds, whether there are cracks visible under magnification, and whether this tooth has already shown warning signs. Then decide, with the reasoning explained.
What should not happen is a blanket recommendation to replace every large filling in the mouth on the strength of their size alone.
What are old fillings replaced with?
Modern replacements are adhesive rather than mechanically retained, and that difference is the point.
An amalgam filling is held in place by the shape of the cavity — the tooth has to be cut with undercuts to grip it, which means removing sound structure purely for retention. It does not bond to the tooth and does not strengthen it.
Bonded restorations join to the enamel and dentine, so the cavity can follow the damage rather than a prescribed shape, and the restoration can help support the remaining walls rather than wedging them apart. Where the cavity is very large or a cusp needs covering, an indirect restoration such as an inlay or onlay may be used instead of a direct filling.
There is also the aesthetic factor, which is a legitimate reason to choose a tooth-coloured material where a filling is being replaced anyway. It is a weaker reason to replace a sound one, though it is a decision a patient is entitled to make once they understand the trade-off.
Are mercury amalgam fillings dangerous?
This concern comes up often and deserves a straight answer rather than a sales pitch.
Dental amalgam contains mercury bound into an alloy. The consensus position of major regulatory and dental bodies is that amalgam fillings are safe for the general population, while use is being reduced internationally for environmental reasons and some authorities advise caution for specific groups, such as during pregnancy or in young children.
What this practice will not do is present amalgam removal as a health treatment. There is no good evidence that removing sound amalgam fillings improves general health, and the removal process itself briefly releases more mercury vapour than leaving them in place. Any practice offering to remove your fillings to treat a systemic illness is making a claim it cannot support.
If you would prefer tooth-coloured restorations, that is a reasonable personal preference and a dental professional should discuss it with you honestly — including the fact that replacement removes tooth structure. If you are worried about mercury specifically, raise it at an examination and discuss it with your medical doctor.
If amalgam is being removed for any reason, it is reasonable to ask what precautions are used — rubber dam isolation, high-volume suction and copious water are standard measures to limit exposure to particles and vapour during removal.
Common questions
How long do fillings last?
There is no fixed lifespan. It depends on the size of the filling, the material, where the tooth sits, your bite, whether you grind, and your oral hygiene. Some fillings last decades; some fail within a few years. Age alone is not a reason to replace one.
Can decay under a filling be seen without an X-ray?
Often not. Decay beneath a filling or between teeth is frequently invisible to direct inspection until it is extensive, which is why radiographs at appropriate intervals are part of an examination rather than an optional extra.
Will replacing a filling make the tooth sensitive?
Some sensitivity for a period after placement is common, particularly with deeper fillings, and usually settles. Sensitivity that increases, lingers after cold, or wakes you at night should be reported, as it can indicate the pulp is inflamed.
Can I replace just part of a filling?
Sometimes. Where only one margin has failed and the rest of the restoration is sound, repairing rather than replacing removes less tooth structure. Whether it is appropriate depends on what is found once the failing portion is opened up.
Does replacing an old filling mean I will need a crown?
Not usually, but it becomes more likely each time. If a replacement leaves the walls too thin to support a direct filling, cuspal coverage may be needed — which can often be a bonded onlay rather than a full crown, depending on what remains.