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A filling does two things: it removes the decayed tissue, and it replaces the shape that decay destroyed. Everything that happens in the appointment is one of those two jobs.
Before anything starts
Your dentist will confirm which tooth, how deep the decay goes, and whether the nerve is likely to be involved. X-rays often matter here, because decay between teeth is invisible from above.
You should be told what is being used, roughly how long it will take and what it will cost before treatment begins, not afterwards.
Numbing
Local anaesthetic is placed next to the nerve supplying that tooth. A gel is often put on the gum first, which takes the edge off the injection itself.
Numbness arrives over two to five minutes and is usually complete before anything else happens. It removes pain, not pressure — you will still feel pushing, and that is expected. What you should not feel is pain. If you do, say so: more anaesthetic can be given, and lower back teeth sometimes need it.
Very shallow fillings in enamel sometimes need no anaesthetic at all. That is a conversation, not an assumption.
Removing the decay
This is the part with the noise. Two instruments are usually involved: a fast handpiece, which is the high-pitched one, and a slow handpiece, which is lower and more of a grinding sound. Water spray keeps the tooth cool throughout, which is why there is suction in your mouth.
Decayed dentine is softer than healthy dentine, and much of it is removed with a hand instrument rather than a drill. The aim is to take out what is diseased and leave everything that is not — modern practice is considerably more conservative than it was thirty years ago.
Filling the space
| What it is | Where it tends to be used | |
|---|---|---|
| Composite | Tooth-coloured resin, set hard by a blue light | Anywhere; the default for visible teeth |
| Glass ionomer | Releases fluoride, less hard-wearing | Children, root surfaces, temporary repairs |
| Amalgam | Silver-coloured metal alloy | Large fillings in back teeth, being phased down |
Composite is placed in layers, each one cured with the blue light before the next goes in. There is no waiting afterwards — it is fully hard the moment it is set.
Amalgam is still a durable material, but its use is being reduced internationally under the Minamata Convention, and in the UK it is not normally used in baby teeth at any age, in children under fifteen, or in women who are pregnant or breastfeeding. The law allows one exception: where a dentist judges it strictly necessary because of that particular patient's medical needs.
Checking the bite
Once the filling is shaped, you will be asked to bite on coloured paper and grind side to side. This marks any spot that is sitting proud.
Say something if it feels high. A filling a fraction of a millimetre too tall is the most common reason a tooth aches afterwards, and it takes seconds to adjust. It is far easier to fix now than next week.
Afterwards
The numbness lasts two to four hours. Avoid chewing on that side until it has gone, because it is genuinely easy to bite your cheek or tongue without noticing.
Some sensitivity to cold for a few days is normal, particularly with a deeper filling. It should fade.
A filling is a repair, not a cure. What stops the next one is what happens between appointments.