Do not wait for the appointment if

Ring 999 or go to an emergency department

You are finding it hard to breathe, speak or swallow
Your eye is swollen or painful, or your eyesight has changed
There is a lot of swelling inside your mouth, or under your tongue
You cannot open your mouth properly

Do not drive yourself. Ask somebody to take you, or ring an ambulance.

Ring a dentist today — or 111 if you cannot get through

Swelling of the gum, cheek, jaw or neck, however small it starts
A temperature, shivering, or feeling unwell with the tooth
Pain getting rapidly worse, or no longer held by paracetamol
Toothache you cannot settle, or that keeps you awake

A GP cannot treat this. An infected tooth can spread into the tissues around it, and that can move within hours — a booked appointment next week is not the answer to a swelling that is growing today. Where to go when it will not wait

What this appointment is for

Decay is softened tooth. Once it is through the enamel it does not reliably stop or harden again on its own, and it cannot be brushed away. Where it has gone far enough it is cut out, and the space it leaves is filled. A shallower lesion is sometimes sealed or watched instead, and your dentist will tell you which this is.

That is the whole of a filling: remove the part that has gone, replace the shape that has been lost. The filling is not a cure for anything — it is a repair, and like any repair it has an edge, and edges can eventually leak. That is why a filled tooth still gets looked at.

What actually happens

The tooth is checked, often with an X-ray, because decay runs deeper and wider than it looks from the surface.
The area is numbed, usually. A very shallow filling sometimes does not need it, and your dentist will say.
A cheek retractor, suction, or a rubber sheet goes in. The sheet — a dam — is a small square of rubber clipped around the tooth. It is used more for root canals than fillings, but it turns up in both.
The decay is removed. This is the drilling. It is also the part that is over fastest.
The cavity is cleaned and dried, and sometimes lined.
The filling goes in, in layers if it is a white one, each layer set hard with a blue light.
It is shaped, and your bite is checked. You will be asked to bite on coloured paper and told to grind side to side. Do it properly — this is the step that decides whether the tooth feels right for the next five years.
It is polished.

White or metal

Both are still used on the NHS, and the choice is usually about which tooth rather than about preference.


White (composite)	Bonded to the tooth, so less healthy tooth needs removing. Set hard by the time you leave. Standard for front teeth, and increasingly for back ones.
Metal (amalgam)	Still permitted, and still often used on back teeth because it is hard-wearing. Long-lasting and tolerant of a damp, awkward cavity, which is exactly where back teeth tend to be.

Amalgam is not used for everybody, and that part applies to you rather than to a treaty: it is not normally placed in children under fifteen, or in women who are pregnant or breastfeeding. The law allows an exception where a dentist judges it strictly necessary for your particular situation, so if you are in one of those groups and it is offered, that is the exception rather than a mistake. The restriction is about environmental mercury rather than any concern about amalgam in your mouth.

Beyond that, amalgam is being restricted rather than banned overnight. In the EU its use has been prohibited since January 2025, except where a dentist judges it strictly necessary because of a particular patient’s medical needs. Northern Ireland, where EU rules would otherwise apply, was granted a derogation in July 2024 running to 31 December 2034 — or to whatever phase-out date is eventually agreed under the Minamata Convention, if that comes sooner. No such global date has been agreed yet. So nowhere in the UK has lost it. If you would prefer a white filling in a back tooth, ask. Depending on the tooth and where you are treated it may be available, available privately, or not advisable for that particular cavity — and your dentist can tell you which.

What it feels like

The injection stings briefly, and the pressure of it feels odd.
The noise is the worst part for most people, and it is mostly the suction, not the drill.
You may feel vibration and cold water. Not pain — pressure and temperature travel even through a numb tooth.
You should not feel sharpness. If you do, raise a hand. More anaesthetic can be given; a deep cavity close to the nerve is genuinely harder to numb and that is worth saying out loud rather than enduring.
Your jaw may ache from being held open, and your lip from being held aside.

How long it takes

A small single-surface filling and a large one rebuilding most of a back tooth are different appointments, and so are one filling and four. There is no useful average. The practice will have booked a specific length of time, and you can ask what it is when it is arranged.

Before you come

Eat beforehand. You will be numb afterwards and will not want to.
Take your medicines as normal, and bring a list.
Say what you take and what you have. Bring the list, and say it out loud rather than assuming it is on file: any blood thinner; bisphosphonates, denosumab or any other bone or osteoporosis medicine; steroids; anything that affects your immune system; diabetes; a heart valve problem or replacement, or endocarditis in the past; pregnancy or breastfeeding; any allergy, including latex and penicillin; and any hospital treatment in the last few months. None of it necessarily changes the appointment. All of it changes whether the decision is made with the full picture.
Say if you are anxious, when the appointment is made rather than when you are in the chair.
Mention a tooth that has been difficult to numb before. It is useful information and most people never think to offer it.
Allow for being numb afterwards if you have something to do that involves talking or eating.

Worth asking

How deep is it, and how close to the nerve? This is the question that predicts whether the tooth settles quietly or grumbles for a month, and it is the one people never ask.
Is a filling still the right repair, or has the tooth passed that point? Where very little wall is left, a filling can be the thing that cracks it. An onlay or a crown is sometimes the better answer.
Will I need to come back for the bite? Say yes now rather than putting up with it later.

Afterwards

Mostly a question of sensitivity, and of a bite that should feel like your own tooth within a day or two.

→ After a filling

Your dentist’s instructions come first

The instructions you are given by the dentist who is treating you take precedence over anything on this page. They know your tooth, your history and their plan; this page does not.

Sources

Dental amalgam phase-out under the Minamata Convention, and the Northern Ireland position — British Dental Association; trade reporting, November 2025
Fillings and NHS dental charges — NHS
Dental extractions: post-operative instructions — University College London Hospitals