Tooth decay: stages, treatment and prevention

Tooth decay is common and, in most cases, preventable. It also often starts without any symptoms, which is why regular dental visits matter. This guide explains how decay develops, how dentists treat it and what helps prevent it, drawing on the NHS and the Oral Health Foundation, checked on 6 October 2026.

It gives general information only. It cannot tell you what is wrong with your own teeth, and it has not yet been reviewed by a dental professional.

What tooth decay is

The NHS says tooth decay is often caused by having too much sugary food and drink and not cleaning the teeth and gums regularly. Bacteria form plaque, a sticky film that builds up on teeth every day.

The Oral Health Foundation explains the process. When you eat or drink something with sugar in it, the bacteria in plaque produce acid. The acid attacks the tooth surface and, over time, can dissolve the tooth structure and create a hole, which is called a cavity. The foundation says each attack lasts for around an hour, so frequent sugar leaves the tooth little time to recover.

‘Cavity’, ‘tooth cavity’ and ‘dental cavity’ all describe the same thing: a hole in a tooth caused by decay. The NHS says that if decay is left untreated, cavities can develop and may lead to a dental abscess, which is why early treatment matters.

Plaque also causes gum problems. Our guide to gingivitis and its signs covers that side of the story.

Stages of tooth decay

The Oral Health Foundation describes decay moving through the layers of the tooth:

• Enamel, the hard outer layer. In early decay you may not feel anything at all.
• Dentine, the layer beneath. As decay reaches it, teeth may become sensitive to hot, cold or sweet foods.
• Pulp, the innermost layer. Advanced decay here can cause severe pain and may lead to infection or an abscess.

The NHS lists the symptoms as toothache, sharp pain when eating or drinking hot, cold or sweet things, and white, brown or black spots on a tooth. It notes that early decay may cause no symptoms. That is the reason to attend check-ups even when nothing hurts.

How a dentist treats decay

Treatment depends on how far the decay has gone. The NHS sets out the main options:

• Fluoride treatments, such as mouthwash or varnish, which it says can reverse early decay.
• Fillings to repair cavities.
• Root canal treatment when decay has reached the pulp.
• Extraction when a tooth is severely affected.

The Oral Health Foundation lists the same later-stage options: fillings for small to moderate decay, root canal treatment when the nerve is infected or dying, and extraction for severely damaged teeth. You can read about root canal treatment and tooth extractions on their own pages.

The steps are in order of how far decay has travelled. The earlier it is found, the less a tooth usually needs doing, which is the practical reason the Oral Health Foundation says regular check-ups let dentists spot decay in its early stages, before cavities or extractions become necessary.

Only a dentist can say which treatment fits a particular tooth. This guide does not describe silver diamine fluoride because no official source opened for it covered the subject.

If you have severe toothache or swelling, do not wait for a routine slot. nidirect says registered patients should contact their own dentist, as some surgeries offer emergency appointments, and that weekend and bank holiday cover is through the Emergency Dental Clinics, which you contact directly. See emergency dental care for more.

Preventing decay (fluoride, diet, check-ups)

The NHS advice is to brush at least twice a day with fluoride toothpaste, clean between the teeth every day with floss or interdental brushes, and cut down on sugary food and drink. It also recommends regular check-ups.

The Oral Health Foundation adds detail. It recommends fluoride toothpaste at 1450ppm, says to spit out toothpaste after brushing rather than rinsing so the fluoride stays on the teeth, and says dentists may prescribe a higher-fluoride toothpaste for people at increased risk. It advises having sugar less often, because sugar before bed is a particular problem as you produce less saliva while asleep. It also mentions chewing sugar-free gum after meals.

On check-ups, nidirect says regular check-ups are important for spotting dental problems but does not state how often. The NHS page gives an interval guide. Ask your own dentist how often you should go. A general dentist can check for early decay before it causes symptoms.

Children and decay

The NHS says decay is common in children, which makes early habits important. For Northern Ireland, HSC Northern Ireland states that patients aged 18 or under, and those aged 18 in full-time education, do not pay for Health Service dental treatment when registered. That is according to the Business Services Organisation page checked on 6 October 2026, which carries an old date for its charge figures, so confirm current rules with a practice or on nidirect.

To see how practices describe family care, look at children’s dentistry and ask what each practice offers.

Next step

Decay is far easier to deal with when it is found early, and a check-up is how most people find out.

If you have not had a check-up for a while, or if a tooth is sensitive or marked, book one. You can find a practice through our general dentistry directory and call to ask about appointments and costs.