Tooth decay (dental caries)

16 min read

What is tooth decay?

Tooth decay is when acids in your mouth dissolve the outer layers of your teeth.

You may also have heard it called dental decay or dental caries.

Over time,

symptoms of tooth decay
can include:

  • toothache
  • pain when eating or drinking
  • visible discoloured spots on your teeth

If left untreated, a build up of plaque (see below) could lead to

complications of tooth decay
such as
gum disease
(gingivitis) or a
dental abscess

Regular dental checks can help your dentist spot signs of tooth decay early and identify any cavities (holes or damage in the teeth). Tooth decay is much easier to treat successfully in its early stages.

Read more about

how tooth decay is diagnosed

Why do I have tooth decay?

Your mouth is full of bacteria which combine with small food particles and saliva to form a sticky film known as plaque which builds up on your teeth.

When you consume food and drink high in carbohydrates (sugary or starchy), bacteria in plaque turns carbohydrates into the energy they need, producing acid at the same time.

Over time, acid in plaque begins to break down your tooth's surface. Left untreated, plaque can completely destroy the outside of the tooth and expose nerves inside. Once this happens, you will have toothache.

Read more about the

causes of tooth decay
including risk factors.

Treating and preventing tooth decay

Although widespread, tooth decay is one of the most preventable health conditions. As long as you look after your teeth well and visit your dentist regularly, you should be able to prevent tooth decay.

There are also some changes you can make to your diet to minimise your risk of tooth decay. For example, cutting down on sugary food and drinks, particularly between meals or within one hour of going to bed.

Read more about

preventing tooth decay

If you get tooth decay, there are techniques that can help repair damaged teeth, such as fillings and crowns.

In more advanced cases of tooth decay, there may be a need for

root canal treatment
, or the tooth may need to be removed.

Read more about

how tooth decay is treated

How common is it?

Tooth decay is one of the most widespread health problems in the UK. It is estimated that 31% of adults in the UK have tooth decay.

Tooth decay is also a problem for children. It is thought around 31% of children starting school and around a third of children aged 12 have visible tooth decay.

Tooth decay symptoms

Tooth decay may not cause symptoms until it has reached an advanced stage. This is why it is important to have regular dental checks. Tooth decay is much easier to treat successfully in its early stages.

Adults over 18 should have a check-up at least once every two years. People under the age of 18 should have a check-up at least once a year. Young children may require a check-up every 4-6 months.

However, your dentist may recommend more frequent check-ups if you have had a history of dental problems, or you are thought to be at a higher risk of developing tooth decay.

Read about the

causes of tooth decay
for more information on risk factors.

Symptoms of advanced tooth decay

The symptoms of advanced tooth decay include:

  • toothache
  • tooth sensitivity – you may feel tenderness or pain when eating or drinking something hot, cold or sweet
  • discoloured spots (grey, brown or black) appearing on your teeth
  • bad breath
  • an unpleasant taste in your mouth

Toothache is a warning that something is wrong and that you should visit your dentist as soon as possible. If you ignore the problem it will get worse, and you could end up losing a tooth.

What causes tooth decay?

Tooth decay is caused over time by plaque forming on your teeth. There are several risk factors which increase the chances of this happening.

A tooth is made up of three parts:

  • enamel – the hard outer coating of a tooth
  • dentine – the softer, bone-like material underneath the enamel
  • pulp – the soft centre of the tooth that contains nerves and blood vessels

How dental decay develops

Your mouth is full of bacteria, which combine with small food particles and saliva to form a sticky film known as plaque, which builds up on your teeth.

When you consume food and drink high in carbohydrates (sugary or starchy), the bacteria in plaque turn the carbohydrates into energy they need, producing acid at the same time.

Over time, the acid in plaque begins to break down the surface of your tooth.

The plaque will first start to erode the enamel. Over time, a small hole known as a cavity can develop on the surface. This will cause


Once cavities have formed in the enamel, the plaque and bacteria can reach the dentine. As the dentine is softer than the enamel, the process of tooth decay speeds up.

Without treatment, plaque and bacteria will enter the pulp. At this stage, your nerves will be exposed to bacteria, making your tooth very painful. The bacteria can also infect tissue within the pulp, causing a

dental abscess

Tooth decay typically occurs in teeth at the back of your mouth, known as molars and premolars. These are large flat teeth used to chew food. Due to their size and shape, it is easy for particles of food to get stuck on and in between these teeth. They are also harder to clean properly.

It is more common for a front tooth to be affected by tooth decay when it is touching another tooth alongside it.

Increased risk of tooth decay

Factors that increase your risk of tooth decay include:


Eating food and drink high in carbohydrates, particularly between meals, will increase your risk of tooth decay.

Tooth decay is often associated with sweet and sticky food and drink, such as chocolate, sweets, sugar and fizzy drinks. Starchy food, such as crisps, white bread, pretzels and biscuits also contain high levels of carbohydrates.

Poor oral hygiene

If you do not regularly brush your teeth, you are at a higher risk of tooth decay. You should brush your teeth at least twice a day.


Smokers have a higher chance of developing tooth decay as tobacco smoke interferes with production of saliva, which helps keep the surface of your teeth clean. Studies have also shown passive smoking can be a risk factor, particularly for children.

Dry mouth

People who have lower levels of saliva in their mouth are at higher risk of developing tooth decay, because saliva helps to keep the surface of your teeth clean.

A number of medicines and medical treatments can lower the amount of saliva in your mouth. For example:

  • tricyclic antidepressants
  • antihistamines
    (used in the treatment of allergies)
  • some antiepileptic medicines
  • some antipsychotic medicines
  • beta-blockers
    (used to treat a number of heart conditions)
  • radiotherapy

If you are taking a medicine or receiving treatment known to cause dry mouth, take frequent sips of still, unflavoured water and make sure you have a good oral hygiene routine.

Read more about

preventing tooth decay
for tips on how to keep your teeth healthy.

Diagnosis of tooth decay

A dentist should be able to spot tooth decay in its initial stages by physically examining your mouth during a dental check-up.

At each check-up your dentist should:

  • examine your teeth, mouth and gums
  • ask about your general health and any problems you have had with your teeth, mouth and gums since your last visit
  • ask about and give advice on your diet, tobacco and alcohol consumption, and teeth-cleaning habits
  • discuss a date for your next visit

Read more information about [dental check-ups].

Types of cavities

Through an examination, your dentist can see what type of cavity you have. There are three main types:

  • pit cavities occur on the top of your 'chewing teeth' – these quickly lead to more extensive tooth decay if not treated
  • smooth surface cavities occur on the flat surface of your tooth – they are usually at the gumline in teeth at the side of your mouth
  • root cavities occur at the root of the front of your tooth – they are more common in older people because gums tend to recede slightly with age, making the root more vulnerable to plaque

If you have advanced tooth decay or it is in a part of your mouth which is hard to examine, your dentist may use a dental

to check for cavities.

Tooth decay treatment

If your decay is in the early stages, your dentist may apply a fluoride varnish to the area. This can help to stop further decay, particularly if you lower your intake of sugar.

If decay has worn away your enamel and caused a cavity, your dentist will remove the decay and restore your tooth with a filling. If the nerve in the middle of your tooth is damaged, you will need a

root canal treatment
, which removes the nerve and restores the tooth with a filling or crown.

If the tooth is so badly damaged it cannot be restored, the only option may be to remove it.


is probably the most effective treatment available for preventing and limiting the spread of tooth decay. It is a naturally occurring mineral found in foods and drinks, such as fish and tea, but it can also be synthesised (manufactured). Synthetic fluoride is used in toothpaste, from which most people get their fluoride.

Fluoride protects teeth by strengthening the enamel, making teeth more resistant to acid attacks that can cause tooth decay. It reduces the ability of plaque bacteria to produce acid, and enhances the repair (remineralisation) of enamel.

If your cavity is in its early stages, your dentist may be able to repair the decay by using a concentrated fluoride gel, varnish or paste.

Fillings and crowns

If the decay to one of your teeth is more extensive, it may be necessary to repair the damage with a filling or crown.

A filling replaces your missing enamel. There are many different filling materials available, including amalgam (silver coloured), composite (tooth coloured) and glass ionomer (tooth coloured).

Inlays and onlays can also be used to fill teeth. They specifically fill the size and shape of your cavity, and are fixed in place with dental cement. Inlays and onlays are usually made from gold, as it is the most long-lasting and hard-wearing filling material.

Crowns are used to treat extensively damaged teeth. The decayed section of the tooth is drilled away and the crown is placed over the remaining section. Crowns are made of gold, porcelain, ceramic or glass.

Root canal treatment

If tooth decay has spread to the pulp, the pulp may have to be removed and replaced with an artificial pulp (gutta percha) that will keep the tooth in place. This is known as root canal treatment.

Root canal therapy has had a reputation of being painful, but improved dental techniques mean it is now comparatively painless.

Read more about

how root canal treatment is performed

Tooth extraction

In serious cases of tooth decay, the tooth may be removed to prevent the spread of infection from a

dental abscess
. Losing certain teeth can affect the shape and function of surrounding teeth, so the dentist may have to replace the tooth with a partial denture, bridge or implant.

How to prevent tooth decay

Maintaining good oral hygiene through brushing and flossing your teeth is one of the most effective ways to prevent tooth decay. You can also change your diet.


Brush your teeth at least twice a day with fluoride toothpaste.

Ideally, brush your teeth after eating rather than before. However, do not brush your teeth for at least 30 minutes after a meal as this can damage your teeth, particularly if you have eaten food high in carbohydrates or sugar.

It is also important you brush your teeth in the right way. The following advice may help:

  • Place the head of your toothbrush against your teeth, then tilt the bristle tips to a 45-degree angle against the gumline. Move the brush in small circular movements, several times, on all surfaces of every tooth
  • Brush the outer surfaces of each tooth, upper and lower, keeping the bristles angled against the gumline
  • Use the same method on the inside surfaces of all your teeth
  • Brush the biting surfaces of the teeth
  • To clean the inside surfaces of the front teeth, tilt the brush vertically and make several small circular strokes with the front part of the brush
  • Brushing your tongue will help freshen your breath and will clean your mouth by removing bacteria
  • Do not rinse your mouth with water or mouthwash after brushing as this washes the protective toothpaste away. Just spit out excess toothpaste

It is important to replace your toothbrush on a regular basis because they wear out and become less effective in removing plaque. Most toothbrushes need to be replaced every two to three months.

If you are considering buying an electric toothbrush, studies have shown the most effective type is one in which the head has a rotating oscillation action – meaning the head spins one way and then the other. As with manual toothbrushes, you need to replace the head of your electric toothbrush every two to three months.


Flossing is an important part of oral hygiene. It removes plaque and food particles from between your teeth and under the gumline – areas a toothbrush can not always reach. You should clean between your teeth at least once a day with floss.

Your dentist or hygienist can advise you on flossing techniques, but the following tips may help:

  • Break off about 45cm of floss or dental tape and wind most of it around one of your middle fingers. Wind the remaining floss around the same finger of the other hand. As you use the floss, you will take up the used section with this finger
  • Hold the floss tightly between your thumb and forefingers, with about an inch of floss between them, leaving no slack. Use a gentle rocking motion to guide the floss between your teeth. Do not jerk the floss or snap the floss into the gums
  • When the floss reaches the gumline, curve it into a C-shape against one tooth until you feel resistance
  • Hold the floss against the tooth. Gently scrape the side of the tooth, moving the floss away from the gum. Repeat on the other side of the gap, along the side of the next tooth
  • Keep to a regular pattern when you floss your teeth, which should help make sure you do not miss any food particles


Using dental mouthwash that contains

can also help prevent tooth decay. However, this should not be used directly after toothbrushing. Choose a separate time to use mouthwash, such as after lunch. Do not eat or drink for 30 minutes after using a fluoride mouthwash.


Try to avoid eating lots of food and drink high in fermented carbohydrates. This includes:

  • fizzy drinks
  • coffee and tea with sugar added
  • chocolate
  • sweets
  • cakes
  • crisps
  • biscuits
  • white bread

Healthier alternatives for snacks and drinks include:

  • cheese
  • fruit and vegetables
  • sugar-free gum
  • unsweetened tea, coffee

You should not avoid carbohydrates altogether, as they are an important part of a balanced diet. But try and choose the type of carbohydrates known as unrefined carbohydrates, as bacteria finds it harder to break these down into acid.

Good sources of unrefined carbohydrates include:

  • wholemeal or brown bread
  • pasta
  • rice
  • potatoes
  • leafy green vegetables
  • eggs

Sugar and food labels

Check labels on foods to see how much sugar they contain. Sugar comes in many forms, so look out for the following ingredients:

  • glucose
  • sucrose
  • honey
  • dextrose
  • maltose
  • fructose
  • hydrolysed starch or syrup

Ingredients are usually listed in order of the amount used, with the main ingredient listed first. If sugar, or one of the ingredients above, is near the top of the ingredients list, it may mean the food is high in sugar.

Some products also use the traffic light system as part of their labelling to indicate whether they are high or low in sugar:

  • a red light indicates a high amount of sugar
  • an amber light indicates a medium amount of sugar
  • a green light indicates a low amount of sugar

In general:

  • high in sugar means more than 15g of sugar for every 100g of product
  • low in sugar means less than 5g of sugar for every 100g of product

Chewing sugar-free gum after you have eaten may also help prevent tooth decay. When you chew gum, your mouth produces saliva, which neutralises the acid in your mouth before it can damage your teeth.

Tooth decay complications

If you have a lot of plaque on your teeth, bacteria can infect your gums as well as the tissue and bones that support your teeth. Advanced cases of tooth decay can lead to abscesses in your mouth.

Gum disease

Gum disease
(also known as gingivitis) causes:

  • red and inflamed gums
  • bleeding gums when brushing teeth

It is usually caused by a build-up of plaque on the teeth.

Periodontitis is a more severe form of gum disease. In periodontitis, inflammation that affects the gums also affects:

  • the tissue that connects the tooth to the tooth socket, called the periodontal ligament
  • the bone in the jaw that contains the sockets of the teeth, called the alveolar bone

Periodontitis can cause a gap to develop between tooth and gum, making the tooth feel loose and, in some cases, fall out.

A mild case of gum disease can usually be successfully treated with good oral hygiene. This should include brushing teeth twice a day (in the morning and last thing at night) and flossing at least three times a week.

If gum disease is not treated, it can develop into periodontitis and more serious complications.

Periodontitis can never be cured. But further loss of bone can be stopped if you keep your teeth clean and remove plaque daily. You will need regular check-ups with your dentist and hygienist.

Dental abscesses

In some cases of advanced tooth decay, bacteria can cause a pus-filled swelling to develop in your mouth. This is known as a

dental abscess

A dental abscess can cause severe pain, and you may also have other symptoms of infection, such as fever.

Dental abscesses can be treated by draining away the pus and removing damaged tissue, known as

root canal treatment

Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.