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Tooth decay


Tooth decay also known as dental decay and dental caries is when acids in your mouth dissolve the outer layers of your teeth.

Why it occurs

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 that is high in carbohydrates (sugary or starchy), the bacteria in plaque turn the carbohydrates into the energy they need, producing acid at the same time.

Over time, the acid in plaque begins to break down the surface of your tooth. Left untreated, the plaque can completely destroy the outside of the tooth and expose the nerves inside. Once this happens, you will have toothache. Without treatment the tooth eventually falls out.

 How common is it?

Tooth decay is one of the most widespread health problems in the UK. More than half (55%) of adults in the UK have one or more decayed teeth.

Tooth decay is also a problem for children. It is estimated that between 52% and 77% children aged 8 to 15 years have some obvious tooth decay in their permanent teeth.


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.

If you get tooth decay, there are a number of techniques that can help repair damaged teeth, such as fillings and crowns (see Tooth decay - treatment for more information). In more advanced cases of tooth decay, the tooth may need to be removed. 

Tips for looking after your teeth

  • brush your teeth twice a day, in the morning and in the evening
  • spend at least three minutes each time
  • always use a fluoride toothpaste
  • use a small toothbrush so that you can reach the back teeth, applying no more than a pea-sized amount of toothpaste for adults
  • flossing is very important as the toothbrush does not always reach the gaps between the teeth
  • do not brush too hard – this can damage gums
  • limit your consumption of sugar and starchy foods
  • visit your dentist regularly
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The importance of regular dental checks

Tooth decay does not cause any symptoms until it has reached an advanced stage. This is why it is important to have regular check-ups with your dentist. 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 every year.

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.

See the 'causes' section for more information on risk factors.

Symptoms of advanced tooth decay

The symptoms of advanced tooth decay include:

  • toothache,
  • tooth sensitivity - you may experience tenderness or pain when eating or drinking something hot, cold, or sweet. 
  • discoloured spots, either grey, brown or black, can appear on your teeth,
  • bad breath, and
  • 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.


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A tooth is made up of three parts:

  • enamel - the hard outer coating of a tooth
  • dentin - the softer, bone-like material underneath the enamel
  • pulp - the soft centre of the tooth that contains the 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 that is high in carbohydrates (sugary or starchy), the bacteria in plaque turn the carbohydrates into the 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 toothache.

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, the plaque and bacteria will then enter the pulp. At this stage, your nerves will be exposed to the bacteria, making your tooth very painful. The bacteria can also infect the tissue within the pulp, causing a dental abscess.

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

Risk factors for tooth decay

There are a number of identified risk factors for tooth decay. These are outlined below.


Consuming food and drink that is high in carbohydrates will increase your risk of tooth decay.

Tooth decay is often associated with sweet and sticky foods, such as chocolate, sweets, sugar and fizzy drinks. Starchy foods, 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 the tobacco smoke interferes with the production of saliva, which helps keep the surface of your teeth clean. Studies have also shown that passive smoking can also be a risk factor, particularly for children.

Dry mouth

People who have lower levels of saliva in their mouth are at a 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 can also often lower the levels of saliva in your mouth.

If you are taking a medicine, or receiving a treatment, that is known to cause dry mouth, drink plenty of water and make sure you have a good oral hygiene routine.

See Tooth decay - prevention for tips on how to keep your teeth healthy.

Eating disorders

Both anorexia and bulimia can increase the risk of tooth decay. Anorexia can decrease your production of saliva, while the vomiting associated with bulimia can expose your teeth to corrosive stomach acids.

Gastro-oesophageal Reflux Disease (GORD)

Gastro-oesophageal Reflux Disease (GORD) is a digestive condition where stomach acid leaks back up out of the stomach and into the throat. In some case of GORD, the acid can enter the mouth and erode the surfaces of the teeth.

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A dentist should be able to spot tooth decay in its initial stages by physically examining your mouth. If the tooth decay is particularly advanced, or it is in a part of your mouth that is hard to examine, they may X-Ray your mouth to check for cavities

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 usually occur at the gumline in teeth that are in the side of your mouth
  • root cavities - occur at the root of the front of the tooth - they are more common in older people because gums tend to recede slightly with age, making the root more vulnerable to plaque.

What happens at each 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
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If your decay is in the early stages, your dentist may apply a fluoride varnish to the area, which can help to stop further decay.

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

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


Fluoride 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 the acid attacks that can cause tooth decay. It reduces the ability of plaque bacteria to produce acid, and it 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 teeth that have been extensively damaged. The decayed section of the tooth is drilled away and the crown is placed over the remaining section of the tooth. Crowns are made out of gold,or porcelain, ceramic or glass

Root canal treatment

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

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

Tooth extraction

In  very serious cases of tooth decay,  the tooth may be  removed to prevent the spread of infection. Losing certain teeth can affect the shape and function of the surrounding teeth so the dentist may have to replace the tooth with an artificial implant.

Paying for treatment

Many people are concerned about the cost of their dental treatment.
NHS charges are set by the government and are standard for all NHS patients. The charges are assessed each year and usually change every April.

From April 2010, NHS dental charges are £12 or £39 for most courses of treatment; the maximum charge for a complex course of treatment is £177.

There are several ways of paying for dental treatment, including many types of payment plan that allow you to spread your payment over a period of time.

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In more advanced cases of tooth decay, the bacteria can infect your gums  (gum disease)  as well as the tissue and bones that support your teeth (periodontitis).  It can also lead to abscesses in your mouth.

Gum disease


Gum disease (also known as gingivitis) causes:

  • red and inflamed (swollen) 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, the 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 the 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 the 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 every day. You will need to go for 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 experience other symptoms of infection such as fever. 

Dental abscesses can be treated by draining away the pus and removing any damaged tissue. For more information, see the Encyclopaedia topic on dental abscess.

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Oral hygiene

Maintaining good oral hygiene is one of the most effective ways to prevent tooth decay.


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

It is also important that 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 the 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.

It is important to replace your toothbrush on a regular basis as they can 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 that the most effective type of electric toothbrush 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 will need to replace the head of your electric toothbrush once every two to three months.


Flossing is also 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 18 inches 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 can also help prevent tooth decay.


Try to avoid eating lots of food and drink that are high in fermented carbohydrates. These include:

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

Healthier alternative for snacks and drinks include:

  • cheese,
  • fruit and vegetables,
  • sugar free gum, and
  • unsweetened tea, coffer or carbonated drinks.

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 the 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.
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