Tooth Decay

tooth-diagramTooth decay, sometimes known as dental caries, occurs when harmful bacteria (bugs) produce acids from sugar found in food and drinks. When enough acid is produced it dissolves the tooth enamel. (acid attack) A hole occurs when the amount and frequency of sugar is not controlled. Controlling the number of ‘acid attacks’ by controlling how often sugar is eaten and keeping it to mealtimes is the key to preventing tooth decay.

The acid produced causes an acid attack.

  • Sugar + Bacteria (Plaque) = Acid
  • Acid + Enamel + No. of acid attacks = Decay

The attack of the acid on the teeth can be stopped with thorough brushing, change in diet and fluoride treatment.

The enamel is a very hard layer of the tooth designed to protect the softer, inner dentine layer. Once the decay breaks through the enamel, it quickly destroys the dentine.

decayAt this point the enamel collapses in to form a cavity. The decay can then affect the dentine at a greater rate than enamel. The tooth can now be painful to cold at first and then hot.

When the decay reaches the pulp, an abscess may form which may cause continuous pain or pain on biting. At this stage a dentist can extract the tooth or perform root treatment on it.




There are four factors needed for tooth decay:

a tooth surface, decay-causing bacteria; sugars and time.


timeHow often a person has a meal or snack affects the chances of a tooth becoming decayed. The bacteria in the mouth break down the sugar, to produce acid. As time goes on, the acid disappears due to the saliva washing it away. When acid is produced, some of the tooth is damaged. The tooth recovers after about two hours. The more frequent the snacks, the more damage is done to the teeth and the less time for the tooth to recover. The picture shows the acid (red) produced when snacks are eaten frequently.


Dental decay can be prevented by:

  • Fluoride in toothpaste, mouth rinses and drinking water can strengthen the teeth and protect them from tooth decay.
  • Reducing the amount of plaque and bacteria on the surface of the teeth by brushing with fluoride toothpaste. Parents should supervise or help with toothbrushing until children can do it effectively, usually by the age of seven.
  • Using a fluoride containing toothpaste when brushing last thing at night and one other time during the day.
  • Reducing the amount and frequency of sugars and restricting them to mealtimes.
  • Increasing the concentration of fluoride in the mouth with fluoride varnish applied by a dental professional.

Dental Erosion

This is the wearing away of the tooth by acid and is very different to decay. The acid softens the enamel and the wear and tear on the teeth speeds up the process.


It is caused by acids entering the mouth either from drinking a lot of carbonated drinks (or pure fruit juice) or from the stomach (due to reflux or vomiting). It is seen mostly on the backs of the front upper teeth or the biting surfaces of the back teeth. The teeth become very worn and can be sensitive to hot or cold.


Erosion can be prevented by reducing the amount of erosive / acidic drinks and foods and by thorough toothbrushing twice daily with a family fluoride toothpaste. It is sensible to avoid toothbrushing straight after the consumption of acidic food or drinks as the tooth enamel will be soft after the acid, and there is a danger of damage with the toothbrush.

If someone suffers from an eating disorder where there is vomiting or from reflux, consult the doctor. Dental advice should be got also to look for some preventative measures.

Last updated: March 19, 2014

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