the Australian Dental Association
Written by the Australian Dental Association, Nov 25, 2023
Fact Checked
Tooth decay is a disease that is strongly related to what we eat and drink. It is the most common chronic disease in Australia, yet it is largely preventable.

The latest research reports that 1 in 3 Australian adults over 15 years of age has untreated tooth decay. By 5 years of age, 1 in 3 children aged 5 - 6 years have already had tooth decay in a baby tooth and this goes up to 1 in 2 for Aboriginal and Torres Strait Islander Children.

How does tooth decay occur?

A few factors are required for tooth decay to develop. All must be present and interplay.


Millions of bacteria live inside the mouth. There are certain types of mouth bacteria that are known to cause tooth decay. One of the most common bacteria to cause tooth decay is called Streptococcus Mutans. These decay-causing bacteria use the sugar from the foods and drinks we consume as energy to create acid.

The acid created by the bacteria attacks the surface of the teeth. It causes the minerals inside the tooth enamel to dissolve. This process is known as demineralisation. The minerals being removed from the tooth surfaces causes it to weaken. This process happens every time we consume foods or drinks with sugar as an ingredient.

If these acid attacks occur repeatedly and not enough protection is provided to the teeth, over time this can lead to the development of tooth decay. Factors such as saliva and fluoride help to protect the teeth by neutralizing the acids and replacing the minerals back into the tooth’s surface. This is a process known as remineralisation.

The development of tooth decay can be considered a balancing act. When the harmful factors outweigh the protective factors, that is when tooth decay can occur.

A balancing act

There are factors that increase the risk of tooth decay developing as well as factors that protect the teeth to try and prevent tooth decay from developing. When the harmful factors outweigh the protective factors, that is when tooth decay begins to form.

Factors that increase the risk of tooth decay
  • Poor oral hygiene
  • Hidden sugars in foods and drinks
  • Frequent snacking
  • A diet filled with sugary foods
  • Decay-causing mouth bacteria
  • Reduced saliva
Factors that protect and decrease tooth decay risk
  • Regular brushing
  • Cleaning between the teeth, e.g. flossing
  • Saliva
  • Diet
  • Fluoride
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Protecting against tooth decay is a balancing act. 

How is tooth decay prevented?

Completing the four key steps recommended by the Australian Dental Association will help you to protect and care for the health of your teeth and gums.

  • Brush twice per day using a fluoride toothpaste.
  • Clean between the teeth daily using floss or interdental brushes.
  • Eat a healthy, balanced diet that is low in added sugar.
  • Visit the dentist regularly.

Practicing these four steps will go a long way to preventing tooth decay from developing.

Fluoride is a very important factor in the prevention of tooth decay. It is best to use a fluoride toothpaste when brushing your teeth. After brushing, spit out the excess toothpaste but do not rinse with water. Not rinsing allows a layer of the toothpaste to remain on the surface of the teeth providing protection for longer.

Tap water is a tooth-friendly drink as in 89% of Australian communities, the community water supply has fluoride added to an optimum level to help protect and strengthen teeth.

How does diet influence tooth decay

Some foods and drinks increase the risk of tooth decay developing. Sweet treats such as cakes, biscuits, and lollies that contain sugar are well known foods that can increase your risk of developing tooth decay. However, many foods that are often thought of as healthy can contain a lot more sugar than we expect. Watch out for sugars hidden in foods such as breakfast cereal, bread and pre-made sauces. It is not just white or brown sugar that is of concern; there are multiple forms of sugar that can contribute to tooth decay, including honey and syrups. Sugary drinks including soft drinks, energy drinks, cordial and fruit juice also increase the risk of tooth decay.

Repeatedly snacking on these foods and/or frequently sipping on sugary drinks can do the greatest damage to the teeth. This is because the teeth are exposed to the sugar repeatedly and frequently and the teeth do not have time to recover after each exposure.

Fruit contains natural sugar. Fresh fruit is less likely to contribute to tooth decay than sugar that is added to foods and drinks. Fresh fruit is a more tooth-friendly food option than dried fruit or fruit juice. Dairy foods without added sugar are also tooth-friendly options. Cheese contains the minerals calcium and phosphorus and the protein casein, which can help to protect the teeth.

How is tooth decay treated?

If tooth decay develops, this may require a filling that replaces the damaged part of the tooth. During this treatment, the soft tooth decay is cut out of the tooth and a filling material is placed in the space.

If tooth decay is detected at a very early stage, your dentist may be able to help you to try and stop the tooth decay from developing any further. If the tooth decay process is stopped, you may not need a filling however a white or brown mark may remain on the tooth surface. This is like a scar from the early stages of tooth decay. This is why it is important to see your dentist regularly.

Summary

Tooth decay is Australia's most common chronic illness and is largely preventable. Diet is the most prevalent factor in the cause of tooth decay, with sugary foods and drinks the largest risk factor. If you're experiencing symptoms of tooth decay, or would like more information about how your diet may be affecting your teeth, use our find a dentist service to find an ADA member dentist near you.