Tooth decay

Tooth plaque is a sticky layer of bacteria (germs) which coats the teeth. When the bacteria in plaque react with sugar (from our food and drink), it produces acid. The acid causes decay or ‘cavities’ in the teeth.

Decay is preventable when there is good oral hygiene with fluoride toothpaste, a reduced sugar intake and regular dental check-ups.

The following things make decay more likely:

  • frequent daily sugar intake (food, drink, medicine)
  • snacking between meals. Acid attacks the teeth for up to an hour after eating. Teeth will be under constant attack without time to recover when someone sips a sugary drink or eats sugary snacks throughout the day.
  • oral intake of sugar food, drinks or medication last thing at night
  • not brushing twice each day with fluoride toothpaste (morning and night)
  • bottle feeding for a prolonged time (especially overnight)
  • not visiting the dentist for regular check-ups
  • a dry mouth

What are the signs and symptoms of tooth decay?

At first there won’t be any symptoms. The dentist might spot a new cavity forming during a check-up and looking at X-rays.

If the tooth continues to decay and the cavity gets bigger it can reach the dentine (under the enamel). At this stage the tooth may become more sensitive to sweet foods and hot or cold drinks and food.

As the cavity gets closer to the dental pulp (soft tissue in middle of tooth), it is likely to cause toothache.

How is tooth decay normally treated?

Decay is usually treated with a filling or extraction. If the decay is extensive and has reached the nerve in the centre of the tooth, it will require extraction or root canal treatment.

A filling involves the dentist removing the infected decay in the tooth. The cavity or hole is filled with a filling or crown.

Fluoride toothpaste

  • fluoride helps prevent decay
  • use a fluoride toothpaste twice per day
Toothpaste is available for different age groups depending on the fluoride concentration. This is displayed on the toothpaste tube as ‘ppm’ which means ‘parts per million’:

  • under 3 years: use a small smear of paste with 1000ppm fluoride
  • 3 to 6 years: use a pea-sized amount of paste with 1000ppm fluoride
  • over 6 years: use a pea-sized amount of paste with 1450ppm fluoride


  • avoid sugary snacks (cake, biscuits, sweets) between meals
  • avoid sugary food/drink last thing before bed
  • sugar-free snacks include: bread, cheese, milk and water
  • most fruit juices contain sugar
  • fizzy drinks (regular and diet) can damage teeth (limit these to special occasions)
  • milk and water are the only drinks you should fill a bottle with

What about sugars in medication?

There are some sugar-free medicines available (ask the doctor if there is a sugar-free alternative).

If there is not a sugar-free option:

  • clean the teeth or have a drink of water after swallowing the medicine, this will dilute the sugar on the teeth
  • ask the dentist for advice about fluoride mouth rinse

What happens next?

Decay can be prevented. The following will help to prevent the problem:

  • brush twice a day with fluoride toothpaste
  • avoid sugary snacks and drinks between meals
  • avoid giving a bottle overnight
  • a bottle during the day should only contain water or milk
  • register children with a dentist for regular check-ups (the dentist will advise on the frequency)
Compiled by:
The Child and Family Information Group
Last review date:
February 2017