Fluoride is a natural substance that helps protect our teeth by making them stronger and by reducing tooth decay. It exists naturally in air, soil, fresh water, sea water, plants and in lots of food.
Fluoride and its role in oral health
Fluoride works in three ways to help protect our teeth from decay:
- Fluoride makes teeth more resistant to decay by strengthening the tooth surface
- Fluoride interferes with the growth of the bacteria which cause cavities
- Fluoride helps to repair the early stages of tooth decay.
Eating and drinking increases the acidity in the mouth – this can remove the minerals from teeth, leading to tooth decay. Drinking fluoridated water and brushing teeth with fluoride toothpaste increases the concentration of fluoride in saliva and plaque fluid. Fluoride in water acts like a constant repair kit that neutralises the effect of acids that cause decay and helps to repair damage before it becomes permanent.
Fluoride toothpaste is an effective method of reducing dental decay. It provides an additional benefit above that of fluoridated water.
Most fluoridated toothpastes on sale in New Zealand contain 1000 ppm of fluoride (i.e. 0.221% sodium fluoride or 0.76% sodium monofluorophosphate). This is the recommended strength for adults and children, based on the consensus of many years of research on the effectiveness of different strengths of toothpaste. Adults and children (6 and over) should us a ‘pea’ sized amount and children under 6 should use half a pea-sized amount of the same strength toothpaste on a small toothbrush. Children should be discouraged from swallowing or eating toothpaste.
Water fluoridation is the process of adjusting the natural level of fluoride in the water supply to between 0.7 ppm and 1.0 ppm. This is the optimal amount that provides protection against tooth decay, and is recommended by the World Health Organization.
The current level of fluoride found in untreated water supplies in New Zealand is not effective enough to be of benefit in helping to prevent tooth decay, so ‘topping up’ the fluoride levels in reticulated water supplies has been done in many regions around New Zealand over several decades. The amount added is monitored to make sure that the levels stay within that range.
Along with brushing twice a day with fluoride toothpaste, eating healthy foods and timely check-ups with a dental provider, water fluoridation is a proven public health measure to reduce tooth decay. The World Health Organization and other international and national health and scientific experts endorse water fluoridation as the most effective public health measure for the prevention of dental decay. The role of fluoride in water has been examined in many locations and in many countries, including New Zealand, over the last 60 years.
Relevant legislative framework
The Health (Fluoridation of Drinking Water) Amendment Act 2021 shifted decision-making on fluoridation from local authorities to the Director-General of Health. The change allows for a nationally consistent approach to community water fluoridation based on its well-established health benefits.
Local authorities will be required to fluoridate a water supply if directed to do so by the Director-General of Health. Those already fluoridating are required to continue to do so.
The Director-General of Health may direct a local authority to add fluoride to drinking water supplied.
Supreme Court judgment
In 2018, the Supreme Court has issued a judgment confirming that local authorities have the legal authority to fluoridate water supplies. In doing so, local authorities are not breaching people’s individual right to refuse to undergo medical treatment.
You can download the judgment and the media release from the Courts of New Zealand website: New Health New Zealand Incorporated v South Taranaki District Council  NZSC 60.
Visit the Fluoride Facts section for more information about water fluoridation.