Water fluoridation
Water fluoridation is the addition of fluoride to drinking water to strengthen and protect teeth against tooth decay. Some communities already have fluoride naturally present in their drinking water. In these communities, the fluoride is topped up to be at the recommended level to protect teeth.
Fluoridated drinking water safely strengthens everyone's teeth, from the very young to the very old. Drinking fluoridated water as a child has shown to decrease your risk of tooth decay as an adult. Water fluoridation has been found to reduce tooth decay by 26% to 44% in children and adolescents, and by around 27% in adults.
Water fluoridation began in America in 1945 and has been added to water supplies in Australian towns and cities since 1953. Beaconsfield in Tasmania became the first town in Australia with fluoridated water.
The level of fluoride in drinking water should be within the range of 0.6 - 1.1 mg/L (also known as parts per million - ppm).
The US-based Centers for Disease Control and Prevention hails water fluoridation as one of the great public health achievements of the 20th century. It has proven so effective at reducing tooth decay in children and adults that health authorities around the world such as the World Health Organization, the National Health and Medical Research Council and the Australian Medical Association strongly back its use.
Since 2017, 89% of the Australian population has had access to fluoridated drinking water.

Image: Percentage of the Australian population with access to fluoridated drinking water as of 2017.
Not all Australians have access to fluoridated community water, however DIY water fluoridation is not recommended. Read more at I cannot access fluoridated water. Should I add fluoride to my own water?