Tooth decay (dental caries) is a major chronic disease among New Zealanders of all ages. It is often accompanied by pain, infection, and tooth loss, and can lead to absence from work or school (Royal Society of New Zealand 2014). Dental caries (cavities) are caused by acids that are produced by bacteria in the mouth. The acids dissolve the hard enamel of the tooth surface and start dental decay. A high-sugar diet can raise the number of bacteria, which in turn increases the production of decay-causing acids (Ministry of Health 2010; Royal Society of New Zealand 2014).
Fluoride is known to protect teeth against dental caries, so adding fluoride to drinking-water supplies can help limit tooth decay. Fluoride works to protect teeth in three ways (Royal Society of New Zealand 2014):
- strengthening of tooth enamel, making teeth more resistant to decay
- interference with the growth of bacteria that cause cavities
- repair of the early stages of tooth decay.
About 60% of New Zealanders have access to fluoridated drinking-water
About 4.2 million New Zealanders (83.6% of the population) received water from registered drinking-water supplies during the 2020/21 reporting period. The remainder received water from very small community supplies (typically serving fewer than 100 people) or sourced their own water from ‘self-supplies’ (eg, rainwater tanks). Of the population on registered supplies, 60.6% (2.5 million) had access to fluoridated drinking-water. From 2014/15 onwards, this percentage of people with access to fluoridated water has remained largely unchanged, never going above 62% (Figure 1).
Figure 1: Percentage of the population on registered drinking-water supplies with access to fluoridated drinking-water, 2009/10–2020/2021
Note: The grey zone around the 2010/11 reporting period indicates that this is considered an outlier and should not be used when making interpretations on the overall percentage of people with access to fluoridated drinking-water.
Information about this indicator
The datasets for this indicator come from the Ministry of Health’s ‘Annual report on drinking-water quality’. Drinking water statistics are presented for all registered community drinking water supplies that served more than 100 people.
Ministry of Health. (2022). Annual report on drinking water quality 2020-2021. Wellington: Ministry of Health.
Royal Society of New Zealand. 2014. Health Effects of Water Fluoridation: A review of the scientific evidence. Wellington: Office of the Prime Minister’s Chief Science Advisor and Royal Society of New Zealand.