Plain English Summary of the 2022 study:

Tooth decay is the commonest disease of childhood and tooth extraction due to decay is the main reason why children have a general anaesthetic in hospital. We have known for over 90 years that fluoride can prevent tooth decay; it is present in nearly all toothpastes and can be provided in mouthwashes, gels and varnishes. The oldest method of applying fluoride is via the water supply at a concentration of 1 part per million. Water fluoridation has a 70-year history; virtually all of Australia drinks fluoridated water, 70% of the USA is fluoridated and about 10% of the population of England have a fluoridated water supply. People in the UK are often surprised to learn that their water supply is not fluoridated. Early trials of water fluoridation in the USA and UK in the 40s and 50s showed very dramatic falls in tooth decay. However since the introduction of fluoride toothpaste in the 1970s there has been a significant fall in tooth decay, particularly in the permanent teeth. Public debate on water fluoridation tends to be very polarised with very strong views held by the pro and anti lobbies. Unfortunately the scientific evidence to tell us how well water fluoridation works and how cost effective it is in the current climate of falling decay levels is lacking. We have a unique opportunity to study the impact of water fluoridation in West Cumbria. A water fluoridation scheme was established in the 1960s but has been off line for several years; a new plant will come on line in 2013. This project aims to provide strong evidence of the effects and costs of a ‘new’ water fluoridation scheme on young children. Two important scientific committees have recommended that the best way of assessing the current value of water fluoridation is to assess a ‘new’ scheme such as that in Cumbria. Water fluoridation works in two ways: Systemic (from birth) – built into the teeth strengthening them as they develop before birth and in the first 5 years of life. Topical – strengthening the surface of the teeth after they have erupted in the mouth. The design of this study aims to assess both the systemic and topical effects of water fluoridation by recruiting two groups of children and following them up over the next 6 years. We will attempt recruit all children born in West Cumbria (fluoridated) in a one year period, nine months after the resumption in supply, and all of the children in North Cumbria who will be used as a control (children not receiving fluoridated water). We will examine the children’s teeth aged 3 and when they are 5-years-old. This will let us assess the systemic and topical effects of water fluoridation on the primary (milk) teeth. Many people think that milk teeth aren’t so important – we do get another set after all! However, around 16,000 in the North West of England will need to have a general anaesthetic to remove some or all of these baby teeth. There are risks to the children, both from the anaesthetic itself, but also in the future in terms of their relationship with dentistry. Early extraction of teeth can cause longer term problems with tooth positioning and can lead to further decay risk. Starting at the same time we will recruit all 5-year-old children in West Cumbria and North Cumbria schools and examine their teeth at aged 7 and 11-years-old. This will enable us to assess the topical effects alone of fluoridation on the permanent (adult) teeth. Our main outcome measure (what we will look at to see if water fluoridation works) in each age group will be to compare the number of children in fluoridated and non-fluoridated groups who develop any tooth decay. A group of trained examiners will examine the children, this will be supported by using a small pen-like camera which takes digital photographs of individual teeth. This technique means that other examiners can independently check our findings and also that examiners will not know if children live in a fluoridated or non-fluoridated area (known as bias). We will also look at the number of teeth affected once decay starts, episodes of pain and also if any teeth are extracted. In both age groups over the 6 years we will collect information on diet, amount of toothpaste used and dental visiting patterns, all of which have an effect on tooth decay levels, so that these can be separated out to identify the effect of water fluoridation alone. As tooth decay is closely associated with poverty, we will measure social and economic status of parents to assess the effect water fluoridation has on inequalities in the level of decay experienced by children from rich and poor families. We will also collect information on the costs of fluoridating the water and any treatment received by children in both fluoridated and non-fluoridated areas. This will allow us to assess value for money. We will also collect information on any chronic diseases or serious conditions children in fluoridated and non-fluoridated groups develop over the 6 years to assess any untoward effects. We will not be able to assess fluorosis (white speckling of the teeth due to exposure to fluoride) in this application, as this will not be evident until a child is 9 years-old. We will submit an application at the appropriate time to undertake this important assessment. This project will make a major contribution to the understanding of the costs and effects of water fluoridation in the UK in the 21st Century. Its findings will inform UK policy on this important public health intervention and its findings will have a significant impact on public health policy in other developed countries.

• Original Summary online at https://fundingawards.nihr.ac.uk/award/12/3000/40