Title: How effective and cost-effective is water fluoridation for adults? A 10-year retrospective cohort study
Funder: Department of Health and Social Care

Abstract: Tooth decay is the most common disease affecting mankind. It can cause pain, infection, sleepless nights and time off from work. Having dental treatment creates worry for many, because of the discomfort involved, the inconvenience and the costs. Tooth decay is costly for the NHS, and patients themselves if they are not exempt from NHS charges. The NHS currently spends £3.4 billion on NHS dental services, and patients pay another £653 million in patient charges. The majority of these costs are spent on the treatment of tooth decay and its consequences. _x000D_ _x000D_ It has long been known that fluoride can prevent tooth decay. Since the 1940s, fluoride has been added to some public water supplies and it was first added to toothpastes in the 1970s. Since fluoride toothpastes became available, there has been dramatic improvement in dental health. People have fewer cavities and keep their teeth for longer, particularly in more affluent communities. In America and Australia, almost all public water supplies have fluoride added. In England, only 10% of our water supply has fluoride added to reduce decay. Local Councils decide if they want to add fluoride to the water to improve the dental health of local people. The problem for Local Councils is there is very little modern research on water fluoridation to help them decide if this is a good idea. We don’t know the present-day costs and benefits of water fluoridation, when almost everyone uses fluoride toothpastes. There is also very little research on adults, because it is difficult and very costly to enrol lots of adults into a long-term research study. For children, it is much easier and cheaper because they can be followed up in school. This study will provide added information to give a full picture of this issue. _x000D_ _x000D_ We plan to use the information collected in NHS dental practice records to understand the impact of water fluoridation on adults. We will compare the number and type of dental treatments provided to around 6 million people living in fluoridated or non-fluoridated areas over ten years. NHS dental records include lots of useful information about the patient, their dentist, and their dental practice. All names and identifying information will be removed before we look at the records. We will only compare people who are as similar as possible, except for the fact they have lived in a fluoridated or non-fluoridated area. Comparing people who are very similar is called ‘matching’. Knowing the number and types of treatments received will tell us if living in an area with water fluoridation reduces the costs of NHS dental care, for both the NHS and for patients. Using the information recorded by NHS dental practices means that we will be able to access information on very large numbers of people, over a period of ten years. This will keep the costs of the research low, and provide answers quickly. _x000D_ _x000D_ We want our research to be as useful as possible. We have already checked that this research topic is important to members of the public and dental professionals, and we have included two members of the public on the research team to help us make sure our results are relevant and understandable. We will share our results in different ways to reach members of the public and Local Councils, as well as dentists and researchers. This will include; media briefings, blogs, and social media posts containing a video animation and infographic that can be shared.

Lay abstract: Research question: How effective and cost-effective is 10-year exposure to water fluoridation in preventing dental treatment and improving oral health in a contemporary adult population? _x000D_ Background: Tooth decay can cause pain, sleepless nights, sepsis, overuse of antibiotics, embarrassment, and loss of productive workdays. It can also lead to complete tooth loss; one of the leading global causes of disability. Dental treatment can provoke severe anxiety, and is also very costly, both to the NHS and to patients. Health inequalities exist, with poor dental health strongly associated with deprivation. Artificial fluoridation of water was identified in the 1940s as a cost-effective method to prevent tooth decay. However, in the mid-1970s, toothpastes containing fluoride became widely available. It is now unclear how much added benefit fluoride in water provides for contemporary populations. Most water fluoridation research was carried out before the mid-1970s, and there is a paucity of evidence on the effects and costs of water fluoridation particularly in adults. _x000D_ Aim: To pragmatically assess the clinical effectiveness and cost-effectiveness of water fluoridation in preventing the need for dental treatment and improving oral health and in a contemporary population of adults and adolescents, using a natural experiment design._x000D_ Primary Objective: To compare the effect of 10-year exposure to fluoridated water with no exposure on the number of invasive dental treatments, including restorations, endodontics or extractions, received by adults attending NHS dental practices _x000D_ Secondary Objectives: To evaluate the cost-effectiveness of water fluoridation. To evaluate the impact of fluoridated water on oral health (number of remaining natural teeth and decay experience). To measure the impact of water fluoridation on oral health inequalities._x000D_ Methods: Retrospective cohort study using routinely collected NHS dental treatment data. Individuals exposed to water fluoridation will be identified by continuous residence in a fluoridated area during the follow up period of 2009-2019. The outcomes will be based on the number of invasive dental treatments received per participant, over ten years of observation (fillings, extractions, root canal treatments). Exposed individuals will be matched to non-exposed individuals (controls) using propensity scoring. Participants will be matched on a range of individual-level, dental practice-level and location-level characteristics. Cost-effectiveness will be assessed using the incremental cost-effectiveness ratio with uncertainty summarised using the cost-effectiveness acceptability curve (CEAC)._x000D_ Timelines: 01.02.2020 to 31.01.2022_x000D_ Impact and dissemination: Prevention of tooth decay for populations has recently been identified as the top priority for dental research in a recent James Lind Alliance facilitated priority setting partnership. The proposed study will supplement the outputs of the CATFISH study of the costs and effects of fluoridation on children to inform local authorities’ decisions on the introduction or cessation of water fluoridation schemes. A comprehensive dissemination strategy will be developed with input from key stakeholders. This will include sharing the results in a range of formats, both traditional academic routes and more innovative channels, including press releases, policy briefings, blog posts, and an animated video and infographic which can be shared on social media.

Research activity codes: 3.2 INTERVENTIONS TO ALTER PHYSICAL AND BIOLOGICAL ENVIRONMENTAL RISKS
Health categories: ORAL AND GASTROINTESTINAL