Condition category
Oral Health
Date applied
Date assigned
Last edited
Prospectively registered
Overall trial status
Recruitment status
Not yet recruiting

Plain English Summary

Background and study aims
Tooth decay is the most common disease affecting mankind. It causes 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 unless they are 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.
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 contains fluoride. 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.
The aim of the study is to find out how effective and cost-effective water fluoridation is in preventing dental treatment and improving oral health in modern adult populations who also have access to fluoride in toothpastes.

Who can participate?
The study will use anonymised NHS data that has already been collected from adolescents and adults attending NHS dental practices in England, therefore the researchers will not be seeking to recruit any participants

What does the study involve?
The researchers will use information that was submitted in payment claims by NHS dentists between 2010 and 2020. This information is held by the NHS Business Services Authority, who are part of NHS Digital. The researchers will compare the number and type of NHS dental treatments that were provided to adults and adolescents who lived in fluoridated or non-fluoridated areas of England. All names, addresses and identifying information about both patients and dentists will be removed before the researchers access the payment records.
Knowing the number and types of dental treatments received will show whether 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 the researchers 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.

What are the possible benefits and risks of participating?
The data has already been collected as part of routine NHS dental care in England, therefore there won’t be any active ‘participation’ by individuals. Using this anonymised NHS data for research is in the public interest because it will provide information on how to improve oral health in adults, reduce the need for invasive dental treatments such as fillings and extractions, and how to save money for both the NHS and for dental patients themselves.
As this is a data-only study the only risks are related to data security. Despite the anonymity of the data the researchers take data security very seriously and will apply the same governance requirements as those we would use for identifiable data. Data access will be subject to appropriate ethical and legal approvals and will be carried out according to a formal data sharing agreement.

Where is the study run from?
The University of Manchester (UK)

When is the study starting and how long is it expected to run for?
February 2020 to January 2022

Who is funding the study?
National Institute of Health Research (NIHR) Public Health Research programme (UK)

Who is the main contact?
Deborah Moore

Trial website

Contact information



Primary contact

Ms Deborah Moore


Contact details

Dental Public Health
Dental Health Unit
Lloyd Street North
Manchester Science Park
M15 6SE
United Kingdom
+44 (0)161 226 1211

Additional identifiers

EudraCT number

Nil known number

Nil known

Protocol/serial number

CPMS 44419, IRAS 274705

Study information

Scientific title

How effective and cost-effective is water fluoridation for adults? A 10-year retrospective cohort study


FLuOridaTion for AdUltS (LOTUS)

Study hypothesis

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?

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.

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, using a natural experiment design.

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

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.

Ethics approval

Approved 02/12/2019, University of Manchester Research Ethics Committee (Mrs Genevieve Pridham, Research Governance, Ethics and Integrity, 2nd Floor Christie Building, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK; Tel: +44 (0)161 275 2206/2674; Email:, ref: 2019-8391-12289

Study design

Observational; Design type: Cohort study

Primary study design


Secondary study design

Cohort study

Trial setting


Trial type


Patient information sheet

Not available in web format, please use the contact details to request a patient information sheet


Oral health


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 2010-2020. 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).

Intervention type



Drug names

Primary outcome measure

Mean number of invasive dental treatments (restorations, endodontics, extractions) received by adults attending NHS dental practices, measured using routinely collected NHS dental treatment data over ten years of observation (2010-2020)

Secondary outcome measures

Measured using routinely collected NHS dental treatment data over ten years of observation (2010-2020):
1. Mean cost (£) per episode of invasive dental treatment avoided over ten years (2010-2020)
2. Mean number of natural remaining teeth at the most recent dental visit
3. Mean number of teeth affected by decay at the most recent dental visit, measured using the Decayed, Missing, Filled Index (DMFT)

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

Adolescents and adults (>12 years) attending NHS dental practices in England

Participant type


Age group




Target number of participants

Planned Sample Size: 8000000; UK Sample Size: 8000000

Participant exclusion criteria

Does not meet inclusion criteria

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

University of Manchester
Faculty of Biology, Medicine and Health Division of Dentistry Dental Health Unit Lloyd Street North Manchester Science Park
M15 6SE
United Kingdom

Sponsor information


University of Manchester

Sponsor details

c/o Ms Lynne Macrae
Faculty Research Practice Co-ordinator
FBMH Research Office
3.53 Simon Building
University of Manchester
M13 9PL
United Kingdom
+44 (0)1612755436

Sponsor type

Hospital/treatment centre



Funder type


Funder name

NIHR Evaluation, Trials and Studies Co-ordinating Centre (NETSCC); Grant Codes: NIHR128533

Alternative name(s)

Funding Body Type

Funding Body Subtype


Funder name

National Institute for Health Research (NIHR) (UK)

Alternative name(s)


Funding Body Type

government organisation

Funding Body Subtype

National government


United Kingdom

Results and Publications

Publication and dissemination plan

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.

IPD sharing statement
The data sharing plans for the current study are unknown and will be made available at a later date.

Intention to publish date


Participant level data

To be made available at a later date

Basic results (scientific)

Publication list

Publication citations

Additional files

Editorial Notes

25/03/2020: Uploaded protocol (not peer reviewed) as an additional file. 13/01/2020: Trial's existence confirmed by the NIHR.