Existing drinking water fluoridation programmes in England still provide marginal savings for the NHS, but there is no guarantee new schemes would continue to do so, a study led by University of Manchester researchers finds.

It is the largest-ever study of the effects of water fluoridation on the dental health of adults.

The National Institute for Health and Care Research funded a data study of 6.4m UK adults and adolescents across England and published in Community Dentistry and Oral Epidemiology estimated the public sector saved £16.9m between 2010 and 2020 due to water fluoridation.

People receiving optimally fluoridated water in the study experienced a three per cent reduction in NHS invasive dental treatments such as fillings and extractions, and a two per cent reduction in the numbers decayed, missing, and filled teeth, when compared to the non-optimally fluoridated cohort over 10 years.

The research team found no compelling evidence that water fluoridation reduced social inequalities in dental health, and the numbers of missing teeth between the cohorts were the same.

Around six million people in England live in areas that receive drinking water with fluoride added to prevent tooth decay, including those in Birmingham and Newcastle. Water containing enough fluoride to prevent tooth decay is known as ‘’optimally fluoridated’’.

Most research on the benefits of water fluoridation was carried out before fluoride was added to toothpaste in the 1970s and only included children, showing water fluoridation had a large impact on dental health – almost halving levels of tooth decay.

New research was needed to investigate the dental health benefits in people who have access to fluoride in toothpastes. More people now keep their teeth into old age, so understanding the benefits for adults was also a priority.

Over the 10-year period studied, optimal water fluoridation cost £10.30 per person. NHS treatment costs were £22.26 lower per person (5.5 per cent) and patients paid £7.64 less ( two per cent) in dental charges.

Using the data, the researchers estimate if 62 per cent of the adults and teenagers in England attended NHS dental services at least twice within 10 years, the total return on investment would have been £16.9m between 2010 and 2020.

The findings echo the recently published NIHR CATFISH prospective cohort study in UK children, which showed smaller-than-expected health benefits of water fluoridation in children.

Deborah Moore, lead author and honorary lecturer at The University of Manchester said, “This study is the first in the UK to capture health and economic effects of water fluoridation on adults with widespread access to fluorides in toothpaste, mouthwashes and dentist-applied varnishes.

“The patients who received optimal water fluoridation had very small positive health effects.

“But as the costs of NHS dentistry are much higher than the costs of water fluoridation, the relatively small observed reductions in visits to the dentist still resulted in a positive return for the public sector.

“This return should be evaluated against the projected costs and lifespan of any proposed capital investment in water fluoridation, including new programmes.”

The capital costs of setting up a new scheme covering a similar number of people in 2009 have been estimated at around £50m in today’s prices; which would take 30 years to recover in NHS dental treatment savings.

Cost-recovery for new schemes say the researchers, may not be guaranteed in future generations, as children’s teeth are in much better condition than their parents, and they may not need as much dental treatment as they reach adulthood.

Deborah added, “Fluoridation of drinking water is justifiably recognised as one of the twentieth century’s greatest public health achievements.

“But as fluoride toothpaste became available in the mid-1970s - considered to be the key factor in the dramatic decline in the prevalence and severity of dental decay – the context of water fluoridation has changed.

“There is no doubt that population-level, mass preventive interventions for tooth decay are still required.

“Tooth decay remains almost universal by adulthood, even in populations that have had access to fluoride toothpaste and fluoridated water from birth.

“However, in high-income countries, we may be reaching the limit of what can be achieved through fluorides alone.

“The relationship between sugar consumption and tooth decay is very clear: average consumption of sugars in the UK is more than double the recommended level for adolescents and is almost double for adults.

“Managing sugar consumption is another area of policy that needs to be investigated.”