OIder people who lived in areas where fluoride was added to the water have better teeth than those who did not, a new study by researchers at Trinity College Dublin has found.

Using data from 4,977 adults that was gathered as part of the Irish Longitudinal Study on Ageing (TILDA), the researchers assessed oral health and bone density in adults over the age of 50 and compared it to the 2006 census.

At that time eight out of every ten households had a fluoridated water supply and the census of that year records the type of water supply in each location.

The analysis, carried out in conjunction with the School of Dental Science in Trinity, found the higher the prevalence of fluoridated water, the greater the chance that an older person had all their own teeth.

However, the researchers found no association between the prevalence of fluoridated water and bone density, even though fluoride can increase bone mass.

In carrying out their analysis, the team controlled other factors which can impact on the health of teeth and bones, to ensure they didn't influence the results.

"While the initial focus of water fluoridation in Ireland was to prevent tooth cavities in children, much less attention has been paid to the effects of fluoridation later in life," Professor of Restorative Dentistry at the Dublin Dental School & Hospital Brian O'Connell said.

"There are now large adult populations that have lived several decades with fluoridated water supplies, yet the benefits and risks for these populations have remained unclear.

"This study shows a measurable positive relationship between fluoridation and maintaining a person's own teeth.

"There are however limitations with these results as tooth loss could be the result of other processes such as gum disease, wear, trauma and access to dental care.

"In addition, it was not possible to assess the impact of other sources of fluoride, such as diet, toothpaste and mouth rinses which could all have an impact on oral health," he said. 

Fluoridation of public water supplies began in Ireland in 1964 and was extended to major cities and towns by 1970.

It remains a controversial topic though, amid a level of concern about the risk it might pose to public health.

Over the past year, a number of local councils have passed motions calling on the Government to end mandatory fluoridation of the public water supply.

However, the authors of this research say the safety of water fluoridation has been extensively reviewed internationally and has been found to have either no detrimental effect on general health or no clear evidence of toxicity.