Fluoride has been getting a rough ride in the letters pages of The Irish Times in recent weeks, with claims of all kinds of health hazards by those opposed to its use. There is little doubt, however, that fluoride in water and toothpastes is a powerful defence against caries and the oral diseases which arise from them.
Particular concern is raised about the amount of fluoride which small children ingest when they brush their teeth. However, a three-year study at the department of oral health and development at University College Cork should help reduce the fears of concerned parents.
The department is co-ordinating the EU-funded study which involves seven countries, including Ireland, the UK, Iceland, Finland, Portugal, the Netherlands and Greece.
The principal investigator for the project is Prof Denis O'Mullane, head of the department of oral health and development.
His department was responsible for standardising methods for the measurement procedures and for analysing the data from the participating European centres, explained research fellow Ms Judith Cochran, who is doing her Ph.D thesis on the study.
"We were looking at fluoride ingestion in particular from toothpaste and, in slightly older children, signs of dental fluorosis," she said.
Dental fluorosis, a white marking sometimes noted on children's teeth, is a sign of excess fluoride ingestion.
The study ends later this month but the analysis and preparation of the data are still under way. The methodology was complex and involved visits to the children's homes, 200 in each country, parental questionnaires and laboratory measurements.
The children were divided into two groupings, 1.5 to 2.5 years and 2.5 to 3.5 years. A surveyor visited each of the children's homes to watch the child brush, Ms Cochran explained. The amount of paste used was measured and then the material spat out by the child was collected and measured. The gap between the two was the amount of fluoride swallowed by the child.
There were several other parallel measurements taken. Urine samples were collected from 20 children in each country and measured for fluoride content.
Ms Cochran said people take in fluoride which occurs naturally in food, from fluoridated water and toothpaste and half of all this is excreted. The urine measurements provided an indication of the total amount absorbed.
She said the figures were not yet ready for presentation but there were preliminary findings. "The results in general showed that most children were using the recommended or less than recommended levels of toothpaste. They weren't ingesting large quantities of fluoride."
UCC has also established the procedures for assessing dental fluorosis, which involved taking pictures of the teeth of 300 eight-year-olds from each country under defined conditions, including when tooth surfaces were wet and dry. All together, the study produced 5,000 slides for analysis, a job which fell to Ms Cochran. It was decided that it would be better for a single reviewer to assess the slides for signs of fluorosis.
SHE said preliminary results suggested that between 4 per cent and 5 per cent of the Irish samples had signs of fluorosis, but the level was lower in most other countries and in some there was virtually none. Telephone questionnaires in Ireland suggested, however, that people were not concerned about fluorosis.
Dr Helen Whelton, deputy director of UCC's oral health services research centre, said such testing was an important contribution to public health because fluoridation of water was undertaken as a public health measure.
"People really need to know the facts about how much fluoride they are getting," she said.
UCC researchers have been studying the impact of water fluoridation for many years and carried out national oral health surveys of children in 1984 and adults in 1989. "Our conclusion from both studies was fluoride was a great success in Ireland."
A 1995 study for the Southern Health Board of teeth damaged by caries in five-year-olds had shown that on average 2.3 teeth were damaged in non-fluoridated areas but only 1.1 teeth in areas where fluoridation was available.
A similar 1997 study for the Midlands Health Board indicated that on average 2.9 teeth were damaged where water fluoridation was not available but just 1.7 teeth in fluoridated areas.
"There is no cause for concern at the levels of fluoride people are getting. There is no reason to remove fluoride from the water," said Dr Whelton. It provided a useful protective against caries despite the possibility of dental fluorosis.