New research has found that despite a general improvement in Irish children's dental health, two thirds of all 15-year-olds have decay in their permanent teeth.

Full details of the survey, which also shows that fluoridation is effective, were announced by the Minister for Health, Micheál Martin, this afternoon.

The investigation was carried out by Dr Helen Whelton, Director of the Oral Health Services Research Centre at University College Cork, and completed in June 2002. It involved 1950 children in the North and South.

Among the main findings was that the policy of adding fluoride to the water supply was having a positive effect on dental health.

The survey found that for every 1,000 fifteen year olds in areas where flouride was present in drinking water there was an estimated 2,100 decayed, missing or filled teeth. However, that was 50% less than in non flouridated areas.

The survey also found the the social divide is mirrored in dental health statistics, with children from disadvantaged backgrounds much more likely to suffer from tooth decay.

However, an increase in enamel fluorosis is also reported. This is the product of too much flouridation and results in white spots appearing on the surface of teeth. This has led to calls for the level of flouride in water to be reduced.

Decay levels are also up in five-year-olds. The study suggests that this could be down to dietary habits. While the overall intake of sugar has not increased, it is believed that snacking on sweets and the consumption of soft drinks has become much more frequent.

Parents are also recommended not to brush their children's teeth with tooth paste before the age of two.