The Scots' notorious sweet tooth appears to be as decayed as ever among the latest batch of adolescents, with Dundee University's dental health services research unit reporting that the state of 12-year-olds' teeth has not improved over the past four years, and remains worse than the average for most of England.

But Dundee dentists have now enlisted more than 1,200 local schoolchildren in a three-year study of a new varnish which could protect against tooth decay.

The university's department of dental health is working with a Canadian company to test the effect of a preparation called Chlorzoin, developed at Toronto University. It fights streptococcus mutans, which converts carbohydrates into acid and is one of the principal factors in tooth decay.

The children, who have been divided into four groups, all have medium-to-high levels of streptococcus mutans.

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The first group will be monitored annually, without intervention in their dental care. The other three groups will be more closely monitored, with the researchers ensuring that they have any necessary dental treatment. They have been issued with new toothbrushes, and taught how to brush their teeth properly.

The intervention will stop there for one group, while the other two will have their teeth varnished, either with a placebo or with Chlorzoin, although principal investigators Nigel Pitts and Cynthia Pine will not know which varnish has been used.

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The treatment does not need a dentist, and is being provided by less expensive healthcare teams of dental therapists, hygienists and nurses.

"The children have an application of varnish every week for a month. We leave them for three months, then give them another saliva test to check the levels of streptococcus mutans, and if they're high, give them another varnish," said Dr Pine.

The project aims to find a cost effective way of preventing tooth decay in high-risk children, said Professor Pitts.

"An awful lot of time and effort is devoted to picking up the pieces after the damage is done. We won't be able to say until the end of the study how effective this is, but we're very encouraged that it's a useful way to go," he added.

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