I NOTE the fluoride varnish trials in parts of the North-East on children under five (Echo, Sept 25), but these may be futile, as a recent Japanese study indicates.

I would urge our dentists and health professionals to read this paper, from Meikai University School of Dentistry and Nihon University School of Dentistry (May 5, 2012): “Aspects Regarding Fluoride Treatment for Reinforcement and Remineralization of Apatite Crystals”. This is a paragraph from the abstract (header): “Electron micrographs indicated no signs of remineralization of artificially damaged crystals after incubation in a remineralizing solution and further revealed that treatment with acidulated phosphate fluoride (APF) gel caused crystal dissolution rather than crystal improvement.”

Note the gel application makes enamel weaker. I would suspect that the improvement in tooth decay rates seen in Stockton and Redcar areas is therefore entirely due to better education in oral hygiene and brushing.

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It would be a simple matter to carry out a ‘blind’ comparative test, using a placebo gel varnish in half the trials. Then we would know.

Plainly, the Japanese are not taking anything the Americans have been saying for 60 years for granted, and neither should we.

M Watson, Darlington