Sir, the article History of water fluoridation by Dr Joe Mullen (BDJ 2005; 199: supplement) recounts some of the early observations that people drinking from water sources that were naturally higher in fluoride content tended to have lower rates of cavities than that observed in areas that were not naturally high in fluoride content. The problem arises from assuming that fluoride content was the sole variable in these observations. The more sophisticated developments of the role of trace minerals in nutritional science were not understood at the time that fluoride appeared to be the responsible factor. Dr Fred Losee and Dr Basil Bibby re-examined some of Dr Dean's figures in their article in the New York State Dental Journal (1970; 37: 15–19), Caries inhibition by trace elements other than fluoride. They showed that in cases where tooth decay rates went down in the naturally fluoridated sources, the water was also high in the trace minerals strontium and/or boron, important elements for building strong bones and teeth. Most of the other countries of Western Europe no longer add fluoride to the water supply. It is time for dentists and scientists to revisit this issue with an open mind.

The author of the article Dr Joe Mullen responds: The ability of water fluoridation to reduce both the prevalence and severity of tooth decay has been demonstrated beyond all reasonable doubt. Given the evidence of efficacy that has accumulated since Dean's studies of naturally fluoridated communities, it is difficult to explain the success of artificial fluoridation without drawing the conclusion that fluoride is the true preventive agent, and was indeed correctly identified as such the original studies. I agree with A. Gore, however, that certain other elements can affect dental enamel — Selenium, for example, is thought to be the cause of some fluorosis-type staining.