Henry Trendley Dean, a U.S. Public Health Service public-health dentist, collaborated with McKay in identifying “mottled enamel” or fluorosis as being associated with fluoride in the drinking water. Dean also discovered that there was an association between caries in children, mottled enamel and fluoride levels in the drinking water. He advocated that 1 ppm of fluoride be tested for its effects on caries.

So independently, in fact, that in 1922, one page of the JDR displayed the IADR next to last in a list of its affiliated organizations (those that used the Journal pages as an outlet for their scientific proceedings). The IADR finally voted to take ownership of the Journal in 1934, with its Editor functioning as a major office-bearer in the Association.

In 1922 they were the first to describe the gross appearance of dental caries in rats fed faulty diets. In 1931 Klein and McCollum showed that diets relatively high in phosphate are probably protective against dental caries. McCollum, however, always cautioned that the calcium-phosphorus ratio must be kept within a fairly limited range for health maintenance.