 Numerous attempts to produce the toothpaste by pharmacists in Europe were uneconomic.After returning to the US, he continued experimenting with Harry Ward Foote (1875-1942), professor of chemistry at Sheffield Chemical Laboratory of Yale University.After 17 years of development of Kolynos and clinical trials Jenkins retired and transferred the production and distribution to his son Leonard A. Jenkins, who brought the first toothpaste tubes on the market on April 13, 1908.