"Levi Spear Parmly (1790-1859) was one of the outstanding dental practitioners and teachers in the early part of the eighteenth century, both in America and Europe. He published two highly regarded books, practiced and taught in London for several years, before returning to America, where he became the most eminent dental practitioner in the southern United States. He had great financial success and used his time and money to offer free dental service to children. His major contribution to dental science was the concept that dental caries was caused by external influences related to foreign material on the tooth surface. This was before our knowledge of dental plaque and the action of the oral bacteria. Based upon this concept, he stressed the importance of clean teeth to prevent tooth decay" (https://pubmed.ncbi.nlm.nih.gov/12641168/).