The supply in Bauxite itself was measured at 13.7ppm (parts per million).
Ainsworth was aware of Churchill's research and decided to compare the water supplies from the endemic staining area around Maldon in Essex with that of the nearby town of Witham.
The most recent New Zealand oral health survey (2009) showed that children and adolescents living in areas with fluoridated water have 40 percent less tooth decay than those living in areas without.
The significant benefits of water fluoridation for oral health are also supported by over 60 years of studies around the world.
The Witham water proved to have 0.5ppm fluoride, the samples from around Maldon ranged from 4.5 to 5.5ppm. In a series of classic shoe-leather epidemiological investigations, culminating in his famous "21-City Study", Dean established that mottling of the teeth was extremely rare at fluoride levels of 1ppm or below, while the greater part of the caries preventive effect was to be seen at 1ppm. During the Second World War, children from South Shields, an industrial town on the river Tyne in north eastern England, were evacuated to the Lake District.
Churchill analysed water from several areas where the staining was endemic for unusual element concentrations and found the one common factor to all sites to be elevated levels of fluoride.Water fluoridation is the process of adjusting the natural level of fluoride in the water supply to between 0.7 ppm and 1.0 ppm.This is the optimal amount that provides protection against tooth decay.Education on benefits of fluoridation is a part of most, if not all, dental school curriculums.The American Dental Association (ADA) has endorsed water fluoridation and fluoride-containing product usage as safe and effective measures for preventing tooth decay. Department of Health and Human Services updated its recommendation for the optimal fluoride level in drinking water to prevent tooth decay to a single level of 0.7 milligrams per liter of water.