Obviously, dental hygiene is a priority to conscientious parents. Yet, in spite of the improved toothpastes and professional dental techniques and equipment, more than one quarter of 2- to 5-year-olds and half of kids 12 to 15 years old have one or more cavities, and tooth decay has affected two thirds of 16- to 19-year-olds. Many feel that adding fluoride to public water is one way to curb the problem of tooth decay. But this opinion is in no w...