Fluorine is an enzyme poison. Enzymes are important to digestion and utilization of food and thousands of other body chemistry activities. To put fluorine in the water supply to treat a disease is sheer nonsense. The dosage or amount of the chemical any one person would get would be in direct proportion to the amount of water he drinks. One who drinks twice as much water would get twice the fluorine.
Tooth decay is a disease.
Besides, one should take into consideration the amount of fluorine that is present in foods and beverages they consume. Many foods such as butter, cheese, liver, chicken, wheat and apples contain between one and two parts per million. Dry tea contains from 30 to 60 parts per million. In spite of the heavy use of tea in England, the caries rate is abominable. You would think the dental association would have researched just how much fluorine is actually present in the food and beverages of the average person's diet.