Natural flouraid decrees dental caries same as added flouraid?

It all has to do with the concentration of FLUORIDE. Through extensive research over many decades, it has been determined that the optimal fluoride concentration in drinking water supplies to reduce the incidence of dental cavities in the population is 1 part per billion. If this concentration occurs naturally in a water supply, nothing needs to be done. If the naturally occurring fluoride is below the optimal concentration, addition fluoride can be added as necessary.