Iodine is essential, you cannot survive without it, and it is added to supplement a deficiency.
Fluoride is not essential, you can survive without it, and its addition is purely therapeutic, not due to some deficiency
Iodine is essential, you cannot survive without it, and it is added to supplement a deficiency.
Fluoride is not essential, you can survive without it, and its addition is purely therapeutic, not due to some deficiency