Aside from the obvious inadequacy of controls for the numerous confounders involved in diabetes, this study makes false claims  which render it completely void of  credibility.

1.  Fluoride is the anion of the element fluorine.  An anion is a negatively charged atom.  One such atom of fluorine is identical to all other such atoms of fluorine.  There is no difference between "naturally occurring" atoms of fluorine and those added through fluoridation.

2.  Calcium fluoride is not a "form of fluoride".  It is a compound that contains fluoride. An atom is not a compound.  Calcium fluoride is therefore not "natural fluoride", nor does it even exist in groundwater.  As this water flows over rocks it picks up fluoride ions leached from calcium fluoride and fluorosilicates in those rocks.  It is  these fluoride ions, not the compound calcium fluoride,  which are to what is commonly referred as being "naturally occurring" fluoride.

3.  Fluorosilicates are immediately and completely hydrolyzed upon addition to drinking water.    After that point they no longer exist in that water.  They do not reach the tap.  They are therefore not ingested.  The product of this hydrolysis is fluoride ions, identical to those "natural" fluoride ions already existing in water.   As such, there is no difference between "natural" fluoride, and that added through fluoridation.  Additionally, as fluorosilicates are not ingested, it is not possible for them to have any effect on incidence or prevalence of diabetes.

Given the false claims put forth in this "study" it can be clearly seen that the study has no credibility whatsoever.

Steven D. Slott, DDS