Inhibition of Experimental Dental Caries by Fluorine in the Absence of Saliva. ∗

Abstract

Although the inhibition of dental caries by fluorine has been demonstrated in endemic areas 1 , 2 and in laboratory rats fed on a caries-producing diet 3 , 4 the mechanism by which the action takes place has not yet been adequately demonstrated. Armstrong and Brekhus 5 found a higher fluorine content of sound enamel than in carious and offered the hypothesis that this may be the factor responsible for the inhibition. In this report we have attempted a further investigation of this mechanism. Since the enamel of the molar teeth of the animals used was fully formed before fluorine was applied it would appear that the action of fluorine must be due to its being held in the region of the tooth surface or, as far as the dentin is concerned, to the possibility of fluorine reaching it through the circulation.

Previous studies are inclined to disregard the ability of fluorine becoming incorporated into the tooth surface after formation and thus causing an increased resistance to the mechanism responsible for decalcification because the role exerted by saliva could not be accurately determined. By using rats in which all the principal salivary glands had been removed 6 we have practically eliminated the possibility of fluorine acting through the saliva. Further, since the fluorine was administered as potassium fluoride in a drop of water in our experiments it is not likely that the fluorine would remain in the mouth in this form sufficiently long to have a prolonged effect. However, evidence is presented that fluorine administered in this way can decrease the incidence of caries in spite of the interference with the salivary secretions or mode of administration.