“Mottling of Enamel” Effected by a Single Fluorine Dose

Abstract

In a study of the minimal effective dosage of fluorine, as determined by various biological criteria, one of the authors 1 observed “fluorine-rickets” as a significant response to very small amounts of fluorine. The biological effectiveness of even smaller amounts of this element has been established by the discovery of the “mottling of enamel.” 2 Until now, mottling of enamel has been studied only on frequently repeated fluorine administration. The question arose whether it can also be produced by a short “fluorine shock.”

The following is a report on a preliminary series of experiments on 20 young rats. In the first experiment (Table I) doses from 9 to 37 mg. fluorine per kilo of b.w. were administered through a stomach tube to just weaned albino rats weighing from 21 to 35 gm. (solutions of 0.625% or less NaF and a finely dispersed sol of 0.375% or less CaF₂ 3 ). Such a single dose was able to produce a definite alteration on the enamel. In 3 out of 10 animals, a sharply limited milky white spot of about 1-2 mm. in diameter, round or oval, appeared on the frontal surface of one lower incisor between the 12th and 14th day following fluorine ingestion. First, the spot was seen only at the base of the incisor after slight retraction of the gum. Later, it moved slowly along the tooth and finally between the 21st and 24th day it disappeared at the cutting surface. The incidence of positive results is not increased by increasing the fluorine dosage, nor does it depend on the degree of general effects of fluorine shown by the growth curve (cf., animal No. 1 vs. animal No. 6). Nor is there an obvious difference between the 2 compounds used. Thus, fluorine is but one of several factors capable of impairing enamel development. In the range of the dosage studied the behavior of these other coefficients (e. g., vitamin D, food calcium, food fluorine, natural irradiation) must be decisive for the issue.

In another group, single doses of 20 or 30 mg. F per kg. as NaF and 10 or 30 mg. F per kg. as CaF₂ were administered to 10 albino rats of 40 to 116 gm. No lesions were detectable; thus, age is a further factor controlling fluorine action on enamel formation.