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[Effects of strontium on incisor and femurs in rats under drinking condition at constant concentrations of fluoride].

Thirty 28-day-old male Wistar rats were randomly divided into 5 experimental groups of 6 animals, and fed low-fluoride diet (0.07 ppm F) and drinking water containing fluoride at constant concentration (20 ppm F) ad libitum for 49 days in combination with strontium chloride added to provide 0, 5, 10, 20, 40 ppm Sr. Enamel mottling was observed through over-all experimental period, and at an end of the experiment, all animals were sacrificed. There was no significant difference in weight gain among groups. Enamel mottling of mandibular incisors in Sr groups appeared at 7th day (cumulated fluoride ingested: under 3.0mg), while mottling in control group (0 ppm Sr and 20 ppm F) appeared at 14th day (cumulated fluoride ingested: ca. 6.6 mg). However, severity of mottling was higher in low-strontium group (5 and 10 ppm Sr) than in high-strontium groups (20 and 40 ppm Sr). Data of contents of Sr, F, Ca and P in incisors and femurs obtained through chemical analysis suggested that an exchange of Sr and Ca would take place in apatite and that the exchange reaction of F- and OH- could be urged by Sr. Further, data of serum F level demonstrated that the fluoride retention in serum could be urged by lower level of strontium rather than higher one.