Norethynodrel and mestranol in a ratio identical to that used for contraception were injected subcutaneously daily for five weeks into young adult female rats. These rats were fed with a purified caries test diet. The various lesions of the treated rats increased proportionately with increased doses of the agents.In previous studies, it was observed that the administration of some oral contraceptive steroids caused an increase in dental caries activity in female rats when a caries test diet was composed principally of coarse rice particles and powdered whole milk.1,2 Thus, the various lesions were observed only in the sulci. Furthermore, the steroid treatments were begun when the rats were 22 days of age, at which age the molars were more susceptible to caries attack.3 In the present study, we tried to determine whether these steroids would still be cariogenic under the following experimental conditions: (1) a purified caries test diet, ad libitum, beginning at 21 days of age; (2) steroid treatments begun at 50 days of age, that is, after the rats attained puberty, which occurs at about 35 days of age; and (3) steroid doses similar to and greater than those used for contraception in female rats. Materials and MethodsWeanling female rats of the SpragueThis paper was presented at the 50th General Session of the IADR in Las Vegas, Nev, March 1972. Dawley strain were separated randomly into three groups and were supplied, ad libitum, with a caries test diet4 of MIT diet no. 200b and distilled water. They were housed in individual suspended hardware cloth cages at a room temperature of 72 + 1 F and light exposure was controlled automatically between 6:00 AM and 6:00 PM. Beginning at 50 days of age, rats in the first test group received daily (except Saturdays and Sundays) subcutaneous injections of 100 jig norethynodrele plus 4 ftg mestranole in steroid diluent. These steroid doses were given on a body weight basis. Norethynodrel(1 7a-ethynyl-1 7,8-hydroxy 5 (10) -estren-3-one) and mestranol (17-ethynyl-estradiol 3-methyl ether) are, respectively, synthetic progestogenic and estrogenic steroids. Rats in the second test group were injected at similar intervals with four times the amount of these steroid doses; the control rats were given the steroid vehicle alone.At 85 days of age, all rats were killed by chloroform inhalation. The final body and organ weights of ten rats from each group were measured immediately. All the heads were autoclaved and the attached soft tissues then were removed. Dental caries was assessed by the method of Keyes,5 except that the molars were stained with Schiff's reagent.6 Body and organ weights and dental carious lesions of both treated groups of rats were compared with those of the controls by Student's t test at a 5% level of significance. ResultsThe mean number carious enamel regions of combined smooth surface lesions and
Drinking water of rats aged 21 days was supplemented with 1, 10, 30, 50, 100, or 283 ppm of boron or 10 or 25 ppm of fluoride individually or in combination. All rats were fed a cariogenic diet. Boron did not reduce dental caries activity in erupted molars after eight weeks. When given in combination, it partially antagonized the cariostatic effect of fluoride.
Weanling female rats were given subcutaneous injections of contraceptive steroids (norethynodrel and mestranol), tetracycline supplements in drinking water, or both, for seven weeks. Norethynodrel-mestranol treatment caused a significant increase in dental caries activity; this increase was prevented by intermittent supplements of tetracycline in drinking water.
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