Annotation The Effect of Strontium and Fluoride Upon in vitro Plaque and Rat Caries BYRON L. OLSON, JAMES L. MCDONALD, JR., and GEORGE K. STOOKEY Oral Health Research Institute, Indiana University School of Dentistry, 410 Beauty Avenue, Indianapolis, Indiana 46202 J Dent Res 57(9-10):903, September-October 1978
Considerable evidence suggests that strontium is one of the trace elements other than fluoride which may influence caries susceptibility. (Losee, Caries Res 3:23, 1969; Curzon, CariesRes 11:321, 1977). Little information exists, however concerning the influence of the combination of fluoride and strontium upon dental plaque formation. Thus this study tested combinations of strontium and fluoride with regard to plaque formation, acid production, and rat caries. An in vitro glass-slide technique was utilized to assess adherent plaque formation using Streptococcus mutans 6715 (NIH) as the test organism. Jordan's complex medium (J. Dent. Res., 39: 116, 1960) containing 5% sucrose was used as the control. The test compounds consisted of strontium chloride and sodium fluoride. The concentrations of strontium and fluoride tested in the medium included 50 ppm Sr, 100 ppm Sr, 10 ppm F, 50 ppm Sr plus 10 ppm F, and 100 ppm Sr plus 10 ppm F. Conventional glass microscope slides (2 x 7.5 cm) were incubated in test tubes (3 x 20 cm) containing 50 ml of the appropriate test medium. The tubes were inoculated with 0.5 ml of an 18hour culture of Streptococcus mutans 6715 (NIH) and incubated for 18 hours at 370C. At the end of this period, the plaque dry weight on the glass slides was determined along with the terminal pH of the medium. In the rat caries test, mixed-sex littermate Wistar rats (18 days of age and inoculated with S. mutans 6715 for 5 days prior to the study initiation) were utilized. Under this experimental regimen, extensive carious lesions are present after
Received for publication October 5, 1977. Accepted for publication May 4, 1978.
two weeks of ingesting a high sucrose diet. The animals were then provided NIH diet 2000 and deionized drinking water or water containing 50 ppm Sr, 10 ppm F, or a combination thereof for a 3-week experimental period. Following sectioning, the teeth were evaluated for dental caries microscopically using criteria previously described (Francis, Arch. Oral Biol., 11:141, 1966). The overall results of both the laboratory and animal data are summarized in the table. There were no significant differences in the plaque dry weights between any of the groups, although numerically lower plaque values occurred in the groups provided 100 ppm strontium alone and 10 ppm fluoride in combination with strontium. The lack of significance in spite of the rather marked directional trends suggests that if increased numbers of samples had been used, some of the differences would have been significant. There were, however, significantly higher final pH values in the different media containing fluoride as compared with the groups containing no fluoride. Thus the fluoride appeared to reduce acid production under these experimental conditions. However, no significant difference in the terminal pH values of the medium containing fluoride alone and fluoride plus strontium was observed. The rat caries data indicate that while 10 ppm fluoride in the water resulted in a numerical reduction in pit and fissure caries of about 13%, none of the experimental regimens resulted in a signifilcant effect upon caries. Thus, the results of this experiment indicate no signifilcant effect of strontium alone or in combination with fluoride upon in vitro plaque formation, or terminal pH of the incubation medium. Furthermore, exposure to strontium posteruptively (beginning at 23 days of age) did not influence occlusal caries in the rat.
Rat Caries Data
In Vitro Plaque Data Dry Plaque
pH of Media
10 10 10
Number Number Animal Lesions wt (mg) 9.1±1.2 ** 9.0±1.2* ** 4.5±0.02 ** 15 9.6 ± 1.7 ** 15 4.5 ± 0.01 7.4 ± 1.0 Not Studied 4.5 ± 0.01 5.7 ± 0.7
10 10 10
7.0 ± 0.4 5.7 ± 0.6 5.6 ± 0.6j
4.9 ± 0.0T1 4.9 ± 0.011 4.9 ± 0.01
Elements
Conc.
Number
Studied None Strontium Strontium
(ppm)
Samples
50 100
10 50 + 10 100 + 10 Standard error of the mean
Fluoride Sr + F Sr + F *
15 15
7.9 ± 0.8 9.5 ± 1.7 Not Studied
**Means within brackets do not differ signif-lcantly (ca = 0.05) as determined by the Newman-Keul's sequential ranking procedure 903 Downloaded from jdr.sagepub.com at OAKLAND UNIV on June 10, 2015 For personal use only. No other uses without permission.
Considerable evidence suggests that strontium is one of the trace elements other than fluoride which may influence caries susceptibility. (Losee, Caries Res 3:23, 1969; Curzon, CariesRes 11:321, 1977). Little information exists, however concerning the influence of the combination of fluoride and strontium upon dental plaque formation. Thus this study tested combinations of strontium and fluoride with regard to plaque formation, acid production, and rat caries. An in vitro glass-slide technique was utilized to assess adherent plaque formation using Streptococcus mutans 6715 (NIH) as the test organism. Jordan's complex medium (J. Dent. Res., 39: 116, 1960) containing 5% sucrose was used as the control. The test compounds consisted of strontium chloride and sodium fluoride. The concentrations of strontium and fluoride tested in the medium included 50 ppm Sr, 100 ppm Sr, 10 ppm F, 50 ppm Sr plus 10 ppm F, and 100 ppm Sr plus 10 ppm F. Conventional glass microscope slides (2 x 7.5 cm) were incubated in test tubes (3 x 20 cm) containing 50 ml of the appropriate test medium. The tubes were inoculated with 0.5 ml of an 18hour culture of Streptococcus mutans 6715 (NIH) and incubated for 18 hours at 370C. At the end of this period, the plaque dry weight on the glass slides was determined along with the terminal pH of the medium. In the rat caries test, mixed-sex littermate Wistar rats (18 days of age and inoculated with S. mutans 6715 for 5 days prior to the study initiation) were utilized. Under this experimental regimen, extensive carious lesions are present after
Received for publication October 5, 1977. Accepted for publication May 4, 1978.
two weeks of ingesting a high sucrose diet. The animals were then provided NIH diet 2000 and deionized drinking water or water containing 50 ppm Sr, 10 ppm F, or a combination thereof for a 3-week experimental period. Following sectioning, the teeth were evaluated for dental caries microscopically using criteria previously described (Francis, Arch. Oral Biol., 11:141, 1966). The overall results of both the laboratory and animal data are summarized in the table. There were no significant differences in the plaque dry weights between any of the groups, although numerically lower plaque values occurred in the groups provided 100 ppm strontium alone and 10 ppm fluoride in combination with strontium. The lack of significance in spite of the rather marked directional trends suggests that if increased numbers of samples had been used, some of the differences would have been significant. There were, however, significantly higher final pH values in the different media containing fluoride as compared with the groups containing no fluoride. Thus the fluoride appeared to reduce acid production under these experimental conditions. However, no significant difference in the terminal pH values of the medium containing fluoride alone and fluoride plus strontium was observed. The rat caries data indicate that while 10 ppm fluoride in the water resulted in a numerical reduction in pit and fissure caries of about 13%, none of the experimental regimens resulted in a signifilcant effect upon caries. Thus, the results of this experiment indicate no signifilcant effect of strontium alone or in combination with fluoride upon in vitro plaque formation, or terminal pH of the incubation medium. Furthermore, exposure to strontium posteruptively (beginning at 23 days of age) did not influence occlusal caries in the rat.
Rat Caries Data
In Vitro Plaque Data Dry Plaque
pH of Media
10 10 10
Number Number Animal Lesions wt (mg) 9.1±1.2 ** 9.0±1.2* ** 4.5±0.02 ** 15 9.6 ± 1.7 ** 15 4.5 ± 0.01 7.4 ± 1.0 Not Studied 4.5 ± 0.01 5.7 ± 0.7
10 10 10
7.0 ± 0.4 5.7 ± 0.6 5.6 ± 0.6j
4.9 ± 0.0T1 4.9 ± 0.011 4.9 ± 0.01
Elements
Conc.
Number
Studied None Strontium Strontium
(ppm)
Samples
50 100
10 50 + 10 100 + 10 Standard error of the mean
Fluoride Sr + F Sr + F *
15 15
7.9 ± 0.8 9.5 ± 1.7 Not Studied
**Means within brackets do not differ signif-lcantly (ca = 0.05) as determined by the Newman-Keul's sequential ranking procedure 903 Downloaded from jdr.sagepub.com at OAKLAND UNIV on June 10, 2015 For personal use only. No other uses without permission.
