Plaque and saliva samples were obtained from 55 children aged 13–15 years: 23 of them were caries free (group N) while the other 32 had evidence of high-caries activity over the preceding 2 years, with a mean DMFS of 25.9 (group H). The average concentration of calcium in posterior plaque of children in group N was 3.57 μg/mg (dry weight), compared with 1.63 μg/mg for group H. The average concentration of calcium in anterior plaque was 11.55 μg/mg in group N and 2.57 μg/mg in group H. The differences between groups N and H were statistically significant (p < 0.01). Similar significant differences were found between phosphorus levels in plaque. Although the mean levels of both calcium and phosphorus in saliva were higher for group N than for group H, only for phosphorus did the difference reach statistical significance (p < 0.05). The present study therefore shows that levels of both calcium and phosphorus are significantly higher in plaque taken from children with no caries experience than they are in plaque from children who are caries susceptible.

No abstract

This paper describes an attempt to follow the migration of fluoride in the mouth following dissolution of a fluoride tablet, placed at one asymetrically situated position in the mouth, by measuring fluoride concentrations in saliva and by using particles of dentine as semi-quantitative fluoride monitors. The findings demonstrate the failure for the fluoride released from the tablet to result in an overall, elevation of fluoride levels in the oral environment.

Certain metal salts inhibit the growth of dental plaque. The effect of zinc salts was investigated because of contradictory reports in the literature. Using cultures of human plaque, artificial dental plaques were grown in vitro on aluminium strips. The effect of various zinc salts was examined by treating the strips intermittently with solutions of the salts during the period of growth. The action of mouthwashes containing zinc salts in vivo on plaque growth was determined in human volunteers.All the water-soluble zinc salts that were tested gave a similar concentration-dependent inhibition of plaque growth in vitro. The effectiveness of the treatment was reduced by increasing the time allowed for growth after the final application of zinc.Solutions of zinc (17-19 mM) as the citrate or phenolsulphonate salt, gave about 30% reduction in the extension of plaque along the gingival margin in vivo over 16 hours. Subjects with high rates of plaque growth with the placebo mouthwash were most affected by zinc salts. Increasing the zinc concentration to 30 mM did not further increase the activity. Previous reports of low activity of zinc against plaque growth in vivo are explained by too low a concentration of zinc or too low a frequency of application. The results confirm that zinc salts, including zinc citrate, inhibit the growth of plaque in vivo and in vitro. Fishman et al. (1973) used a mixture of Address:

Measurement of fluoride concentrations in rat molars indicates that several areas of the dentition might be inaccessible to extraneous ions. In rats of all ages, much of the enamel, situated below the gingival margin, in occluded approximal regions or within the fissures might be unavailable to agents administered topically or otherwise. The paper discusses sampling the enamel surface of rat molars in the light of these findings.