A study of the relationship between trace elements in saliva and dental caries in children

Trace elements in saliva and dental caries in young adults

The results of a study on Zn, Cu, Ca and Mg content in whole saliva and supernatant of young adults in relation to caries prevalence are reported. A total of 225 university students were selected for the study on the basis of voluntary participation. The salivary electrolytes showed a high intersubjective variability and females had significantly lower levels than males. In whole saliva, the trace elements were highly correlated, whereas the correlations were weaker in the supernatant. The ratio supernatant/whole saliva varied between subjects and according to the examined electrolytes. No association could be found between the measured trace elements and DMFT. When we analysed the relation with recent caries experience in the subgroup of subjects undergoing oral examinations for at least 1 year, we found evidence that the Zn/Cu molar ratios in whole saliva were significantly decreased in subjects with more than three decayed teeth compared with those with no caries (1.54 vs. 1.11, P < 0.05). No significant association was found when supernatant was analysed. We conclude that the electrolytes' levels in whole saliva might be more adequate than the levels in supernatant to evaluate the relationship with caries.

Caries-protective factors in saliva

Saliva influences caries attack mainly by its rate of flow and by its content of fluoride. The salivary flow rate influences to a high degree the rate of oral and salivary clearance of bacterial substrates included in foods and snacks. This influence is site-dependent. The basal salivary fluoride concentration is low, about 1 mumol/L, independent of salivary flow rate, and not influenced by diurnal variation. After an exposure of the oral cavity to fluoride, the increased fluoride level is decreased by a process influenced mainly by the salivary flow rate and the volumes of saliva in the mouth before and after swallowing. Other less important caries-protective factors in saliva include its buffer ability, its content of calcium, inorganic phosphate, pH-increasing substances, and anti-microbial agents.

Chelating agents inhibit activity and prevent expression of streptococcal glucan-binding lectins

Several of the cariogenic mutans streptococci produce cell wall-associated glucan-binding lectins (GBLs). The lectins bind alpha-1,6-linked glucans and have no affinity for other polysaccharides or anomeric linkages. When citrate or lactate was included in the growth medium, expression of the activities of the GBLs of Streptococcus cricetus and S. sobrinus was prevented. Furthermore, chelating agents, including citrate, lactate, EDTA, and acetylacetone, were able to reversibly inhibit glucan-induced aggregation of GBL+ streptococci. In addition, the chelating agents prevented sucrose-dependent streptococcal adhesion to glass surfaces and dispersed preformed adherent masses of the streptococci. Neither citrate nor other chelating agents modified the activities of glucosyltransferases. Expression of the lectin could only be achieved by the addition of manganous ion to the growth medium. Chloramphenicol and other metabolic inhibitors prevented synthesis of GBL in cells obtained from manganese-deficient medium and shifted to manganous ion-sufficient medium. The GBL may be a manganoprotein, the manganese of which may be perturbed, but not removed, by chelating agents. During synthesis of the GBL, manganous ion may be required in order for the protein to achieve an active conformation. Citrate or other chelating agents may have promise as anticaries agents.