The conditioning role of saliva in streptococcal attachment to hydroxyapatite surfaces

The solution properties of saliva and its role in conditioning both the substrate and the bacterial surface have been investigated with regard to the attachment of oral streptococci to hydroxyapatite surfaces. Saliva from eight subjects was used and the attachment of three organisms, Streptococcus mutans strains FA-1 (serotype b) and KPSK2 (serotype c) and S. sanguis T175-1, was studied. An adsorbed salivary layer on a hydroxyapatite surface substantially reduced the affinity of the organisms for the surface. Adsorbed saliva on the bacterial surfaces, however, tended to increase the organisms' affinity for saliva-coated apatite. The source of saliva was important in determining the extent of inhibition of attachment. The data indicated that the negatively charged and hydrophilic nature of salivary conditioning films was important in controlling bacterial adsorption to hydroxyapatite. The results also suggested that hydrophobic salivas could promote binding of the more hydrophobic bacteria known to be early colonizers of the teeth.