Aetiological factors for susceptibility : saliva (roles, pH scoring) and bacteria

Saliva plays a significant role in the prevention of dental caries. Adequate salivary flow and unique composition of saliva are essential to the maintenance of health of oral tissues. Saliva lubricates and protects oral tissues, acting as a barrier against mechanical, thermal and chemical irritants. Clearance is another important function of saliva as normal salivary flow allows removal of sugars, acids and bacteria. Bicarbonate, phosphate and urea are responsible for buffering action of saliva. Of salivary electrolytes, calcium, phosphate and fluoride are of particular importance for oral health and remineralization. Saliva is supersaturated with calcium, phosphate and fluoride ions in comparison to hydroxylapatite. Thus, the main mineral of teeth will not dissolve in saliva or plaque, unless the saliva or plaque is acidified. Saliva testing includes complete assessment of resting and stimulated saliva. Salivary parameters, which are tested are hydration, viscosity of saliva, flow rate and pH of resting and stimulated saliva and buffer capacity of stimulated saliva. Samples of stimulated saliva are also used for microbial analysis of Streptococcus mutans. Salivary level of this bacterium is useful for caries susceptibility assessment in individual patients, when used in conjunction with other clinical information. If the result of the test shows high number of Streptococcus mutans, some kind of antimicrobial therapy should be introduced.