Newly-developed Buffer Capacity Test, Mutans Streptococci and Lactobacilli in Saliva

Objectives: To evaluate the relationship between salivary acid buffer capacity, and salivary mutans streptococci and lactobacilli counts in adult patients at risk of caries, and to establish a simplified quantitative buffer test for caries risk assessment. Methods: The stimulated whole saliva of 39 patients (21-83 years old) was collected by paraffin wax chewing for 5 min. Fifty μl of 0.1N HCl was titrated into 0.5 ml of collected saliva, and then the pH value was measured using a handy-type pH meter (B-212 TWIN/pH, Horiba Ltd., Japan). The individual buffer capacities were ranked into three categories (High: > pH5.5, Medium: pH5.5-4.5, Low: < pH4.5). The residual saliva was dispersed by sonication for 10 s at 60 W powers. Duplicate samples of 50 μl of appropriate dilutions made in 0.01 mol/l phosphate buffered saline (pH 7.2-7.4) were placed on mitis-salivarious- bacitracin (MSB) agar and Rogosa SL agar. After anaerobic culture at 37 ^oC for 48 hours, the number of CFU/ml of saliva of mutans streptococci and lactobaicilli was determined. The correlation between buffer capacity and the number of mutans streptococci (high level: ≧10⁶ CFU/ml, low level: <10⁶ CFU/ml) and lactobacilli (high level: ≧10⁵ CFU/ml, low level: <10⁵ CFU/ml) were statistically analyzed by Fisher's exact test (p<0.05). Results: The table shows the distribution of the individuals in the categories of buffer capacity on the number of mutans streptococci and lactobacilli. The number of mutans streptococci did not indicate a significant difference between high and low buffer capacity (p<0.05). The number of lactobacilli indicated a significant difference between high and low buffer capacity (p<0.05).   

 Conclusions: The salivary buffer capacity was related to the salivary lactobacilli counts and this simplified quantitative salivary buffer capacity test could add important information for clinical caries risk assessment. Supported by grant from COE Program, FRMDRTB at TMDU.