Abstract
Comparing the pH drop method using a pH meter for human salivary ability against the formation of calcium phosphate precipitates, we studied a convenient method using a pH indicator, bromothymol blue (BTB). The addition of 250μM NaF widened the range of color change of BTB. As the pH was changed, BTB's color changed from blue to blue-green, yellow-green and yellow. The addition of 2.5, 5.0 and 7.5% (v/v) of whole saliva in the reaction mixture containing 250μM NaF showed yellow, blue green and blue, respectively, after incubation at 37℃ for 40 min. This indicated that the grade of inhibition with whole saliva of the formation of calcium phosphate precipitates was semi-quantitatively assessed by the BTB colorization. In practice, the evaluation of inhibitory ability against the formation of calcium phosphate precipitates using 10 individuals' whole saliva was carried out. The correlation coefficient (r) between the induction time (from pH drop method) and the pH value (from BTB method using the color standard) was higher (0.79〜0.86). The result strongly suggests that the inhibitory capability of human whole saliva on oral calcification (re-mineralization and calculus formation) may be easily evaluated by the method using BTB.
