[A preliminary study of the modulation of Actinomyces naeslundii urease to the pH balance of dental biofilm]

Abstract

Purpose: To explore whether the ureolysis of Actinomyces naeslundii could keep high level in the natural dental biofilm and the effect of ureolysis on the environmental pH balance preliminarily.

Methods: Enzyme kinetic test was used to detect the optimal condition for ureolysis; and the pH change was measured under ureolysis after acidgenesis.SPSS software package was used for linear regression and correlation analysis.

Results: The Km of urease was 7.5mmol/L, it could keep 20% to 63% of the optimal activity with the concentration of urea normally found in the mouth which was at the range of 3-10mmol/L; The optimal pH of ureolysis was 6.5, but at pH 5.0 which was the threshold pH of dental plaque, the enzyme had 40% of the optimal activity; with the concentration of urea normally found in the mouth, pH would not decrease to the threshold pH with ureolysis after acidification.

Conclusion: In the dental plaque biofilm, A. naeslundii could ureolyze highly actively; ureolysis could moderate the pH balance of plaque significantly.