Acid Production from Mutans streptococci in Glucan-biofilm Model

Abstract

Nursing caries is defined as the rampant caries in infants when the smooth enamel surface of the primary dentition is extensively decalcified, having been a serious problem in pediatric dentistry. It has been thought that lactose contained at a concentration of 7% in infant formula and mother's milk is an important pathogenic factor in nursing caries. There have therefore been many reports concerning the relationship between nursing caries and infant formula or mother's milk. The formation mechanism of nursing caries and, especially the participation of lactose are however unknown. In this study, we investigated acid production from lactose of mutans streptococci enclosed in glucan-biofilm to discuss its cariogenicity in nursing caries.
Streptococcus mutans and Streptococcus sobrinus were cultured with sucrose containing broth in a tilted test tube to allow biofilm formation. The glucan-biofirm was washed and test sugar solutions were added to determine acid formation.
Mutans streptococci cultured in the planktonic condition were able to metabolize lactose and produce the organic acid. On the other hand, mutans streptococci enclosed in glucan-biofilm scarcely showed the metabolism of lactose and the production of acid. Moreover, addition of low concentration of sucrose as the reproduced in vitro model, the mutans streptococci enclosed in glucan-biofilm could not also produce acid from lactose.