Comparative plaque acidogenesis of caries-resistant vs. caries-susceptible adults

The authors conducted a comparative study of plaque acids in three-day fasting or resting plaque samples from ten pairs of caries-resistant (CR) and caries-susceptible (CS) subjects chewing a sucrose gum for a period of 45 min. The study disclosed two important differences: 1) The amount and rate of production of lactic acid were lower in the CR group, especially at ten min; and 2) in contrast to lactic acid levels, the level of acetic acid was significantly higher in the CR group at zero time (before chewing), and after 20 and 45 min of chewing the sucrose gum. Both the lower levels of lactic acid and the higher levels of acetic acid are (paradoxically) consistent with the higher plaque pH values reported for CR when compared to CS subjects. High pK' acids (such as acetic, as well as propionic and butyric) can provide a buffering system (acetate-acetic acid) capable of countering the pH decrement generated by the low pK' acids (lactic, formic and pyruvic).