Dynamic analysis of organic acids in extracellular fluids of human dental plaques

Organic acids in unstimulated saliva and extracellular fluids of dental plaques from 12 middle school students were measured by ion-chromatography. The acids in the plaques were analyzed before and 5-10, 30-35, 60-65 minutes after rinsing with 10% sucrose solution. The differences of the acids between the extracellular fluids of resting plaques and unstimulated saliva were significant. In the extracellular fluids of plaques, the concentration of high pK acids, i.e. acetic and propionic acids was higher than that of low pK acids i.e., lactic and formic acids before and after sucrose rinse. The relations of time-dependent changes between the ratio of low pK to high pK acids and pH were observed in the extracellular fluids of plaques after sucrose rinse. No significant difference of lactic acid concentrations was found between the caries-active and caries-free subjects 30-35 minutes after sugar rinse. The concentration of acetic acid was much higher in the extracellular fluids of dental plaque at any time. It is suggested that there may be some relationship between acetic acid and caries process.