H-1-NMR analysis of microbial-derived organic acids in primary root carious lesions and saliva

In addition to lowered pH values, the molecular profile and concentrations of microbial-derived organic acids in carious dentin are important deminera lization parameters involved in the induction, development and progression of dental caries. High-resolution proton (H-1) NMR spectroscopy was employe d to examine the organic acid status of primary root carious lesions. H-1-N MR analysis of post-neutralized perchloric acid extracts of active carious lesions revealed that at an operating frequency of 600 MHz, the H-1-NMR-det ectable organic acid composition of carious dentin samples (mean molecular percentage content +/- standard error; the mean molecular percentage conten t is defined here as the mean of the concentration of each H-1-NMR-visible organic acid/anion expressed as a percentage of total H-1-NMR-detectable or ganic acid/anion level in each sample) was acetate 51 +/- 2%, formate 37 +/ - 2%, lactate 5 +/- 1%, propionate 3 +/- 0.8%, pyruvate 2.4 +/- 0.3%, n-but yrate 1.2 +/- 0.2%; succinate 0.1 +/- 0.1%; iso-butyrate, n- and iso-valera te, and n- and iso-caproate (total) <0.2%. Further components detectable in cluded alanine, glycine, choline, phosphorylcholine, trimethylamine oxide, methanol, glycolate and assorted saccharides. Tn view of their 10(-3) disso ciation constants (K-a), our results demonstrate that formic and pyruvic ac ids (K-a = 1.77 x 10(-4) and 3.20 x 10(-3) mol/dm(3), respectively) contrib ute substantially to the decreased pH values associated with active caries lesions (cf. lactate K-a = 1.40 x 10(-4) mol/dm(3)), and hence the pathogen esis of primary root caries. Copyright (C) 1999 John Wiley & Sons, Ltd.