Oral Bacterial Acid-Base Metabolism in Caries Screening: A Proof-Of-Concept Study

The objective of this cross-sectional study was to clinically validate an array of biochemical tests for oral acid/alkali generation as caries screening instruments. 185 adult subjects (mean 33.6±10.6 years) were examined clinically for dental caries using the ICDAS criteria. Bitewing radiographs were used to confirm interproximal surfaces of posterior teeth. For the purposes of this study, subjects were classified as "caries-active" if they had at least one untreated caries lesion with ICDAS 4 or higher. Pooled supragingival plaque and unstimulated saliva samples were collected and assayed for pH changes from sucrose and urea metabolism using colorimetric tests. The validity of each test to discriminate between "caries-inactive" and "caries-active" subjects was assessed and compared to a commercial bacteriological caries-screening test using roc regression and logistic regression models. The AUCs of the plaque-urea (PU: 0.59 (0.51, 0.67)), plaque-urea-glucose (PUG: 0.59 (0.51, 0.67)) and saliva-urea-glucose (SUG: 0.59 (0.51, 0.67)) tests did not differ significantly from the bacteriological tests (CRT-mutans: 0.62 (0.54, 0.70); CRT-lactobacillus: 0.63 (0.56, 0.71) (P>0.05), but the plaque-glucose (SG), saliva-glucose (SG), saliva-urea (SU) and saliva-plaque-glucose (SPG) tests had significantly smaller AUCs (P<0.05). The AUCs for the PU, PUG, SUG, and the CRT-mutans tests were higher in subjects who had no existing dental restorations (PU: 0.90 (0.77, 1.04); PUG: 0.90 (0.79, 1.01); SUG: 0.89 (0.69, 1.08); CRT-mutans: 0.90 (0.73, 1.08)). The incorporation of the biochemical tests into a multidimensional bacteriological/psychosocial caries screening model significantly increased its diagnostic values (Se+Sp: 160.6, AUC: 0.846). In conclusion, as a proof of concept, the results of this study indicate that measuring the ability of dental plaque and saliva to metabolize urea together with the ability to generate acid from sugars may have a promising role in caries screening either independently, or as part of a multidimensional biological test.