Correlation between parotid saliva composition and dental caries using ³¹P-NMR and ICDAS score

The preservation of enamel mineral is influenced by the supersaturation of salivary secretions with respect to calcium phosphate salts. The aim was to measure the chemical environmental state of phosphate ions in a subject's parotid saliva, and to correlate this with their dental caries score, by means of ³¹P-Nuclear Magnetic Resonance Spectroscopy (³¹P-NMR) and the International Caries Detection and Assessment System (ICDAS).

Unilateral paraffin wax stimulated parotid saliva samples were collected from 21 healthy adult subjects using a Lashley cup. The flowrate was recorded during collection. Clinical caries scores of each subject were classified using the ICDAS score. The pH was recorded for each saliva sample. ³¹P-NMR spectra of each saliva sample were obtained to determine the phosphorus chemical environment. All the collected data were analysed by Pearson's correlation.

Parotid saliva flow rates were in the range from 0.07 to 0.56 ml/min. The pH varied from 5.9 to 7.6. Each ³¹P-NMR spectrum showed a single broad line with a chemical shift between 0.07 and 2.38 ppm. At neutral pH the maximum chemical shift was 2.05 ppm, whereas at a lower pH values the phosphorous chemical shift reduced, to 0.34 at pH 5.9. The flowrate and the ³¹P-NMR chemical shift correlated positively (r = 0.71; p < 0.05). The ICDAS score correlated negatively with the ³¹P-NMR chemical shift (r = 0.43; p < 0.05).

This parotid saliva ³¹P-NMR study has shown that different phosphate states exist within saliva, which significantly influence its inorganic chemical behaviour, and therefore its cariostatic activity.