Influence of Parotid Saliva Composition on Phosphate Species' Chemical State in Relation to Dental Caries.

OBJECTIVES: The aim of the present study was to analyze the influence of parotid saliva (PS) composition on the phosphate species' chemical state in relation to dental caries. METHODS: Unilateral stimulated PS samples were collected from 21 healthy adult subjects using a Lashley cup. Clinical caries scores of each subject were classified using the ICDAS score. The pH was recorded for each saliva sample. The concentration of specific inorganic elements (K(+), Na(+), Ca(2+), Al(3+), Sr(2+), Li(+), Zn(2+), and Mg(2+)) was measured using an Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES). The PS effective concentration of ions and the degree of saturation (DS) with respect to enamel mineral were determined by speciation calculation. The PS chemical environment was determined using (31)P-Nuclear-Magnetic-Resonance-Spectroscopy ((31)P-NMR). Pearson's correlation test was applied to evaluate the influence of PS composition on the ICDAS score. RESULTS: The pH varied from 5.9 to 7.6. The ICDAS scores varied from 0.03 to 2.48. PS was supersaturated with respect to HAp at all pH values. The (31)P-NMR peak position value reflects the phosphate chemical state within PS and its change in relation to pH. Only calcium ion concentration [Ca(2+)], aluminum activity Al(3+), and DS(HAp) significantly correlated with the (31)P-NMR peak position value (ppm), whereas no correlation was observed between the (31)P-NMR peak position value and the activities of K(+), Na(+), Sr(2+), Mg(2+), Li(+), and Zn(2+). CONCLUSIONS: This parotid saliva (31)P-NMR study has shown that calcium ion concentration [Ca(2+)], aluminum activity Al(3+), and DS(HAp) significantly influence the phosphate species' chemical state existing within PS and provides extended knowledge on the main biochemical determinants of the caries process.