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

Abstract

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⁺, Ca²⁺, Al³⁺, Sr²⁺, Li⁺, Zn²⁺, and Mg²⁺) 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 ³¹P-Nuclear-Magnetic-Resonance-Spectroscopy (³¹P-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 ³¹P-NMR peak position value reflects the phosphate chemical state within PS and its change in relation to pH. Only calcium ion concentration [Ca²⁺], aluminum activity {Al³⁺}, and DS_HAp significantly correlated with the ³¹P-NMR peak position value (ppm), whereas no correlation was observed between the ³¹P-NMR peak position value and the activities of K⁺, Na⁺, Sr²⁺, Mg²⁺, Li⁺, and Zn²⁺.

Conclusions

This parotid saliva ³¹P-NMR study has shown that calcium ion concentration [Ca²⁺], aluminum activity {Al³⁺}, 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.