Characterization of Phosphate Speciation in Saliva and Oral Care Products

Objectives: The aim was to investigate the speciation of typically sourced soluble phosphates from saliva, oral care products, and phosphate glasses. The effect of the alkaline phosphatase on the oral ecosystem of the phosphates was monitored using ³¹P NMR spectroscopy.
Methods: The Tris solution was used as a medium to dissolve selected type of phosphates. Three concentrations of total phosphates 30 ppm, 100 ppm, and 300 ppm mimicking their amount in toothpaste and the remineralizing agents. The following phosphates were selected KH₂PO₄, Na₂HPO₄, Na₂FPO₃, (NaPO₃)₆, Ca(H₂PO₄)₂.H₂O and K₂HPO₄.3H₂O in addition to the buffer solutions of artificial saliva at pH 4, pH 7, and PBS. Solution-/solid-state ³¹P NMR spectroscopy, and X-ray diffraction were used to characterize the dissolved state of phosphates available in oral health products and other phosphate sources including phosphate glasses in the oral environment with and without alkaline phosphatase.
Results: The results indicate that various types of soluble phosphates exhibited different ³¹P NMR spectra. The signals observed in the ³¹P NMR spectra fall into three distinct regions. The chemical shifts of ³¹P NMR spectra were affected by the pH. Enzymatic hydrolysis of condensed phosphate groups in solution by alkaline phosphatase was found to occur.
Conclusions: Qualitative and quantitative evaluation of the P species in phosphates used in oral care products were done. These findings are important for the development of the new phosphates-containing remineralizing products or generation of bone grafts, including the for the periodontium repair.