2021 Volume 64 Issue 2 Pages 107-115
Purpose: Inorganic polyphosphates (polyPs) bind to the tooth surface and aid in removing stains and preventing stain deposition. In this study, we investigated whether the degree of polymerization of polyP affects the stain removal and prevention of stain deposition on the tooth surface. We also investigated whether polyP bound to the tooth surface suppresses demineralization.
Methods: Hydroxyapatite powders stained with tea and coffee extracts were placed in centrifuge tubes, and purified water or polyPs solution of various chain lengths was added to it. The solution was mixed and then centrifuged to separate the hydroxyapatite. Further, unstained hydroxyapatite powder was mixed with polyPs solution or purified water in the same manner, and dyed with tea and coffee. The color of the hydroxyapatite powder for each sample was scanned using an image scanner, and the color density was measured to evaluate the extents of stain removal and prevention of deposition. An ivory plate was then sanded to prepare a smooth specimen. Each specimen was immersed in 1% polyP9.7-Saliveht solution or Saliveht for 10 min and then washed with water and dried. The specimen was then treated with 40% phosphoric acid for 20 min. After this, the phosphoric acid was washed off with water, and the specimen was dried. The cross-sectional depth of the demineralized portion after drying was observed with an optical microscope.
Results: PolyP with a degree of polymerization of 9.7 (polyP9.7) was highly effective in removing stains and preventing deposition. PolyP9.7 was more effective in removing stains and preventing deposition than tripolyphosphate, a polymer of three phosphate residues commonly used in dentifrices, and polyP, which has a degree of polymerization of 60. In addition, demineralization was suppressed on the ivory surface treated with polyP9.7 upon phosphoric acid etching.
Conclusion: PolyP9.7 is highly effective in removing stains and preventing deposition on the tooth surface and can suppress the demineralization by binding to the tooth surface.
