Dentinal Tubule-occluding Ability of S-PRG Filler Extract Solutions on Artificially Demineralized Bovine Dentin

Abstract

 Purpose: The surface pre-reacted glass ionomer (S-PRG) filler is a bioactive material able to release various ions, and water-extract solutions of the S-PRG filler are known to form precipitates when mixed with phosphate-buffered saline (PBS) or artificial saliva (AS). This study focused on the precipitate formation, and investigated the dentinal tubule-occluding ability of S-PRG filler extract solutions on artificially demineralized bovine dentin.
 Methods: An S-PRG filler extract solution without filler particles (SF0), and an S-PRG filler slurry containing 50% of filler particles (SF50) were used as test materials. The test materials were mixed with either PBS or AS, and the elemental compositions of supernatants and precipitates were analyzed with inductively coupled plasma atomic emission spectroscopy and wavelength-dispersed electron probe microanalysis, respectively. Qualitative phase analysis of the precipitates was made with X-ray diffraction. To analyze the tubule-occluding ability, artificially-demineralized bovine dentin specimens were created by phosphoric acid etching (10%, 10 minutes) followed by polishing with a paste containing hydroxyapatite; treated with the S-PRG filler extract solutions followed by either PBS or AS; and observed with a scanning electron microscope.
 Results: Na, B, P, F, Sr, Si and Al were detected from the supernatant of the SF0-PBS mixture; Ca in addition to the 7 elements were detected from the supernatant of the SF0-AS mixture. The precipitate contained elements originating from the S-PRG filler extract solutions (Na, Sr, Si, Al, B and F) and PBS/AS (P, Na and Ca). X-ray diffraction revealed the presence of NaCl and Na₃H₂P₃O₁₀・1.5H₂O in the precipitates of the SF0-PBS and SF0-AS mixtures, respectively. Moreover, insoluble deposits were formed on the tubule openings and peritubular area of the artificial hypersensitive dentin specimens treated with SF0 or SF50 followed by PBS or AS. The deposit formation was most prominent on the SF50-treated followed by the AS-treated dentin specimens.
 Conclusion: The two-step application of S-PRG filler extract solutions followed by PBS or AS exhibited dentinal tubule-occluding ability on artificially-demineralized bovine dentin.