title: Ammonium hexafluorosilicate elicits calcium phosphate precipitation and shows continuous dentin tubule occlusion.
abstract: Diamine silver fluoride [AgF: (NH(3))(2)AgF] has been used clinically in Japan, as it reduces dental caries and dentin hypersensitivity. However, AgF stains the teeth black due to silver precipitation. To overcome this drawback, the authors prepared ammonium hexafluorosilicate [SiF: (NH(4))(2)SiF(6)], which does not stain the teeth, and SiF occluded open dentin tubules completely with silica-calcium phosphate precipitate.
  
  
  OBJECTIVE
  The aim of this study was to evaluate the duration of dentin tubule occlusion after SiF treatment in a simulated oral environment.
  
  
  METHODS
  To simulate dentin tubules subject to dentin hypersensitivity, dentin disks were treated with EDTA for 2 min. The disks were treated with 0.476 mol/L SiF for 3 min, and then the disks were immersed in synthetic saliva, which was regularly replenished to maintain its ionic concentration, for up to 7 days. The occluding ability of the dentin tubules was evaluated using scanning electron microscopy (SEM), and the hydraulic conductance was measured following Pashley's method at regular intervals.
  
  
  RESULTS
  SEM photographs demonstrated that dentin tubules were occluded homogeneously and completely with the precipitate at 7 days after treatment with SiF. In addition, newly formed calcium phosphate precipitate was present at the dentin surface. The dentin permeability showed a consistently low value throughout the experimental period. The values immediately after SiF treatment and 7 days after immersion were 11.9+/-3.7% and 7.9+/-2.9%, respectively.
  
  
  CONCLUSIONS
  Ammonium hexafluorosilicate is useful for the treatment of dentin hypersensitivity, since ammonium hexafluorosilicate induced calcium phosphate precipitation from the saliva; therefore, it has a continuous effect on dentin tubules occlusion under a simulated oral environment.
authors.affiliation: Department of Conservative Dentistry, Institute of Health Biosciences, The University of Tokushima Graduate School, 3-18-15 Kuramoto, Tokushima 770-8504, Japan. suge@dent.tokushima-u.ac.jp
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Suge
authors.forename: Akiko
authors.initials: A
authors.lastname: Kawasaki
authors.forename: Kunio
authors.initials: K
authors.lastname: Ishikawa
authors.forename: Takashi
authors.initials: T
authors.lastname: Matsuo
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Ebisu
mesh_terms: D000328:Adult; D002130:Calcium Phosphates / Q000737:chemistry*; D002614:Chelating Agents / Q000494:pharmacology; D011232:Chemical Precipitation; D003804:Dentin / Q000187:drug effects / Q000648:ultrastructure*; D003806:Dentin Permeability / Q000502:physiology; D003807:Dentin Sensitivity / Q000503:physiopathology; D004492:Edetic Acid / Q000494:pharmacology; D004577:Electron Probe Microanalysis; D005459:Fluorides / Q000737:chemistry*; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D012464:Saliva, Artificial / Q000737:chemistry; D012824:Silicic Acid / Q000737:chemistry*; D016369:Smear Layer; D013997:Time Factors
chemical_list: D002130:Calcium Phosphates; D002614:Chelating Agents; D012464:Saliva, Artificial; D012824:Silicic Acid; C004832:hexafluorosilicate; C020243:calcium phosphate; D004492:Edetic Acid; D005459:Fluorides