title: Biomimetic remineralization of human dentin using promising innovative calcium-silicate hybrid "smart" materials.
abstract: BACKGROUND
  The hypothesis was that experimental ion-leaching bioactive composites enhance remineralization of apatite-depleted dentin.
  
  
  METHODS
  Calcium-aluminosilicate (wTC-Ba) or fluoride-containing calcium-aluminosilicate (FTC-Ba) Portland-derived mineral powders were mixed with HTP-M methacrylate HEMA/TEGDMA/PAA-based resin to prepare experimental composites. Controls were Vitrebond and Gradia Direct LoFlo. Calcium- and fluoride-release, pH of soaking water, solubility and water uptake were evaluated in deionized water using material disks (8 mm diameter and 1.6 mm thick). The apatite-formation ability (bioactivity) and the ability to remineralize previously demineralized dentin were assessed by ESEM-EDX and FTIR after soaking in a phosphate-containing solution. Human dentin slices (0.8 mm thickness) were demineralized in EDTA 17% for 2 h, placed in close contact with the material disks and immersed in a phosphate-containing solution (Dulbecco's Phosphate Buffered Saline, DPBS) to assess the ability of the materials to remineralize apatite-depleted dentin.
  
  
  RESULTS
  Only the experimental materials released calcium and basified the soaking water (released hydroxyl ions). A correlation between calcium release and solubility was observed. FTC-Ba composite released more fluoride than Vitrebond and formed calcium fluoride (fluorite) precipitates. Polyacrylate calcium complexes (between COO(-) groups of polyacrylate and released calcium ions) formed at high pH. The formation of apatite was noticed only on the experimental materials, due to the combination of calcium ions provided by the materials and phosphate from the DPBS. Apatite deposits (spherulites showing Ca and P EDX peaks and IR bands due to phosphate stretching and bending) were detected early on the experimental material disks after only 24 h of soaking in DPBS. Only the experimental composites proved to have the ability to remineralize apatite-depleted dentin surfaces. After 7 days in DPBS, only the demineralized dentin treated with the experimental materials showed the appearance of carbonated apatite (IR bands at about 1400, 1020, 600 cm(-1)). EDX compositional depth profile through the fractured demineralized dentin slices showed the reappearance of Ca and P peaks (remineralization of dentin surface) to 30-50 μm depth.
  
  
  CONCLUSIONS
  The ion-leachable experimental composites remineralized the human apatite-depleted dentin. Ion release promotes the formation of a bone-like carbonated-apatite on demineralized dentin within 7 days of immersion in DPBS. The use of bioactive "smart" composites containing reactive calcium-silicate Portland-derived mineral powder as tailored filler may be an innovative method for the biomimetic remineralization of apatite-depleted dentin surfaces and to prevent the demineralization of hypomineralized/carious dentin, with potentially great advantage in clinical applications.
authors.affiliation: Laboratory of Biomaterials, Department of Odontostomatological Science, University of Bologna, Bologna, Italy. mgiovanna.gandolfi@unibo.it
authors.forename: Maria Giovanna
authors.initials: MG
authors.lastname: Gandolfi
authors.forename: Paola
authors.initials: P
authors.lastname: Taddei
authors.forename: Francesco
authors.initials: F
authors.lastname: Siboni
authors.forename: Enrico
authors.initials: E
authors.lastname: Modena
authors.forename: Elettra Dorigo
authors.initials: ED
authors.lastname: De Stefano
authors.forename: Carlo
authors.initials: C
authors.lastname: Prati
mesh_terms: D000042:Absorption; D000179:Acrylates / Q000737:chemistry; D000535:Aluminum; D000538:Aluminum Silicates; D001031:Apatites / Q000138:chemical synthesis; D040761:Biomimetic Materials / Q000737:chemistry*; D002118:Calcium / Q000032:analysis; D017610:Calcium Compounds; D003804:Dentin / Q000737:chemistry*; D005459:Fluorides / Q000032:analysis; D005461:Fluorine; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006878:Hydroxides / Q000032:analysis; D008422:Materials Testing; D010758:Phosphorus / Q000032:analysis; D017640:Silicates; D012995:Solubility; D013052:Spectrometry, X-Ray Emission; D017550:Spectroscopy, Fourier Transform Infrared; D014089:Tooth Remineralization / Q000379:methods*
chemical_list: D000179:Acrylates; D000538:Aluminum Silicates; D001031:Apatites; D017610:Calcium Compounds; D006878:Hydroxides; D017640:Silicates; C053629:fluoroaluminum; D010758:Phosphorus; D005461:Fluorine; C031356:hydroxide ion; D000535:Aluminum; D005459:Fluorides; C031293:calcium silicate; D002118:Calcium