title: Glass ionomer cements: effect of strontium substitution on esthetics, radiopacity and fluoride release.
abstract: OBJECTIVE
  SrO and SrF2 are widely used to replace CaO and CaF2 in ionomer glasses to produce radiopaque glass ionomer cements (GIC). The purpose of this study was to evaluate the effects of this substitution on release of ions from GIC as well as its effect on esthetics (translucency) and radiopacity.
  
  
  METHODS
  Cements were produced from ionomer glasses with varying content of Sr, Ca and F. The cements were stored in dilute acetic acid (pH 4.0) for up to 7 days at 37°C. Thereafter, the cements were removed and the solution was tested for F(-), Sr(2+), Ca(2+), and Al(3+) release. Radiopacity and translucency were measured according to BS EN ISO 9917-1:2003.
  
  
  RESULTS
  Ion release was linear to t(1/2) suggesting that this is a diffusion controlled mechanism rather than dissolution. The fluoride release from the cements is enhanced where some or all calcium is replaced by strontium. Radiopacity shows a strong linear correlation with Sr content. All cements were more opaque than the C0.70 0.55 standard but less opaque than the C0.70 0.90 standard which is the limit for the ISO requirement for acceptance.
  
  
  CONCLUSIONS
  This study shows that the replacement of calcium by strontium in a glass ionomer glass produces the expected increase in radiopacity of the cement without adverse effects on visual properties of the cement. The fluoride release from the cements is enhanced where some or all calcium is replaced by strontium.
authors.affiliation: Dental Physical Sciences Unit, Institute of Dentistry, Barts and London School of Medicine and Dentistry, Queen Mary University of London, UK. Electronic address: s.shahid@qmul.ac.uk.
authors.forename: S
authors.initials: S
authors.lastname: Shahid
authors.affiliation: Dental Physical Sciences Unit, Institute of Dentistry, Barts and London School of Medicine and Dentistry, Queen Mary University of London, UK.
authors.forename: U
authors.initials: U
authors.lastname: Hassan
authors.affiliation: Dental Physical Sciences Unit, Institute of Dentistry, Barts and London School of Medicine and Dentistry, Queen Mary University of London, UK.
authors.forename: R W
authors.initials: RW
authors.lastname: Billington
authors.affiliation: Dental Physical Sciences Unit, Institute of Dentistry, Barts and London School of Medicine and Dentistry, Queen Mary University of London, UK.
authors.forename: R G
authors.initials: RG
authors.lastname: Hill
authors.affiliation: Dental Physical Sciences Unit, Institute of Dentistry, Barts and London School of Medicine and Dentistry, Queen Mary University of London, UK.
authors.forename: P
authors.initials: P
authors.lastname: Anderson
mesh_terms: D000535:Aluminum / Q000737:chemistry; D002118:Calcium / Q000737:chemistry; D004955:Esthetics, Dental; D005459:Fluorides / Q000737:chemistry*; D005899:Glass Ionomer Cements / Q000737:chemistry*; D006868:Hydrolysis; D017736:Ion-Selective Electrodes; D007700:Kinetics; D008422:Materials Testing; D010100:Oxygen / Q000737:chemistry; D010758:Phosphorus / Q000737:chemistry; D012825:Silicon / Q000737:chemistry; D013324:Strontium / Q000737:chemistry*; D013499:Surface Properties; D013997:Time Factors
chemical_list: D005899:Glass Ionomer Cements; D010758:Phosphorus; D000535:Aluminum; D005459:Fluorides; D010100:Oxygen; D002118:Calcium; D013324:Strontium; D012825:Silicon
keywords: Esthetics; Fluoride release; Glass ionomer cements; Ion release; Radiopacity; Strontium