title: Development of novel strontium containing bioactive glass based calcium phosphate cement.
abstract: The aim of this study was to investigate the effect on properties of increasing strontium substitution for calcium in bioactive glasses used as precursors for novel calcium phosphate cements.
  
  
  
  Glasses were produced by progressively substituting strontium for calcium. Cements were prepared by mixing the glass powder with Ca(H2PO4)2 powder with a 2.5% solution of Na2HPO4. Setting times and compressive strength were measured after 1h, 1 day, 7 days and 28 days immersion in Tris buffer solution. X-ray diffraction (XRD), Fourier transform infrared spectroscopy and radiopacity were measured and crystal morphology was assessed using scanning electron microscopy.
  
  
  
  A correlation between the phases formed, morphology of the crystallites, setting time and compressive strength were analyzed. Setting time increased proportionally with strontium substitution in the glass up to 25%, whereas for higher substitutions it decreased. Compressive strength showed a maximum value of 12.5MPa and was strongly influenced by the interlocking of the crystals and their morphology. XRD showed that the presence of strontium influenced the crystal phases formed. Octacalcium phosphate (Ca8H2(PO4)6·5H2O, OCP) was the main phase present after 1h and 1 day whereas after 28 days OCP was completely transformed to strontium-containing hydroxyapatite (SrxCa(10-x)(PO4)6(OH)2, SrHA). Radiopacity increased proportionally to strontium substitution in the glass.
  
  
  
  A novel method to develop a bone substitute forming in vitro SrHA as a final product by using a bioactive glass as a precursor was shown. These novel injectable bioactive glass cements are promising materials for dental and orthopedic applications. Further in vivo characterizations are being conducted.
authors.affiliation: Dental Physical Sciences Unit, Institute of Dentistry, Queen Mary University of London, Bancroft Road, London E1 4NS, United Kingdom. Electronic address: alessia.donofrio@qmul.ac.uk.
authors.forename: A
authors.initials: A
authors.lastname: D'Onofrio
authors.affiliation: Dental Physical Sciences Unit, Institute of Dentistry, Queen Mary University of London, Bancroft Road, London E1 4NS, United Kingdom. Electronic address: n.kent@ucl.ac.uk.
authors.forename: N W
authors.initials: NW
authors.lastname: Kent
authors.affiliation: Restorative Dentistry, The Royal London Dental Hospital, Turner Street, London E1 1BB, United Kingdom. Electronic address: shakeel.shahdad@bartshealth.nhs.uk.
authors.forename: S A
authors.initials: SA
authors.lastname: Shahdad
authors.affiliation: Dental Physical Sciences Unit, Institute of Dentistry, Queen Mary University of London, Bancroft Road, London E1 4NS, United Kingdom. Electronic address: r.hill@qmul.ac.uk.
authors.forename: R G
authors.initials: RG
authors.lastname: Hill
mesh_terms: D001843:Bone Cements; D002130:Calcium Phosphates; D017886:Durapatite; D005898:Glass; D008422:Materials Testing; D013324:Strontium
chemical_list: D001843:Bone Cements; D002130:Calcium Phosphates; C509320:strontium-containing hydroxyapatite; D017886:Durapatite; D013324:Strontium
keywords: Bioactive glass; Bone graft; Calcium phosphate cement; Strontium