title: Ionic modification of calcium phosphate cement viscosity. Part I: hypodermic injection and strength improvement of apatite cement.
abstract: A broadening of the indications for which calcium phosphate cements (CPC) can be used, for example, in the field of vertebroplasty, would require injectable and higher strength materials. Unmodified CPC are not injectable due to a filter-pressing effect during injection. In this work we demonstrated that an effective method for improving the injection properties of CPC was by the use of sodium citrate solution as a liquid component. Cement consisting of tetracalcium phosphate (TTCP) and monetite (DCPA) mixed with water up to a powder:liquid ratio (P:L) of 3.3 g/ml had an injectability of approximately 60%. The use of 500 mM trisodium citrate solution instead of water decreased the viscosity of the cement paste to a point, where complete injectability (>95%) through an 800 microm diameter hypodermic needle could be achieved at low loads. The reduction in water demand of the cement effected by the use of sodium citrate enabled high P:L mixes to be formed which were 400% stronger than cements made with water. The effect was less pronounced with compacted cements such that at 9 MPa applied pressure, 58% improvement was obtained and at 50 MPa 36% improvement was measured yielding a cement with a compressive strength of 154 MPa. The liquefying effect of sodium citrate was thought to derive from a strong increase in the surface charge of both the reactants and the product as determined by zeta-potential measurement.
authors.affiliation: Department for Functional Materials in Medicine and Dentistry, University of Wuerzburg, Pleicherwall 2, D17 97070 Würzburg, Germany. uwe.gbureck@fmz.uni-wuerzburg.de
authors.forename: Uwe
authors.initials: U
authors.lastname: Gbureck
authors.forename: Jake E
authors.initials: JE
authors.lastname: Barralet
authors.forename: Kerstin
authors.initials: K
authors.lastname: Spatz
authors.forename: Liam M
authors.initials: LM
authors.lastname: Grover
authors.forename: Roger
authors.initials: R
authors.lastname: Thull
mesh_terms: D001672:Biocompatible Materials / Q000138:chemical synthesis / Q000737:chemistry*; D001843:Bone Cements / Q000138:chemical synthesis / Q000737:chemistry*; D002130:Calcium Phosphates / Q000008:administration & dosage* / Q000138:chemical synthesis / Q000737:chemistry*; D002951:Citrates / Q000737:chemistry*; D019245:Compressive Strength; D006244:Hardness; D006863:Hydrogen-Ion Concentration; D007267:Injections / Q000379:methods*; D007477:Ions; D008422:Materials Testing; D044367:Phase Transition; D012212:Rheology / Q000379:methods; D000077559:Sodium Citrate; D013696:Temperature; D014783:Viscosity
chemical_list: D001672:Biocompatible Materials; D001843:Bone Cements; D002130:Calcium Phosphates; D002951:Citrates; D007477:Ions; D000077559:Sodium Citrate; C485838:calcium phosphate, monobasic, anhydrous; C020243:calcium phosphate