title: Ionic modification of calcium phosphate cement viscosity. Part II: hypodermic injection and strength improvement of brushite cement.
abstract: Brushite-forming calcium phosphate cements are of great interest as bone replacement materials because they are resorbable in physiological conditions. However, their short setting times, low mechanical strengths and limited injectability limit broad clinical application. In this study, we showed that a significant improvement of these properties of brushite cement could be achieved by the use of sodium citrate or citric acid as setting retardants, such that workable cement pastes with a powder to liquid ratio of up to 5 could be manufactured. The cement used in this study consisted of an equimolar powder mixture of beta-tricalcium phosphate and monocalcium phosphate hydrate The use of 500 mM-1M retardant solutions as liquid phase enabled initial setting times of 8-12 min. Wet compressive strength were found to be in the range between 12-18 MPa after immersion of uncompacted cement samples in serum for 24 h. A further strength improvement to 32 MPa was obtained by compaction of the cement paste during samples preparation. This is significant because high-temperature processes cannot be used to fabricate hydrated calcium phosphate materials. Cement pastes were injectable through a hypodermic needle at a powder to liquid ratio of 3.3 g/ml when a 1M citric acid was used as liquid phase, thus enabling precise controlled delivery to small defects.
authors.affiliation: Biomaterials Unit, School of Dentistry, University of Birmingham, St Chad's Queensway, Birmingham B4 6NN, UK. j.e.barralet@bham.ac.uk
authors.forename: J E
authors.initials: JE
authors.lastname: Barralet
authors.forename: L M
authors.initials: LM
authors.lastname: Grover
authors.forename: U
authors.initials: U
authors.lastname: Gbureck
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; D013499:Surface Properties; 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; C494366:calcium phosphate, dibasic, dihydrate