Ionic modification of calcium phosphate cement viscosity. Part II: hypodermic injection and strength improvement of brushite cement

• Published in: Biomaterials 2004-05, Vol.25 (11), p.2197-2203
• Main Authors: Barralet, J.E., Grover, L.M., Gbureck, U.
• Format: Article
• Language: English
• Subjects: Biocompatible Materials - chemical synthesis; Biocompatible Materials - chemistry; Bone Cements - chemical synthesis; Bone Cements - chemistry; Brushite; Calcium phosphate cement; Calcium Phosphates - administration & dosage; Calcium Phosphates - chemical synthesis; Calcium Phosphates - chemistry; Citrates - chemistry; Compressive Strength; Delivery; Hardness; Hydrogen-Ion Concentration; Injection; Injections - methods; Ions; Materials Testing; Mechanical properties; Phase Transition; Rheology - methods; Sodium Citrate; Surface Properties; Temperature; Viscosity
• ISSN: 0142-9612; 1878-5905
• DOI: 10.1016/j.biomaterials.2003.09.085

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 β-tricalcium phosphate and monocalcium phosphate hydrate The use of 500 m m–1 m 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 1 m citric acid was used as liquid phase, thus enabling precise controlled delivery to small defects.