title: Injectable calcium phosphate cement: effects of powder-to-liquid ratio and needle size.
abstract: Calcium phosphate cement (CPC) sets in situ and forms apatite with excellent osteoconductivity and bone-replacement capability. The objectives of this study were to formulate an injectable tetracalcium phosphate-dicalcium phosphate cement (CPC(D)), and investigate the powder/liquid ratio and needle-size effects. The injection force (mean +/- SD; n = 4) to extrude the paste increased from (8 +/- 2) N using a 10-gauge needle to (144 +/- 17) N using a 21-gauge needle (p < 0.05). With the 10-gauge needle, the mass percentage of extruded paste was (95 +/- 4)% at a powder/liquid ratio of 3; it decreased to (70 +/- 12)% at powder/liquid = 3.5 (p < 0.05). A relationship was established between injection force, F, and needle lumen cross-sectional area, A: F = 5.0 + 38.7/A(0.8). Flexural strength, S, (mean +/- SD; n = 5) increased from (5.3 +/- 0.8) MPa at powder/liquid= 2 to (11.0 +/- 0.8) MPa at powder/liquid = 3.5 (p < 0.05). Pore volume fraction, P, ranged from 62.4% to 47.9%. A relationship was established: S = 47.7 x (1 - P)(2.3). The strength of the injectable CPC(D) matched/exceeded the reported strengths of sintered porous hydroxyapatite implants that required machining. The novel injectable CPC(D) with a relatively high strength may be useful in filling defects with limited accessibility such as periodontal repair and tooth root-canal fillings, and in minimally-invasive techniques such as percutaneous vertebroplasty to fill the lesions and to strengthen the osteoporotic bone.
authors.affiliation: Paffenbarger Research Center, American Dental Association Foundation, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8546, USA.
authors.forename: Elena F
authors.initials: EF
authors.lastname: Burguera
authors.forename: Hockin H K
authors.initials: HH
authors.lastname: Xu
authors.forename: Limin
authors.initials: L
authors.lastname: Sun
mesh_terms: D001843:Bone Cements; D002130:Calcium Phosphates; D017886:Durapatite; D007267:Injections / Q000295:instrumentation*; D009339:Needles; D011208:Powders
chemical_list: D001843:Bone Cements; D002130:Calcium Phosphates; D011208:Powders; C485830:tetracalcium phosphate; D017886:Durapatite; C485829:calcium phosphate, dibasic, anhydrous