Evaluation of resistance to fragmentation of injectable calcium-phosphate cement paste using X-ray microcomputed tomography

Abstract

Property of resistance to fragmentation of injectable calcium-phosphate cement (CPC) pastes was evaluated. CPC pastes are widely used as bone fillers due to their biocompatibility and osteoconductivity. However, the potential for fractures due to the formation of voids and cracks in the CPC, called "fragmentation," reduces the biomechanical strength of CPCs. To develop new CPCs that do not exhibit fragmentation, a method for assessing the presence or absence of fragmentation is required. For in vitro evaluation of the fragmentation resistance, the internal structure of cement specimens allowed to stand in pure water or blood was observed using X-ray micro-computed tomography (X-ray¯-CT) method. In the case of cement specimens derived from commercially-available ¢-tricalcium phosphate powder ball milled and surface modified in 3,000 ppm inositol phosphate solution, no cracks or voids in the internal structure were observed in samples allowed to set in either pure water or blood. For in vivo verification of the fragmentation resistance, the same CPC pastes were implanted into pig thigh muscle and tibiae for 4 and 24 weeks, respectively. The implanted CPC specimens formed a lump without internal voids or cracks. These data showed that the CPC pastes with the fragmentation resistance both in vitro and in vivo and are thus unlikely to generate fractures. Furthermore, the evaluation method using X-ray¯-CT could enables rapid and simple verification of the fragmentation resistance of the injectable CPC pastes. To our knowledge, this is the first report of the use of this method to evaluate resistance to fragmentation of CPC pastes. Furthermore, because of its simplicity and ease of use, the X-ray¯-CT method shows promise as a gold standard.

Bioresorbable porous β-tricalcium phosphate chelate-setting cements with poly(lactic-co-glycolic acid) particles as pore-forming agent: fabrication, material properties, cytotoxicity, and in vivo evaluation

“…One approach to reduce the setting time is to increase the amount of Na 2 HPO 4 in the mixture. Nagata et al [ 20 ] reported that Na 2 HPO 4 plays a role in shortening the setting time of cement paste; however, it also decreases the compressive strength. Thus, it is necessary to balance the material properties.…”

“…To prepare the mixing solution, 2.5 g of disodium hydrogen phosphate (Na 2 HPO 4 ), 1.0 g of sodium alginate (C 6 H 7 O 6 Na) n ) and 1.5 g of citric acid anhydride (C 6 H 8 O 7 ) were added in this order to 95 g of pure water. The role of each component is as follows: disodium hydrogen phosphate shortens the setting time, sodium alginate enhances the anti-washout property, and citric acid anhydride improves the dispersibility of β-TCP, to improve the consistency of the final cement [ 20 ]. The pH of the solution was adjusted to 7.0 using NaOH solution.…”

Development of paste-like organic/inorganic artificial bones compatible with bone remodeling cycles, consisting of β-tricalcium phosphate, calcium sulfate hemihydrate, and poly(lactic-co-glycolic acid) particles

“…Subsequently, 10 g of commercially available b-TCP powder (b-TCP-100, Taihei Chemical Industrial Co. Ltd, Japan) was placed in a 3000 ppm 40 cm 3 IP6 solution in a zirconia pot. According to a previous report, 13 the amount of IP6 absorbed on b-TCP powder was determined to be 0.5 mg g À1 under these surface modification conditions. Then, the mixture was simultaneously ground and its surface modified with IP6 using a planetary ball mill (Pulverisette 6, Fritsch Japan Co. Ltd, Japan) in a ZrO 2 pot with 180 g of ZrO 2 beads with a diameter of 2 mm at 300 rpm for 3 h. After ball milling, the resulting slurry was filtered and freeze-dried for 24 h to yield b-TCP powders surface-modified with IP6 (hereafter referred to as IP6/b-TCP powder).…”

“…9 As given in Table 1, the role of each component is as follows: (i) citric acid anhydride binds to Ca 2+ ions in b-TCP, and negatively charging the particles improves the dispersibility of b-TCP to improve dispersion by repulsion between particles, (ii) disodium hydrogen phosphate converts b-TCP to HAp increasing compressive strength and shortening setting time, and (iii) sodium alginate binds to Ca 2+ ions in b-TCP and gelatinizes to inhibit disintegration. 13 The solution was adjusted to pH 7.0 with NaOH solution, and all reagents (Wako Pure Chemical Industries, Ltd, Japan) were used as received, without requiring further purification.…”

“…In vivo quantitative evaluation of the cement pastes was carried out using a miniature pig tibia model according to the methods reported in our previous study. 9,13 The samples used in this experiment were (i) b-TCP-cement, (ii) PLGA( 10)-cement, (iii) CSH/PLGA(10)-cement, (iv) CSH/PLGA(20)-cement, and these powders were sterilized with ethylene oxide gas. Additionally, the mixing liquid was filter sterilized.…”