PubMed · 13675836
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
J INK. 1959-05-20. [Internal environment].. https://pubmed.ncbi.nlm.nih.gov/13675836/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Hydrolysis and polycondensation of triethoxysilane end-capped Poly (tetramethylene oxide) (Si-PTMO), tetraethoxysilane (TEOS), tetraisopropyltitanate (TiPT) and calcium nitrate (Ca(NO(3))(2)) gave transparent monolithics of PTMO-modified CaO-SiO(2)-TiO(2) hybrids. The samples with (TiPT)/(TEOS+TiPT) molar ratios from 0 to 0.20 under constant ratio of (Si-PTMO)/(TEOS+TiPT) of 2/3 in weight were prepared. It was found that the incorporation of TiO(2) component into a PTMO-CaO-SiO(2) hybrid results in an increase in the apatite-forming ability in a simulated body fluid: the hybrids with (TiPT)/(TEOS+TiPT) of 0.10 and 0.20 in mol formed an apatite on their surfaces within only 0.5 day. It seemed that, within the range of compositions studied, the TiO(2) content little affects the overall mechanical properties: Young's modulus were 52-55MPa, tensile strength, 7-9MPa, and strain at failure, about 30%. Thus, the organic-inorganic hybrids exhibiting both fairly high apatite-forming ability and high capability for deformation were obtained. These hybrid materials may be useful as new kind of bioactive bone-repairing materials.
Calcium phosphate cement (CPC) hardens in situ to form solid hydroxyapatite, can conform to complex cavity shapes without machining, has excellent osteoconductivity, and is able to be resorbed and replaced by new bone. Therefore, CPC is promising for use in craniofacial and orthopaedic repairs. However, the low strength and lack of macroporosity of CPC limit its use. The aim of the present study was to increase the strength and toughness of CPC while creating macropores suitable for cell infiltration and bone ingrowth, and to investigate the effects of chitosan and mesh reinforcement on the composite properties. Specimens were self-hardened in 3 mm x 4 mm x 25 mm molds, immersed in a physiological solution for 1-84 d, and tested in three-point flexure. After 1d, the unreinforced CPC control had a flexural strength (mean+/-s.d.; n=6) of (3.3+/-0.4)MPa. The incorporation of chitosan or mesh into CPC increased the strength to (11.9+/-0.8) and (21.3+/-2.7)MPa, respectively. The incorporation of both chitosan and mesh synergistically into CPC dramatically increased the strength to (43.2+/-4.1)MPa. The work-of-fracture (WOF) (toughness) was also increased by two orders of magnitude. After 84 d immersion in a simulated physiological solution, the meshes in CPC dissolved and formed interconnected cylindrical macropores. The novel CPC scaffold had a flexural strength 39% higher, and WOF 256% higher than the conventional CPC without macropores. The new composite had an elastic modulus within the range for cortical bone and cancellous bone, and a flexural strength higher than those for cancellous bone and sintered porous hydroxyapatite implants. In conclusion, combining two different reinforcing agents together in self-hardening CPC resulted in superior synergistic strengthening compared to the traditional use of a single reinforcing agent. The strong and macroprous CPC scaffold may be useful in stress-bearing craniofacial and orthopaedic repairs.
A self-hardening calcium-phosphate cement (CPC) containing Ca(4)(PO(4))(2)O and CaHPO(4) has been shown in clinical studies to be efficacious for repairing bone defects. This and several other similar CPCs harden in 10 min with the use of a phosphate solution as the liquid and form hydroxyapatite (HA) as the product. The present study investigated the properties of water-free, glycerol-containing CPC pastes that are stable in the package and would harden only after being delivered to a defect site where glycerol-tissue fluids exchange occurs. Premixed CPC pastes were prepared by combining cement liquids containing glycerol and various amounts of hydroxypropyl methylcellulose/Na(2)HPO(4), with CPC powders that contained (1) Ca(4)(PO(4))(2)O and CaHPO(4), (2) alpha-Ca(3)(PO(4))(2) and CaCO(3), or (3) CaHPO(4) and Ca(OH)(2). The hardening times and 1-d and 7-d diametral tensile strengths were measured on samples that hardened in an in vitro model that allowed exchange of glycerol and physiologic-like solution (PLS) through fritted glass slides at 37 degrees C. All pastes had excellent washout resistance; they remained intact and hardened while immersed in PLS and formed HA as products. Newman-Keuls multiple comparison tests indicated that the Na(2)HPO(4) amount, not the hydroxypropyl methylcellulose (HMC) amount, significantly (p < 0.05) affected the strength and hardening time. Although the premixed CPCs generally have longer hardening times and lower strengths, these pastes have excellent washout resistance before hardening and can be prepared in advance under well-controlled conditions.