Effect on Hydration and Hardening of Tricalcium Phosphate Bone Cement

The bioactive α-Ca3（ PO4 ）2 bone cement was studied by XRD , SEM and isothermal calorimetric measurements. The results showed that a mixed pattern of TCP and hydroxylapatite were obtained after hydration and hardening. The mechanism of hydration and hardening of the α-Ca3 （ PO4）2 was dissolution-precipitation, （ NH4 ） 112 PO4 was the best set accelerator to the α-Ca3 （ PO4）2 cement, and the HAP powers and the （ NH4）H2 PO4 concentration had a great effect on the hydration rate of a-Ca3（ PO4）2.

Effect of Phosphorus and Fluorine on Hydration Process of Tricalcium Silicate and Tricalcium Aluminate

By means of hydration heat, XRD and SEM, effect of phosphorus and fluorine （P205 and F-） in phosphorous slag on hydration process of tricalcium silicate （C3S） and tricalcium aluminate （C3A） was explored. The results indicated that the early hydration exothermic rate of C3S and C3A was obviously lowered by P205 and F- in phosphorous slag, the second peak occurring time of C3A was delayed by 0.9 h, the exothermal output of C3S was reduced by 25.04% and the time of accelerating stage was postponed by 0.86 h. The early hydration degree of C3S and C3A was also decreased. Due to the influence of P205 and F, more pores and thinner crystals can be observed in the microstructure of hardened paste and the chance of cracks was reduced.

Effect of Borax on Hydration and Hardening Properties of Magnesium and Pottassium Phosphate Cement Pastes

Magnesium and potassium phosphate cement （MKPC） sample were prepared by mixing dead burnt MgO powder, potassium phosphate and different dosages of retarder borax to investigate the effect of borax on its hydration and hardening characteristics. The pH value, fluidity, hydration temperature and strength development of MKPC paste were investigated, and the mineralogical composition and microstructural morphology of its hydration products were analyzed. The experimental results indicated that, within a certain dosage, borax caused an endothermal effect for MKPC paste, which decreased the early hydration rate of MKPC paste, increased the fluidity of MKPC paste. Thus, strength and micro-morphology of hardened MKPC are affected. It can be concluded that borax in MKPC paste retards the early hydration rate of MKPC paste by forming a film onto surface of MgO, decreasing the temperature and increasing the pH value of the system. As borax dosage varying, different factors may dorminate the effects.

Influence of Alkalis Doping on the Hydration Reactivities of Tricalcium Silicate

Influences of alkali oxides doping on the crystal structure, defects and hydration behavior of tricalcium silicate C_3S were investigated by X-ray powder diffraction with the Rietveld method, inductively coupled plasma optical emission spectroscopy, thermoluminescence and isothermal calorimetry. All the samples were stabilized as T1 form C_3S. Changes in the crystal structure of C_3S could mainly be monitored by changes in lattice parameters, which were closely correlated with the incorporation concentration and substitution types of alkalis. Although alkalis were incorporated at trace level in C_3S, the thermoluminescence and hydration behavior of C_3S were significantly influenced. Initial hydration activity was dramatically increased and highly related to the intensity of the irradiation-induced thermoluminescence peaks at low temperatures due to their direct correlation with defects. The oxygen vacancy sites resulting from the substitution of alkalis for Ca could readily account for the acceleration of the initial hydration of C_3S.

Preparation and properties of β-tricalcium phosphate porous bioceramic

Porous β-tricalcium phosphate bioceramic （PTCP） has important roles in surgical implants because of good biocompatibility. But the low compressive strength of the ceramic limits its application. The preparation of PTCP was improved with the adjustment of the constituents and the sintering-process. A new type of PTCP material with high compressive strength was made. The compositions, microstructure and properties of PTCP were analyzed by TG-DSC, XRD, TEM, SEM and so on. The result indicates that stearic acid burns sufficiently and gives out carbon dioxide and water vapor when slowly heated between 200 ℃ and 400 ℃ so that the porous structure like coral in β-TCP bioceramic is formed. Through crystallization at 470 ℃ and 570 ℃, more CaO-P2O5 glass-cement is converted into crystallite-glass, which is beneficial for improving the compressive strength of β-TCP bioceramic. PTCP can form a support action in bone imperfect section with good solubility.

Effect of coral sand on the mechanical properties and hydration mechanism of magnesium potassium phosphate cement mortar

Damaged structures on coral islands have been spalling and cracking due to the dual corrosion of tides and waves.To ensure easy access to aggregate materials,magnesium potassium phosphate cement(MKPC)and coral sand(CS)are mixed to repair damaged structures on coral islands.However,CS is significantly different from land-sourced sand in mineral composition,particle morphology,and strength.This has a substantial impact on the hydration characteristics and macroscopic properties of MKPC mortar.Therefore,in this study we investigated the compressive strength,interfacial mechanical properties,and corrosion resistance of MKPC CS mortar.Changes in the morphology,microstructure,and relative contents of hydration products were revealed by scanning electron microscope-energy dispersive spectrometer(SEM-EDS)and X-ray diffraction(XRD).The results indicated that the compressive strength increased linearly with the interfacial micro-hardness,and then stabilized after long-term immersion in pure water and Na2SO4 solution,showing excellent corrosion resistance.Compared with MKPC river sand(RS)mortar,the hydration products of CS mortar were an intermediate product 6KPO2·8H2O with a relative content of 3.9%at 1 h and 4.1%at 12 h.The hydration product MgKPO_(4)·6H_(2)O increased rapidly after 7-d curing,with an increased growth rate of 1100%.Our results showed that CS promoted the nucleation and formation of hydration products of MKPC,resulting in better crystallinity,tighter overlapping,and a denser interfacial transition zone.The results of this study provide technical support for applying MKPC mortar as a rapid repair material for damaged structures on coral islands.

Effects of Molecular Structure of Polycarboxylate-type Superplasticizer on the Hydration Properties of C_3S

Effects of polycarboxylate-type superplasticizer（PC） molecular structure on the hydration heat of tricalcium silicate（C3S） paste and polymerization degree of hydration products（C-S-H gel） were researched by using TAM AIR isothermal microcalorimetry（TA） and 29Si nuclear magnetic resonance（NMR）.Methoxy polyethylene glycol-methacrylates-based polycarboxylate superplasticizers with different side chain lengths and main chain lengths were employed.PC molecules with shorter main chain or longer side chains caused stronger retardation of C3S early hydration and lesser increase of C3S 3 d hydration degree.NMR measurement indicated that the incorporation of PC increased the hydration degree of C3S paste and the polymerization degree of silicon-oxygen tetrahedron of C-S-H gel.The tendency for C3S 7 d hydration degree to improve was more pronounced while PC molecules with longer main chain or shorter side chain were added.Whereas,PC molecules with longer main chains or longer side chains increased the 7 d polymerization degree of C-S-H gel.

Biodegradation of Tricalcium Phosphate Ceramics by Osteoclasts

Biodegradation of tricalcium phosphate (TCP) ceramics was observed through mixed culture of osteoclasts and TCP discs in vitro in this study. Osteo-clasts were isolated from newborn SD rat's marrow of long bone and cultured on TCP discs. The culture terminated at the 48th h and 96th h respectively. Under an inverted microscope, the osteoclasts imparted round or oval body with multinu-clear and many thin processes. These cells were positively stained for tartrate-re-sistance acid phosphatase (TRAP). Scanning electron microscope showed that many resorption lacunae on TCP disc surface and their diameters were smaller than 20 μm. Osteoclasts were located in the lacunae. At the 96th h, the resorption lacunae become larger and osteoclasts showed degeneration. It is suggested that osteoclasts possess ability to re-absorb TCP ceramics under in vitro culturing condition.

Osteogenesis process of tricalcium phosphate ceramics in vivo

To investigate the osteogenesis of calcium phosphate ceramics, β-TCP ceramics were implanted into the condyle femur of rabbits, and tetracycline was injected termly. Specimens were host at 1, 2, 3, 4, 5, 6 months after implanted. The new bone formation and osteogenesis process were observed by the histomorphology, fluorescent microscope, SEM and EPMA. The results demonstrate that, osteogenesis is active, there are abundant osteoblasts on the surface of osteoid, mesenchymal cell hyperplasia and incursion is found in materials after 1 month. After 2 months, there is blood vessel formation and macrophage soakage within materials. Bone-island appears and connects by bone-bridge after 3 months. β-TCP ceramics degrade and are dispersed by new formation bone. Woven bone turns into bone lamella by rebuilding and calcification. The materials entirely change their original shape and combines with bone tissue as a whole after 6 months. The typical structure of spongy bone forms. It is confirmed that β-TCP is a degradable biocompatible artificial bone material which can incorporating in life.

Characterization of tricalcium phosphate solubilization by Stenotrophomonas maltophilia YC isolated from phosphate mines

The phosphate solubilizing characteristics of a strain YC, which was isolated from phosphate mines (Hubei, China), were studied in National Botanical Research Institute’s phosphate (NBRIP) growth medium containing tricalcium phosphate (TCP) as sole phosphorus (P) source. The strain YC is identified as Stenotrophomonas maltophilia (S. maltophilia) based upon the results of morphologic, physiological and biochemical characteristics and 16S rRNA sequences analysis. The results show that the strain S. maltophilia YC can solubilize TCP and release soluble P in NBRIP growth medium. A positive correlation between concentration of soluble P and population of the isolate and a negative correlation between concentration of soluble P and pH in the culture medium are observed from statistical analysis results. Moreover, gluconic acid is detected in the culture medium by HPLC analysis. It indicates that the isolate can release gluconic acid during the solubilizing experiment, which causes acidification of the culture medium and then TCP solubilization. S. maltophilia YC has a maximal TCP solubilizing capability when using maltose as carbon source and ammonium nitrate as nitrogen source, respectively, in NBRIP growth medium.

Hydroxyapatite/β-tricalcium Phosphate Composite for Guiding Bone Tissue Growth into a Titanium Tube in 8 mm Dog Tibia Cavity Defects

We developed a fixation method and evaluate bone regrowth in the cavities of a Ф4 mm× 8 mm titanium（Ti）tube through porous hydroxyapatite（HAP）/β-tricalcium phosphate（β-TCP）composite filling（group A）,chitosan/calcium phosphate composite filling（group B）,and HAP particle modification（group C）.After 2 and 5 months of implantation in dog tibia defects,new bone formation in the three groups was studied by histology and histomorphometry.Group A displayed the most bone regenerated area in both 2 and 5 months post-operation.The chitosan/calcium phosphate composite in group B mostly degraded 2 months after implantation,leading to fibrous tissue invasion after 5 months.By contrast,less bone formation was observed in group C.These results indicated that filling the cavities of metalprostheses with a porous HAP/β-TCP composite can be used for stable long-term fixation in clinicalsettings.

Osteoinduction and Osteoconduction with Porous Beta-Tricalcium Phosphate Implanted after Fibular Resection in Humans

Osteoinductive properties of β-TCP remain unknown in humans. It is important to improve the bone grafts which have been the standard treatment for bone defect due to their biocompatibility and bone-healing properties. The purpose of this study was to radiologically clarify the bone forming property of β-TCP by evaluating the replacement of β-TCP by newly formed bone in the defect after fibular resection and to examine the histological features of a β-TCP specimen three months after grafting. Radiographs of 17 patients who underwent β-TCP grafting were evaluated. Osteoinductive and osteoconductive properties were assessed by examining bone formation from the remnant fibula, periosteum, and β-TCP alone. In one case, β-TCP was removed later because of postoperative complications and was evaluated histologically. Twenty two of 34 sites between the remnant fibula and β-TCP had achieved good bone regeneration. Five of 14 sites between the periosteum and β-TCP had achieved good bone regeneration. We found immature but evident bone formation in three cases with no osseous and periosteal sites. Histological analysis revealed bone formation on the outer macropore surface of β-TCP. Some blood vessels formed in the macropores expressed CD31 and CD34, while a few lymphatic vessels expressed CD34 and podoplanin. Thus, the osteoinductive ability of β-TCP alone was demonstrated in humans radiographically for the first time. The histological morphology of β-TCP was demonstrated at an early stage after grafting in humans.

The Role of Microstructure of Highly Purified Beta-Tricalcium Phosphate for Osteoinduction in Canine Dorsal Muscles

Porous β-tricalcium phosphate (TCP) displays osteoinductivity in certain animals in the absence of osteoinductive agents. We evaluated whether the microstructure may be an important determinant of osteoinduction, and also investigated how bone formation was promoted using β-TCP combined with bone marrow aspirates. We prepared two types of β-TCP, namely, β-TCP A, which possessed interconnected macropores and micropores, and β-TCP B, which possessed macropores but had less detectable micropores. These were implanted with or without marrow in canine muscles. Bone formation and the resorption of each β-TCP implant were evaluated histologically. Newly formed bone began to appear at day 42 in the implants of β-TCP A alone, but the implants of β-TCP B alone did not show any bone formation by day 42. Meanwhile, bone formation was already evident on day 14 by loading with bone marrow aspirates with or without micropores. By immunohistochemistry, the number of cathepsin K-positive cells (osteoclasts) increased as time passed in the implants of β-TCP A alone, while the number of the osteoclasts did not change obviously in the implants of β-TCP B alone from day 14 to 56. Reticular fibrils were evident within the β-TCP A, and were barely observed in the β-TCP B in the silver impregnation. The present result would bring about the possible role to enhance the importance of the surface microstructure for the better osteoinductivity. Our findings suggest that the combination of porous β-TCP and bone marrow facilitates bone formation.

Sustained release of Semaphorin 3A from a-tricalcium phosphate based cement composite contributes to osteoblastic differentiation of MC3T3-E1 cells

The reinforcement of calcium phosphate materials with silk fibroin （SF） has been one of the strategies to overcome the brittleness. However, the lack of osteoinductivity may still restrict their further use. This study aimed to investigate the biocompatibility and osteogenesis capacity of a novel Semaphorin 3A-loaded chitosan microspheres/SF/a-tricalcium phosphate composite （Sema3A CMs/SF/a-TCP） in vitro. Sema3A was first incorporated into CMs, and the Sema3A CMs/SF/a-TCP composite was then prepared. The morphology of the CMs was observed using SEM. The in vitro release kinetics, cytotoxicity, and cell compatibility were evaluated, and the real-time quantitative polymerase chain reaction （RT-qPCR） and activity of alkaline phosphatase （ALP） were used to evaluate the osteogenesis capacity of the composite. The in vitro release of Sema3A from the Sema3A CMs/SF/a-TCP composite showed a temporally controlled manner. The extract of the Sema3A CMs/SF/a-TCP composite presented no obvious side effect on the MC3T3-E1 cell proliferation, nor promote cell proliferation. The MC3T3-E1 cells were well-spread and presented an elongated shape on the Sema3A CMs/SF/a-TCP composite surface; the ALP activity and the osteogenic-related gene expression were higher than those seeded on the surface of the CMs/SF/a-TCP and SF/a-TCP composites. In conclusion, Sema3A CMslSF/a-TCP has excellent biocompatibility and contributes to the osteoblastic differentiation of MC3T3-E1 cells.

Osteogenesis and Degradation Behavior of rhBMP-2／β-Tricalcium Phosphate Porous Composite Materials

Ultrafine-tricalcium phosphate(β-TCP)powders with good crystalline structure were produced by a new process through bone tissue engineering approach rorous β-TCPcermic was combined with recombined human bone morphogenetic proteins-2(rhBMP-2)to develop a novel composite material ,osteogenesis capacity of the composite was investigated intramuscularly in rat with histological analyses and SEM examination pureβ-TCP porous carmic wsa investigated as the control results show that the compostie materials possess good bilcompatibility biodegradation and strong osteogenesis capacity through inductive process after implantation material degradation began from 2 weeks post-implantation accompanying with the changing o pore structure with the enwrapping and separation fo materials by hyperplatic mesenchymal cells and fibroblast and with the phagocytose reaction of multinucleated giant cells early in 72h immature cartilage could be found within novel composite mature lamellar bone was induced to generate after 3 weeks with strong osteoinduction capacity and controlable bildegradation the novel rhBMP-2\β-TCP porous ceramic is expected to be a promising bone grafting substitute for bone tissue engineering

The Bacterial Inhibitory Ability and In Vivo Drug Release Pattern of a New Drug Delivery System:Ciprofloxacine/tricalcium Phosphate Delivery Capsule

The bacterial inhibitory ability of a new drug delivery system (DDS):Ciprofloxacine/tricalcium phosphate delivery capsule (CTDC), its in vivo drug release pattern, and the influence of ultrasonic irradiation on its drug release were investigated. It was found that CTDC had a strong and sustained inhibitory ability to some common pathogens of bone and joint infections, such as staphylococcus aureus, escherichia coli and pseudomonas aeruginosa. In vivo drug-release study in animals demonstrated a high concentration of ciprofloxacine in the bone tissue surrounding CTDC which was placed in the greater trochanter of the rabbit and continued to release ciprofloxacine for at least 5 weeks and the blood level of ciprofloxacine was low. In vivo study also showed ultrasonic irradiation could increase the amount of ciprofloxacine released from CTDC, which may be an economical, effecient and safe new method to achieve the control of drug release from DDS.

The Experimental Study on Mixed Culture of Osteoblasts and Tricalcium Phosphate Ceramics In Vitro

To study the effects of tricalcium phosphate (TCP) ceramics on osteoblasts, the rat osteoblasts were cultured with the TCP ceramics in vitro . Scanning electron microscopy and the colorimetric methyl thiazol tetrazolium assay showed that the osteoblasts could adhere well to the surface of the ceramics and the culture dish, and the proliferation of the cells was not inhibited. The results demonstrated that TCP ceramics possessed an excellent cytocompatibility with the osteoblasts, and had some promoting effects on proliferation of osteoblasts.

Expression of TGF-β in Region of Bone Defect Repaired by Collagen/Nano-beta-Tricalcium Phosphate Composite Artificial Bone

The distribution and function of transforming growth factor-beta (TGF-β) in the region of bone defect repaired by collagen/nano-beta-tricalcium phosphate composite artificial bone (Co/N-TCP) and the ability of Co/N-TCP recruiting osteoblasts to precipitate the repair of bone defect were investigated Twenty-four domestic rabbits were operated on bilateral cranial bone to create an experimental bone defect of 8 0 mm in diameter through the whole bone On the left, Co/N-TCP was implanted as experimental group, but on the right, Co/TCP was implanted as control group At 2nd, 4th, 8th, 12th week after operation, all animals were sacrificed and the implanted materials with surrounding bone were taken out Immunohistochemical staining was performed for TGF-β assay by avidin-biotin complex method (SABC) Simultaneously, TGF-β was quantitatively analyzed by HPIAS-1000 imaging analysis system The inmmunohistochemical staining for TGF-β revealed that osteoblasts and immature osteocytes highly expressed TGF-β Diffused TGF-β positive staining particles appeared in the mesenchymal and fibrous-tissue There was no significant difference in the TGF-β positive staining between two groups in the medial region to original osseous beds at different time points ( P >0 05) However, in distal original osseous bed of the defected region, the positive expression of TGF-β in the Co/N-TCP group was significantly stronger than in the control group ( P <0 05 or 0 01) The Co/N-TCP has good bioactivities and ability of stimulating and conducting TGF-β to aggregate and precipitate the healing of bone defect