Transition element contained partial-stabilized cement (PSC) as a dental retrograde-filling material

A modified silicate cement has previously been developed as a dental retrograde filling; it has great sealing ability, good biocompatibility, and anti-bacterial properties. However, its clinical application is limited by a long setting time and poor handling property. In the present study, the setting time has been shortened by raising the preparation temperature of the cement and adding transition elements into the partial-stabilized cement (PSC) to increase the rate of hydration reaction of the cement. The rate of the hydration was evaluated by micro-hardness measurement. Phase transformation and micro-structure were examined by an X-ray diffractometer and a scanning electron microscope, respectively.When the preparation temperature increased (1400 degrees C), the phase content of Ca(2)SiO(5)(C(2)S) and Ca(3)SiO(6)(C(3)S) increased but the CaO decreased. The setting time was shortened and the micro-hardness increased because the increased amplitude of vibration of the atoms about their equilibrium resting positions increased by increasing the heating temperature. When the transition elements were added to PSC, crystal defects were effectively created and monoclinic structure of C(3)S was favored to form, which would increase the hydrated reaction of PSC and shorten the setting time. Co addition is the most effective due to its ability to create more defects and stabilize the monoclinic structure. The micro-hardness of the PSC with Co 5 wt% addition was about 66 in the Vickers scale. It also exhibited an early setting within 20 min. We believe that the modified PSC will have a great potential in its application to perforation repair and retrograde filling in endodontic surgery.     

Effects of root-end filling materials and eugenol on mitochondrial dehydrogenase activity and cytotoxicity to human periodontal ligament fibroblasts

Various root-end filling materials have been used to prevent the entry of root-canal pathogens into periapical regions. Five root-end filling materials were compared regarding the cytotoxicity, apoptosis, and mitochondrial dehydrogenase (MDH) activities of human periodontal ligament (PDL) fibroblasts, with the use of a novel transwell culture system. Exposure to IRM (a ZnO eugenol-based intermediate restorative material), a 2-ethoxybenzoic acid cement (Super EBA), and amalgam for 3 days inhibited the MDH activity of PDL fibroblasts as indicated by decrease in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) reduction by 97%, 95%, and 51%, respectively. Evident suppression of MTT reduction by amalgam and glass ionomer cement (GIC) was noted after 5 days of exposure, with 73% and 46% of inhibition, respectively. Mineral trioxide aggregates (MTA) showed little effect on MDH activity. IRM and Super EBA were cytotoxic to PDL fibroblasts as indicated by a trypan blue dye exclusion technique. GIC and amalgam showed mild cytotoxicity. IRM, GIC, and amalgam further induced apoptosis of PDL cells, as revealed by the presence of sub-G0/G1 DNA content in flow cytometric histogram. Twenty-four-hour exposure to IRM and Super EBA elevated the MDH activities to 156% and 117%, correspondingly, of that of control. Eugenol, a phenolic ingredient in Super EBA and IRM, also increases MDH activity of PDL fibroblasts by 45% and 51%, at concentrations of 0.5 and 1 mM. However, at concentrations higher than 0.5 mM, eugenol decreased the number of viable PDL fibroblasts. These results suggest that MTA is a biocompatible root-end filling material, followed by self-curing Fuji II GIC and amalgam. IRM and Super EBA ingredients induced marked cytotoxicity and transiently stimulate MDH activities, which is possibly due to their content of eugenol and induction of cellular adaptive response.     

Inflammatory cytokines reaction elicited by root-end filling materials

Cytokines are inflammation in the list of tissue reactions that cytokines control of cell and tissue growth, development, and differentiation. Root-end filling materials often contact with existing periapical tissue, and they need to be biocompatible with remnant periapical tissue. The aim of this study was to focus the effects of the root end filling materials on bone cell viability and expression of inflammatory cytokines and their role in maintaining health and stability of the restored dental tissues. Calcium hydroxide-based (Life), zinc oxide eugenol-based (Super EBA), and mineral trioxide aggregate-based (MTA) root-end filling materials were used to investigate their effect on a human osteosarcoma cell line (U2OS). The cell attachment assay was observed microscopically, and the expression of interleukin-2, -4, and -10 were quantified by enzyme-linked immunosorbent assay. Any resultant difference between the root-end filling material was analyzed statistically by one-way analysis of variance. The results showed that the best cell attachment to root-end filling material occurred with MTA. The IL-4 (0.824 +/- 0.396) and IL-10 (2.06 +/- 1.24) levels were greater for the MTA group, whereas IL-2 expression for the three kinds of root-end filling materials was similar. All materials were able to induce expression of inflammatory cytokines from cultured bone cells.     

Sealing ability of a novel endodontic cement as a root-end filling material

This study investigated the potential usage of novel endodontic cement (NEC) as a root-end filling material by comparing its sealing ability with that of mineral trioxide aggregate (MTA) and intermediate restorative material (IRM). Sixty-six single rooted extracted human teeth were cleaned, shaped, and obturated in a similar method. After root-end resection, 3-mm deep root-end cavities were ultrasonically prepared. The samples were divided randomly into 3 test groups, having 20 roots each. Six roots were used as positive and negative controls. Samples were filled with test materials and after one day were immersed in methylene blue dye for 24 h. Roots were sectioned longitudinally and examined under stereomicroscope. Positive and negative controls responded as expected. The increasing order of mean dye microleakage values was NEC < MTA < IRM. ANOVA test showed statistically significant differences among experimental groups (p < 0.001). Tukey's test revealed no significant difference between NEC and MTA. It was concluded that the sealing ability of NEC and MTA is the same and superior to IRM.     

A novel injectable bioactive bone cement for spinal surgery: a developmental and preclinical study

The injection of bone cement by minimally invasive techniques for the treatment of vertebral body fractures or for stabilization of an osteoporotic vertebral body is regarded as promising in spinal surgery. The purpose of this study was to develop a novel injectable bioactive bone cement to address such concerns. The cement was composed mainly of strontium-containing hydroxyapatite (Sr-HA) filler and Bisphenol A Diglycidylether Dimethacrylate (D-GMA) resin. The Sr-HA filler was prepared by precipitation and calcination, then analyzed with Fourier transform infrared (FTIR) spectra and X-ray diffraction (XRD) patterns. Samples of strontium-containing hydroxyapatite cement (SrHAC) were formed by a combination of powder filler and resin matrix, with the setting time and peak temperature recorded. Cell relative growth rate (RGR), Tetrazolium bromide (MTT), and haemolysis tests were used to detect initial in vitro biocompatibility of the new cement. In vitro spinal biomechanical testing and morphological observation after bone cement injection were performed on pig spines. Results indicate that the setting time and peak temperature of the cement was 15 min and 55 degrees C, respectively. Cytotoxicity of the cement was class 1 (no cytotoxicity) and haemolysis was 1% (no haemolysis). Stiffness after cement injection and fatigue loading were 112% and 95% of the intact bone, respectively, which is similar to that of natural bone. Radiopacity of SrHAC allowed easy radiographic imaging. The use of SrHAC cement is, thus, promising in spinal surgery.     

磷酸钙骨水泥的改性研究进展

磷酸钙骨水泥作为一种新型人工骨替代材料 ,以其良好的生物相容性和骨传导性被广泛应用于临床骨缺损修复。但其存在固化时间较长、机械性能不足及降解缓慢等缺点 ,使其应用受到一定限制 ,故需要对其进行改性研究 ,本文就此做一综述如下     

Surface characterization and cell response of a PLA/CaP glass biodegradable composite material

Silicate-based filling materials were designed to obtain new endodontic sealers and root-end filling materials with adequate workability and consistency. Four different formulations (TC, TC 1%, TCf 1%, and TCf) were prepared incorporating calcium chloride as accelerant agent. A plasticizing compound (phyllosilicate) was added to TC 1% and TCf 1%. TC and TC 1% were prepared with water, whereas TCf and TCf 1% were mixed with a latex polymer as fluidizing agent. The aim of this study was to assess the in vitro biological compatibility of designed materials. White-MTA and AH Plus were tested as reference materials. Human osteoblast-like Saos-2 cells were challenged in short-term cultures (72 h) with solid materials and with material extracts in culture medium, and cell viability and number, cellular adhesion, and morphology were assessed. The new cements exerted no acute toxicity in the assay systems. Saos-2 like cells adhered and proliferated on solid samples of the experimental cements and MTA whilst AH Plus did not allowed cell growth. The extracts from the latex-containing cements showed some toxicity. By SEM analysis, osteoblast-like cells appeared adherent and spread on the new materials, and showed the maintenance of polygonal osteoblastic phenotype. Similar morphology was observed for cells on MTA, whereas only few cells were noted on the AH Plus surface. In conclusion, the new materials proved non toxic and supported the growth of bone-like cells, and resulted suitable to be used as endodontic sealers and root-end filling materials.     

新型复合壳聚糖季铵盐纳米粒子抗感染骨水泥的生物学特性

BACKGROUND: Postoperative infection in patients underlying total knee arthroplasty is a long-standing puzzle. Current bone cement with antibiotics cannot effectively treat kidney function deficiency and bacterial resistance. OBJECTIVE: To develop a novel kind of bone cement prepared by quaternary ammonium salt chitosan nanoparticles. METHODS: There were three groups including QCSNP-15, Palacos R and Palacos R+G groups. Morphology of the bone cement in each group was observed using scanning electron microscope, the setting time of bone cement was measured, and the in vitro compression strength, cytotoxicity and antibacterial activity tests were performed. RESULTS AND CONCLUSION: Scanning electron microscope observed that QCSNP-15 was made of quaternary ammonium salt chitosan nanoparticles and methyl methacrylate copolymer, and these nanoparticles distributed onto the material surface. The setting time of QCSNP-15 was longer than that of the Palacos R+G bone cement. The compressive strength of QCSNP-15 was significantly lower than that of the Palacos R bone cement (P < 0.05), but was larger than 70 MPa stipulated by ISO 5833. Osteoblasts MC3T3-E1adhered well on the QCSNP-15, and pseudopodia fully expanded. Similar findings were observed on the Palacos R+G bone cement. The attachment rate of osteoblasts of the QCSNP-15 at 3 hours was significantly lower than that of the Palacos R+G bone cement (P < 0.05). The antibacterial activity did not significantly differ between QCSNP-15 and Palacos R+G bone cements, even after 2-week immersion in the PBS. These findings suggest that QCSNP-15 exhibits appropriate setting time, good biomechanical property and antibacterial activity in vitro with no obvious cytotoxicity.     

Biocompatibility of human osteosarcoma cells to root end filling materials

Ideal root end filling materials should have good physical and chemical properties, and the most important is that the material should be biocompatible with periradicular tissue. The biocompatibility of three root end filling materials, mineral trioxide aggregate, calcium hydroxide-based cement, and eugenol-based cement, were investigated in vitro by culturing extracts of these materials with human osteogenic sarcoma cells (U2OS). Extracts of each of the materials were made after incubation of the materials for 1 day and 1 week with complete McCoy's medium. The extracts were serially diluted and then incubated with U2OS cells for 24 and 48 h. Cell survival rates were assessed by means of a viability assay for mitochondrial dehydrogenase activity. Differences in mean cell survival rates were statistically assessed using one-way ANOVA. Results showed that the survival rates of U2OS cells were largest with mineral trioxide aggregate, followed by calcium hydroxide-based cement and eugenol-based cement at 24- and 48-h exposures using the 1-day and 1-week extracts. The duration of root end filling material extraction time and treatment time showed variable influence on the survival rates. The results suggest that mineral trioxide aggregate is more biocompatible than the other root end filling materials and is suitable for use in the clinical setting.     

Liquid-solid phase transition alloy as reversible and rapid molding bone cement

Acrylic bone cement has been an essential non-metallic implant used as fixing agent in the cemented total joint arthroplasty (THA). However, the currently available materials based mainly on polymethylmethacrylate (PMMA) still encounter certain limitations, such as time-consuming polymerization, thermal and chemical necrosis and troublesome revision procedure. Here from an alternative way, we proposed for the first time to adopt the injectable alloy cement to address such tough issues through introducing its unique liquid–solid phase transition mechanism. A typical cement along this way is thus made of an alloy Bi/In/Sn/Zn with a specifically designed low melting point 57.5 °C, which enables its rapid molding into various desired shapes with high plasticity and ultimate metallic behaviors. The fundamental characteristics including the mechanical strength, biocompatibility and phase transition-induced thermal effects have been clarified to demonstrate the importance of such alloy as unconventional cement with favorable merits. In addition, we also disclosed its advantage as an excellent contrast agent for radiation imaging on the bone interior structure which is highly beneficial for guiding the surgery and monitoring the therapeutic effects. Particularly, the proposed alloy cement with reversible phase transition feature significantly simplifies the revision of the cement and prosthesis. This study opens the way for employing the injectable alloy materials as reversible bone cement to fulfill diverse clinical needs in the coming time.     

Generic tendency of metal salt cytotoxicity for six cell lines.

Systematic cytotoxicity evaluation of various metallic elements may contribute to the development of new metallic biomaterials with superior biocompatibility. It is generally reported that the cytotoxicity of a chemical differs with cell lines. However, our previous study revealed a high correlation in the cytotoxicity of 43 metal salts between two murine cell lines. If there is any generic tendency toward metal salt cytotoxicity for many kinds of cells, that information is helpful for the determination of the chemical composition of new metallic biomaterials that are expected to have lower cytotoxicity. In this study, the cytotoxicity of 12 metal salts was evaluated using four cell lines, and the results were compared, including those for two other cell lines obtained in our previous study. A metal salt concentration that reduced cell viability to 50% of that without any metal salt (IC(50)) was used as an index to compare the metal salt cytotoxicity between cell lines. The correlation was statistically proved by the IC(50)s of 12 metal salts among these cell lines (p < 0.01), suggesting the existence of a generic tendency to metal salt cytotoxicity beyond cell lines. The metal salt order of toxicity from the highest was K(2)Cr(2)O(7), AgNO(3), VCl(3), SbCl(3), CuCl(2), CoCl(2), NiCl(2), ZnCl(2), Cr(NO(3))(3), FeCl(3), TiCl(4), and Al(NO(3))(3). The sensitivity for metal salt cytotoxicity differed with cell lines; IMR-32 had the highest sensitivity among the six cell lines.     

Evaluation of a new press-fit in situ setting composite porous scaffold for cancellous bone repair: Towards a “surgeon-friendly” bone filler?

In this study, a composite porous material obtained by coating a poly(ester urethane) foam with a calcium phosphate cement is proposed as novel cancellous bone filler with easy handling, in situ hardening and press-fitting properties. The coating can be applied to the foam in the surgical theater, allowing refinement of scaffold shape to the needs of the ongoing surgery. An innovative experiment was developed in order to determine the setting curve of the composite scaffold as well as the time of manipulation available to the surgeon without risk of material damage. This composite material is soft and can be press-fit in a cavity without damaging the scaffold in the first 5 min after coating application. The composite scaffold hardens quickly (22 min) and, once the cement has set, its compressive strength and fracture energy are increased by over an order of magnitude as compared to the initial poly(ester urethane) foam. This set of interesting properties makes calcium phosphate cement-coated elastomeric scaffolds a new promising strategy for cancellous bone filling.     

Influence of mixing method on the cement temperature-mixing time history and doughing time of three acrylic cements for vertebroplasty

Acrylic cements are increasingly being used to augment osteoporotic vertebrae in a procedure called vertebroplasty. Two significant factors that may complicate the use of acrylic cements are: (a) short handling time, which may result in insufficient filling of the vertebra; and (b) exothermic setting (curing) behavior, which may result in thermal damage of the surrounding tissue. It has been previously reported that mixing the cement components under oscillation, as compared to manual mixing, increases the handling time. More specifically, it seems that oscillatory mixing slows down the cement polymerization process and, consequently, widens the time window during which cement is injectable. However, the effect of oscillatory mixing on the exothermic setting behavior of cement undergoing polymerization has not been examined. In this study, the exothermic setting behavior of three commercially available acrylic cements--Antibiotic Simplex, DP-Pour&trade, and Vertebroplastic--were examined for both manual and oscillatory mixing methods. For each combination of cement and mixing method, the parameters that were measured were the exothermic setting curve (and hence the cement setting temperature and setting time) and the cement doughing time. It was found that oscillatory mixing had no significant effect on any of these parameters. Based on the results of this study, it can be concluded that, for the tested cements, the setting process is a reaction-controlled process rather than a diffusion-controlled one. Clinically, this implies that oscillatory mixing may be used to increase the working period for acrylic cements without increasing the risk of thermal damage to surrounding tissue.     

复合N-乙酰半胱氨酸丝素蛋白磷酸钙骨水泥的理化性能及细胞毒性

BACKGROUND: Calcium phosphate cements (CPCs) possess the bio-degradation and osteoconduction, and its final hydration product, hydroxyapatite, is the main inorganic constituent of bones. However, its poor mechanical property makes it unable to be used for repairing weight-bearing bone defects. OBJECTIVE: To develop a kind of bioactive bone cements with decent biomechanical property and biocompatibility. METHODS: 6% silk fibroin aqueous solutions containing different concentrations of N-acetylcysteine (0, 10 and 25 mmol/L) were prepared. Each cement sample was prepared by mixing the curing liquid and α-tricalcium phosphate powder with the ratio of 0.4 mL: 1 g; α-tricalcium phosphate powder mixed with ddH2O as control group. The compressive strength, setting time of the cements were measured. The crystal components of the cements were characterized using X-ray diffraction and the microstructure was observed using scanning electron microscope. MC3T3-E1 cells were seeded onto the material in each group, and cell morphology was observed under scanning electron microscope at 24 hours. MC3T3-E1 cells were cultured in the extract of each material, cell proliferation was detected at 1, 3, 5 and 7 days, and the lactate dehydrogenase level was detected at 1 and 3 days. RESULTS AND CONCLUSION: X-ray diffraction and scanning electron microscope showed that the final hydration products of α-tricalcium phosphate in all specimens were hydroxyapatite. When the concentration of N-acetylcysteine was 25 mmol/L, the compressive strength of the material reached (49.39±1.68) MPa, with the initial setting time of (21.77±1.07) minutes and the final setting time of (31.88±1.69) minutes. There was no significant difference in cell morphology among cements. These results suggest that the cement containing N-acetylcysteine exhibites good biocompatibility and high mechanical strength.     

Impaired T and NK cell response of bone marrow and peripheral blood stem cell products to interleukin (IL)-2.

The function of steady-state and interleukin (IL)-2-co-cultured mononuclear cells differs significantly between bone marrow (BM) products, growth factor-mobilized peripheral blood stem cell (PSC) products and normal peripheral blood mononuclear cells (PBMC). The natural killer (NK) cell activity and T cell proliferative response of PSC products from non-Hodgkin's lymphoma (NHL) patients are significantly higher than that of BM products and similar to normal PBMC. However, following a five-day co-culture with IL-2 (100 IU/ml), the NK activity of PSC, PBMC, and BM products (lytic units) was increased 176-, 40-, and 14-fold, respectively, compared to that observed prior to IL-2 culture. In contrast, lymphokine activated killer (LAK) cytotoxicity prior to IL-2 culture was low in PSC and BM products and normal PBMC, but was significantly increased in PSC products and PBMC following IL-2 co-culture. The proliferative response of PSC and BM products to the T cell mitogen phytohemagglutinin (PHA) was significantly lower than that observed with normal PBMC; however, PSC had a significantly higher response than cells from BM products. Similar patterns of T cell PHA mitogenic response were observed after IL-2 co-culture. In addition, the IL-2 mitogenic responses of IL-2-co-cultured PSC and BM products were also significantly lower than that observed with PBMC co-cultured with IL-2. The IL-2 mitogenic response of PBMC was also significantly increased compared to prior to IL-2 co-culture; whereas, the IL-2 mitogenic responses from PSC and BM cells were not. In summary, co-culture with IL-2 can increase the NK and LAK cell cytotoxicity of PSC and BM products from NHL patients, but IL-2 co-culture does not improve T cell function within either BM or PSC products.     

新型氯化锂复合磷酸钙骨水泥的理化性能及成骨特性

BACKGROUND: Lithium chloride is a widely used inorganic ion inhibitor of glycogen synthase kinase-3β, and it can be combined with glycogen synthase kinase-3β to activate the classical Wnt/β-catenin pathway, thereby promoting human bone marrow mesenchymal stem cells and osteoblasts proliferation and accelerating bone repair. OBJECTIVE: To observe the physicochemical properties of novel lithium chloride/calcium phosphate cement, and to explore its osteoinductive biological property. METHODS: Calcium phosphate cement served as control group, and lithium chloride/calcium phosphate cement containing different lithium content as experimental groups. The setting time and compressive strength of bone cement in each group were detected, and the microstructure of the material surface observed under scanning electron microscopy. Bone cement and MC3T3-E1 cells were co-cultured in vitro, and the growth and adhesion morphology of MC3T3-E1 cells on the surface of bone cement were observed under the scanning electron microscope. Effect of bone cement extracts on cell proliferation was determined through MTT assay, and alkaline phosphatase kit used for determining alkaline phosphatase activity. RESULTS AND CONCLUSION: Lithium chloride/calcium phosphate cement had the same physicochemical properties to the calcium phosphate cement. Initial and final setting time, compressive strength and morphology of bone cement had no significant differences among groups. MC3T3-E1 cells grew and adhered well on the material surface. Results of MTT assay showed that compared with the calcium phosphate cement, the lithium chloride/calcium phosphate cement was better to improve osteoblast proliferation in vitro. In addition, the alkaline phosphatase activity in MC3T3-E1 cells was higher in experimental groups than the control group. These findings indicate that lithium chloride/calcium phosphate cement can maintain good physicochemical properties, and release lithium ions to promote bone formation.       

Physicochemical properties of TTCP/DCPA system cement formed in physiological saline solution and its cytotoxicity

In this paper, the physicochemical properties and cytotoxicity of calcium phosphate cement (CPC), prepared by mixing cement powders of tetracalcium phosphate (TTCP) and dicalcium phosphate (DCPA) with a cement liquid of physiological saline solution, were investigated. The microstructure evolution of various hardened cement bodies and their hydration crystals as a function of immersion time in similar physiological fluids, physiological saline solution (0.9% NaCl), or simulated body fluids (SBF), were also studied. Results show that the setting time of CPC is in the range of 12-15 min, which meets the clinical application demands. We also found that the mean compressive strength of the CPC samples immersed in SBF for 3 days is 104+/-10 MPa which reaches the transverse compressive strength, 106-133 MPa, of human long bone. The results obtained from both the X-ray powder diffraction analyses (XRD) and scanning electron microscopy (SEM) observations indicated that a reinforcing effect of some remaining TTCP particles in the early stages of immersion is mainly responsible for the increase in the initial strength. Although the CPC failed to keep this high level when immersed for a longer time, the initial reinforcing effect of the remaining TTCP particles provides advantages for clinical applications. This would be effective when the material is loaded at the very beginning of the implantation, especially for the material used as a fixation, which requires a certain initial strength in the early stages of the implantation. The cytotoxicity results showed that the relative growth rate (RGR%) of L929 cells on the CPC samples using physiological saline solution as a cement liquid was slightly superior to that of the samples using the 0.5 mol/L phosphate acid solution as the cement liquid. This was most likely caused by the pH difference between the two CPC samples immersed in a DMEM-BFS medium.     

Self-setting properties of a beta-dicalcium silicate reinforced calcium phosphate cement

Beta-dicalcium silicate was used to reinforce the injectable calcium phosphate cement (iCPC) for the first time in this study. The influence of the content of beta-dicalcium silicate on the mechanical properties, setting time, rheological properties, injectability, phase evolution, microstructure, and biodegradability of iCPC was systematically investigated. The results demonstrated that the addition of 8 wt % beta-dicalcium silicate obviously enhanced the compressive strength of the CPC from 26.5 to 47.5 MPa, and did not significantly influence the biodegradability, setting time, injectability, phase evolution, and microstructure of the CPC. The beta-dicalcium silicate-reinforced iCPC with relatively high mechanical property should have potential prospects for the wider applications in surgery such as orthopedics, oral, and maxillofacial surgery.     

Pigment epithelium derived factor (PEDF) prevents methyl methacrylate monomer-induced cytotoxicity in H9c2 cells

Acrylic bone cements are currently the most frequently and extensively used materials in orthopedic implant treatment. However, adverse effects have been described of acrylic bone cement on the cardiovascular system. In the present study, we examined the cytotoxicity of bone cement ingredient methyl methacrylate (MMA) to cardiomyocytes and the potential detoxifying effect of pigment epithelium-derived factor (PEDF) in H9c2 cells. We found that high concentration of MMA ( > 120 mmol/L) led to necrotic cell death in H9c2 cells. However, MMA at low concentrations (30-90 mmol/L) caused apoptosis. Pretreatment of PEDF prevented MMA-induced cytotoxicity. In addition, PEDF enhanced total superoxide dismutase activities, and decreased MMA-induced production of malonaldehyde. Furthermore, MMA-induced downregulation of Akt activity was suppressed by PEDF. PEDF also increased the levels of peroxisome proliferator activated receptor gamma (PPARg) and lysophosphatidic acids (LPA) through PEDF receptor. These results indicated that PEDF inhibited MMA-induced cytotoxicity through attenuating oxidative stress, activating the phosphatidylinositol 3-kinase (PI3K)/Akt pathway and/or PEDF receptorLPA-PPARg pathways in H9c2 cells. PEDF may be explored as a candidate therapeutic agent for alleviating bone cement implantation syndrome during orthopedic surgery.     

Trabecular bone response to injectable calcium phosphate (Ca-P) cement

The aim of this study was to investigate the physicochemical, biological, and handling properties of a new developed calcium phosphate (Ca-P) cement when implanted in trabecular bone. Ca-P cement consisting of a powder and a liquid phase was implanted as a paste into femoral trabecular bone of goats for 3 days and 2, 8, 16, and 24 weeks. The cement was tested using three clinically relevant liquid-to-powder ratios. Polymethylmethacrylate bone cement, routinely used in orthopedics, was used as a control. The Ca-P cement was easy to handle and was fast setting with good cohesion when in contact with body fluids. X-ray diffraction at the different implantation periods showed that the cement had set as an apatite and remained stable over time. Histological evaluation after 2 weeks, performed on 10 microm un-decalcified sections, showed abundant bone apposition on the cement surface without any inflammatory reaction or fibrous encapsulation. At later time points, the Ca-P cement implants were totally covered by a thin layer of bone. Osteoclast-like cells, as present at the interface, had resorbed parts of the cement mass. At locations where Ca-P cement was resorbed, new bone was formed without loss of integrity between the bone bed and the cement. This demonstrated the osteotransductive property of the cement, i.e., resorption of the material by osteoclast-like cells, directly followed by the formation of new bone. Histological and histomorphometrical evaluation did not show any significant differences between the Ca-P cement implanted at the three different liquid/powder ratios. The results indicate that the investigated Ca-P cement is biocompatible, osteoconductive, as well as osteotransductive and is a candidate material for use as a bone substitute.