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Results for “Compressive Strength”

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PubMed2005

The construction and investigation of PLGA artificial bone by biomimetic mineralization.

To modify the surface property of poly lactide-co-glycolide (PLGA) by biomimetic mineralization to construct a new kind of artificial bone. PLGA films and 3-diamensional (3-D) porous scaffolds hydrolyzed in alkaline solution were minerilized in SBF for 14 days. The morphology and composition of the mineral grown on PLGA were analyzed with SEM, FTIR and XRD. The porosity of the scaffolds was detected by using the liquid displacement method. The compressive strength of the scaffolds was detected by using a Shimadzu universal mechanic tester. An obvious mineral coating was detected on the surface of films and scaffolds. The main component of the mineral was carbonated hydroxyapatite (HA) similar to the major mineral component of bone tissues. The porosity of the un-mineralized and mineralized porous scaffolds was (84.86 +/- 8.52) % and (79.70 +/- 7.70) % respectively. The compressive strength was 0.784 +/- 0.156 N/mm2 in un-mineralized 3-D porous PLGA and 0.858 +/- 0.145 N/mm2 in mineralized 3-D porous PLGA. There were no significant differences between the mineralized and un-mineralized scaffolds (P > 0.05) in porosity and biomechanics. Biomimetic mineralization is a suitable method to construct artificial bone.

Biocompatible Materials↗

PubMed1992

The physical properties of a new sealing cement.

This study was performed on a newly developed sealing cement, TS60, to evaluate its physical properties, namely sealing, setting time, compressive strength, solubility and ease of removal. It was compared with Temporary Stopping (GC Dental Industrial Corp., Tokyo, Japan), Eugedain (zinc oxide-eugenol based material, Showa Yakuhin Kako Co. Ltd, Tokyo, Japan) and Cavit-G (calcium sulphate based material, Espe Gmbh, Seefeld, Germany), which are typical commercially available sealing cements. The results of the study revealed that TS60 had excellent sealing properties, good compressive strength, low solubility, and was readily removable by heating and melting.

Dental Cements↗

PubMed1993

[A biomechanical study in the repairing process of avascular necrosis of the femoral head in dogs].

We report the result of an animal experiment studying the biomechanical, radiological and histological changes during the repairing process of avascular necrosis of the femoral head. At 1/2 month, histology showed complete necrotic changes involving both marrow content and bone trabecula. However, biomechanical tests showed there was no significant difference in material properties between experimental and control sides. A2 2 and 4 months, reparative changes were observed by histology and radiography. The decrease in mean compressive strength in the subchondral bone was 17.5% at 2 months and 35.5% at 4 months. Subchondral bone mean modulus of elasticity decreased by 25.1% at 2 months, 43.0% at 4 months. Greater decrease in mean strain energy in the cancellous bone occurred at 2 months (43.2%) and 4 months (42.9%). In the 6 months group, all necrotic femoral heads showed varying degrees of collapse. The compressive strength and the modulus in the subchondral bone decreased by 73.3% and 76.9% respectively. The strain energy in the cancellous bone decreased by 37.9%. The present study indicates that the biological resorptive cativity of the advancing reparative processes may lead to significant decrease in the mechanical properties. This is probably the most direct cause of late femoral head collapse.

Animals↗

PubMed2005

Effects of nano HAP on biological and structural properties of glass bone cement.

A novel type of glass-based nanoscale hydroxyapatite (HAP) bioactive bone cement (designed as GBNHAPC) was synthesized by adding nanoscale hydroxyapatite crystalline (20-40 nm), into the self-setting glass-based bone cement (GBC). The inhibition rate of nanoscale HAP and micron HAP on osteosarcoma U2-OS cells was examined. The effects of nanoscale HAP on the crystal phase, microstructure and compressive strength of GBNHAPC were studied, respectively. It was concluded that nanoscale HAP could inhibit the cell proliferation, whereas micron HAP could not, and that nanoscale HAP could be dispersed in the cement evenly and the morphology did not change significantly after a longer immersion time. XRD and FTIR results show nanoscale HAP did not affect the setting reaction of the cement. Furthermore, GBNHAPC had a higher compressive strength (92.6 +/- 3.8 MPa) than GBC (80.1 +/- 3.0 MPa). It was believed that GBNHAPC might be a desirable biomaterial that could not only fill bone defects but also inhibit cancer cell growth.

Bone Cements↗

PubMed2004

Preparation and characterization of a novel bioactive bone cement: glass based nanoscale hydroxyapatite bone cement.

A novel type of glass-based nanoscale hydorxypatite (HAP) bioactive bone cement (designed as GBNHAPC) was synthesized by adding nanoscale hydroxyapatite (HAP) crystalline (20-40 nm), into the self-setting glass-based bone cement (GBC). The inhibition rate of nanoscale HAP and micron HAP on osteosarcoma U2-OS cells was examined. The effects of nanoscale HAP on the crystal phase, microstructure and compressive strength of GBNHAPC were studied respectively. It was concluded that nanoscale HAP could inhibit the cell proliferation, while micron HAP could not, and that nanoscale HAP could be dispersed in the cement evenly and the morphology did not change significantly after a longer immersion time. XRD and FTIR results show nanoscale HAP did not affect the setting reaction of the cement. Furthermore, GBNHAPC had a higher compressive strength (92 MPa) than GBC. It was believed that GBNHAPC might be a desirable biomaterial that could not only fill bone defects but also inhibit cancer cell growth.

Bone Cements↗

PubMed1983

The amount of bone mineral and Schmorl's nodes in lumbar vertebrae.

The bone mineral areal content and the ultimate compressive strength were determined in 109 lumbar vertebrae from 36 subjects. The bone mineral areal content was related to the number, shape, and localization of the Schmorl's nodes detected in the x-rayed and sectioned vertebral bodies. One type of node, irregular in shape and localization, occurred only in the vertebrae with low bone mineral areal content values and thus in vertebrae with relatively low compressive strength. A second type of Schmorl's nodes, regular in shape and localization, did not reflect any general weakness of the vertebral bodies.

Adult↗

PubMed2001

Structural characterization of phosphorylated chitosan and their applications as effective additives of calcium phosphate cements.

Chitosan was phosphorylated by P2O5 in methanesulfonic acid and the product as water-soluble phosphorylated chitosan (P-chitosans) was then characterized by phosphorus elemental analysis, IR and 31P-NMR spectroscopy. Two calcium phosphate cement (CPC) systems, i.e. (1) monocalcium phosphate monohydrate (MCPM) and calcium oxide (CaO) in 1 M phosphate buffer (pH = 7.4) and (2) dicalcium phosphate dihydrate (DCPD) and calcium hydroxide [Ca(OH)2] in 1 M Na2HPO4 solution, were chosen to improve their mechanical properties by the addition of water-soluble P-chitosans with various values for molecular weight, degree of deacetylation (DD) and degree of substitution (DS). The results show that the compressive strength (CS) and Young's modulus of both CPC formulations after setting were obviously increased and setting time was slightly prolonged by adding water-soluble P-chitosan to the liquid phases. When a suitable amount of P-chitosan was used, two improved CPC formulations were obtained with much better mechanical properties while the setting times were not longer than 15 min. The enhancement of compressive strength was due to high Ca2+-binding ability of phosphorylated chitosan, which could tightly bind the newly formed hydroxyapatite (HA) particles together by polymeric chains. It was noted that excessive addition of P-chitosan would lead to slow setting or no setting at all. The hardened CPC samples containing P-chitosan were characterized via X-ray diffraction spectra and scanning electron microscopy. Their leaching experiment was also carried out. The results indicated that P-chitosan-forced calcium phosphate cements have some good characteristics for clinical applications.

Bone Cements↗

PubMed1995

Disinfection of dental stone casts: antimicrobial effects and physical property alterations.

OBJECTIVES: The purpose of this study was to evaluate the effectiveness of disinfecting solutions incorporated into dental stone casts against a standard and representative group of microorganisms and to note changes in the physical properties of the casts. METHODS: Irreversible hydrocolloid impressions were contaminated individually with Escherichia coli, Staphylococcus aureus, Enterobacter cloacae, Pseudomonas aeruginosa, Klebsiella pneumoniae, Actinobacter calcoaceticus, Bacillus subtilis, Mycobacterium phlei and Candida albicans. Four readily available disinfecting solutions (glutaraldehyde, povidone-iodine, chlorhexidine and sodium hypochlorite) were added to the die stone mix used to pour up the impressions. The set cast surfaces were swabbed at 1 h and 24 h, the samples plated on agar and incubated at 37 degrees C for 24 h and 3 d for M. phlei. Subsequently, colony forming units were counted. The physical properties assessed were setting time, setting expansion, compressive strength, detail reproduction and delayed expansion of the stone. RESULTS: Only glutaraldehyde and povidone-iodine killed all contaminating microorganisms within 1 h, while the 1:5 dilution of sodium hypochlorite solution was equally effective after 24 h. Two percent glutaraldehyde was the most effective disinfectant with the least adverse effects on the physical properties of the set cast. Although povidone-iodine caused a decrease in the compressive strength of the set cast, it can be considered to be a sound alternative. SIGNIFICANCE: This study supports the concept of incorporating disinfectants into model stone as a standard operating procedure for impressions of unknown history and, most sensibly, all dental impressions.

Analysis of Variance↗

PubMed2000

Stabilization and solidification of metal-laden wastes by compaction and magnesium phosphate-based binder.

Bench-scale and full-scale investigations of waste stabilization and volume reduction were conducted using spiked soil and ash wastes containing heavy metals such as Cd, Cr, Pb, Ni, and Hg. The waste streams were stabilized and solidified using chemically bonded phosphate ceramic (CBPC) binder, and then compacted by either uniaxial or harmonic press for volume reduction. The physical properties of the final waste forms were determined by measuring volume reduction, density, porosity, and compressive strength. The leachability of heavy metals in the final waste forms was determined by a toxicity characteristic leaching procedure (TCLP) test and a 90-day immersion test (ANS 16.1). The structural composition and nature of waste forms were determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. CBPC binder and compaction can achieve 80-wt% waste loading and 39-47% reduction in waste volume. Compressive strength of final waste forms ranged from 1500 to 2000 psi. TCLP testing of waste forms showed that all heavy metals except Hg passed the TCLP limits using the phosphate-based binder. When Na2S was added to the binder, the waste forms also passed TCLP limits for Hg. Long-term leachability resistance of the final waste forms was achieved for all metals in both soil and ash wastes, and the leachability index was approximately 14. XRD patterns of waste forms indicated vermiculite in the ash waste was chemically incorporated into the CBPC matrix. SEM showed that waste forms are layered when compacted by uniaxial press and are homogeneous when compacted by harmonic press.

Hazardous Waste↗

PubMed1996

Kinetic study of the setting reaction of a calcium phosphate bone cement.

The setting reaction of a calcium phosphate bone cement consisting of a mixture of 63.2 wt % alpha-tertiary calcium phosphate (TCP)[alpha-Ca3(PO4)2], 27.7 wt % dicalcium phosphate (DCP) (CaHPO4), and 9.1 wt % of precipitated hydroxyapatite [(PHA) used as seed material] was investigated. The cement samples were prepared at a liquid-to-powder ratio of: L/P = 0.30 ml/g. Bi-distilled water was used as liquid solution. After mixing the powder and liquid, some samples were molded and aged in Ringer's solution at 37 degrees C. At fixed time intervals they were unmolded and then immediately frozen in liquid nitrogen at a temperature of TN = -196 degrees C, lyofilized, and examined by X-ray diffraction as powder samples. The compressive strength versus time was also measured in setting samples of this calcium phosphate bone cement. The crystal entanglement morphology was examined by scanning electron microscopy. The results showed that: 1) alpha-TCP reacted to a calcium-deficient hydroxyapatite (CDHA), Ca9(HPO4)(PO4)5O H, whereas DCP did not react significantly; 2) the reaction was nearly finished within 32 h, during which both the reaction percentage and the compressive strength increased versus time, with a strong correlation between them; and 3) the calcium phosphate bone cement showed in general a structure of groups of interconnected large plates distributed among agglomerations of small crystal plates arranged in very dense packings.

Bone Cements↗

PubMed1978

The effect of antibiotic additions on the mechanical properties of acrylic cement.

Early work on hip prosthesis showed that the metal component would loosen in bone even when screws were used. This practice resulted in the death and resorption of the bone; thus cement was used in orthopedic surgery for firm implantation of prostheses. In recent years antibiotics have been added to the cement as a prophylaxis against infection. This research investigates the effects of antibiotics on the diametral tensile and compression strength of the cement. Samples made with 2 g of antibiotic per surgical packet of bone cement containing the antibiotics gentamicin, keflin, and a combination of the two were tested. These samples were aged at ambient temperature for periods of 1 day and 1, 2, 8, 13, and over 30 weeks. A stastical analysis using a two-way analysis of variance with interaction was conducted. It was concluded that the compression strength was affected by the antibiotic, and not by the aging period, but that there is an antibiotic-aging period interaction. The tensile strength is not affected by either the antibiotic or the aging period, and there is an antibiotic-aging period interaction. Current work being conducted will analyze additional factors and interactions.

Anti-Bacterial Agents↗

PubMed2006

Injectable PLGA microsphere/calcium phosphate cements: physical properties and degradation characteristics.

Calcium phosphate (CaP) cements show an excellent biocompatibility and often have a high mechanical strength, but in general degrade relatively slow. To increase degradation rates, macropores can be introduced into the cement, e.g., by the inclusion of biodegradable microspheres into the cement. The aim of this research is to develop an injectable PLGA microsphere/CaP cement with sufficient setting/cohesive properties and good mechanical and physical properties. PLGA microspheres were prepared using a water-in-oil-in-water double-emulsion technique. The CaP-cement used was Calcibon, a commercially available hydroxyapatite-based cement. 10:90 and 20:80 dry wt% PLGA microsphere/CaP cylindrical scaffolds were prepared as well as microporous cement (reference material). Injectability, setting time, cohesive properties and porosity were determined. Also, a 12-week degradation study in PBS (37 degree C) was performed. Results showed that injectability decreased with an increase in PLGA microsphere content. Initial and final setting time of the PLGA/CaP samples was higher than the microporous sample. Porosity of the different formulations was 40.8% (microporous), 60.2% (10:90) and 69.3% (20:80). The degradation study showed distinct mass loss and a pH decrease of the surrounding medium starting from week 6 with the 10:90 and 20:80 formulations, indicating PLGA erosion. Compression strength of the PLGA microsphere/CaP samples decreased siginificantly in time, the microporous sample remained constant. After 12 weeks both PLGA/CaP samples showed a structure of spherical micropores and had a compressive strength of 12.2 MPa (10:90) and 4.3 MPa (20:80). Signs of cement degradation were also found with the 20:80 formulation. In conclusion, all physical parameters were well within workable ranges with both 10:90 and 20:80 PLGA microsphere/CaP cements. After 12 weeks the PLGA was totally degraded and a highly porous, but strong scaffold remained.

Biocompatible Materials↗

PubMed1986

The effects of a calcium deficient diet on the mechanical properties and morphology of goose bone.

A control group of geese (Anser anser) on a normal calcium diet for egg laying poultry was compared to egg laying geese on a calcium deficient diet. The ultimate compressive strength and modulus of elasticity of femoral cortical bone from each group were determined by compressing right circular cylinders which were 2.4 mm in height and 0.8 mm in diameter. The bending strength and bending modulus of elasticity of tibial cortical bone were determined by three point bend tests on rectangular prisms which were approximately 25 mm by 0.8 mm by 0.8 mm. Bone calcium content and eggshell calcium content were determined by atomic absorption spectrophotometry. Blood samples were analyzed for free calcium ion concentration. Histological observations included studies of cross-sectional microradiographs, examinations of cross sections stained by a modified Masson's technique, and a determination of fractional area of voids by quantitative microscopy. The average compressive modulus for the control birds was 12.0 GPa (S.D.: 6.2 GPa) while the ultimate compressive strength was 165 MPa (S.D.: 27 MPa). Calcium deprived birds showed slight, but not statistically significant, decreases in both the compressive modulus and compressive strength. The tibial three point bending modulus for the control birds was 16.5 GPa (S.D.: 2.6 GPa) while the ultimate bending strength was 256 MPa (S.D.: 58 MPa). Once again, slight though not statistically significant decreases in the bending modulus and strength were seen in the geese on the calcium deficient diet. The average calcium content (wt%) of the femora of the control birds was 20.5% (S.D.: 4.3%) and 20.6% (S.D.: 4.8%) for the tibiae. No significant differences were noted in the calcium deprived birds. The average fractional void area for the control bird femoral bone was 12.0% (S.D.: 2.6%) and 9.8% (S.D.: 1.8%) for the tibial bone. Significantly greater fractional void areas were noted in the calcium deficient birds as were profound changes in the macrocellular structure of these bones.

Animals↗

PubMedDate not supplied

Estimation of vertebral body strength by dual photon absorptiometry in elderly individuals: comparison between measurements of total vertebral and vertebral body bone mineral.

The aim of the present study was to investigate the predictive value of bone mineral measurements by dual photon absorptiometry (DPA) in vitro for strength and ash weight of lumbar vertebral bodies in elderly, otherwise nonselected individuals. The material comprised 46 individuals: 26 males (43-95 years) and 20 females (63-95 years) without malignant diseases. Spinal segments, including L2, L3, and L4, were removed en bloc at autopsy. Bone mineral content (BMC) measurements imitating the normal DPA procedure were performed on the segments suspended in a water bath. The segments were measured in toto (BMCT) and remeasured after removal of the posterior elements (BMCB). The second lumbar vertebral body (L2) was then dissected and sawed below the endplates to obtain samples with planoparallel ends before compression in a materials testing machine. Finally, the bone specimens were incinerated for ash weight estimations. BMCT showed significant correlations to vertebral body ash weight (r = 0.79), compressive strength (load, r = 0.69), and stress (load per unit area, r = 0.47). The correlations were improved by removing the posterior elements (BMCB-ash weight, r = 0.86, BMCB-load, r = 0.74, BMCB-stress, r = 0.49). Correction of BMC for differences in vertebral body height (BMC/cm) further increased the correlation coefficients (BMCB/cm-ash weight, r = 0.92, BMCB/cm-load, r = 0.78, BMCB/cm-stress, r = 0.55). We conclude that lumbar BMC is predictive for lumbar vertebral body compressive strength in vitro and ash weight. The correlation coefficient is improved by removing the posterior non-weight-bearing element.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗

PubMed2005

[Physicomechanical properties of plantation poplar wood under different eco-environments].

The measurement of the physicomechanical properties of 9 plantation poplar I-69 (Populus deltoides CV. 1-69/55) woods under fertilization and seasonal flooding showed that compared with no fertilization, fertilization increased the ring width, static modulus of elasticity, and compressive strength parallel to the grain by 0.99 % (P > 0.05), 2.73% (P < 0.05) and 1.06% (P < 0.05), while decreased the air-dry radial, tangential, volumetric shrinkage, oven-dry radial, tangential, volumetric shrinkage, basic density, MOR, and dynamic modulus of elasticity by 4.2%, 7.7%, 6.6%, 15.6%, 6.3%, 11.1%, 2%, 1.79% and 8.13%, respectively. Seasonal flooding decreased the basic density, air-dry radial, tangential, volumetric shrinkage, oven-dry radial, tangential, volumetric shrinkage, MOR, MOE, and compressive strength parallel to the grain by 5.5%, 11.1%, 9.2%, 9.6%, 16.7%, 10.9%, 8.5%, 24.29%, 18.18% and 16.81%, respectively, in comparing with non-flooding.

Ecosystem↗

PubMed2006

[A study on alpha-tricalcium phosphate bone cement carbon fiber-reinforced].

In order to improve the mechanical properties of alpha-tricalcium phosphate (alpha-TCP), we prepared surface-modified carbon fibers (CF) reinforced alpha-TCP composite bone cement. Bone cement was soaked in Ringer's body solution to test its capacity of fast formation of hydroxyapatite crystals and self-solidification. Scan electronic microscope (SEM) observation and compressive strength measurement were taken to analyze the mechanical properties and the micro- morphological structure of CF reinforced alpha-TCP bone cement. The results showed that the bone cement was transferred into hydroxyapatite plates after being soaked in Ringer's simulated body fluid for 5 days. Suitable amount of carbon fibers could well spread in and bond with the matrix of the bone cement. The mechanical properties of the bone cement have been improved by CF reinforcing; the compressive strength reaches 46.7 MPa when the amount of carbon fibers is 0.5% in weight percent, which is 22% higher than that of the non-reinforced alpha-TCP bone cement.

Bone Cements↗

PubMed2006

Phase evaluation of an effervescent-added apatitic calcium phosphate bone cement.

Development of macroporosity during setting would allow fast bone ingrowth and good osteointegration of the implant. The interconnected macropores could be created in calcium phosphate cements (CPCs) through the addition of an effervescent porogen mixture to the component of the cements. But this addition could also affect other characteristics of CPCs, such as setting time, mechanical strength, extent of conversion of reactant to apatite phase, crystallinity, and chemical composition of apatite lattice. In this study, these properties were investigated in an effervescent-added calcium phosphate bone cement. From 0 to 20 wt % of an effervescent mixture was added to calcium phosphate cement (CPC) components and phase evaluations were performed after 24 h incubation at 37 degrees C and 28% relative humidity and 1, 3, 7, and 14 days immersion in a specific simulated body fluid. XRD and FTIR techniques were used to characterize the cement composition, crystallinity, and chemical groups in final CPCs. The results showed that addition of effervescent porogen affects the extent of conversion of reactant to apatite phase and crystallinity. In other words, using the effervescent porogen in CPCs could accelerate the rate of conversion of TTCP/DCPA reactant to apatite phase with smaller crystallites, so that it was the predominant phase (about 67%) after only 3 days soaking in SBF solution. The content of carbonate groups substituted for phosphate groups in apatite lattice increased when the effervescent additive was further added. The compressive strength of the set calcium phosphate cement decreased significantly with the addition of the effervescent agent and reached from 8 MPa for additive-free CPC to 1.3 MPa for 20% effervescent-added CPC. The compressive strength was improved after 3 days immersing of CPC in the simulated body fluid solution.

Apatites↗

PubMed2006

Porous akermanite scaffolds for bone tissue engineering: preparation, characterization, and in vitro studies.

The aim of this study was to develop a bioactive, degradable, and cytocompatible akermanite (Ca2MgSi2O7) scaffold with high porosity and pore interconnectivity. In brief, porous akermanite scaffolds were prepared using polymer sponge method. The porosity and corresponding compressive strength were evaluated. The in vitro degradability was investigated by soaking the scaffolds in Ringer's solution. Hydroxyapatite (HAp)-formation ability of akermantite scaffolds in simulated body fluid (SBF) and the effect of ionic products from the scaffolds dissolution on osteoblasts were investigated. In addition, bone marrow stromal cells (BMSC) adhesion and proliferation on the scaffolds were evaluated. Differentiation of the cells was assessed by measuring alkaline phosphatase (ALP) activity. The results showed that akermanite scaffolds possessed 63.5-90.3% of porosity, with a corresponding compressive strength between 1130 and 530 kPa. The weight loss of the scaffolds and ionic content of the Ringer's solution increased with the increase in soaking time, indicating the degradability of scaffolds. HAp was formed on the scaffolds in SBF and the ionic products from akermanite scaffolds dissolution stimulated osteoblasts proliferation, indicating good in vitro bioactivity. Furthermore, BMSC adhered and spread well on akermanite scaffolds and proliferated with the increase in the culture time, and the differentiation rate of osteoblasts on scaffolds was comparable to that on blank culture plate control. Our results suggested that akermanite scaffolds were bioactive, degradable, and cytocompatible, and might be used as bone tissue engineering materials.

Animals↗