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Results for “Elastic Modulus”

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PubMed1998

Variations in heel pad mechanical properties variation between children and young adults.

The purpose of this study was to compare the mechanical properties of the heel pads of adults and children, using ultrasound to assess the responses of the heel pad during compression. Thirty volunteers without heel problems, aged from 4 to 36 years, were recruited. There were 10 children (< 15 years old) and 20 adults (> 18 years old). A 7.5-MHz linear array ultrasound transducer was incorporated into a specially designed device to measure the thickness of the heel pad under different loads. The load on the heel pad was increased serially in increments of 0.5 kg, to a maximum of 3 kg, and then reduced sequentially. The load-displacement curve of the heel pad during a loading-unloading cycle was then plotted. Mechanical properties of the heel, including unloaded heel-pad thickness (UHPT), compressibility index, elastic modulus, and energy dissipation ratio (EDR), were calculated from the load-displacement curves. The average UHPT was 1.53 +/- 0.09 cm in children and 1.76 +/- 0.20 cm in adults (p < 0.001). The EDR, which represents the shock absorbency of the heel pad, was 13.5 +/- 2.0% in the children and 23.7 +/- 6.9% in adults (p < 0.001). The average compressibility index and elastic modulus were also higher in adults than in children, although the differences were not statistically significant. These findings suggest that the mechanical properties of the heel pad change from childhood to adulthood. Less energy is absorbed in the heel pad of children, which may partially explain why children tend to have fewer heel problems than adults.

Adolescent↗

PubMed1994

Measurement of regional elastic properties of the human aorta. A new application of transesophageal echocardiography with automated border detection and calibrated subclavian pulse tracings.

BACKGROUND: Evaluation of regional aortic elastic properties in humans has been hampered by the need for invasive techniques to access instantaneous aortic pressure, wall thickness, and cross-sectional area or diameter. In this study, a new noninvasive method is presented for quantification of regional aortic elastic properties. METHODS AND RESULTS: Twenty-five patients were studied during transesophageal echocardiographic procedures. Measurements of instantaneous aortic cross-sectional area were obtained with an automated border detection algorithm applied to short-axis transesophageal two-dimensional echocardiographic images of the proximal descending thoracic aorta. Instantaneous aortic wall thickness was derived from combined two-dimensional targeted M-mode end-diastolic wall thickness and instantaneous aortic area measurements. Instantaneous aortic pressures were estimated from calibrated subclavian pulse tracings recorded simultaneously. Data were digitized to generate aortic area-pressure loops. Regional aortic mechanical properties were quantified in terms of compliance per unit length (C is the slope of the area-pressure regression), aortic midwall radius (Rm), and incremental elastic modulus of the aortic wall (Einc). To assess the independent effect of age, Rm and Einc values were compared at a common level of aortic midwall stress (0.666 x 10(6) dynes/cm2). Mean values (+/- SD) for C, Rm, and Einc were 0.01 +/- 0.004 cm2/mm Hg, 1.14 +/- 0.17 cm, and 7.059 +/- 4.091 x 10(6) dynes/cm2, respectively. An inverse linear correlation was found between aortic compliance per unit length and age (r = -.68, P < .0007). Incremental elastic modulus was related to age (r = +.80, P < .00003) in a nonlinear fashion such that it increased sharply after the age of 60 years. Finally, midwall radius was less tightly correlated with age (r = +.45, P < .05). Values for C, Rm, and Einc as well as the age dependency of these properties are similar to those reported previously when invasive techniques were used. CONCLUSIONS: This methodology constitutes a new tool to improve the clinical evaluation of regional aortic elastic properties in multiple disease states.

Adult↗

PubMed1996

Interaction of adrenocorticotropin-(1-24)-tetracosapeptide with lipid bilayers.

The interaction of the peptide hormone adrenocorticotropin with solvent-free planar lipid bilayers (BLM) and liposomes was studied by measurements of elasticity modulus perpendicular to the plane of the membrane (E perpendicular, measured by electrostriction), surface potential difference (delta phi m), electrical capacitance, capacitance relaxation following a voltage jump (yielding relaxation times for molecular dipoles or dipolar domains), and fluorescence polarization. Addition of the 6-fold positively charged peptide to one side of the membrane leads to a more positive membrane surface potential, an increase of BLM capacitance, a decrease of elasticity modulus, and faster relaxation time constants. This also caused a decrease of DPH fluorescence anisotropy of the liposome suspension modified by fluorescent dye DPH. Mixed BLM of palmitoyl-oleoyl-phosphatidylcholine (POPC)+soybean phosphatidylcholine (SBPC) (10:1 w/w), which carry a negative surface charge, exhibit considerably larger changes than electroneutral POPC membranes. Our results confirm that ACTH1-24 binds to BLM and interacts with the hydrophobic part of the bilayer.

Cosyntropin↗

PubMed1999

Histological and biomechanical studies of two bone colonizable cements in rabbits.

We have developed two colonizable bone cements: the first is a partially resorbable bisphenol-alpha-glycidyl methacrylate (Bis-GMA)-based cement (PRC) and the second is a calcium phosphate cement (CPC). PRC is composed of aluminous silanized ceramic and particles of a bioresorbable polymer embedded in a matrix of Bis-GMA. CPC consisted of tricalcium phosphate, monocalcium phosphate monohydrate, dicalcium phosphate dihydrate, and xanthane. Both cements were implanted into cavities drilled in rabbit femoral and tibial condyles. After 2, 4, 12, and 24 weeks of implantation, histological observations and biomechanical tests were performed. With CPC, a progressive osteointegration with a concomitant biodegradation in the presence of macrophages were observed. The mechanical study revealed a decrease of the compressive strength until the 4th week, followed by a slight increase. There was a general decrease in the elastic modulus with time. Moreover, by week 4, the histological study showed that the new bone was in direct contact with CPC margins. No inflammation was observed during the observation period. With PRC, the osteointegration as well as the biodegradation were slight, but its compressive strength was higher than that of cancellous bone and CPC (p < 0.05) at all observation periods. Its elastic modulus was greater than that of cancellous bone and CPC until the 4th week, then fell under the values of the cancellous bone.

Animals↗

PubMed2000

Cellular hypertrophy in subcutaneous small arteries of patients with renovascular hypertension.

Structural alterations of small arteries in patients with essential hypertension are characterized by inward eutrophic remodeling. However, small arteries in patients with secondary hypertension, as well as in experimental models of hypertension with high circulating renin, are characterized by inward hypertrophic remodeling, which is characterized by smooth muscle cell hypertrophy in animal models. The aim of our study was to determine whether remodeling of subcutaneous small arteries in patients with secondary forms of hypertension is associated with smooth muscle cell hypertrophy and/or alterations in the elastic modulus of the vessel wall. Fifteen patients with renovascular hypertension, 9 with primary aldosteronism, and 13 with essential hypertension and 9 normotensive subjects were included in the study. A biopsy of subcutaneous fat was taken from all subjects. Small arteries were dissected, and morphology was determined on a micromyograph. Unbiased estimates of cell volume and number were made in fixed material. From the resting tension-internal circumference relation of the small arteries, the incremental elastic modulus was calculated and plotted as a function of wall stress. Blood pressure was greater in patients with essential hypertension, renovascular hypertension, or primary aldosteronism than in normotensive subjects, but no significant difference was observed among the 3 groups of hypertensive patients. The media/lumen ratio, the medial cross-sectional area, and the smooth muscle cell volume were significantly greater in patients with renovascular hypertension than in normotensive subjects and patients with essential hypertension. No difference in cell number or in the elastic properties was observed among the 4 groups of subjects. In conclusion, our data demonstrate for the first time that a pronounced activation of the renin-angiotensin-aldosterone system is associated with vascular smooth muscle cell hypertrophy in human hypertension in a manner similar to that found in animal models.

Arteries↗

PubMed1997

Quantitative ultrasound of the calcaneus reflects the mechanical properties of calcaneal trabecular bone.

To provide new information about the potential role of quantitative ultrasound (QUS) in fracture risk prediction, we assessed whether QUS and densitometric variables derived from measurements of intact cadaveric feet were associated with the mechanical properties of calcaneal trabecular bone. We obtained 31 intact cadaveric feet from the local anatomic gifts program, including 13 men and 18 women, with a mean age of 77 years (range 50-91 years). Broadband ultrasound attenuation (BUA) and ultrasound transit velocity (SOS) were assessed in the intact cadaveric feet using a water-based ultrasound system. In addition, we measured the bone mineral density (BMD) of the posterior calcaneus using dual-energy X-ray absorptiometry. Cubes of trabecular bone were then removed from the calcaneus at approximately the same location as the QUS measurements were obtained, and the elastic modulus and ultimate strength of the trabecular bone specimens were measured by compressing them in the mediolateral direction. We found that QUS variables were moderately to strongly correlated with the mechanical properties of calcaneal trabecular bone (r2 = 0.48-0.63, p < 0.001 for all). However, the strongest associations with the mechanical properties trabecular bone were provided by calcaneus BMD and trabecular bone apparent density (r2 = 0.66-0.88). BUA and densitometric measurements were independently associated with elastic modulus, but not with ultimate strength. Our results indicate that QUS measurements of the intact heel are associated with the mechanical properties of calcaneal trabecular bone and, in some cases, provide information in addition to that provided by BMD or density measurements.

Absorptiometry, Photon↗

PubMed2004

Controlling modulus and morphology of hydrogel tubes through surface modification.

Crosslinked, porous poly(2-hydroxyethyl methacrylate-co-methyl methacrylate) (PHEMA-MMA) tubes were prepared in cylindrical glass molds using a new centrifugal casting process developed in our group. The resulting hydrogel tubes have a bi-phasic wall structure, with a spongy inner layer and a gel-like outer layer, the latter of which provides mechanical strength to the tube. While many factors influence wall morphology and, thus, mechanical properties, we focused on the effect of the surface properties of the glass mold in which tubes are synthesized. Specifically, we investigated the impact of a diverse set of silane modifications of the glass mold on tube morphology, elastic modulus and mold release. We treated activated glass surfaces with one of three alkoxysilanes having either ethoxy, amine or fluorocarbon end-groups. Silane-modified glass surfaces were found to be more hydrophobic than the unmodified glass mold, with the most hydrophobic surface being that of the fluorocarbon-terminated silane. The presence of the silane layer on the mold was confirmed by X-ray photoelectron spectroscopy and the stability of this modification was confirmed by examining the surface chemistry of the hydrogel tubes. The biphasic hydrogel tube wall structure was observed for all tubes, yet those tubes synthesized in unmodified molds had a cracked outer morphology, whereas those synthesized in silane-modified molds had a smooth outer morphology. This influenced the mechanical properties of the tubes where tubes synthesized in silane-modified molds had a significantly greater elastic modulus than those tubes synthesized in unmodified molds. Release from the molds was easiest with ethoxy- and amine-functionalized silane mold modifications.

Biocompatible Materials↗

PubMed2000

Mineralized collagen fibrils: a mechanical model with a staggered arrangement of mineral particles.

Both elastic modulus and fracture stress are known to increase with the amount of mineral deposited within collagen fibrils. Current mechanical models of mineralized fibrils, where mineral platelets are arranged in parallel arrays, reproduce the first effect but fail to predict an increase in fracture stress. Here, we propose a model with a staggered array of platelets that is in better agreement with results on molecular packing in collagen fibrils and that accounts for an increase of both elastic modulus and fracture stress with the amount of mineral in the fibril. Finally, we explore the dependence of the mechanical properties within the model, when the degree of mineralization and the thickness of the platelets as well as their distance varies.

Animals↗

PubMed2002

Mechanical property measurements of nanoscale structures using an atomic force microscope.

This paper describes nanometer-scale bending tests of fixed single-crystal silicon (Si) and silicon dioxide (SiO2) nanobeams using an atomic force microscope (AFM). The technique is used to evaluate elastic modulus of the beam materials and bending strength of the beams. Nanometer-scale Si beams with widths ranging from 200 to 800 nm were fabricated on a Si diaphragm using field-enhanced anodization using an AFM followed by anisotropic wet etching. Subsequent thermal oxidation of Si beams was carried out to create SiO2 beams. Results from the bending tests indicate that elastic modulus values are comparable to bulk values. However, the bending strength appears to be higher for these nanoscale structures than for large-scale specimens. Observations of the fracture surface and calculations of the crack length from Griffith's theory appear to indicate that the maximum peak-to-valley distance on the beam top surfaces influence the values of the observed bending strengths.

Journal Article↗

PubMed1976

Turgor Pressure Regulation in Valonia utricularis: Effect of Cell Wall Elasticity and Auxin.

The electrical membrane resistance rho(0) of the marine alga Valonia utricularis shows a marked maximum in dependence on the turgor pressure. The critical pressure, P(c), at which the maximum occurs, as well as its absolute value, rho(0) (max), are strongly volume-dependent. Both P(c) and rho(0) (max), increase with decreasing cell volume. It seems likely, that these relationships reflect the elastic properties of the cell wall, because the volumetric elastic modulus, epsilon, is also volume-dependent, increasing hyperbolically with cell volume. Both P(c) and rho(0) (max) can be affected by external application of indole-3-acetic acid at concentrations of 2.10(-7)m to 2 .10(-5)m. The critical pressure is shifted by 1.2 to 6 bars toward higher pressures and the maximum membrane resistance increased up to 5.6-fold. During the course of the experiments (up to 4 hours), however, IAA had no effect on the volumetric elastic modulus, epsilon.The maximum in membrane resistance is discussed in terms of a pressure-dependent change of potassium fluxes. The volume dependence of P(c) and rho(0) (max) suggests that not only turgor pressure but also epsilon must be considered as a regulating parameter during turgor pressure regulation. On this basis a hypothesis is presented for the transformation of both, a pressure signal and of changes in the elastic properties of the cell wall into alterations of ion fluxes. It is assumed that the combined effects of tension and compression of the membranes as well as the interaction between membrane and cell wall opposingly change the number of transport sites for K(+) providing a turgor-sensing mechanism that regulates ion fluxes. The IAA effects demonstrated are consistent with this view, suggesting that the basic mechanisms for turgor pressure regulation and growth regulation are similar.Any relation connecting growth rate with turgor pressure should be governed by two parameters, i.e. by a yielding pressure, at which cell growth starts, and by the critical pressure, at which it ceases again.

Journal Article↗

PubMed2002

Arterial stiffness is not improved in long-term use of estrogen.

OBJECTIVE: The purpose of this study was to compare arterial stiffness in long-term users of estrogen who were postmenopausal, age-matched women who did not use estrogen, and women of fertile age. STUDY DESIGN: In this clinical cross-sectional study, carotid, femoral, and aortic stiffness (estimated as elastic modulus and stiffness beta index) were assessed by ultrasonic phase-locked echo-tracking in 17 women who were postmenopausal and who were treated with 17 beta-estradiol implants (mean age, 68.8 years; mean duration of treatment, 20 years), 17 age-matched (+/-1 year) untreated women, and 20 women in the fertile age period. RESULTS: Compared with women of fertile age, both postmenopausal groups had significantly higher stiffness elastic modulus and stiffness beta index (carotid, P <.001; femoral, P <.05; aorta, P <.001). However, for all 3 arteries, both stiffness indices were similar in estrogen users and nonusers and did not differ significantly. These results remained after an adjustment for systolic blood pressure, body mass index, and low-density lipoprotein cholesterol levels. CONCLUSION: These data indicate that the arterial stiffening that is related to aging/menopause is not substantially affected by long-term estrogen therapy.

Adult↗

PubMed2005

Fatigue behavior of packable composites.

The aim of this study was to investigate the flexural fatigue behavior of 11 packable composites. Of each material 30 rectangular samples (1.2 x 5 x 35 mm) for flexural fatigue test were prepared. The clamped fracture strength and flexural fatigue limit (FFL) of each material were determined using a custom-made fatigue machine, after storage of the samples for one month in water at 37 degrees C. All data were analyzed using one-way ANOVA and Bonferroni/Dunn's test for multiple comparisons (p<0.05). Regression analysis was used to evaluate the relationship between elastic modulus (Abe et al., 2001), clamped fracture strength or FFL and inorganic filler fraction (vol%). The fracture strengths of all but two materials were in between those of the compact-filled densified composites and the microfine ones. The FFL of the packable composites tested were significantly lower than those of the compact-filled densified composites. Three of the tested materials showed even significantly lower FFL than did the microfine composites. There were statistically significant relationships between both the elastic modulus and the volumetric filler fraction (R(2)=0.974, p=1.990 x 10(-7)). The great diversity in packable composites makes clinical assessment necessary with regard to a justified use in posterior teeth.

Composite Resins↗

PubMed2006

Brachial pressure-independent reduction in carotid stiffness after long-term angiotensin-converting enzyme inhibition in diabetic hypertensives.

Hypertension and diabetes are associated with an increased arterial stiffness. A direct blood pressure-independent effect of angiotensin-converting enzyme inhibitors on arterial stiffness has never been unequivocally demonstrated. In this mechanistic study, we used an experimental design in which patients responding to 1 month treatment with 4 mg perindopril were randomized double-blind to either 4 mg perindopril or 8 mg perindopril for 6 months. We determined carotid distensibility with echotracking and applanation tonometry at baseline and after the 7-month treatment period in 57 essential hypertensive patients with type 2 diabetes (age 63+/-7 years). We monitored ambulatory blood pressure at baseline and after treatment. After 7 months treatment, 24-hour ambulatory blood pressure significantly decreased, with no significant difference between 4 mg and 8 mg perindopril. Carotid distensibility increased more after 8 mg perindopril compared with 4 mg perindopril (8 mg: from 13.1+/-5.9 to 16.0+/-6.7 kPa(-1)x10(-3); 4 mg: from 13.2+/-5.2 to 12.7+/-5.9 kPa(-1)x10(-3); ANOVA, dose-period interaction, P<0.05). Carotid internal diameter and elastic modulus were significantly lower after 8 mg perindopril compared with 4 mg perindopril, independent of blood pressure reduction. These results indicate a dose-dependent and blood pressure-independent reduction in carotid stiffness under chronic treatment with an angiotensin-converting enzyme inhibitor. They suggest that arterial distensibility was increased through an inward remodeling, leading to a reduction in wall stress, thus reducing elastic modulus. They also suggest that long-term administration of high doses (8 mg) of perindopril is required to improve carotid structure and function in hypertensive patients with type 2 diabetes.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1997

Long-bone biomechanics in mice selected for body conformation.

Two lines of mice divergently selected from the control strain (CBi) against the positive phenotypic correlation between body weight (b.w.) and tail (skeletal) length were obtained (CBi/C: high weight, short tail; CBi/L: low weight, long tail). The selected animals showed a different relationship between body and skeletal masses. To compare the adequacy between biomass and load-bearing ability of the skeleton, and to describe the eventual role of bone mechanostat in the production of these changes, cross-sectional and bending properties of both femur diaphyses were determined in CBi, CBi/C, and CBi/L adult mice of both genders. Cortical bone material quality (elastic modulus) was reduced in the selected lines (p < 0.001), significantly less in CBi/C than in CBi/L. In contrast, cross-sectional design (b.w.-adjusted values of moment of inertia, CSMI) was largely improved (p < 0.001), significantly more in CBi/C than in CBi/L. These effects determined a greater stiffness and strength in CBi/C than in CBi/L or CBi weight-paired mice. The elevations of the negative regression lines between elastic modulus and CSMI ("distribution/quality" curves) decreased in the order CBi/C > CBi/L > CBi. Data show that selection improved diaphyseal stiffness and strength in CBi/C animals because of an architectural overcompensation for the reduced bone material quality. Therefore, an inadequate control of long-bone architectural design as a function of the mechanical quality of cortical bone and b.w. bearing could have been induced in that line. Assuming bone mechanostatic regulation to be genetically programmed, some of the corresponding biological determinants should be transmitted independently, because artificial selection separately affected material quality and architectural design. The possibility of transmission of an inadequate mechanostatic function (inability to adapt bone modeling to bone material quality as a function of the biomass to be supported) was also shown, as some genotypes could express architectural modifications that largely exceed bone material quality deterioration.

Animals↗

PubMed1988

Correlation of mechanical properties of vertebral trabecular bone with equivalent mineral density as measured by computed tomography.

We tried to determine whether mineral-equivalent measurements that were obtained using computed tomography could be used to predict the mechanical properties of vertebral trabecular bone. Vertebral bodies that had been obtained during routine autopsy were evaluated by computed tomography. The mechanical properties of the vertebral trabecular bone were determined by subjecting cylindrical specimens to simple compression until failure occurred. The ultimate strength and elastic modulus were determined from load time curves, using constant displacement rate loading. Atomic absorption spectrophotometry was used to determine the weight per cent calcium of each specimen, and quantitative light microscopy was used to determine area fraction bone. Significant positive correlations were found between the observed mechanical properties of the trabecular bone and the equivalent mineral density as measured by computed tomography. Compressive strength (r = 0.720), elastic modulus (r = 0.574), trabecular calcium density (r = 0.780), and area fraction bone (r = 0.579) were all correlated with the equivalent mineral density.

Aged↗

PubMed2005

Biomechanical properties of decellularized porcine common carotid arteries.

To analyze the effects of decellularization on the biomechanical properties of porcine common carotid arteries, decellularization was performed by a detergent-enzymatic procedure that preserves extracellular matrix scaffold. Internal diameter, external diameter, and wall thickness were measured by optical microscopy on neighboring histological sections before and after decellularization. Rupture tests were conducted. Inner diameter and wall thickness were measured by echo tracking during pressure inflation from 10 to 145 mmHg. Distensibility and incremental elastic modulus were computed. At 10 mmHg, mean diameter of decellularized arteries was 5.38 mm, substantially higher than controls (4.1 mm), whereas decellularized and control arteries reached the same internal diameter (6.7 mm) at 145 mmHg. Wall thickness decreased 16% for decellularized and 32% for normal arteries after pressure was increased from 10 to 145 mmHg. Decellularized arteries withstood pressure >2,200 mmHg before rupture. At 145 mmHg, decellularization reduced compliance by 66% and increased incremental elastic modulus by 54%. Removal of cellular elements from media led to changes in arterial dimensions. Collagen fibers engaged more rapidly during inflation, yielding a stiffer vessel. Distensibility was therefore significantly lower (by a factor of 3) in decellularized than in normal vessels: reduced in the physiological range of pressures. In conclusion, decellularization yields vessels that can withstand high inflation pressures with, however, markedly different geometrical and biomechanical properties. This may mean that the potential use of a decellularized artery as a scaffold for the creation of xenografts may be compromised because of geometrical and compliance mismatch.

Animals↗

PubMed2001

Brachial artery elastic mechanics in patients with heart failure.

Studies of arterial elasticity in patients with heart failure (HF) have produced varying results. In addition, the direct effects of smooth muscle relaxation on arterial wall mechanics in these patients have not been well characterized. Nineteen patients with New York Heart Association class II to IV HF and 17 age- and size-matched normal subjects were studied by using a recently validated technique for measuring brachial arterial wall mechanics over a wide pressure range. The left brachial artery was imaged through a water-filled blood pressure cuff by use of an ultrasound wall-tracking system at baseline and after 0.4 mg sublingual nitroglycerin (NTG). Simultaneous radial artery pressure waveforms were recorded by tonometry. Transmural pressure (TP) was reduced by increasing water pressure in the cuff. Baseline area, compliance, and pulse wave velocity versus TP curves were similar in the normal subjects and the patients with HF. The incremental elastic modulus versus TP curve tended to be lower in the patients with HF. The wall-to-lumen ratio was increased in HF (P=0.05). NTG significantly shifted the area versus TP (P<0.001) and compliance versus TP (P<0.05) curves upward and the pulse wave velocity versus TP (P<0.05) curve downward in both groups. NTG also significantly (P<0.001) shifted the stress versus strain curve to the right in both groups but did not alter the incremental elastic modulus versus TP curve. We conclude that the brachial arterial wall-to-lumen ratio is increased in HF. This finding occurs together with a trend toward reduced arterial stiffness such that overall mechanical behavior of the brachial artery is preserved. Smooth muscle relaxation with NTG produces similar improvements in brachial arterial wall mechanics in normal subjects and in patients with HF.

Administration, Sublingual↗

PubMed1998

Biomechanical characterization of a biodegradable calcium phosphate hydraulic cement: a comparison with porous biphasic calcium phosphate ceramics.

Biomechanical properties of a biodegradable calcium phosphate hydraulic cement (CPHC) were tested with rabbits. The cement was composed of beta-tricalcium phosphate (beta-TCP), monocalcium phosphate monohydrate (MCPM), and calcium sulfate hemihydrate (CSH), beta-TCP-MCPM-CSH cement. Cylinders of 4.7 mm in diameter and 10 mm in length were put into bone cavities created in the distal epiphysis of femurs in rabbits. Cylinders of the same size of porous biphasic calcium phosphate ceramics (BCPC, 75% hydroxyapatite and 25% beta-TCP) were implanted as references. Two, 4, 12, and 16 weeks after the operation, the rabbits were sacrificed. Histomorphometry showed that the cement was resorbed, leaving only 7.67 +/- 1.81% of bone cavity after 12 weeks. Newly formed bone occupied 34.59 +/- 4.00% of the cavity. Cylindrical bone-material composites were cut out with a small dental burr. Compressive force was applied to the specimens and compressive strength, elastic modulus, and toughness were calculated. The same tests were performed on cylinders of normal bone from the same site, which served as controls. The compressive strength and the toughness of the cement-bone composite were higher than those of normal bone and porous ceramics 12 weeks after the operation (p < 0.05). At 16 weeks the compressive strength and the toughness returned to the normal bone values. The elastic modulus of the porous ceramic-bone composite was higher than the normal bone at 4, 12, and 16 weeks after surgery (p < 0.05). We found that the beta-TCP-MCPM-CSH cement is replaced by new bone and that the cement-new bone composite has similar or better mechanical properties than normal bone within 16 weeks. This study suggests the usefulness of a particular cement for filling bone defects or for temporary fixation of orthopedic implants.

Animals↗