PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Compressive Strength”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,351 records · Page 75Linked to original sources
PubMed2004

Comparison of the elastic and yield properties of human femoral trabecular and cortical bone tissue.

The ability to determine trabecular bone tissue elastic and failure properties has biological and clinical importance. To date, trabecular tissue yield strains remain unknown due to experimental difficulties, and elastic moduli studies have reported controversial results. We hypothesized that the elastic and tensile and compressive yield properties of trabecular tissue are similar to those of cortical tissue. Effective tissue modulus and yield strains were calibrated for cadaveric human femoral neck specimens taken from 11 donors, using a combination of apparent-level mechanical testing and specimen-specific, high-resolution, nonlinear finite element modeling. The trabecular tissue properties were then compared to measured elastic modulus and tensile yield strain of human femoral diaphyseal cortical bone specimens obtained from a similar cohort of 34 donors. Cortical tissue properties were obtained by statistically eliminating the effects of vascular porosity. Results indicated that mean elastic modulus was 10% lower (p<0.05) for the trabecular tissue (18.0+/-2.8 GPa) than for the cortical tissue (19.9+/-1.8 GPa), and the 0.2% offset tensile yield strain was 15% lower for the trabecular tissue (0.62+/-0.04% vs. 0.73+/-0.05%, p<0.001). The tensile-compressive yield strength asymmetry for the trabecular tissue, 0.62 on average, was similar to values reported in the literature for cortical bone. We conclude that while the elastic modulus and yield strains for trabecular tissue are just slightly lower than those of cortical tissue, because of the cumulative effect of these differences, tissue strength is about 25% greater for cortical bone.

Aged↗
PubMed2000

An evaluation of the bond strengths to enamel of two fissure sealants.

The objective of this study was to carry out a comparative evaluation of the bond strength to enamel of two present-day fissure sealants, Helioseal and Concise; good adhesion of the material to the tooth surface is one of the requisites for the success of this preventive technique. To this end, 16 caries-free human premolars extracted for orthodontic reasons were used. Proximal, mesial, and distal surfaces were treated and studied. Bond strength was evaluated by the application of compression forces (Instron) at a velocity of 0.5 mm/mm. The overall results obtained do not show significant differences between the two materials.

Analysis of Variance↗
PubMedDate not supplied

The physical and adhesive properties of dental cements used for atraumatic restorative treatment.

Atraumatic restorative treatment (ART), a recently reported field dentistry technique, involves removal of carious debris using only hand instruments and placement of a glass-ionomer cement (GIC) restoration. While small ART-GIC restorations are effective short-term replacements for lost tooth form, many larger ART-GIC restorations are defective after two years. Presently, resin-modified GICs (R-M GIC) are available which require no special activation equipment and handle easily in field settings. This study measured the compressive, tensile, and shear bond strengths to enamel and dentin of a conventional ART-GIC (Fuji IX) and two R-M GICs (Fuji Plus and Advance) at a powder-to-liquid ratio of 3.6:1. The compressive strengths of the GICs tested were significantly different. Fuji IX had the highest compressive strength, and Advance had the lowest strength (p < 0.05). The tensile strength of the R-M GICs was greater than that of the ART-GIC. Fuji Plus showed the highest shear bond strength to enamel and dentin and was significantly different from both Fuji IX and Advance. A clinical protocol is presented followed by case reports where the ART technique was used for management of acute caries in a modern dental setting.

Acute Disease↗
PubMed2006

Fabrication and characterization of poly(DL-lactic-co-glycolic acid)/zirconia-hybridized amorphous calcium phosphate composites.

Several minerals, such as hydroxyapatite and beta-tricalcium phosphate, have been incorporated into bioresorbable polyester bone scaffolds to increase the osteoconductivity both in vitro and in vivo. More soluble forms of calcium phosphate that release calcium and phosphate ions have been postulated as factors that increase osteoblast differentiation and mineralization. Recently, a zirconia-hybridized pyrophosphate-stabilized amorphous calcium phosphate (Zr-ACP) has been synthesized allowing controlled release of calcium and phosphate ions. When incorporated into bioresorbable scaffolds, Zr-ACP has the potential to induce osteoconductivity. In this study, 80-90% (w/v) porous poly(DL-lactic-co-glycolic acid) (PLGA) scaffolds were formed by thermal phase separation from dioxane while incorporating Zr-ACP. Scanning electron microscopy revealed a highly porous structure with a pore size ranging from a few microm to about 100 microm, smaller than we had hoped for. Zr-ACP particles were evenly dispersed in the composite structure and incorporated into the pore walls. The amorphous structure of the Zr-ACP was maintained during composite fabrication, as found by X-ray diffraction. Composite scaffolds had larger compressive yield strengths and moduli compared to pure polymer scaffolds. These initial efforts demonstrate that PLGA/Zr-ACP composites can be formed in ways that ultimately serve as promising bone scaffolds in tissue engineering.

Bone Substitutes↗
PubMed1998

The effect of compression force on surface structure, crushing strength, friability and disintegration time of erythromycin acistrate tablets.

The surface roughness of erythromycin acistrate tablets was studied by non-contact laser profilometry. Seven roughness parameters and 3D fractal dimension were examined. The mechanical properties (including crushing strength, friability and disintegration time) were determined, and SEM data were taken from the tablets. According to the results, the crushing strength and the disintegration time of the tablets increased with increasing compression force. At higher compression forces the crushing strength reached a constant level. The friability of the tablets behaved quite unexpectedly and minimum friability was observed at a compression force of 14 kN. Except for fractal dimension, the roughness parameters behaved very much in the same way as the friability of the tablets. The SEM data supported the friability and surface roughness data of the tablets.

Chemistry, Pharmaceutical↗
PubMed2000

Prediction of femoral fracture load using finite element models: an examination of stress- and strain-based failure theories.

Finite element (FE) models are often used to model bone failure. However, no failure theory for bone has been validated at this time. In this study, we examined the performance of nine stress- and strain-based failure theories, six of which could account for differences in tensile and compressive material strengths. The distortion energy, Hoffman and a strain-based Hoffman analog, maximum normal stress, maximum normal strain, maximum shear strain, maximum shear stress (tau(max)), Coulomb-Mohr, and modified Mohr failure theories were evaluated using automatically generated, computed tomographic scan-based FE models of the femur. Eighteen matched pairs of proximal femora were examined in two load configurations, one approximating joint loading during single-limb stance and one simulating impact from a fall. Mechanical testing was performed to assess model and failure theory performance in the context of predicting femoral fracture load. Measured and FE-computed fracture load were significantly correlated for both loading conditions and all failure criteria (p < or = 0.001). The distortion energy and tau(max) failure theories were the most robust of those examined, providing the most consistently strong FE model performance for two very different loading conditions. The more complex failure theories and the strain-based theories examined did not improve performance over the simpler distortion energy and tau(max) theories, and often degraded performance, even when differences between tensile and compressive failure properties were represented. The relatively strong performance of the distortion energy and tau(max) theories supports the hypothesis that shear/distortion is an important failure mode during femoral fracture.

Aged↗
PubMed2006

Prevention of recurrence of venous ulceration: randomized controlled trial of class 2 and class 3 elastic compression.

OBJECTIVE: To compare venous ulcer recurrence and compliance with two strengths of compression hosiery. METHODS: This study was a randomized controlled trial with a 5-year follow-up. The setting was the leg ulcer clinics of a teaching and a district general hospital in Scotland, United Kingdom. Patients were 300 outpatients with recently healed venous ulcers, with no significant arterial disease, rheumatoid disease, or diabetes mellitus. Interventions were fitting and supply of class 2 or class 3 compression hosiery. Four-monthly refitting by trained orthotists and surveillance by specialist nurses were performed. The main outcome measures were recurrence of leg ulceration and compliance with treatment. RESULTS: Thirty-six percent (107/300) of patients had recurrent leg ulceration by 5 years. Recurrence occurred in 59 (39%) of 151 class 2 elastic compression cases and in 48 (32%) of class 3 compression cases. One hundred six patients did not comply with their randomized compression class, 63 (42%) in class 3 and 43 (28%) in class 2. The difference in recurrence is not statistically significant, but our estimate of the effectiveness of class 3 hosiery is diluted by the lower compliance rate in this group. Restricted ankle movement and four or more previous ulcers were associated with a higher risk of recurrence. CONCLUSIONS: There was no evidence of a difference in recurrence rates at the classic level of significance (5%), but the lowest recurrence rates were seen in people who wore the highest degree of compression. Therefore, patients should wear the highest level of compression that is comfortable.

Adult↗
PubMedDate not supplied

An assessment of encapsulated versus hand-mixed glass ionomer restoratives.

Capsulation should enable uniform proportioning and mixing of dental restoratives so that functional properties of the cementitious mass will not be susceptible to clinically induced variability. Mechanical mixing induces a definite pore distribution determined by the viscosity of the system. This study evaluated the mixing process on the performance of a range of glass ionomer dental restoratives. Mean compressive fracture strengths and standard deviations and the associated Weibull Moduli (m) were determined for six glass ionomer restoratives that were either encapsulated or mixed by hand. Working characteristics were assessed using an oscillating rheometer. Scanning electron microscopy and image analysis was used to investigate the influence of the mixing method on pore distribution. The fracture strength data for some encapsulated restoratives resulted in significant differences compared with hand-mixing. Rotomix (compared with the Capmix mechanical agitator) resulted in increased Weibull moduli and 10% failure stress for the two restoratives that were investigated. Encapsulated restoratives that were prepared utilizing Rotomix or Capmix resulted in no significant differences for working characteristics; however, the setting time for the ChemFlex in Caps was extended compared with the hand-mixed ChemFlex. Not all restoratives had reduced porosity and improved performance following mixing with a Rotomix. This suggested that optimization of the initial viscosity of the system by manipulating the individual proportions of the constituents may not have been appropriate for all the restoratives investigated. The increased viscosity for hand-mixed ChemFlex prepared to a consistency of 3.8 g/ml compared with encapsulated ChemFlex in Caps prepared to a consistency of 3.5 g/ml was responsible for the reduced setting time.

Analysis of Variance↗
PubMed2004

Injectable self-curing bioactive acrylic-glass composites charged with specific anti-inflammatory/analgesic agent.

Injectable bioactive acrylic formulations based on poly(methyl methacrylate) (PMMA) and different amounts of bioactive glasses in the system SiO2-CaO-Na2O-P2O5 have been prepared in the presence of the anti-inflammatory analgesic drug fosfosal, the sodium salt of 2-phosphonoxibenzoic acid, to be used in minimally invasive surgery. The injectability of the formulations evaluated according to the established protocol was around 80%. The experimental formulations provided maximum temperatures in the range 50-60 degrees C, which were lower than those of commercial acrylic bone cements currently used in percutaneous vertebroplasty (PVP). Residual monomer content of any formulation was inferior to 5%. Compressive yield strength of dry specimens was in the range 80-95 MPa, but it decreased after immersion in SBF to values in the range 30-50 MPa, due to the dissolution of the bioactive glasses and the drug in the medium. The release of fosfosal was evaluated in vitro (pH = 7.0). The release profile against time obtained from a PMMA cement was quasi-linear and the 80% of the initial amount of drug was released in 175 h. However, for bioactive cements, the 80-100% of the fosfosal charged was released in approximately 48 h, due to the dissolution of the glasses in the medium. Values of weight loss of the cements determined gravimetrically ranged between 16% and 26% depending on the initial amount of fosfosal, i.e. 20 or 30 wt%, respectively. The weight loss and the water uptake were simultaneous processes, and values of hydration degree were around 10-14%. The formation of an apatite-like layer was detected on the surface of the cements at different periods of time depending on the composition of the bioactive glasses. The cements containing the glasses with P2O5 produced the growth of the apatite layer in shorter periods of time. The presence of fosfosal accelerated the precipitation of this layer independently on the glasses. The in vivo biocompatibility studied by intramuscular implantation in rats showed the absence of an anti-inflammatory response and a fibrous layer around the implant for the cement prepared with PMMA/fosfosal which is attributed to the therapeutic action of fosfosal acting in situ. The response to cements prepared with bioactive glasses and fosfosal showed a mild inflammatory reaction with the formation of the typical fibrous capsule around the implanted material.

Analgesics↗
PubMed1979

The healing of experimental fractures by compression osteosynthesis. I. Torsional strength.

Biomechanical properties of osteotomized rabbit tibio-fibular bones fixed with 6-hole stainless steel AO/DCP plates were investigated with torsional loading 3 to 24 weeks postoperatively. During the first 9 weeks maximum torque capacity, energy absorption and torsional rigidity increased, reflecting progressive bony union between the fractured bone ends. From 9 to 24 weeks the values of torque capacity and energy absorption decreased, whereas torsional rigidity seemed to reach a steady state without further significant changes. For the three parameters considered, the mean percentage differences between the osteotomized plated bones and their paired-sham-operated controls were 69, 64 and 80 per cent, respectively. The results suggest that internal fixation of fractured bones provides conditions for undisturbed fracture healing, but that subsequently the rigid nature of the implant has an adverse effect on the cortical bone, which slowly loses strength. Thus the optimal time for removal of the plate seems to be shortly after the fracture has healed and before the bony tissue had been weakened by secondary changes, such as cancellous transformation and spatial rearrangement of the tubular bone.

Animals↗
PubMed1991

[Tensile strength of dental porcelains].

Flexural, compressive and tensile strength as well as the modulus of elasticity of 15 different dental ceramics were evaluated. Conventional dental ceramics differed insignificantly in their mechanical properties. By testing new products like Cerec 2 and especially In-Ceram there was found an evident increase in inner strength. For comparison the strength of some other new ceramics as Dicor increased slightly related to conventional ceramics.

Aluminum Oxide↗
PubMed2005

Correlation of back pain, compression fracture and quadriceps muscle strength with bone mineral density in renal insufficiency patients.

AIM: The purpose of this study was to evaluate bone mineral density (BMD), bone parameters, complete blood count, erythrocyte sedimentation rate, electrolyte values, back pain, compression fracture and quadriceps muscle strength in mild and moderate renal insufficiency patients. METHODS: Thirty-six female, 3 male, patients with the diagnosis of osteoporosis in addition to mild or moderate chronic renal insufficiency who were followed in Istanbul University, Cerrahpasa Faculty of Medicine, Physical Therapy and Rehabilitation Department, Osteoporosis and Nephrology Outpatient Clinics between March 2003 and March 2004, were included in the study. In the control group there were 17 female, 5 male patients with osteoporosis but without renal insufficiency. The inclusion criteria were to have osteoporosis, be aged between 40-70 with a creatinine clearance between 30-70 mL/min in the case group, >70 mL/min in the control group. The patients whose creatinine clearance was <30 mL/min, and whose BMD was normal or osteopenic even though creatinine clearance was >30 mL/min were excluded from the study. RESULTS: There was no significant difference with respect to back pain, compression fracture and quadriceps muscle strength between the 2 groups. The mean value of neck BMD, T and Z score were significantly lower in the case group (P<0.05). CONCLUSIONS: As a conclusion, PTH related bone disease had an important effect on BMD, although, the risk factors for osteoporosis were equally important. In various researches, the relationship between BMD values and history of fracture in renal osteodystrophy patients could not be shown. In our study, the history of prior fracture or fracture in the family were important risk factors for osteoporosis. Renal osteodystrophy patients had low BMD values in mild and moderate stages of the disease. Prior fracture as well as osteoporotic fractures in the family should be part of a comprehensive evaluation of the patient.

Adult↗
PubMed1992

The comparative strengths of commercial glass-ionomer cements with and without metal additions.

Metal reinforced glass-ionomer cements are said to possess superior mechanical properties when compared to non-metal reinforced glass-ionomer cements. However, the literature to date does not always support this view, owing to the variety of materials and test methods employed. In this study the mechanical properties of three reinforced and three standard materials were tested using the standard specification tests of compressive and diametral strength in addition to tensile strength using the four point bend test. The tensile strength was also measured using the shell test in order that this test, which on theoretical grounds is more suited to these materials, may be evaluated. Six specimens of each material were prepared for each of the test modalities resulting in the conclusion that the addition of metal to glass-ionomer cements can markedly increase the strength of the materials. However, the method of fusing the metal to the glass rather than by simple addition does not produce any advantages in strength. In this evaluation one reinforced material was significantly stronger than all other materials in all four test modalities. The compressive strength test which appears in most standards does not appear to be very discriminatory. Of the tensile tests, which have more clinical significance, the results of the diametral strength tests, which are included in some standards, appear to be at variance with the other two tensile tests, suggesting that the flexural or shell test would be more appropriate.

Cermet Cements↗
PubMed1989

[AE characteristics during compression test of high-copper amalgams and visible light-cured composite resins].

Differences in environmental strength of high-copper amalgams and photo-cured composite resins for posterior after storage in deionized water at 37 degrees C for 1 year were evaluated by examining compressive strength and acoustic emission (AE) characteristics. The results were as follows: Microfailure in amalgams and composite resins was detected from the onset of stress and their microfailures toward catastrophic failure occurred at 70 to 90% of their ultimate strength. One-year compressive strength for amalgam decreased to 80 to 98% of its 24-hour compressive strength and that for composite resin to 65 to 75%.

Composite Resins↗