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Results for “Compressive Strength”

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At least 649 records · Page 36Linked to original sources

PubMed1978

Bond strength of three cements determined by centrifugal testing.

1. Each tooth preparation and crown should be used to test only one cement, since recementation will alter the bond strength associated with the second trial. 2. Recementation of a restoration should include a thorough cleaning of the preparation and the restoration. 3. Although zinc polycarboxylate cement possessed the highest bond strength, there were no statistically significant differences among the cements tested. 4. No correlation was found between bond strength and any individual property of compressive strength, tensile strength, or film thickness. 5. Values of ADA film thickness predicted the order of values of film thickness determined by a simulated clinical method.

Aluminum↗

PubMed2006

Development of bioconcrete material using an enrichment culture of novel thermophilic anaerobic bacteria.

In the biosphere, bacteria can function as geo-chemical agents, promoting the dispersion, fractionation and/or concentration of materials. Microbial mineral precipitation is resulted from metabolic activities of microorganisms. Based on this biomineralogy concept, an attempt has been made to develop bioconcrete material incorporating of an enrichment culture of thermophilic and anaerobic bacteria within cement-sand mortar/concrete. The results showed a significant increase in compressive strength of both cement-sand mortar and concrete due to the development of filler material within the pores of cement sand matrix. Maximum strength was observed at concentration 10(5)cell/ml of water used in mortar/concrete. Addition of Escherichia coil or media composition on mortar showed no such improvement in strength.

Anaerobiosis↗

PubMed2000

MSW fly ash stabilized with coal ash for geotechnical application.

The solidification and stabilization of municipal solid waste (MSW) fly ash for the purpose of minimizing the geo-environmental impact caused by toxic heavy metals as well as ensuring engineering safety (strength and soaking durability) are experimentally evaluated. The mixtures of MSW fly ash stabilized with cement and fluidized bed combustion coal fly ash (FCA) were used for unconfined compressive strength tests, leachate tests, and soaking tests. The behavior of soluble salts contained in the MSW fly ash significantly affects strength development, soaking durability, and the hardening reaction of the stabilized MSW fly ash mixtures. The cement stabilization of the MSW fly ash does not have enough effect on strength development and soaking durability. The addition of cement only contributes to the containment of heavy metals due to the high level of alkalinity. When using FCA as a stabilizing agent for MSW fly ash, the mixture exhibits high strength and durability. However, the Cd leachate cannot be prevented in the early stages of curing. Using a combination of cement and FCA as a MSW fly ash stabilizer can attain high strength, high soaking durability, and the containment of heavy metals. The stabilized MSW fly ash with cement and FCA can be practically applied to embankments.

Alkalies↗

PubMed2003

Effects of added bioactive glass on the setting and mechanical properties of resin-modified glass ionomer cement.

In this study, the effects of added bioactive glass on the basic setting properties of a commercially available resin-modified glass ionomer cement were investigated with respect to setting time, mechanical strength, and setting mechanism. It was found to be clinically acceptable whether the setting time was extended or shortened depending on the type of bioactive glass added. The compressive strength of the set cement containing the bioactive glass decreased and was much higher when compared with the conventional type glass ionomer cement containing bioactive glass. The Fourier-transform infrared and 13C CP/MAS-NMR spectroscopies revealed that the extent of the acid-base reaction was larger in the cements containing bioactive glass than in the commercial resin-modified glass ionomer cement because of its high basicity in the bioactive glass. The 27Al MAS-NMR showed that crosslinking of the carboxylates in the polymeric acid by Al proceeded less in the cement containing the bioactive glass.

Biocompatible Materials↗

PubMed2005

Siloranes in dental composites.

OBJECTIVE: The purpose of this study was to compare the product profile of a Silorane based composite which polymerizes by a cationic ring opening process with the product profile of different methacrylate based restoratives. METHODS: Four methacrylate based materials Filtek Z250, Filtek P60,Tetric ceram, Spectrum TPH and a Silorane based material were investigated with regard to their compressive strength, flexural strength, E-Modulus and ambient light stability. The data were analyzed by 1-way ANOVA and 2 sample t test (p<0.05). Shrinkage data were determined by the Archimedes method and the bonded disk method. The reactivity of the Silorane and Tetric ceram were derived from the time resolved shrinkage behaviour and the development of the E-Modulus over time. RESULTS: The Silorane Composite revealed with 0.94 vol% (bonded disk method) and 0.99 vol% (Archimedes method) the lowest polymerization shrinkage among all tested composites. Its reactivity was comparable to the reactivity of Tetric Ceram. However, the ambient light stability of >10 min for Silorane was higher than the ambient light reactivity of the other tested methacrylates (55-90 s). SIGNIFICANCE: The ring opening chemistry of the Siloranes enables at the first time shrinkage values lower than 1 vol% and mechanical parameters as E-Modulus and flexural strength comparable to those of clinically well accepted methacrylate based composites.

Composite Resins↗

PubMed2005

High-strength apatitic cement by modification with superplasticizers.

This study reports on a novel method to improve the strength of apatitic bone cements. The liquid phase of Biocement-H was modified with commercial superplasticizers. The results showed that small additions, i.e. 0.5 vol%, in the aqueous liquid phase improved the maximum compressive strength of Biocement-H (35 MPa) by 71%, i.e. 60 MPa. Moreover, the addition of high amounts of superplasticizers, i.e. 50 vol.%, allowed for a significant reduction of the liquid-to-powder ratio from 0.32 to 0.256 mL/g, without affecting the maximum strength and/or the workability of the cement. These results open up new ways to develop injectable and high-strength apatitic bone cements for load-bearing applications.

Bone Cements↗

PubMed1985

Trabecular bone strength patterns at the proximal tibial epiphysis.

The longitudinal compressive strength of trabecular bone from the human proximal tibial epiphysis was investigated in 12 autopsy specimens using multiple penetration tests with a small diameter indentor. Strength profiles were visualized by three-dimensional computerized reconstruction as a function of location on the resection surfaces. There were large variations of the maximal values between individuals, but the patterns obtained were remarkably uniform. The medial condyle showed the highest peak value in all but one knee with a mean medial-to-lateral peak value-ratio of 1.7. At the medial condyle the high strength area was relatively large with peak values being obtained centrally and anteriorly; the lateral condyle showed a more restricted, posteriorly localized area of high strength. Beneath the menisci, bone strength gradually decreased toward the margins of the condyles; likewise, bone strength decreased to reach very low values at the intercondylar region. There was a significant reduction of bone strength with the distance from the subchondral resection surface. This reduction was most pronounced at the high strength areas.

Biomechanical Phenomena↗

PubMed2002

The effect of the monomer-to-powder ratio on the material properties of acrylic bone cement.

The procedure percutaneous vertebroplasty consists of injecting polymethylmethacrylate cement into vertebral bodies for the treatment of osteoporotic compression fractures and tumors of the spine. Clinicians practicing vertebroplasty commonly alter the mixture of monomer-to-powder recommended by the manufacturer in an effort to decrease viscosity and increase the working time. The purpose of the current study was to measure the effect of varying the monomer-to-powder ratio on the compressive material properties (compressive modulus, yield stress, and ultimate compressive strength) of the cement Simplex P (Stryker-Howmedica-Osteonics, Rutherford, NJ). Cylindrical specimens were prepared using monomer-to-powder ratios of 0.45 to 1.00 mL/g and tested in compression. Peak compressive material properties occurred at the mixture ratio recommended by the manufacturer (0.5 mL/g) but decreased as the ratio of monomer to powder was increased. The material properties of specimens cured for 1 hour were significantly less than those for specimens cured for 24 hours. The monomer-to-powder ratio affects the compressive material properties of cement. The clinical significance of these results with respect to vertebroplasty is yet to be determined.

Bone Cements↗

PubMed2004

Bone mineral mass in males and females with and without Down syndrome.

Previous bone comparison studies between subjects with and without Down syndrome (DS) were performed using bone mineral density (BMD) as the dependent variable, and mainly focused on lumbar spine region. The purpose of this study was to compare bone mineral mass adjusted for bone and body size, in limbs, lumbar spine, and femoral neck between males and females with and without DS. Subjects were 66 females (33 with DS) and 68 males (34 with DS) aged 14-40 years. Analysis of covariance (ANCOVA) was used to analyze the main and interaction effects of gender and condition on bone mineral mass. For this purpose, adjusted bone mineral content (BMC) (for bone area, height, and age), volumetric bone mineral density (vBMD) (for age), and composite indices of femoral neck strength (for age), were used as the dependent variables, corrected additionally for body composition variables selected by regression analysis. ANCOVA revealed lower lumbar spine vBMD in DS than in control subjects with (-5%, P = 0.013), or without body weight adjustments (-6%, P = 0.003). In femoral neck, the mean of each strength measure was also lower in DS than in control subjects. Mean differences between groups were, with and without additional adjustments for fat mass, respectively, -8% (P = 0.009), and -13% (P < 0.001) for compressive strength, -11% (P = 0.036), and -16% (P = 0.004) for bending strength, and -7% (P = 0.031), and -11% (P = 0.002) for impact strength. These lumbar spine and femoral neck differences between groups were highest in young adults (> 20 years) and not significant in adolescents. No interaction effect was observed between gender and condition. In conclusion, DS was shown to be a risk factor for low vBMD in lumbar spine, and for diminished bone strength relative to the loads that the femoral neck must bear. Body composition did not reach statistical significance as predictor of bone differences in these sites between subjects with and without DS, suggesting that other factors may be involved in this detrimental bone status, particularly in young adults compared with adolescents.

Absorptiometry, Photon↗

PubMed2001

Trabecular domain factor and its influence on the strength of cancellous bone of the vertebral body.

The effects of architectural differences on the strength of cancellous bone of the vertebral body have not been clarified. This study was aimed at determining the influence of trabecular domain factor (TDF), a new histomorphometric parameter, on the maximum compressive strength (MCS) in vertebral cancellous bone. TDF is a variation coefficient representing the ratio dispersion of the area of each trabecula (Sd) to the area of its domain (D). A Voronoi diagram was used to determine trabecular domains. The materials comprised 35 lumbar vertebral bodies obtained at autopsy from 35 subjects aged 25-83 years. A mechanical test sample (12 x 12 x 16 mm) was cut out from each right half, and two large, undecalcified, horizontal sections from each left half. The fields (144 mm2 x 2) for image analyses were symmetrical with those for mechanical test samples in the other half of the same vertebral body. Bone volume (BV/TV), Sd, and D were semiautomatically measured. BV/TV correlated negatively with TDF (r = -0.73). Multiple regression analysis revealed the contributions of BV/TV (partial r = 0.75, p < 0.001) and TDF (partial r = -0.42, p < 0.02) to MCS. The model with BV/TV and TDF predicted MCS, 1.50 +0.15 BV/TV -0.03 TDF, more accurately (R2 = 0.83) than that with BV/TV alone (r2 = 0.79). We conclude that the bone volume primarily contributes to the MCS of vertebral cancellous bones but that the influence of TDF on the fragility becomes increasingly important as the bone volume decreases.

Adult↗

PubMed2006

Utilization of waste glass in ECO-cement: strength properties and microstructural observations.

Waste glass creates a serious environmental problem, mainly because of the inconsistency of the waste glass streams. The use of waste glass as a finely ground mineral additive (FGMA) in cement is a promising direction for recycling. Based on the method of mechano-chemical activation, a new group of ECO-cements was developed. In ECO-cement, relatively large amounts (up to 70%) of portland cement clinker can be replaced with waste glass. This report examines the effect of waste glass on the microstructure and strength of ECO-cement based materials. Scanning electron microscopy (SEM) investigations were used to observe the changes in the cement hydrates and interface between the cement matrix and waste glass particles. According to the research results, the developed ECO-cement with 50% of waste glass possessed compressive strength properties at a level similar to normal portland cement.

Compressive Strength↗

PubMed1998

Mechanical strength of calcium phosphate cement in vivo and in vitro.

Two different kinds of calcium phosphate cement were developed for implant fixation: cement A comprised of alpha-tricalcium phosphate (alpha-TCP) 95% and dicalcium phosphate dihydrate (DCPD) 5%, and cement B comprised of alpha-tricalcium phosphate 90% and dicalcium phosphate dihydrate 10%. The compression strength and pullout force of the new materials were tested both in vitro and in vivo. Microscopic observations were performed on the interface between bone and cement. Cement A showed a greater mechanical strength than cement B. The results suggest the clinical possibility of this calcium phosphate cement, which could be used as a material for enhancing implant fixation.

Animals↗

PubMed1997

Effect of provisional cements on the bond strength of various adhesive bonding systems on dentine.

Temporization of prepared teeth is needed for protection of the pulp and the restoration of the patients' aesthetic and functional needs. When zinc-oxyphosphate cement is used, eugenol-containing provisional cements are preferred because of their sedative effect to the pulp and because of their acceptable compressive strength. However, prior to definitive adhesive cementation with composite luting resins and dentine bonding agents the use of eugenol-containing provisional cements has to be considered critical because eugenol severely disturbs the polymerization of resinous materials. The purpose of this study was to compare shear bond strength values of various adhesive luting systems on dentine which had been in contact with various provisional cements prior to dentine bonding. The results show that the provisional cements which were used considerably decreased some of the bond strength values of the dentine bonding systems tested. Freegenol and Fermit, however, seem to have beneficial effects on the SBS values of Syntac and ART Bond. The only bonding system which produces acceptably high average SBS values with a eugenol-containing provisional cement was P-Bond.

Adhesives↗

PubMed2001

Calcium alginate gel: a biocompatible and mechanically stable polymer for endovascular embolization.

The development and optimization of calcium alginate for potential use in endovascular occlusion was investigated by testing its in vitro and in vivo mechanical stability and biocompatibility. The compressive resistance, rheology, and polymer yield of reacted alginate, and the polymer viscosity of unreacted alginate, were assessed. Biocompatibility was tested by injecting calcium alginate into the kidney capsule of rats. The reactivity of alginates with various structures and levels of purity were compared visually and histologically. Results suggest that calcium alginate is a biocompatible and mechanically stable gel for endovascular applications. Purified alginates exhibited compressive strength of 22 kPa and above at 40% compression, with no significant loss in elasticity. Purified alginate strength was significantly higher than that of crude alginates (p < 0.08). Purified alginates also exhibited significantly lower tissue reaction than crude alginates (p < 0.05). Of the alginates tested, purified high guluronic acid alginates (PHG) exhibited optimal strength and polymer yield, increased biocompatibility, and decreased viscosity. Clinical embolization treatments may be improved with the development of stable and biocompatible polymers such as calcium alginate. Possible uses of improved endovascular polymers include treating arteriovenous malformations (AVMs), aneurysms, blood flow to tumors, and vascular hemorrhaging.

Alginates↗

PubMed2004

Effect of lipid absorption on wear and compressive properties of unirradiated and highly crosslinked UHMWPE: an in vitro experimental model.

Ultra-high molecular weight polyethylene (UHMWPE or polyethylene) components used in total joint arthroplasty absorb lipids in vivo. However, the effect, if any, of this lipid uptake on both the wear and the mechanical properties of polyethylene is not known. We contrasted the effects of lipid diffusion into the polyethylene on the wear and mechanical properties of unirradiated UHMWPE versus that into highly crosslinked UHMWPE preparation (a 95-kGy irradiated and melted UHMWPE). We doped test samples of both types of polyethylenes with either squalene alone or a 15% (w/v) solution of cholestene/squalene (CH/SQ) solution. The diffusion profiles were quantified using infrared microscopy as a function of depth away from free surfaces; we used the 1620 and 1680 cm(-1) absorbances characteristic of CH and SQ, respectively. There were no statistically significant changes in the bi-directional pin-on-disk wear rates of neither type of polyethylene after lipid absorption. On the other hand, compressive modulus and compressive strength of both polyethylenes decreased after doping with either lipid.

Absorption↗

PubMed1998

Norian SRS cement augmentation in hip fracture treatment. Laboratory and initial clinical results.

Bone quality, initial fracture displacement, severity of fracture comminution, accuracy of fracture reduction, and the placement of the internal fixation device are important factors that affect fixation stability. New high strength cements that are susceptible to remodeling and replacement for fracture fixation may lead to improved clinical outcome in the treatment of hip fractures. Norian SRS is an injectable, fast setting cement that cures in vivo to form an osteoconductive carbonated apatite of high compressive strength (55 MPa) with chemical and physical characteristics similar to the mineral phase of bone. It can be used as a space filling internal fixation device to facilitate the geometric reconstruction, load transfer, and healing of bone with defects and/or fractures in regions of cancellous bone. Furthermore, this cement can improve the mechanical holding strength of conventional fixation devices. Use of this material potentially could improve fracture stability, retain anatomy during fracture healing and improve hip function, thus achieving better clinical outcomes. In vivo animal studies have shown the material's biocompatibility, and cadaveric studies have shown the biomechanical advantage of its use in hip fractures. Initial clinical experience (in 52 femoral neck fractures and 39 intertrochanteric fractures) showed the potential clinical use of this innovative cement in the treatment of hip fractures.

Aged↗

PubMed2004

Preparation and characterization of a highly macroporous biodegradable composite tissue engineering scaffold.

A unique composite scaffold for bone-tissue engineering applications has been prepared by combining biodegradable poly(lactide-co-glycolide) (PLGA) with bioresorbable calcium phosphate (CaP) cement particles through the process of particle fusion and phase separation/particle leaching. The scaffold is characterized by a highly interconnected macroporosity, with macropores of 0.8-1.8 mm and porosities ranging from 81% to 91%, and improved mechanical properties with respect to the polymer alone, producing excellent dimensional stability. The scaffold properties were controlled by adjusting the processing parameters, including PLGA molar mass and concentration, CaP/PLGA ratio, and porogen size. The differences in mechanical properties between dry, wet/room temperature, and wet/37 degrees C testing conditions, of which the latter are more relevant for materials to be employed in a biological milieu, were investigated. Thus, a scaffold made from PLGA IV 1.13, PLGA concentration 12.5%, and CaP/PLGA ratio 2:1 exhibited significantly different compressive strengths of 0.16 MPa and 0.04 MPa when tested under dry and wet/37 degrees C conditions, respectively. .

Absorbable Implants↗

PubMed2002

A new method to produce macropores in calcium phosphate cements.

A new way to create macropores in calcium phosphate cements has been developed. The method consists in adding NaHCO3 to the starting cement powder (Biocement D) and using two different liquids: first a basic liquid to form the paste and later an acid liquid to obtain CO2 bubbles. Mercury intrusion measurements showed a dramatic increase both in macropores with an average size of 100 m and in the total porosity (even higher than 50% with respect to the Biocement D). This method does not change in any significant way the final reaction products of the starting material after being soaked 3 days in Ringer solution. Only, due to the increase of the porosity. the compressive strength of the porous cement decreases significantly.

Biodegradation, Environmental↗