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Results for “Compressive Strength”

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At least 91 records · Page 5Linked to original sources

PubMed1995

Cortical mineral content of the radius assessed by peripheral QCT predicts compressive strength on biomechanical testing.

Our aim was to evaluate the role of cortical bone in resistance to compression in the human radius. Thirty-three left cadaver forearms were scanned on an XCT 960 Stratec CT scanner. Cortical density and cortical thickness were measured at the junction of the middle and distal third of the radius. Subsequently, 2-cm-high cylindrical specimens, centrated on the level of the CT slice, were cut. After removal of the endosteal trabecular bone, the specimens were submitted to compressive testing, using an Instron machine, and load deformation curves were obtained. Maximal stress (load corrected for cross-sectional area) showed a significant relationship with the density (r = 0.78) as well as with the thickness (r = 0.74) of the cortex. The closest correlation involved the maximal load and the mineral content of the cortex specimens (r = 0.87). We conclude that the mineral content of these radius cortex specimens, measured using peripheral QCT, predicts their compressive strength on biomechanical testing.

Aged↗

PubMed2026

Unconfined compressive strength prediction for the ordinary Portland cement-steel slag-silica fume ternary system based on response surface methodology.

This research was undertaken to address environmental concerns associated with industrial solid waste and to reduce cement consumption in geotechnical engineering. It specifically investigates the feasibility of using steel slag (SS) and silica fume (SF) as partial substitutes for ordinary Portland cement (OPC) in soil stabilization. The effects of SS, SF, OPC, and initial moisture content on the unconfined compressive strength (UCS) of stabilized soil were investigated through single-factor experiments and response surface methodology (RSM). The results show that SS and SF can synergistically enhance the strength of stabilized soil, although their interaction effect was not statistically significant within the investigated ranges. Compared with soil stabilized solely with OPC, the addition of 18 % SS and 10 % SF reduced OPC consumption by 3 % without compromising strength. Microstructural and compositional analyses further revealed that SS mainly supplied calcium- and silica-bearing components, while SF provided highly reactive silica and micro-filling effects, jointly promoting hydration reactions and improving the compactness of the stabilized soil matrix. As a result, more hydration products were formed in the OPC/SS/SF-stabilized soil than in the OPC-stabilized soil, which contributed to pore filling and strength enhancement. This study provides useful guidance for the sustainable utilization of industrial solid waste and the low-carbon development of soil stabilization materials.

Construction Materials↗

PubMed2000

Study of resin-bonded calcia investment: Part 1. Setting time and compressive strength.

This study was carried out to develop a new titanium casting investment consisting of calcia as the refractory material and a cold-curing resin system as the binder. The setting time of the investment was investigated under different N,N-dimethyl-p-toluidine (DMPT) contents in methyl methacrylate monomer (MMA) and benzoyl peroxide (BPO) contents in calcia without any sintering agent. The effects of the sintering agents, which were calcium fluoride (CaF2) and calcium chloride (CaCl2), on the compressive strength of the investments were investigated at room temperature before and after heating to two different temperatures. The shortest setting time (68 minutes) of the investment was obtained at 0.37 DMPT/BPO (1.5 vol% /1.0 mass%) ratio by mass. The highest strength (16.5 MPa) was obtained from the investment which contained 2 mass% CaF2 and was heated to 1,100 degrees C. It was found that the developed calcia investment containing 2 mass% CaF2 has a possibility for use in titanium castings.

Alloys↗

PubMed1997

Changes in compressive strength on ageing in glass polyalkenoate (glass-ionomer) cements prepared from acrylic/maleic acid copolymers.

Previous studies have shown that glass-ionomers made from acrylic/maleic copolymers stored in water reach a maximum strength at about 1 week, and after 4 months have become significantly weaker. This finding, which contrasts with the behaviour of glass-ionomers based on poly(acrylic acid), was originally attributed to hydrolytic instability. This interpretation has been tested in the current work. Specimens of glass-ionomer prepared from acrylic/maleic acid copolymer have been stored for up to 4 months in different media, namely deionized water, dry air and vegetable oil, then tested for compressive strength. Specimens were in the form of cylinders of dimensions 6 mm high x 4 mm diameter, and storage temperature was 37 degrees C. Data were analysed using two-way analysis of variance (ANOVA) and in all three media specimens became weaker at 4 months than they had been at 1 week (P < 0.05). However, for the specimens stored in dry air and in water, the 1-week values were not the maximum. The fact that there was a loss of strength under all conditions led to the conclusion that it is not, after all, due to hydrolysis.

Acrylates↗

PubMed1986

The compressive strength of nonprecious versus precious ceramometal restorations with various frame designs.

This study was designed as a comparative analysis of the compressive strengths of precious versus nonprecious metals with various framework designs used in clinical restorations. One hundred thirty-five statistically uniform ceramometal restorations were fabricated. The restorations were cemented to the die and then subjected to stroke-control compression forces in an Instron loading machine. Simulated clinical failure was recorded by the Instron load cell recorder in pounds of load.

Chromium Alloys↗

PubMed1999

Biomechanical behavior of hydroxyapatite as bone substitute material in a loaded implant model. On the surface strain measurement and the maximum compression strength determination of material crash.

Many investigators have advocated that hydroxyapatite ceramics may be extremely prospective bone substitute material mainly through evidence with its given biocompatibility towards bone and demonstrated continuity between living bone and hydroxyapatite. Its mechanical brittleness and strength, however, have been the most serious considerations. In this paper, a study has been performed using animal experiments, massive hydroxyapatite ceramics are implanted into rectangular bone defect created by operation at the load-bearing area in close contact with tibia plateau. The changes of surface strain at the hydroxyapatite implantation of retrieved tibiae are measured at any week after implantation when the compressive stress were applied in the direction of long axis in order to clarify the mechanical behaviors of hydroxyapatite living bone complex. The compression strength of hydroxyapatite implant crash was also determined at each week after implantation. Results revealed that the hydroxyapatite living bone complex has been proven to have sufficient flexibility such that it shows no hysteresis in stress versus strain relationship up to 200 kg of applied load. The strain pattern on the surface of hydroxyapatite implant develops quite similar to that of natural cortical bone. The material crash of hydroxyapatite implant tolerates up to 500 kg of load at 52 weeks after implantation. These characteristics suggest that it achieves normal skeletal function in the points of biomechanical properties in vivo.

Animals↗

PubMed2002

Effect of porosity reduction by compaction on compressive strength and microstructure of calcium phosphate cement.

Hydroxyapatite (HA) calcium phosphate cements (CPCs) are attractive materials for orthopedic applications because they can be molded into shape during implantation. However their low strength and brittle nature limits their potential applications to principally non-load-bearing applications. Little if any use has been made of the HA cement systems as manufacturing routes for preset HA bone grafts, which although not moldable pastes, are resorbable, unlike HA sintered ceramic. It is known that the strength of cements can be increased beyond that attainable from slurry systems by compaction, and this study investigates whether compaction significantly alters the specific surface area and pore-size distribution of CPC prepared according to the method of Brown and Chow. Compaction pressures of between 18 and 106 MPa were used to decrease the porosity from 50 to 31%, which resulted in an increase in the wet compressive strength from 4 to 37 MPa. The Weibull modulus was found to increase as porosity decreased; in addition the amount of porosity larger than the reactant particle size increased as porosity decreased. It is proposed that this was caused by a combination of voids created by the aqueous solvent used in fabrication and shrinkage that occurs on reaction. The specific surface area was unchanged by compaction.

Biocompatible Materials↗

PubMed1982

Effects of phase transformations of silicas and calcium sulfates on the compressive strength of gypsum-bonded investments at high temperatures.

The effects of transformations of silicas and calcium sulfates on high temperature compressive strength were investigated in commercial and experimental investment materials containing fused quartz as silica. The strength is only slightly affected by the alpha leads to beta transformation of cristobalite and not by the quartz alpha leads to beta transformation. The state of the calcium sulfates is the main factor influencing variations in the strength at a particular temperature.

Calcium Sulfate↗

PubMed1985

Correlation between the compressive strength of iliac and vertebral trabecular bone in normal individuals.

Intrabone and interbone variations and age-related changes in vertical and horizontal trabecular bone compressive strength (CS) were evaluated for loadbearing (vertebral) and nonloadbearing (iliac crest) trabecular bone from 30 normal individuals, 17 females and 13 males, aged 15-87 years. All had died suddenly. The vertebral bodies of Th6, L1, and L3 and the right and left iliac crests were frozen at -20 degrees C immediately after removal. Cylindrical bone samples in the vertical and horizontal direction were taken from the frozen bone, and load-deformation curves were recorded by a materials testing machine. For all vertebral bodies, the vertical CS was much larger than the horizontal CS (P less than 0.01), whereas no significant difference was found for the iliac crests. The anisotropy expressed as an index of vertical to horizontal CS, therefore, was higher in the vertebrae than in the iliac crest. The anisotropy index (Al) increased with age in the vertebrae but not in the iliac crest (r = 0.56, P less than 0.01). Age related, almost identical decreases in CS were observed in the vertebrae (vertical direction) (r = 0.81, P less than 0.01) and in the iliac crest (horizontal direction) (r = -0.69, P less than 0.01). In spite of the pronounced differences in the architecture between the vertebral body and iliac trabecular bone, the vertical vertebral CS could be predicted from the horizontal iliac crest CS (r = 0.88, P less than 0.01, SEE = 0.9 MPa). The vertical iliac crest CS showed a less significant correlation to the average vertical vertebral CS (r = 0.53, P less than 0.05, SEE = 1.25 MPa).

Adolescent↗

PubMed1991

Changes in compressive strength of glass ionomer restorative materials with respect to time periods of 24 h to 4 months.

This study investigated whether long-term changes occur in the compressive strength of a number of glass ionomer restorative materials, in view of the fact that little information is available from the manufacturers, and any variations with time might affect suitability for clinical use. It was found that, over the period of 24 h to 4 months, some materials, namely those based on polyacrylic acid, maintained or even showed a slight increase in their strength, whereas others based on copolymers of acrylic acid first increased in strength, but thereafter showed deterioration. In one case the strength decreased by nearly 50% compared to that at 24 h.

Dental Restoration, Permanent↗

PubMed1989

[Studies on the compressive strength of ceramic veneers].

Ceramic veneers were constructed following either a chamfer or a shoulder preparation (with rounded internal line angles). In laboratory tests both veneer forms displayed adequate compressive strengths. A beveled incisal finish line proved to be slightly superior to complete incisal coverage.

Aluminum↗

PubMed1993

Erosion and compressive strength of hybrid glass ionomer cements when light activated or chemically set.

It is claimed that light-activated hybrid glass ionomer cements offer advantages over the conventional glass ionomer lining materials. The compressive strengths and erosion rates of two hybrid glass ionomer lining cements, when light activated and chemically set, were compared with conventional glass ionomer cements. The results demonstrated that the erosion rates of the light-activated materials were comparable with those of the conventional materials. The conventional material, Ketac-Bond, was stronger than the light-activated hybrids. When the hybrid materials were allowed to set chemically alone, their performance was inferior to the conventional glass ionomer lining cements.

Glass Ionomer Cements↗

PubMed2001

Compressive strength of interocclusal recording materials.

Many materials are used for making interocclusal records to mount casts on dental articulators. The strength of these materials during the compressive forces encountered in the mounting process is important because any deformation will cause incorrect occlusal relationships. This investigation compared the deformation of 4 thicknesses (2 mm, 5 mm, 10 mm, 20 mm), when subjected to 25 N compressive force, of 3 interocclusal recording materials: condensation silicone, recording wax, and rubber-based polyvinylsiloxane. Significant differences were recorded for all materials of 20 mm, 10 mm and 2 mm thickness. However, there was no significant difference among the 5 mm groups. Interocclusal records should be made of a minimal thickness, using a recording material which exhibits minimal distortion during compression.

Analysis of Variance↗

PubMed1989

Increase in compressive strength of glass ionomer restorative materials with respect to time: a guide to their suitability for use in posterior primary dentition.

Glass ionomer restorative cements have been used in anterior restorations for a number of years but have not been considered strong enough for use in posterior restorations. The compressive strengths of a number of materials currently available were measured at 30 min, 1 hour and 24 hours. It was concluded that some of the materials might be considered for posterior restorations in deciduous teeth where no other considerations, such as radiopacity, apply.

Dental Cements↗

PubMed1984

Compressive strength of implanted porous replamineform hydroxyapatite.

Porous replamineform hydroxyapatite is a nontoxic, nonallergenic synthetic ceramic currently under investigation as an implant for restoration of atrophic edentulous ridges. Previous studies have demonstrated its capacity to permit the ingrowth of bone into its pores. Evaluation of the material was carried out to determine its eventual compressive strength following implantation. Bony penetration results in a significant increase in strength, judged to be sufficient for support of dentures.

Animals↗

PubMed1989

[Comparison of brush and moulding techniques in condensation of porcelain work, through shrinkage, compression strength and SEM images].

A general character of porcelain is the firing shrinkage which creates some problems in the fabrication of porcelain restorations. To overcome this matter, a well condensation which increases the strength of porcelain and decreases the shrinkage, is recommended. Taking this point into consideration, a moulding system is developed and it is found that pressing the porcelain in a mould, minimized the shrinkage, strengthened the structure and increased the compression strength. As a result we can say that this technique has important advantages in porcelain work.

Dental Casting Technique↗

PubMed2000

Ultrasonic parameters and relationship between compressive strength, microstructure of gall bladder stones.

Patients with symptomatic stones are at a great risk for complications and these complications are a major cause of morbidity. The gall bladder stones may have a complex structure and variable composition. In the present investigation stones have been grouped into three categories namely cholesterol, bilirubinate and mixed, and a correlation between the surface structure, ultrasonic parameters and compressive strength is estimated. A double-probe through-transmission technique was used for the ultrasonic parameters study, a universal testing instrument for hardness and a scanning electron microscope (SEM) for microstructure study. Gall bladder stones of mixed type with higher ultrasonic velocity, less attenuation and higher crushing strength were found to be more difficult to break in comparison to other types of stones. SEM of mixed type stones showed rough surface as compared to bilirubinate and cholesterol stones. The results obtained as well as the relationship might be useful in the design of a focussed ultrasonic 0lithotripter.

Cholelithiasis↗

PubMed1997

Ex vivo estimation of thoracolumbar vertebral body compressive strength: the relative contributions of bone densitometry and vertebral morphometry.

The estimation of vertebral fracture risk in individuals with suspected osteopenia is commonly based on measurements of lumbar spine bone density. The efficacy of vertebral size and deformity, as assessed by vertebral morphometry, in the prediction of fractures has been less studied. In an ex vivo investigation the regional relationships between vertebral size, vertebral deformity, bone density and compressive strength throughout the thoracolumbar spine were examined. In 16 vertebral columns (T1-L5) the bone mineral content (BMC) and bone mineral density (BMD) of each segment were measured using lateral projection dual-energy X-ray absorptiometry, and the vertebral cancellous density (VCD) and mid-vertebral cross-sectional area (CSA) measured using quantitative computed tomography. Vertebral body heights were determined from mid-sagittal CT scans, and vertical height ratios calculated for each segment. The failure load and failure stress of the isolated vertebral bodies were determined using a material testing device. Separate analyses were performed for the upper (T1-4), middle (T5-8) and lower (T9-12) thoracic, and lumbar (L1-5) segments. In all regions, failure load was strongly correlated with BMD (r = 0.82-0.86), moderately correlated with VCD (r = 0.60-0.71) and vertebral height (r = 0.22-0.49), and poorly correlated with the height ratios (r = 0.04-0.33). Failure stress was best predicted by BMD (r = 0.73-0.78) and VCD (r = 0.70-0.78) but was poorly correlated with all morphometric variables (r = 0.01-0.33). The segmental correlations between BMD and VCD ranged form r = 0.49 to r = 0.79. For all regions, BMD and VCD were included in the stepwise regression models for predicting failure load and failure stress. Either the mid-vertebral height or CSA were included in all the failure load models, while mid-vertebral height was included in only one of the failure stress models. The results suggest that vertebral deformity and size (as assessed by vertebral morphometry) make only a minor contribution to the prediction of vertebral strength additional to that provided by bone densitometry alone. The consistent regional relationships between variables appear to support the practice of global fracture risk assessment based on lumbar spine densitometry.

Adult↗