[Studies on impact strength of tablets. I. Impact compression strength and impact bending strength of tablets (author's transl)].
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Chemistry, Pharmaceutical↗
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Results for “Compressive Strength”
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Risk of vertebral insufficiency fractures in relation to compressive strength predicted by quantitative computed tomography.
Vertebral insufficiency fractures may result from excessive loading of normal and routine loading of osteoporotic spines. Fracture occurs when the mechanical load exceeds the vertebral compressive strength, i.e., the maximum load a vertebra can tolerate. Vertebral compressive strength is determined by trabecular bone density and the size of endplate area. Both parameters can be measured non-invasively by quantitative computed tomography (QCT). In 75 patients compressive strength (i.e., trabecular bone density and endplate area) of the vertebra L3 was determined using QCT. In addition, conventional radiographs of the spines were analysed for the prevalence of insufficiency fractures in each case. By relating fracture prevalence to strength, three fracture risk groups were found: a high-risk group with strength values of L3 less than 3 kN (kilo Newton) and a fracture risk of 100%, an intermediate group with strength values from 3 to 5 kN and a steeply increasing risk with decreasing strength, and a low-risk group with strength values greater than 5 kN and a fracture risk near 0%. Biomechanical measurements and model calculations indicate that spinal loads of 3 to 4 kN at L3/4 will be common in everyday activities. These data and the results described above suggest that spines with strength values of L3 less than 3 kN are at an extremely high risk of insufficiency fractures in daily life. Advantages of fracture risk assessment by strength determination over risk estimation based on clinically used trabecular bone density measurements are discussed.
Adult↗
Effect of luting media on the compressive strengths of two types of all-ceramic crown.
This study evaluated the effect of selected luting media on the compressive strength of two types of all-ceramic crown. Tooth preparation was standardized; each preparation had a shoulder width of approximately 1.2 mm, and all internal preparation angles were rounded. Hi-Ceram and Dicor all-ceramic crowns were fabricated and cemented into the preparations with zinc phosphate, glass-ionomer, or composite resin cement. Coronal compressive fracture strengths were determined, using a set of unrestored teeth as a control. There were no statistically significant differences among the mean compressive strengths of the three luting media, and there was no statistically significant difference between the mean compressive strength of Dicor and that of the natural tooth control.
Aluminum Oxide↗
Lumbar vertebral body compressive strength evaluated by dual-energy X-ray absorptiometry, quantitative computed tomography, and ashing.
Bone densitometry with DXA (dual energy X-ray absorptiometry) and QCT (quantitative computed tomography) techniques are used for in vivo assessment of bone strength and thereby prediction of fracture risk. However, only few in vitro studies have investigated and compared these techniques' ability to determine vertebral compressive strength. The aim of the present study was to (1) assess the predictive value of DXA, QCT, and pQCT (peripheral QCT) for vertebral bone compressive strength assessed by mechanical testing; (2) describe both linear and power relationship between density and strength; and (3) evaluate whether gender-related differences in the above relations were present. The material comprised human lumbar vertebrae L3 from 51 women and 50 men (age range: 18 to 96 years). The study showed that both DXA and CT techniques (QCT and pQCT) have a high predictive value for vertebral strength. The DXA BMD had a high correlation with maximum compressive load (r2 = 0.86). The QCT and pQCT had high correlations with maximum compressive stress (r2 = 0.75 and r2 = 0.86, respectively). The correlation between ash density of the biomechanically tested specimen and maximum compressive stress was r2 = 0.88. There were no differences between linear and power fit in the degree of determination between density and strength. There was no gender-related difference in the relationship between volumetric density and maximum compressive stress. In conclusion, it was demonstrated that DXA, QCT, and pQCT are ex situ equally capable of predicting vertebral compressive strength with a degree of determination (r2) between 75% and 86%. No differences were found between linear and power analysis of the relationship between density and strength, and no difference was found in the density strength relationship between women and men.
Absorptiometry, Photon↗
An evaluation of dental stones after repeated exposure to spray disinfectants. Part I: Abrasion and compressive strength.
This study investigated the effect of repeated applications of spray disinfectants on gypsum surfaces. Types III and IV gypsum products were evaluated in combination with iodophor, acid glutaraldehyde, phenol, and water spray. Results demonstrated greater resistance to abrasion with increasing numbers of water or disinfectant spray applications. Acid glutaraldehyde spray decreased the compressive strength of type III stone by 26%, phenol increased the compressive strength of type IV stone by 18%, and iodophor had no significant effect on either stone relative to compressive strength.
Aerosols↗
Compressive strength mapping of femoral head trabecular bone.
The purpose of this study was to develop a test protocol and complete a relative three-dimensional mapping of the local trabecular bone compressive strengths in healthy and osteoarthritic femoral heads. Five fresh frozen cadaveric femoral heads were compared to five fresh frozen osteoarthritic femoral heads obtained from patients undergoing total hip replacement. Each femoral head was coronally sectioned into eight 5 mm slices, which were compression-tested at 20 sites using a hydraulic testing machine. The results of the femoral head compressive strengths were normalized, mapped, and evaluated. The test protocol produced reproducible results and allowed the determination of diseased portions of osteoarthritic bone. The regions of high compressive strength were similar for normal and diseased bone and were located in the superior medial portions of the head. Ultimate stress was higher in diseased bone than in normal bone, while the yield point and stiffness of diseased bone was lower than for healthy bone.
Biomechanical Phenomena↗
Prediction of the compressive strength of vertebral bodies of the lumbar spine by quantitative computed tomography.
The ultimate compressive strength of 36 thoracolumbar vertebrae was determined experimentally. In addition, the trabecular bone mineral content was measured by single energy quantitative computed tomography. The areas of fractured endplates were also determined by computed tomography. The results show that a linear relationship exists between the compressive strength and the product of bone density and endplate area. These data allow an in vivo prediction of vertebral body strength using a noninvasive method with a standard error of estimate amounting to less than 0.95 kN.
Adult↗
Compressive strength and setting temperatures of mixes with various proportions of plaster to stone.
The compressive strength and setting temperature of different proportions of stone to plaster were measured. The water/powder ratio was 40:100 for all combinations. According to the experimental data, samples of stone to plaster in the ratios of 1:1, 1:3, and 1:4 gave an increased compressive strength of 10.3 MPa compared with the strength of plaster alone (8.3 MPa), possibly because of the low amounts of dental stone in the mix. The lowest amount of heat generated (lowest setting temperature) was recorded by the samples made with the ratio of stone/plaster equal to 1:1, which gave a setting temperature of 43 degrees C. Thus, the mix made with this ratio of stone to plaster may be the material of choice for filling the upper half of the flask during complete denture construction.
Calcium Sulfate↗
Effect of disinfectant on the dimensional stability, compressive strength and hardness on dental stone.
In this investigation it was planned to study the effect of disinfection time on the dimensional stability, compressive strength and hardness of gypsum die materials. Measurements of specimens treated with disinfectant were compared with the corresponding measurements of control specimens. The results of this study indicated that there was no difference in the dimensional stability, compressive strength and hardness. Therefore using the disinfectants will not affect gypsum die material.
Calcium Sulfate↗
[The compressive strength, tensile strength, flexural strength and micro-hardness of Plat-II Castable Ceramics].
In preparation for the clinical use of Plat-II Castable Ceramics (PCC-II), we tested its compressive strength, tensile strength, flexural strength and microhardness. The flexural strength was tested by the three-point bending test. The result showed that the compressive strength was 541.7 MPa; the tensile strength 42.5 MPa; the flexural strength 142.0 MPa; the modulus of elasticity 61.4 GPa; and the micro-hardness 499.6 kg/mm3. The strength anol micro-hardness of PCC-II materials were better than those of human enamel. So PCC-II is applicable to restorations in dentistry.
Ceramics↗
In vitro characteristics of tobramycin-PMMA beads: compressive strength and leaching.
Antibiotic-impregnated polymethylmethacrylate (PMMA) bone cement beads have been used as a local drug delivery system for the treatment of bone and soft tissue infections. The beads deliver a high local level of antibiotic with a decreased risk of toxic systemic levels. This study was undertaken to determine the antibiotic release characteristics of tobramycin-impregnated beads over time and to determine the compressive strength of these beads. Acrylic resin (PMMA) bone cement beads were prepared with three different concentrations of tobramycin. The beads were tested for compressive strength, and their antibiotic release characteristics were determined over a 21 day period by radioimmunoassay and by biological testing against a variety of bacteria. The compressive strength of the beads was found to be adequate to avoid fragmentation during their clinical use. There was gradual release of tobramycin from the beads over the entire 21 days, but the release was most marked during the first 48 hours. There was antibiotic activity against both gram-negative and gram-positive organisms, except Enterococcus, for the entire 21 day period. The release of tobramycin followed a curvilinear relationship and was directly related to the initial antibiotic concentration of the bead. Tobramycin-impregnated polymethylmethacrylate beads may represent a reliable method of local antibiotic delivery with sustained activity against a broad spectrum of organisms.
Bone Cements↗
The effect of placement technique upon the compressive strength and porosity of a composite resin.
This paper examines the effect of two placement techniques upon the compressive strength and level of porosity of specimens of a composite resin. Those specimens prepared by a condensation technique had a significantly lower mean compressive strength (P less than 0.05) and value of Weibull modulus (P less than 0.05) than specimens prepared using a smearing technique. No significant differences in the overall mean percentage area occupied by porosity and mean number of pores were demonstrated (P greater than 0.05) between the two placement techniques. Specimens prepared using the smearing technique, however, had significantly smaller mean maximum pore diameters (P less than 0.05) than those prepared using the condensation technique. It is therefore desirable when placing composite resins to reduce to a minimum handling procedures that are likely to influence the levels of porosity within the material.
Composite Resins↗
Investigation on the compressive strength of several gypsum products dried by microwave oven with different programs.
Different programs in a microwave oven were selected to dry several gypsum products. A type III dental stone (Moldano), a type IV high-strength dental stone (Glastone) and a type III partial denture casting investment (Multi-vest) were selected. Specimens of the products were dried by microwave radiation set at the lowest and highest power levels for 5 and 15 minutes. The dried specimens were tested at intervals of 2, 4, 24, and 48 hours for compressive strength. Specimens dried in ambient room air were used as the control group. A statistical analysis of the test results was performed with Student's t-test at p < or = 0.05 level. Microwave radiation at the highest power level resulted in a decrease in the compressive strength of type IV dental stone (Glastone), whereas the values of the other gypsum products did not differ at any time interval from values attained for the air-dried specimens. The 2-hour low power test of the investment (Multi-vest) had a higher compressive strength than the air-dried specimens after 24 hours.
Air↗
Incorporation of adhesive liners in amalgam: effect on compressive strength and creep.
This study evaluated the effects of two adhesive resin liners (Panavia EX and Amalgambond) on the compressive strength and creep rate of a single composition high-copper amalgam alloy (Tytin). Cylindrical specimens were prepared by dead-loading or hand-condensing amalgam in a Teflon mold which was unlined, lined with Panavia EX, or lined with Amalgambond. Compressive strength specimens were tested at 1 hour, 24 hours, and 7 days after preparation. Creep specimens were tested at 7 days. The adhesive resin liners did not significantly affect the strength of the Tytin specimens prepared by dead-loading (P greater than 0.05). The Panavia EX significantly reduced the strength of the Tytin specimens prepared by hand-condensing (P less than 0.05). The creep rate was not significantly affected by either resin liner.
Analysis of Variance↗
Effects of four mixing methods on setting expansion and compressive strength of six commercial phosphate-bonded silica investments.
Six commercial phosphate-bonded silica investments were mixed with four different mixing methods such as hand, two conventional blade-driven vacuum mixers and a new planetary mixing device, and examined for their setting expansion and compressive strength. The two properties often altered, depending upon the mixing method and the investment. The setting expansion of three investments were significantly affected by the mixing method while those of the other three were not. Compressive strength of all six investments varied by changing the mixing method. It is emphasized here that a mixing method and mixing condition must be properly set for each investment to improve the fit of the final metallic castings. This study also suggests that the planetary mixing device is a useful substitute for conventional blade-driven vacuum mixers.
Compressive Strength↗
Effect of wet and dry cellulose ring liners on setting expansion and compressive strength of a gypsum-bonded investment.
Effective setting expansion of gypsum-bonded investments is influenced by many variables. The purpose of this study was to determine the effect of using either water-saturated or dry cellulose ring lining material on (1) the fit of castings on a steel die and (2) the compressive strengths of investment cores using either type of liner. The mean gingival space in the water-saturated liner group was 0.241 +/- 0.048 mm and was 0.071 +/- 0.029 mm in the dry liner group (p < 0.001). The compressive strengths of investment cores from the dry liner group were 36.5% greater than those of cores from the water-saturated liner group. The results demonstrated that the use of dry liners may improve the fit of castings to dies.
Calcium Sulfate↗
Compressive strength of autologous and allogenous bone grafts for thoracolumbar and cervical spine fusion.
The selection of the bone graft type for stabilization of spinal fusion depends on availability, the clinical situation, and the desired mechanical stability. The authors determined the potential immediate postoperative compressive strength of various types of bone grafts under axial compression on a material testing machine. The fibular strut graft (5,070 +/- 3,250 N, mean +/- standard deviation [SD]) was significantly stronger (P less than 0.05) than the anterior (1,150 +/- 487 N) and posterior (667 +/- 311 N) iliac crest grafts, and the rib grafts (452 +/- 192 N). Hydroxyapatite grafts with a pore size of 200 mu were significantly stronger (P less than 0.05) than those with a pore size of 500 mu (1,420 +/- 480 N versus 338 +/- 78 N). Ethylenoxide sterilization had no significant effect on the immediate compressive strength. Bicortical and tricortical Bailey-Badgley and Cloward bone grafts also were compared. Results showed that all cervical graft types may be sufficiently strong to support sizable loads.
Aged↗
[Effect of aging on compressive strength of lumbar trabecular bone in hemodialyzed and non-hemodialyzed patients].
In order to clarify the effect of aging and bone mineral content on the compressive strength of lumbar trabecular bone, the third lumbar vertebral body (L3) was analyzed by mechanical and chemical tests in hemodialyzed (HD) and non-hemodialyzed (non-HD) patients. L3 was removed from 40 non-HD patients and 10 HD patients at autopsy. Cylindrical trabecular bone samples from L3 were analyzed by compression test, relaxation test and Brinel's test. Bone mineral content was based on Ca, P and Mg measured after incineration of the samples. In non-HD patients, a significant age-related decrease was observed in both Brinel's hardness (HBS) (r = -0.470) and Young's modulus (Qo) (r = -0.527), and there was a significant increase in age and viscoelasticity (B) (r = 0.439). HBS and Qo in about 50 percent of HD patients were larger than those in non-HD patients. C-PTH in HD patients showed a significant positive correlation with HBS and with Qo. Bone Ca content of the 50-69-year-old non-HD patients was 81 percent of that in the patients in their 40s and the content in the patients aged over 70 years was 55.5 percent of that in the patients in their 40s. In non-HD patients, the P/Ca and Mg/Ca weight ratios of bone were nearly constant regardless of age or sex. However, bone P/Ca and Mg/Ca weight ratios were relatively large in 80 percent of the HD patients. Bone Ca content exhibited a significant positive correlation with HBS (r = 0.399) and with bone mineral density measured by quantitative computed tomography (QCT) (r = 0.819). In conclusion, it was indicated that bone mineral content and compressive strength of trabecular bone decreased with aging, and that biomechanical competence in HD patients was much more prominent along with elevated C-PTH.
Adult↗