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Results for “Compressive Strength”

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PubMed1997

An experimental study of lumbar destabilization. Restabilization and bone density.

STUDY DESIGN: An investigation of the effects of bone density on lumbar spine stability using destabilizing and restabilizing procedures. OBJECTIVES: To measure cadaveric vertebral bone densities computed tomographic scans and to correlate the measured densities with lumbar spine stability in the intact and during sequential destabilization and restabilization. SUMMARY OF BACKGROUND DATA: The stabilizing effects of lumbar pedicle screw fixation have been widely described. Numerous construct failure mechanisms have been observed, including screw loosening in osteoporosis. Although previous studies have analyzed the effect of bone density on the compression strength of bone similar to that used in interbody fusion and the relationship of pedicle screw pull-out strength to vertebral bone density, a combined study of bone density and construct stability using an interbody bone spacer with pedicle fixation has not been performed. METHODS: Bone densities were measured in 20 human cadaveric lumbar spines using computed tomography scans and a hydroxyapatite phantom. After the specimens were mounted in a testing frame, the L4-L5 motion segments were subjected to cyclic axial compression-torsional loads, and axial and rotational intervertebral displacements were monitored. Laminectomy, facetectomy, and pedicle screw-plate fixation were performed sequentially in three specimens. Ten others underwent these procedures with an additional destabilization procedure, discectomy, after facetectomy. Seven others underwent the same sequence as the previous group, followed by the insertion of interbody bone. Cyclic testing was resumed after each procedure. RESULTS: Average bone densities varied widely among the specimens. Average bone densities of the pedicle and of the vertebral body for individual specimens were well-correlated (r = 0.897). Displacements were recorded as a percentage of the intact state before destabilization; average percentages are reported as follows: axial displacements increased after facetectomy (145%) and subsequent discectomy (251%), and rotational displacements increased after facetectomy (295%) and discectomy (390%). Instrumentation without interbody bone resulted in specimens with decreased axial (126%) and rotational (156%) displacements. The addition of interbody bone further decreased axial (111%) and rotational (117%) displacements. The rotational stabilization provided by instrumentation was well-correlated with vertebral bone density (r = 0.804). This correlation was enhanced by the use of interbody bone (r = 0.939). CONCLUSION: The unstable lumbar spine can be partially stabilized using fixation. Interbody bone provides additional stability. The immediate stability provided by pedicle screws is greater in lumbar vertebrae with higher bone density.

Adult↗

PubMed2006

The cause and influence of self-cementing properties of fine recycled concrete aggregates on the properties of unbound sub-base.

The use of coarse recycled concrete aggregates (CRCA) in conjunction with fine recycled concrete aggregates (FRCA) as sub-base materials has been widely studied. Although research results indicate that it is feasible to employ both CRCA and FRCA as granular sub-base, the influence of the unhydrated cement in the adhered mortar of the RCA on the properties of the sub-base materials has not been thoroughly studied. Generally, it is known that the strength of the sub-base materials prepared with RCA increases over time. However, this mechanism, known as the self-cementing properties, is not well understood and is believed to be governed by the properties of the fine portion of the RCA (<5mm). This paper presents an investigation on the cause of the self-cementing properties by measuring X-ray diffraction patterns, pH values, compressive strength and permeability of various size fractions of the FRCA obtained from a commercially operated construction and demolition waste recycling plant. Their influence on the overall sub-base materials was determined. The results indicate that the size fractions of <0.15 and 0.3-0.6mm (active fractions) were most likely to be the principal cause of the self-cementing properties of the FRCA. However, the effects on the properties of the overall RCA sub-base materials were minimal if the total quantity of the active fractions was limited to a threshold by weight of the total fine aggregate.

Construction Materials↗

PubMed1998

Modulation of bone mass, strength, and turnover by a new benzamide compound, DU-6712, in adjuvant-induced arthritic rats.

To assess the reductions in bone mass, strength, and turnover in adjuvant-induced arthritic rats and to examine the effect of a new benzamide compound, DU-6712, on these parameters, a 28-day dosing experiment was performed using 8-week-old female Lewis rats. Arthritis was induced by injecting the adjuvant into the hind paw. The age-dependent increases in the body weight, lumbar bone mineral content and density (BMC and BMD) and compressive strength were disturbed in the arthritic rats. At 14 days, the histomorphometric parameters of bone formation (BFR/BS and BFR/BV) and the serum osteocalcin levels were significantly reduced compared with the baseline controls. However, the BMC values corrected for body weight did not differ significantly between the arthritic and normal rats, and the bone minerals were not reduced compared with the baseline controls. At 28 days, the parameters of bone minerals and strength of the lumbar body in the arthritic rats, both with and without correction for body weight, were significantly reduced compared with the baseline controls. The trabecular mineralizing surface remained significantly reduced and the osteoclast numbers were increased. DU-6712 at the doses of 5, 15, and 45 mg/kg, orally administered daily from the start of the experiment, significantly prevented the development of the chronic paw edema at 28 days. The reductions in the parameters of bone minerals, strength, and trabecular bone formation, and the increase in osteoclast number were alleviated by this agent. Age-dependent increases in the lumbar height, disturbed by the adjuvant injection, were also maintained. These data indicated that a 28-day period is necessary to obtain sufficient reductions in the bone mass and strength of the lumbar body concerning the model of secondary osteoporosis in adjuvant arthritic rats. DU-6712 was able to prevent these reductions by modulating the bone turnover in this arthritis model.

Animals↗

PubMed1994

Bone mineral content and fixation strength of femoral neck fractures. A cadaver study.

We measured the bone mineral content (BMC) of 21 human femoral autopsy specimens using Radiographic Attenuation Technique (RAT). The specimens were then tested for stiffness in a material-testing machine. Osteosynthesis was performed after medial femoral neck osteotomy, using 1 of 3 different pinning methods: 2 hook pins (LIH), 2 cannulated screws (Uppsala), and 3 cannulated screws (CHP). The specimens were allocated to each method by grouping them in triplets with similar BMC. Cyclic loading at 500-1000 N and 1 Hz was performed during 50 minutes. The amount of axial compression during loading was measured. Finally, loading to failure was done and post-fixation stiffness and ultimate compression strength recorded. With one exception, all cases failed where the BMC was less than 0.4 g/cm2. No differences between the methods of osteosynthesis were found. The fixation strength was mostly dependent on the strength of the bone, i.e., the degree of osteoporosis.

Aged↗

PubMed2000

Shear stress distribution in the trabeculae of human vertebral bone.

The statistical distribution of von Mises stress in the trabeculae of human vertebral cancellous bone was estimated using large-scale finite element models. The goal was to test the hypothesis that average trabecular von Mises stress is correlated to the maximum trabecular level von Mises stress. The hypothesis was proposed to explain the close experimental correlation between apparent strength and stiffness of human cancellous bone tissue. A three-parameter Weibull function described the probability distribution of the estimated von Mises stress (r2>0.99 for each of 23 cases). The mean von Mises stress was linearly related to the standard deviation (r2=0.63) supporting the hypothesis that average and maximum magnitude stress would be correlated. The coefficient of variation (COV) of the von Mises stress was nonlinearly related to apparent compressive strength, apparent stiffness, and bone volume fraction (adjusted r2=0.66, 0.56, 0.54, respectively) by a saturating exponential function [COV = A + B exp(-x/C)]. The COV of the stress was higher for low volume fraction tissue (<0.12) consistent with the weakness of low volume fraction tissue and suggesting that stress variation is better controlled in higher volume fraction tissue. We propose that the average stress and standard deviation of the stress are both controlled by bone remodeling in response to applied loading.

Adult↗

PubMed1990

Femoral neck fracture fixation. Comparison of a sliding screw with lag screws.

The rigidity of a sliding compression screw and three cannulated lag screws in the treatment of subcapital fractures was compared in five pairs of female cadaver femora. There were no significant differences between the compressive strength, bone density, cortical thickness or Singh index of the bones in each pair. A subcapital fracture was standardised using a perpendicular saw cut across the femoral neck. A uniaxial 'load test system' with force and length measurement facilities was used to mimic cyclical stressing applied in vivo at a frequency of 0.5 Hz from 0 to 3 times body-weight. There was no significant difference between the fixation afforded by the sliding compression screw and three lag screws. Bone quality was the single most important factor in the stability of the bone implant unit.

Aged↗

PubMed2000

Biodegradable foam coating of cortical allografts.

Clinical outcomes of bone allograft procedures may be improved by modifying the surface of the graft with an osteoconductive biopolymeric coating. In this comparative in vitro study, we evaluated the dimensional stability, mechanical strength, hydrophilicity, and water uptake of biodegradable foams of poly(propylene fumarate) (PPF) and poly(d,l-lactic-co glycolic acid) (PLGA) when applied as surface coatings to cortical bone. Cortical bone samples were divided into four groups: Type I, untreated bone; Type II, laser-perforated bone; Type III, partially demineralized bone; and Type IV, laser-perforated and partially demineralized bone. Results show that PPF wets easily, achieving 12.5% wt/wt in 30 min. Compressive tests on the PPF foam material showed that the compressive strength was 6.8 MPa prior to in vitro incubation but then gradually reduced to 1.9 MPa at 8 weeks. Push-out and pulloff strength tests showed that initially both PPF and PLGA foam coatings had comparable adherence strengths to the cortical bone samples (100-150 N). When additional geometrical surface alteration by perforation and demineralization of the bony substrate was employed, in vitro adherence of the PPF foam coating was further increased to 120 N, demonstrating a statistically significant improvement of push-out strength throughout the entire 8-week observation period (p<0.0002 for all four data points). The pore geometry of PPF-foam coatings changed little over the 2-month evaluation period. In comparison, PLGA foam coating around the cortical bone samples rapidly lost structure with a decrease of 67% in strength seen after 1-week in vitro incubation. These new types of bone allografts may be particularly useful where the use of other replacement materials is not feasible or practical.

Bone Remodeling↗

PubMedDate not supplied

Micromechanics of bone strength and fracture.

The mechanical properties of bone were modeled in the context of a filled polymeric composite containing a collagenous matrix and a hydroxyapatite filler. The longitudinal and transverse moduli of cortical bone as a composite with perfect alignment of filler particles were calculated to be 34.5 and 5.3 GPa, respectively. When considering that particle orientation is arranged within a distribution about the long axis, moduli close to the experimentally measured values are achieved. The calculated tensile strength of 1.7 GPa is higher than the experimental values, which may be attributable to intrinsic sample flaws and biological heterogeneity. The mode of tensile failure in this model is particle-matrix debonding, which may explain fatigue or stress fractures. Overall, the filled composite model of bone helps explain the roles of mineralization fraction, particle shape and orientation, and other attributes of the constituent phases in understanding the tensile properties. The fundamentals of bone behavior in compression are less well understood. It is proposed that incorporation of an inorganic phase in bone was teleologically necessary for vertebrates to achieve adequate levels of compressive strength.

Biomechanical Phenomena↗

PubMed1980

The fracture strength of amalgam overlying base materials.

Conclusions reached within the constraints of this study showed the following: 1. Fracture strength of Class II amalgam restorations decreased as the thickness of the bases increased. 2. Fracture strengths of amalgam restorations based with different thicknesses of zinc phosphate cement underline with 0.5 mm Dycal were not different from each other. 3. The strength of the restorations varied with the type of base. Zinc phosphate cement is equal to no base and superior to zinc phosphate cement plus Dycal, which is equal to Dycal. Dycal is superior to Cavitec, which is the same as Cavitec plus Dycal. 4. The base materials did not fracture. The amalgam restorations were stronger over a base with a higher modulus of elasticity, indicating that modulus of elasticity of a base is more important than compressive strength in supporting an amalgam restoration. 5. There is no advantage (no improvement in resistance to fracture of the amalgam restoration) to be gained from placing zinc phosphate cement over Dycal. 6. When a calcium hydroxide liner is not needed, the cements with a higher modulus of elasticity, such as zinc phosphate cement and reinforced ZOE, will provide for stronger amalgam restorations than Cavitec and unreinforced ZOE.

Calcium Hydroxide↗

PubMed1999

Fractal analysis of radiographs: assessment of trabecular bone structure and prediction of elastic modulus and strength.

The purpose of this study was to determine whether fractal dimension of radiographs provide measures of trabecular bone structure which correlate with bone mineral density (BMD) and bone biomechanics, and whether these relationships depend on the technique used to calculate the fractal dimension. Eighty seven cubic specimen of human trabecular bone were obtained from the vertebrae and femur. The cubes were radiographed along all three orientations--superior-inferior (SI), medial-lateral (ML), and anterior-posterior (AP), digitized, corrected for background variations, and fractal based techniques were applied to quantify trabecular structure. Three different techniques namely, semivariance, surface area, and power spectral methods were used. The specimens were tested in compression along three orientations and the Young's modulus (YM) was determined. Compressive strength was measured along the SI direction. Quantitative computed tomography was used to measure trabecular BMD. High-resolution magnetic-resonance images were used to obtain three-dimensional measures of trabecular architecture such as the apparent bone volume fraction, trabecular thickness, spacing, and number. The measures of trabecular structure computed in the different directions showed significant differences (p<0.05). The correlation between BMD, YM, strength, and the fractal dimension were direction and technique dependent. The trends of variation of the fractal dimension with BMD and biomechanical properties also depended on the technique and the range of resolutions over which the data was analyzed. The fractal dimension showed varying trends with bone mineral density changes, and these trends also depended on the range of frequencies over which the fractal dimension was measured. For example, using the power spectral method the fractal dimension increased with BMD when computed over a lower range of spatial frequencies and decreased for higher ranges. However, for the surface area technique the fractal dimension increased with increasing BMD. Fractal measures showed better correlation with trabecular spacing and number, compared to trabecular thickness. In a multivariate regression model inclusion of some of the fractal measures in addition to BMD improved the prediction of strength and elastic modulus. Thus, fractal based texture analysis of radiographs are technique dependent, but may be used to quantify trabecular structure and have a potentially valuable impact in the study of osteoporosis.

Biomechanical Phenomena↗

PubMed2003

Superporous IPN hydrogels having enhanced mechanical properties.

The objective of this study was to improve the mechanical properties of superporous hydrogels (SPHs), which were used to develop gastric retention devices for long-term oral drug delivery. The main approach used in this study was to form an interpenetrating polymer network by incorporating a second polymer network inside an SPH structure. Polyacrylonitrile was used as the second network inside an SPH. Mechanical properties including compression strength and elasticity were significantly improved, up to 50 times as compared with the control SPHs. The enhanced mechanical properties were a result of the scaffold-like fiber network structures formed inside the cell walls of SPHs. The fast swelling property of SPHs was not affected by the incorporation of the second polymer network because the interconnected pore structures were maintained. Gastric retention devices based on superporous IPN hydrogels (SPIHs) with the improved mechanical properties are expected to withstand compression pressure and mechanical frictions in the stomach better than the control SPHs.

Acrylic Resins↗

PubMed2004

[Multislice-CT for structure analysis of trabecular bone - a comparison with micro-CT and biomechanical strength].

OBJECTIVES: MS-CT (Multislice-Spiral-CT) has a higher spatial resolution compared to the SS-CT (Singleslice-CT). The purpose of this study was to investigate, if the higher spatial resolution of the MS-CT has advantages for structural analyses in the assessment of osteoporosis. MATERIAL AND METHODS: 20 cylindrical trabecular bone specimens (diameter 12 mm, length 15 - 20 mm) were harvested from formalin-fixed human thoracic spines. All specimens were examined by Micro-CT and quantitative, histomorphologic parameters were determined. Analogous structural parameters were calculated from the high-resolution images acquired by both MS- and SS-CT. Additionally, the BMD (bone mineral density) was measured by QCT (quantitative CT). The maximum compressive strength (MCS) was determined in a biomechanical test. The structural parameters were correlated with the histomorphologic parameters and with the MCS. RESULTS: The parameters bone fraction and trabecular separation correlated significantly in both MS- and SS-CT with the analogous parameters from Micro-CT (r (2) = 0.84, p < 0.01) and the MCS (r (2) = 0.81, p < 0.01). The highest correlation with the MCS was calculated using the trabecular number measured by MS-CT in the superior region near the endplate of the vertebra with the high-resolution kernel U90 u (r (2) = 0.85, p < 0.01). This correlation was significantly higher than the correlation between MCS and BMD (r (2) = 0.49, p < 0.01). CONCLUSION: Micro-CT- and MS-CT-determined structural parameters of the trabecular bone showed significant, high correlations. Thus, a characterisation of the trabecular structure seems to be possible. The biomechanical stability of the bone can also be predicted well. The structural parameters acquired by MS-CT show higher correlations with the MCS than the BMD or structural parameters determined by SS-CT do. In this study MS-CT was best suited to predict biomechanical strength of trabecular bone.

Aged↗

PubMed1978

[Comparative studies between various amalgams].

A number of dental amalgam products have been compared in the context of a thesis. Four products, each of them possessing different characteristics, have been selected. Six Eighty Amalgam Alloy is a conventional product; Fluor Alloy contains a quantity of SnF2; Amalcap non gamma2 belongs to the group of the so-called non gamma2-alloys; Indiloy is spherical and contains indium. Each product was subjected to a series of tests and investigations: structure, dimensional changes after condensation, compressive strength, behaviour during a relaxation-test and resistance to corrosion. Indiloy was the product with the most interesting structure and it could be ascertained the mercury especially attacked silver and indium of the original alloy. Thus a sort of matrix is formed. The measuring of the dimensional changes was done by introducing a new method. Fluor Alloy and Indiloy present a behaviour that differs a lot from the expected one: at first a contraction followed by a more important expansion. A relaxation-test is an alternative to the creep-test and the connection between both is demonstrated. Combining the results of the resistances to the compressive forces with those of the relaxation-tests shows Indiloy possesses superior mechanical properties while those of Six Eighty Amalgam Alloy are rather inferior. A final series of tests concerns the resistance to corrosion. Amalcap non gamma2 and Indiloy have a much greater rough resistance to corrosion than the two other ones.

Corrosion↗

PubMed2001

[Experimental study on the reinforced effect of light curing composite resins used for crowns and bridges].

OBJECTIVE: To evaluate the reinforced effect of the light curing composite resins used for crowns and bridges. METHODS: Three light curing composite resins which were used for crowns and bridges were chosen, and three polyester fiber sieves and three stainless steel sieves in different mesh were used as the additional reinforced materials. Compressive strength and three point flexural strength of test bars made of those materials were evaluated. The reinforced bridges with special fibers were used as control groups. RESULTS: (1)There was significant increase in the stainless steel sieves groups. Nevertheless, there was some decrease after use of the polyester fibers as the additional reinforced material. (2)The increase of the reinforced crowns was especially obvious. (3)Among the three resins, the property of Targis was better than that of Arglass and Solidex. CONCLUSION: The properties of the whole composite material were closely correlated with the additional reinforced materials, the resistance to compression of the sieves are better than its resistance to bend.

English Abstract↗

PubMed1998

Relationships between static histomorphometry and bone strength measurements in human iliac crest bone biopsies.

It has been well established that trabecular bone strength has a power relationship to apparent bone density. It has been argued that the apparent bone density is not the sole factor determining cancellous bone strength, and that bone strength may also depend on the structure of the trabecular network. Various different measures of bone microstructure have been suggested: marrow space star volume; node-strut analysis; connectivity density; trabecular number; and trabecular separation. The aim of this study was to assess which of the histomorphometric measures, trabecular bone volume, marrow space star volume, node-strut analysis, connectivity density, trabecular number, and trabecular separation, give the best prediction of the bone strength. Moreover, a comparison of the suggested "structural" measures was carried out to establish whether they actually quantified the bone structure or something different. Finally, the influence of age and gender was investigated. The material comprised unilateral transiliac crest bone biopsies from 32 females (21-96 years, mean 59.1 years) and 32 males (24-94 years, mean 59.0 years). The bone biopsies were embedded in Technovit 9100, sectioned, and stained with aniline blue. Trabecular bone volume, marrow space star volume, node-terminus ratio, connectivity density, trabecular number, and trabecular separation were measured. A neighboring biopsy was compressed to obtain the compressive strength of the trabecular network. Trabecular bone volume was the measure that gave the strongest correlation with bone strength (r = 0.76 for females and r = 0.86 for males). High correlation was found between trabecular bone volume, marrow space star volume, node-terminus ratio, and trabecular separation--indicating that they carried the same information. A poor correlation was seen between these measures and connectivity density. Connectivity density was the only measure showing gender-dependent behavior. A multiple regression analysis showed that the trabecular bone volume is the best histomorphometric predictor of bone strength, and neither marrow space star volume, node-terminus ratio, connectivity density, trabecular number, nor trabecular separation could improve the predictive value of trabecular bone volume.

Adult↗

PubMed2003

Glucocorticoids act directly on osteoblasts and osteocytes to induce their apoptosis and reduce bone formation and strength.

Whether the negative impact of excess glucocorticoids on the skeleton is due to direct effects on bone cells, indirect effects on extraskeletal tissues, or both is unknown. To determine the contribution of direct effects of glucocorticoids on osteoblastic/osteocytic cells in vivo, we blocked glucocorticoid action on these cells via transgenic expression of 11beta-hydroxysteroid dehydrogenase type 2, an enzyme that inactivates glucocorticoids. Osteoblast/osteocyte-specific expression was achieved by insertion of the 11beta-hydroxysteroid dehydrogenase type 2 cDNA downstream from the osteoblast-specific osteocalcin promoter. The transgene did not affect normal bone development or turnover as demonstrated by identical bone density, strength, and histomorphometry in adult transgenic and wild-type animals. Administration of excess glucocorticoids induced equivalent bone loss in wild-type and transgenic mice. As expected, cancellous osteoclasts were unaffected by the transgene. However, the increase in osteoblast apoptosis that occurred in wild-type mice was prevented in transgenic mice. Consistent with this, osteoblasts, osteoid area, and bone formation rate were significantly higher in glucocorticoid-treated transgenic mice compared with glucocorticoid-treated wild-type mice. Glucocorticoid-induced osteocyte apoptosis was also prevented in transgenic mice. Strikingly, the loss of vertebral compression strength observed in glucocorticoid-treated wild-type mice was prevented in the transgenic mice, despite equivalent bone loss. These results demonstrate for the first time that excess glucocorticoids directly affect bone forming cells in vivo. Furthermore, our results suggest that glucocorticoid-induced loss of bone strength results in part from increased death of osteocytes, independent of bone loss.

11-beta-Hydroxysteroid Dehydrogenase Type 2↗

PubMed1997

Calcitonin alters bone quality in beagle dogs.

Because of its antiresorptive properties, calcitonin is widely used to prevent and treat osteoporosis. A stimulatory effect of calcitonin on osteoblasts has also been reported; however, a recent histologic study points to a negative effect of calcitonin on mineralization of cancellous bone. The present experiment was performed to determine whether the observed histological signs of alterations in mineralization are also observed in cortical bone and whether this results in changes in mechanical properties, mineral densities, or mineral properties of canine bone. Sixteen female adult beagle dogs were randomly allocated to receive either human calcitonin at a dose of 0.25 mg/dog (50 IU, n = 8) or vehicle (mannitol, n = 8) every other day for 16 weeks. At the end of the study, the dogs were euthanized. Both tibiae, L1 and L5 vertebrae, and iliac crest bone samples were excised and defleshed. Torsional mechanical properties of tibial diaphyses and compressive strengths of vertebrae were measured. Bone mineral densities (BMD) of tibiae and vertebrae were measured by using dual-energy X-ray absorptiometry. Ultrastructural mineral characteristics of iliac crest bone were determined by gravimetry and Fourier transform infrared spectroscopy (FTIR). Bone histomorphometry was performed in the cortical envelope of the iliac crest. Tibiae from dogs treated with calcitonin withstood significantly less maximum torque until failure, required less torsional energy to reach the maximum torque, and had less torsional stiffness than the tibiae from dogs treated with vehicle (p < 0.05). Cancellous cores of vertebrae from calcitonin-treated dogs withstood less compressive mechanical loading than did vertebral cores from vehicle-treated animals (p < 0.05). Dogs treated with calcitonin had less BMD of both tibiae and vertebrae than vehicle-treated animals (p < 0.05). Bones from calcitonin-treated dogs had significantly less ash content, which correlated with the lower phosphate-to-amide I (detected by FTIR) and greater carbonate-to-phosphate ratios than did bones from vehicle-treated dogs (p < 0.05). Calcitonin-treated dogs exhibited a decrease in bone formation and mineralization rates and an increase in mineralization lag time. These results point to a negative effect of calcitonin on bone quality. These findings are intriguing and call for further studies addressing whether the observed abnormalities are transient or permanent.

Absorptiometry, Photon↗

PubMed1989

[Effect of vibration for the rheology of some luting cements].

Vibrant load is known to be effective to thin the film thickness of various luting cements. In this study, a vibrator which can change various conditions such as frequency, form of wave were made, and the changes of viscosity, film thickness and bond strength were tested statistically. Furthermore, the most effective condition for the slurry of some luting cements (i.e. domestic two zinc phosphate cements, one polycarboxylate cement and one glass ionomer cement) were investigated. The results obtained were as follows. 1) When vibrant load was applied to the slurry of cement in the setting process, the rise in viscosity was apt to be slower than the same case of static load. 2) The effect of vibration appears in the early sixty seconds especially, and the effect varied with the kind of cement, frequency or form of wave. 3) Vibration was also effective for the increase of compressive strength and of bond strength.

Dental Cements↗