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At least 649 records · Page 36Linked to original sources
PubMed1998

Assessment of cancellous bone quality in severe osteoarthrosis: bone mineral density, mechanics, and microdamage.

The role of bone microdamage (microscopic cracks or microcracks and ultrastructural collagen matrix and bone mineral damage) in diseases such as osteoarthrosis and osteoporosis is poorly understood. Microdamage accumulation in vivo is influenced by age and cyclic loading, therefore, it would be useful if the burden of microdamage in bone could be assessed by noninvasive measures such as the radiological measurement of bone mineral density (BMD). The aim of this study was to investigate the relationship between BMD, compressive strength and stiffness, and microdamage in the cancellous bone of the proximal femur in patients with severe osteoarthrosis. Trabecular bone core samples, from the intertrochanteric region of the femur, were obtained from 34 patients, with a mean age of 70.3 +/- 11.1 years, undergoing total hip arthroplasty for osteoarthrosis. Cores selected from contact X-ray images were used for BMD measurement, compressive mechanical testing or left untested (uncrushed), en bloc staining for microdamage, and bone histomorphometry. The study shows a strong dependence of both the elastic modulus and ultimate failure stress of the bone samples on BMD and a significant relationship between the elastic modulus and trabecular anisotropy (Tr. An). In multiple linear regression, BMD and Tr. An together account for about 70% of the variance in the elastic modulus. Then including microcrack crack density (Cr.Dn) and damage volume fraction (DxV/BV) variables, Tr. An alone accounts for a relatively small amount of the variation (8.5%) in ultimate failure stress and elastic modulus. The Cr.Dn accounts for more of the variation in the ultimate failure stress than in the elastic modulus (50% vs. 7%). In this experiment, data for Cr.Dn provide a measure of damage associated with the ultimate failure of cancellous bone. In specimens that were not mechanically tested, in vivo microcrack accumulation increases exponentially with age. In conclusion, data from this study suggest that BMD and Cr.Dn are the major determinants of cancellous bone strength, whereas BMD and Tr. An are major determinants of cancellous bone stiffness. In bone specimens subjected to compressive testing there was no relationship between microdamage and BMD, suggesting that BMD cannot be used to monitor changes in the mechanical properties of bone due to microdamage accumulation.

Absorptiometry, Photon↗
PubMed2006

Carbon nanotube/polycarbonate composites as multifunctional strain sensors.

In this study we demonstrate that multiwalled carbon nanotube fillers can impart a strain sensing functionality to a composite. The nanocomposite is fabricated by dispersing 5% weight of multiwalled nanotube fillers into a polycarbonate matrix. When subjected to linear and sinusoidal dynamic strain inputs, the instantaneous change in the electrical resistance (deltaR/R0) of the nanocomposite responds in a manner similar to a strain gage. The sensitivity of the nanocomposite sensor was measured to be approximately 3.5 times that of a typical strain gage. This sensitivity of the nanocomposite's electrical properties to mechanical stress implies that in addition to enhancing mechanical properties (strength, stiffness, structural damping, etc.), these multifunctional materials show the potential to provide real-time structural health monitoring and self-diagnostic functionalities.

Elasticity↗
PubMed2006

Cytoskeletal tension regulates both expression and degradation of h2-calponin in lung alveolar cells.

Calponin is an actin filament-associated regulatory protein, and its h2 isoform is expressed in lung alveolar epithelial cells under postnatal upregulation during lung development corresponding to the commencement of respiratory expansion. Consistent with this correlation to mechanical tension, the expression of h2-calponin in alveolar cells is dependent on substrate stiffness and cytoskeleton tension. The function of h2-calponin in the stability of actin cytoskeleton implicates a role in balancing the strength and compliance of alveoli. An interesting finding is a rapid degradation of h2-calponin in lung after prolonged deflation, which is prevented by inflation of the lung to the in situ expanded volume. Decreasing mechanical tension in cultured alveolar cells by reducing the dimension of culture matrix reproduced the degradation of h2-calponin. Inhibition of myosin II ATPase also resulted in the degradation of h2-calponin in alveolar cells, showing a determining role of the tension in the actin cytoskeleton. Alveolar cells statically cultured on silicon rubber membrane build high tension in the cytoskeleton corresponding to a high expression of h2-calponin. Chronic cyclic stretching of cells on the membrane did not increase but decreased the expression of h2-calponin. This finding suggests that when cellular structure adapts to the stretched dimension, cyclic relaxations periodically release cytoskeleton tension and lower the total amount of tension that the cell senses over time. Therefore, the isometric tension, other than tension dynamics, determines the expression of h2-calponin. The tension regulation of h2-calponin synthesis and degradation demonstrates a novel mechanical regulation of cellular biochemistry.

Animals↗
PubMed1997

Contribution of chondroitin-dermatan sulfate-containing proteoglycans to the function of rat mesenteric arteries.

Proteoglycans are an important nonfibrous matrix component of the arterial wall. Direct evidence for their role in resistance-sized arteries is lacking, although they likely have an important role in coordinating and regulating vessel behavior, presumably via interactions of their glycosaminoglycan chains or core proteins with other matrix molecules and/or the smooth muscle cell surface. The purpose of this study was to determine whether the removal of specific glycosaminoglycan chains from proteoglycans in resistance-sized mesenteric arteries would change the mechanical properties of the arterial wall, thereby affecting their functional behavior. The major finding of the study was that 65% removal of chondroitin-dermatan sulfate-containing glycosaminoglycans from the arterial wall increased vascular wall stiffness and altered the myogenic behavior of the artery. The significant alterations in myogenic behavior associated with changes in passive mechanics following partial glycosaminoglycan chain removal support our hypothesis that chondroitin-dermatan sulfate-containing proteoglycans contribute significantly to the functional behavior of resistance arteries. We speculate that these alterations are the result of changes in stress transfer between collagen fibrils and/or stress transfer between cells and collagen fibrils under applied pressure.

Animals↗
PubMed2006

Maturation-dependent change and regional variations in acoustic stiffness of rabbit articular cartilage: an examination of the superficial collagen-rich zone of cartilage.

OBJECTIVE: The purpose of the study was to investigate maturation-dependent changes of acoustic (ultrasound) stiffness and other ultrasound features of articular cartilage in healthy rabbit knees. METHODS: Five groups of rabbits of various ages (3 weeks, 8 weeks, 6 months, 1 year, 2.5 years) consisting of five rabbits per group were examined. Signal intensity (index of stiffness), signal duration (index of surface irregularity) and interval between signals (index of thickness) of the ultrasound reflection from articular cartilage were examined at four sites: posterior lateral femoral condyle, posterior medial femoral condyle, lateral tibial plateau, and medial tibial plateau. The sites were observed macroscopically and microscopically with a light microscope and a polarized light microscope. RESULTS: At the lateral and medial condyles and the lateral tibial plateau, signal intensity was least in 3-week-old specimens. The intensity increased until 6 months or 1 year of age. At these sites, the signal durations and intervals between signals were least at the ages of 6 months or 1 year. At the medial tibial plateau, the intensity was the least at 2.5 years of age and the interval between signals was least at 3 weeks of age; there was no effect of age on signal duration. Cartilage surfaces of all specimens were smooth and no degenerative changes were macroscopically or microscopically evident. The surface brightness of cartilage under the polarized light microscope was consistent with signal intensity values. CONCLUSIONS: The response of articular cartilage to ultrasound was maturation-dependent. Acoustic properties differed from mechanical stiffness properties, which were determined using indentation. Ultrasound may detect properties of the surface collagen of the articular cartilage.

Aging↗
PubMed1997

Identification of physiological systems: a robust method for non-parametric impulse response estimation.

The identification of non-parametric impulse response functions (IRFs) from noisy finite-length data records is analysed using the techniques of matrix perturbation theory. Based on these findings, a method for IRF estimation is developed that is more robust than existing techniques, particularly when the input is non-white. Furthermore, methods are developed for computing confidence bounds on the resulting IRF estimates. Monte Carlo simulations are used to assess the capabilities of this new method and to demonstrate its superiority over classical techniques. An application to the identification of dynamic ankle stiffness in humans is presented.

Ankle Joint↗
PubMed2000

The effects of 17 alpha-methyltestosterone on myocardial function in vitro.

Testosterone analogs have been used as performance enhancers by athletes for more than 40 yr. We asked whether the anabolic steroid 17 alpha-methyl-4-androstene-17-ol-3-one (17 alpha-MT) would affect intrinsic contractile function of the heart. Male Sprague-Dawley rats, 125-150 g, were treated with 17 alpha-MT either parenterally or orally for up to 8 wk. Intrinsic contractile function of the hearts was assessed utilizing both the isolated working heart and isovolumic perfused heart preparations. Isolated working hearts from 17 alpha-MT-treated rats had a 45% decrease in heart work attributable largely to a similarly decreased stroke volume. Isovolumic perfused hearts from treated animals had elevated left ventricular systolic and diastolic pressures at similar interventricular volumes compared to controls. Rates of ventricular pressure development (+dP/dT) or relaxation (-dP/dT) were unchanged as a result of the treatment. However, static elastance was reduced in potassium-arrested hearts from the 17 alpha-MT treatment (63% increase in interventricular pressure), consistent with a limitation being imposed on stroke volume by a decreased myocardial compliance. Hydroxyproline content of the hearts was not altered by 17 alpha-MT treatment suggesting that increased stiffness was not a consequence of collagen proliferation. Treatment of the steroid rats with beta-aminopropionitrile, a compound that inhibits lysyl oxidase, restored the left ventricular volume-pressure relationship (elastance curve) to that of control hearts. Thus, chronic treatment with anabolic steroids appears to reduce left ventricular compliance, possibly related to an enhanced activity of lysyl oxidase, and results in increased crosslink formation between collagen strands in the extracellular matrix.

Administration, Oral↗
PubMed1999

A review of the curing mechanics of composites and their significance in dental applications.

Much of the technique sensitivity associated with polymer matrix composites is a direct result of their curing shrinkage. Challenges with marginal integrity, adaptation of proximal contact, and residual stress are related to this intrinsic property. There are many test methods described in the literature that measure various aspects of polymerization contraction. Some measure total contraction, which is the sum of pre- and postgelation shrinkage, whereas others are sensitive only to postgelation deformation, which occurs after the onset of measurable stiffness. Development of methods to compensate for curing shrinkage is best described on the basis of an understanding of the polymerization mechanics. The distinction between total and postgelation contraction, and recognition of limitations of test methods are important considerations when interpreting literature data before selecting a restorative material.

Composite Resins↗
PubMed2002

Mechanical properties of adult vertebral cancellous bone: correlation with collagen intermolecular cross-links.

Although the mechanical strength of cancellous bone is well known to depend on its apparent density, little is known about the influence of other structural or biochemical parameters. This study specifically investigates the cross-linking of the collagen in human vertebral bone samples and its potential influence on their mechanical behavior. Multiple cylindrical samples were cored vertically in the vertebral bodies of nine subjects (aged 44-88 years). Three spinal levels (T9, T12 or L1, and L4) and three sample sites within a vertebral body (anterior, posterior, and lateral) were used, for a total of 68 samples. The density was measured with peripheral quantitative computed tomography (pQCT) and all cylinders were mechanically tested in compression. After mechanical testing, they were unmounted and used for biochemical analysis. The amount of collagen (wt/wt of bone) and its content in reduced immature cross-links, that is, hydroxylysinonorleucine (HLNL, mol/mol of collagen) and dihydroxylysinornorleucine (DHLNL), as well as stable mature cross-links, that is, hydroxylysyl-pyridinoline (HP), lysyl-pyridinoline (LP), and pyrrole cross-link were determined for each cylinder. None of the biochemical parameters correlated to the density. On multiple linear regression, the prediction of the mechanical properties was improved by combining density data with direct collagen cross-link assessment. The HP/LP ratio appeared as a significant predictor to the strength (r = 0.40; p = 0.001) and stiffness (r = 0.47; p < 0.001) samples with a high HP/LP ratio being stronger and stiffer. Additionally, the ultimate strain correlated to the HP or LP concentration (r = 0.38 or 0.49; p < 0.01). Different subjects had different HP/LP ratios and different HP or LP concentrations in their vertebral bone samples, and the location of origin within a subject had no influence on the concentration. These observations suggest that the nature of the organic matrix in adult vertebral bone is variable and that these variations influence its mechanical competence.

Adult↗
PubMed1999

A pilot study of the safety and effects of the matrix metalloproteinase inhibitor marimastat in gastric cancer.

The aim of this study was to evaluate the safety and tolerability of 4 weeks administration of marimastat, and to seek evidence of biological activity as observed by changes in the endoscopic appearance of the gastric tumours. 35 patients with advanced, inoperable gastric or gastro-oesophageal tumours were recruited. The dose of marimastat was reduced from the starting dose of 50 mg twice daily (6 patients) to 25 mg once daily (29 patients). 31 completed the 28 day study period. Marimastat was generally well tolerated, with the principal treatment-related toxicity being pain and stiffness of the musculoskeletal system. These symptoms occurred more frequently at the higher-dose, and increased to involve a total of 13 patients (37%) with longer-term treatment. The events were usually rapidly reversible on drug discontinuation. 3 patients receiving prolonged treatment experienced more severe symptoms, with the development of skin thickening and contractures in the hands. At endoscopy, 10 patients showed an increased fibrotic cover of the tumour, 8 had decreased haemorrhagic appearance, and in at least 2 cases where comparative tumour histology was assessable, there was evidence of increased stromal fibrotic tissue.

Adult↗
PubMed2006

Intrinsic mechanical properties of the extracellular matrix affect the behavior of pre-osteoblastic MC3T3-E1 cells.

Mechanical cues present in the ECM have been hypothesized to provide instructive signals that dictate cell behavior. We probed this hypothesis in osteoblastic cells by culturing MC3T3-E1 cells on the surface of type I collagen-modified hydrogels with tunable mechanical properties and assessed their proliferation, migration, and differentiation. On gels functionalized with a low type I collagen density, MC3T3-E1 cells cultured on polystyrene proliferated twice as fast as those cultured on the softest substrate. Quantitative time-lapse video microscopic analysis revealed random motility speeds were significantly retarded on the softest substrate (0.25 +/- 0.01 microm/min), in contrast to maximum speeds on polystyrene substrates (0.42 +/- 0.04 microm/min). On gels functionalized with a high type I collagen density, migration speed exhibited a biphasic dependence on ECM compliance, with maximum speeds (0.34 +/- 0.02 microm/min) observed on gels of intermediate stiffness, whereas minimum speeds (0.24 +/- 0.03 microm/min) occurred on both the softest and most rigid (i.e., polystyrene) substrates. Immature focal contacts and a poorly organized actin cytoskeleton were observed in cells cultured on the softest substrates, whereas those on more rigid substrates assembled mature focal adhesions and robust actin stress fibers. In parallel, focal adhesion kinase (FAK) activity (assessed by detecting pY397-FAK) was influenced by compliance, with maximal activity occurring in cells cultured on polystyrene. Finally, mineral deposition by the MC3T3-E1 cells was also affected by ECM compliance, leading to the conclusion that altering ECM mechanical properties may influence a variety of MC3T3-E1 cell functions, and perhaps ultimately, their differentiated phenotype.

Acrylic Resins↗
PubMed1980

The intrinsic tensile behavior of the matrix of bovine articular cartilage and its variation with age.

To study the age dependence of the uniaxial tensile behavior of bovine articular cartilage, 216 specimens of articular cartilage from the patellofemoral joint were grouped into two age categories: those from joints with growth plates present (open physes) and those from joints without growth plates (no physes). We prepared standard, dumbbell-shaped test specimens from the three ultrastructural zones of the tissue: the superficial tangential zone, the middle zone, and the deep zone. As was done in the early works of Kempson et al. and of Woo et all., we prepared specimens whose long axes were either parallel or perpendicular to the axis of the local split line on the joint surface. In these tensile tests we observed a profound difference between the two age groups in terms of the variations in the tensile properties related to the depth below the surface. With increasing distance from the articular surface, the tensile strength and stiffness increased in the open-physis group and decreased in the no-physis group. Directional dependence of the tensile response was manifested by increased stiffness and strength of the samples oriented parallel to the split-line axis when compared with the samples oriented perpendicular to it. Distortion of the initially flat, straight-sided portion of the gauge section was observed in most of the 216 specimens immediately after the application of tensile strains. This effect casts serious doubts on all previous measurements of cross-sectional dimensional changes. At present, we believe that this distortion occurs because articular cartilage is an inhomogeneous, layered material. We also observed that cartilage exudes substantial amounts of its interstitial fluid when the applied tensile strain becomes large. These two effects create serious problems in assessing the true volumetric changes and the material properties of cartilage specimens during uniaxial tension experiments.

Aging↗
PubMed2003

Zinc and mechanical prowess in the jaws of Nereis, a marine worm.

Higher animals typically rely on calcification to harden certain tissues such as bones and teeth. Some notable exceptions can be found in invertebrates: The fangs, teeth, and mandibles of diverse arthropod species have been reported to contain high levels of zinc. Considerable quantities of zinc also occur in the jaws of the marine polychaete worm Nereis sp. High copper levels in the polychaete worm Glycera dibranchiata recently were attributed to a copper-based biomineral reinforcing the jaws. In the present article, we attempt to unravel the role of zinc in Nereis limbata jaws, using a combination of position-resolved state-of-the-art techniques. It is shown that the local hardness and stiffness of the jaws correlate with the local zinc concentration, pointing toward a structural role for zinc. Zinc always is detected in tight correlation with chlorine, suggesting the presence of a zinc-chlorine compound. No crystalline inorganic phase was found, however, and results from x-ray absorption spectroscopy further exclude the presence of simple inorganic zinc-chlorine compounds in amorphous form. The correlation of local histidine levels in the protein matrix and zinc concentration leads us to hypothesize a direct coordination of zinc and chlorine to the protein. A comparison of the role of the transition metals zinc and copper in the jaws of two polychaete worm species Nereis and Glycera, respectively, is presented.

Animals↗
PubMed1992

Light and electron microscopy of the cornea in systemic mucopolysaccharidosis type I-S (Scheie's syndrome).

A 37-year-old man with coarse facies, stiff joints, corneal clouding, and normal intelligence sought medical attention. The diagnosis of a systemic mucopolysaccharidosis (MPS) type I-S (Scheie's syndrome) was confirmed by the presence of lysosomal alpha-L-iduronidase deficiency and excessive urinary dermatan and heparan sulfate excretion. The corneal button after perforating keratoplasty of the right eye demonstrated mucopolysaccharides consisting of numerous vacuoles containing fibrillogranular and partly membranebound material in epithelial cells, histiocytes, keratocytes, and extracellular matrix. Endothelial cells were distinctly free of storage material. The epithelial basement membrane showed frequent breaks, whereas Bowman's layer was only slightly attenuated. Irregular collagen fibrils and fibrous long-spacing collagen were noted near degenerating distended keratocytes. The Descemet's membrane was normal. The literature of six reported histopathological examinations of the cornea in Scheie's syndrome is reviewed. Detection of fibrous long-spacing collagen seems to be a typical abnormality of the cornea in MPS I-S.

Adult↗
PubMed2004

Effects of dynamic compressive loading on chondrocyte biosynthesis in self-assembling peptide scaffolds.

Dynamic mechanical loading has been reported to affect chondrocyte biosynthesis in both cartilage explant and chondrocyte-seeded constructs. In this study, the effects of dynamic compression on chondrocyte-seeded peptide hydrogels were analyzed for extracellular matrix synthesis and retention over long-term culture. Initial studies were conducted with chondrocyte-seeded agarose hydrogels to explore the effects of various non-continuous loading protocols on chondrocyte biosynthesis. An optimized alternate day loading protocol was identified that increased proteoglycan (PG) synthesis over control cultures maintained in free-swelling conditions. When applied to chondrocyte-seeded peptide hydrogels, alternate day loading stimulated PG synthesis up to two-fold higher than that in free-swelling cultures. While dynamic compression also increased PG loss to the medium throughout the 39-day time course, total PG accumulation in the scaffold was significantly higher than in controls after 16 and 39 days of loading, resulting in an increase in the equilibrium and dynamic compressive stiffness of the constructs. Viable cell densities of dynamically compressed cultures differed from free-swelling controls by less than 20%, demonstrating that changes in PG synthesis were due to an increase in the average biosynthesis per viable cell. Protein synthesis was not greatly affected by loading, demonstrating that dynamic compression differentially regulated the synthesis of PGs. Taken together, these results demonstrate the potential of dynamic compression for stimulating PG synthesis and accumulation for applications to in vitro culture of tissue engineered constructs prior to implantation.

Animals↗
PubMed1995

Interaction of cardiac myocytes and non-myocytes in mechanical stress-induced hypertrophy.

It is known that mechanical stress directly changes the conformation of the functional proteins, or directly activates enzymes such as phospholipase in the plasma membrane. The integrin-cytoskeleton complex may be an alternative candidate structure for a mechanoreceptor and a transducer. The cytoskeleton has been also shown to play an important role in secretion. Mechanical stress may stimulate the secretion of some cytokines or angiotensin II, which may generate multiple intracellular signals as a secondary event. External stimuli are generally transduced into the nucleus through the activation of protein kinase cascade. Stretching of cardiac myocytes stimulates the activity of PKC, Raf-1 kinase, MAP kinase kinase. MAP kinase and S6 kinase. In cardiac myocytes, mechanical stress directly induces gene expression as well as protein synthesis. Immediate early genes are first induced, and then fetal-type genes are reinduced. Both in hypertrophied hearts and in the experimental model of cardiac hypertrophy induced by pressure overload. Ca(2+)-ATPase content of cardiac myocytes is depressed. Reduced function of sarcoplasmic reticulum causes insufficient decrease of intracellular calcium in diastole and induces slowing of ventricular relaxation. In the interstitium of pressure overloaded hearts, the accumulation of collagen fiber is increased. The abnormal deposit leads to increased chamber stiffness and diastolic dysfunction. Furthermore, TGF-beta and tissue renin-angiotensin system are up-regulated in pressure overloaded hearts, both of which accelerate the interstitial fibrosis.

Animals↗
PubMed2004

[Pulse pressure in the therapeutic management of hypertension?].

Data from the Framingham and several other studies have demonstrated a relatively consistent increase of systolic blood pressure over lifetime but a decrease of diastolic blood pressure after the age of 50-60 years-resulting in an increase of pulse pressure (PP). Epidemiologic studies in the past 10-15 years have stressed the importance of PP as an independent risk factor for cardiovascular morbidity and mortality, especially myocardial infarction and congestive heart failure.A wide clinic PP (60-65 mmHg) has been shown to be a marker of increased arterial stiffness and an elevated cardiovascular morbidity. PP is determined by combined hemodynamic cardiac (ventricular ejection) and arterial factors, like arterial stiffness as well as the timing and intensity of wave reflections. Recent careful measurements have suggested that PP is transmitted much deeper into the microcirculation, which is strongly influenced by aging, hypertension, diabetes, and renal insufficiency (endothelial dysfunction, eutrophic and hypertrophic remodeling, progressive loss of microvessels). Antihypertensive drugs may improve vascular compliance and the alterations of microvascular architecture by reducing blood pressure, relaxing vascular smooth muscle, or promoting long-term effects on extracellular matrix, collagen, vascular smooth muscle, and cardiomyocyte growth and remodeling.Diuretics, beta blockers, long-acting calcium channel blockers, angiotensin-converting enzyme (ACE) inhibitors and angiotensin I (AT(1)) receptor antagonists were critically discussed in relation to their influence on vascular compliance, endothelial dysfunction, the remodeling process, PP, and cardiovascular morbidity and mortality. The vascular protective action of some (especially AT(1) antagonists, ACE inhibitors, calcium channel blockers) but not all (beta blockers) may contribute to improve the outcome of hypertensive patients, although this is presently unproven.

Age Distribution↗
PubMed2002

Effect of thermal cycling on whisker-reinforced dental resin composites.

The mechanical properties of dental resin composites need to be improved in order to extend their use to high stress-bearing applications such as crown and bridge restorations. Recent studies used single crystal ceramic whiskers to reinforce dental composites. The aim of this study was to investigate the effects of thermal cycling on whisker-reinforced composites. It was hypothesized that the whisker composites would not show a reduction in mechanical properties or the breakdown of whisker-resin interface after thermal cycling. Silicon carbide whiskers were mixed with silica particles, thermally fused, then silanized and incorporated into resin to make flexural specimens. The filler mass fraction ranged from 0% to 70%. The specimens were thermal cycled in 5 degrees C and 60 degrees C water baths, and then fractured in three-point bending to measure strength. Nano-indentation was used to measure modulus and hardness. No significant loss in composite strength, modulus and hardness was found after 10(5) thermal cycles (family confidence coefficient=0.95; Tukey's multiple comparison test). The strength of whisker composite increased with filler level up to 60%, then plateaued when filler level was further increased to 70%; the modulus and hardness increased monotonically with filler level. The strength and modulus of whisker composite at 70% filler level were significantly higher than the non-whisker controls both before and after thermal cycling. SEM revealed no separation at the whisker-matrix interfaces, and observed resin remnants on the pulled-out whiskers, indicating strong whisker-resin bonding even after 10(5) thermal cycles. In conclusion, novel dental resin composites containing silica-fused whiskers possessed superior strength and modulus compared to non-whisker composites both before and after thermal cycling. The whisker-resin bonding appeared to be resistant to thermal cycling in water, so that no loss in composite strength or stiffness occurred after prolonged thermal cycling.

Journal Article↗