Micro-indentation hardness studies on human bones

Ramrakhiani, Meera; Pal, Deepti; Murty, T. S.

doi:10.1159/000145035

Cited by 37 publications

(21 citation statements)

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“…Among the first studies of the mechanical properties of fingernails, Baden [204] reported elastic modulus values from experimental cut tests and by measuring the velocity of sound in nail plate ($2-4.3 GPa); Ramrakhiani [207] showed that spherical indents on the nail surface recovered over a period of time. Tensile testing on fingernails along the axis of fibers in intermediate layer yielded a strength of 86 MPa under ambient environment.…”

Section: Nailsmentioning

confidence: 99%

Keratin: Structure, mechanical properties, occurrence in biological organisms, and efforts at bioinspiration

Wang

Yang

McKittrick

et al. 2016

Progress in Materials Science

658

474

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a b s t r a c tA ubiquitous biological material, keratin represents a group of insoluble, usually high-sulfur content and filament-forming proteins, constituting the bulk of epidermal appendages such as hair, nails, claws, turtle scutes, horns, whale baleen, beaks, and feathers. These keratinous materials are formed by cells filled with keratin and are considered 'dead tissues'. Nevertheless, they are among the toughest biological materials, serving as a wide variety of interesting functions, e.g. scales to armor body, horns to combat aggressors, hagfish slime as defense against predators, nails and claws to increase prehension, hair and fur to protect against the environment. The vivid inspiring examples can offer useful solutions to design new structural and functional materials.Keratins can be classified as a-and b-types. Both show a characteristic filament-matrix structure: 7 nm diameter intermediate filaments for a-keratin, and 3 nm diameter filaments for b-keratin.Both are embedded in an amorphous keratin matrix. The molecular unit of intermediate filaments is a coiled-coil heterodimer and that of b-keratin filament is a pleated sheet. The mechanical response of a-keratin has been extensively studied and shows linear Hookean, yield and post-yield regions, and in some cases, a high reversible elastic deformation. Thus, they can be also be considered 'biopolymers'. On the other hand, b-keratin has not been investigated as comprehensively. Keratinous materials are strain-rate sensitive, and the effect of hydration is significant.Keratinous materials exhibit a complex hierarchical structure: polypeptide chains and filament-matrix structures at the nanoscale, Progress in Materials Science 76 (2016) 229-318 Contents lists available at ScienceDirect Progress in Materials Sciencej o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / p m a t s c i organization of keratinized cells into lamellar, tubular-intertubular, fiber or layered structures at the microscale, and solid, compact sheaths over porous core, sandwich or threads at the macroscale. These produce a wide range of mechanical properties: the Young's modulus ranges from 10 MPa in stratum corneum to about 2.5 GPa in feathers, and the tensile strength varies from 2 MPa in stratum corneum to 530 MPa in dry hagfish slime threads. Therefore, they are able to serve various functions including diffusion barrier, buffering external attack, energy-absorption, impact-resistance, piercing opponents, withstanding repeated stress and aerodynamic forces, and resisting buckling and penetration.A fascinating part of the new frontier of materials study is the development of bioinspired materials and designs. A comprehensive understanding of the biochemistry, structure and mechanical properties of keratins and keratinous materials is of great importance for keratin-based bioinspired materials and designs. Current bioinspired efforts including the manufacturing of quill-inspired aluminum composites, animal horn-inspired SiC composites, and feather-i...

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Section: Nailsmentioning

confidence: 99%

Keratin: Structure, mechanical properties, occurrence in biological organisms, and efforts at bioinspiration

Wang

Yang

McKittrick

et al. 2016

Progress in Materials Science

658

474

View full text Add to dashboard Cite

show abstract

“…However, one study reported an increase in Vicker's hardness for weights below 50 g [30]. In addition, pile up was observed in the latter study for loads above 100 g. Hardness was generally found to be homogeneous [26,30], but along a long bone, hardness tended to be higher in the diaphysis than in the meta-and epiphysis [4,35,40,45]. Hardness of trabecular bone was shown to be somewhat lower (10-15%) than the interstitial bone of the adjacent cortex [20,45].…”

Section: Tissue Hardnessmentioning

confidence: 99%

Indentation of bone tissue: a short review

Zysset

2009

Osteoporos Int

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“…These were formed from 50 g loading. Loading with lesser weight will result in smaller deformation "squares"; however, at the expense of uniform indent properties [16]. Even 25 g loading, however, would not have produced substantially smaller indents (14-18 ~tm squares).…”

Section: Discussionmentioning

confidence: 99%

“…1): newly-formed endocortical and periosteal bone, and anterior, lateral, medial and posterior preexisting ("extant") bone_ The three measurements per region produced a range of values that, on average, was only 34% of the range of values among all femora from one group. A 50g load, selected to ensure uniform measurements that are less prone to variance due to bone heterogeneity [16], was applied for at least 10 s to ensure complete indent deformation [11]. A separation distance of at least one indent diameter was maintained between the indent sites, sample edges and visible osteocytes and lacunae in order to minimize undesired edge effects [11].…”

Section: Methodsmentioning

confidence: 99%

Effect of suspension on mouse bone microhardness

Simske

Broz

Luttges

1995

J Mater Sci: Mater Med

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Antiorthostatic (hindlimb) suspension of mice results in a considerable reduction of bone formation at the femur mid-diaphysis. Comparisons with appropriate control groups indicate that this reduction is attributable to the unloading aspect of the model, and not to physiological stress or changes in feeding. Microhardness measurements of bone are used to provide information on site-specific mineralization and structural properties. The microhardness of femora formed during suspension is significantly less than that formed in the bone of control mice. These differences are observed both along the endocortical (11%) and periosteal (8%) perimeters. The microhardness of bone formed prior to the experimental period ("extant bone") is not different in comparing suspended and control mice, and increased microhardness values for these areas are observed in comparison to baseline controls. Mice used to control for the physiological stress and feeding portions of the suspension model do not demonstrate reduced microhardness. Thus, the limb unloading effects of suspension, not the induced stress or feeding changes, cause a reduction in microhardness. As microhardness is positively related to mineralization in these bones, it appears that the reduced mineralization accompanying suspension unloading may contribute to compromised structural properties of the bone formed. IntroductionReduced mineralization of newly formed bone is apparently observed in rats exposed to spaceflight [1]. However, direct determination of this hypothesis was not determined using site-specific measurement of structural properties. The site-specific structural properties of bone are highly dependent on the mineral content [2]. Altered mineralization during unloading conditions would also lead to differences in the material behaviour of newly formed bone. Spaceflight appears to affect the collagen phase of the newly formed bone in rats [1]_ Since collagen fibre orientation is ranked highly as a predictor of bone tensile [3] and flexure [4] strength, changes in collagen may determine site-specific structural parameters in bone.Because spaceflight opportunities are limited, a ground-based model for unloading provides researchers with the opportunity to study this aspect of spaceflight. Antiorthostatic tail suspension [5] was introduced as a ground-based model for the effects of spaceflight [6] on the hindlimb bones of rats. Because mice offer cost, size and transgenic advantages over rats, the suspension model has recently been extended to mice. The hindlimb bones of mice are indeed deleteriously affected by suspension [7]. These effects have been demonstrated in strains which respond

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Micro-indentation hardness studies on human bones

Cited by 37 publications

References 1 publication

Keratin: Structure, mechanical properties, occurrence in biological organisms, and efforts at bioinspiration

Keratin: Structure, mechanical properties, occurrence in biological organisms, and efforts at bioinspiration

Indentation of bone tissue: a short review

Effect of suspension on mouse bone microhardness

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