Properties Of Bone Tissue Research Articles

Study of the Stress-Strain State of the "Bone–Fixation Plate" System in Conjunction With Cortical Tissue Mechanical Properties

Background. Bone osteosynthesis is considered one of the most efficient methods of treating fractures of long tubular bones. Deve­lopment of modern computer technology and specialized software makes it possible for a traumatologist to perform preliminary efficiency estimation of osteosynthesis using fixation plates of various designs. Results of such studies can significantly depend on calculation model parameters. In most papers related to the study of a stress-strain state of “bone–fixator” systems, bone tissue is considered as a homogeneous, isotropic, elastic medium. However, in fact it is heterogeneous and has an anisotropy of mechanical characteristics. Accordingly in a case of using a simplified isotropic model of bone tissue, when performing calculations, there is a possibility of obtaining inaccurate results. Objective. Estimation of influence of orthotropy of the bone tissue physical and mechanical properties on a stress-strain state of the “bone–fixator” system. Methods. The study is performed in the software environment based on the finite element method. Osteosynthesis of a low transverse fracture of a fibula using a smooth plate is selected as a computational case. Two computational models simplified in terms of geometry are constructed to solve the problem. These models are different only in properties of cortical bone tissue. Results. Analysis of a stress state in elements of models indicated that normal stresses reached the highest values, and tangential stresses are relatively small. In addition, the character of stress distribution turned out to be significantly inhomogeneous. However, stress state patterns are qualitatively similar for both computational models. A common feature of the maximum stresses both in the bone and in the plate turned out to be that all the maximum stresses are the result of their concentration. Conclusions. Consideration of orthotropy of elastic parameters of a bone led to significant quantitative changes in the indicators of a stress state. It is established that the minimum safety margins for both models turned out to be considered by the maximum tensile stresses acting in the vertical direction. A similar result in estimating bone strength also occurs in a case when only elastic orthotropy is considered, but the orthotropy of strength indicators is not considered. If the strength orthotropy is considered for the isotropic model of cortical bone, the pattern changes qualitatively. The normal tensile stress directed along the tangent to a circumference of bone cross-section is considered unsafe. Calculations results indicate a possibility of using an isotropic model of cortical tissue when performing comparative estimations in order to identify the most efficient, in terms of strength, fixation plate designs.

A filament 3D printing approach for CT-compatible bone tissues replication

PurposeThe aim of this study is the development of a methodology for manufacturing 3D printed anthropomorphic structures, which mimic the X-ray properties of the human bone tissue. MethodsA mixing approach of two different materials is proposed for the fabrication of a radiologically equivalent hip bone for an anthropomorphic abdominal phantom. The materials employed for the phantom were polylactic acid (PLA) and Stonefil, while a custom-made dual motor filament extrusion setup and a custom-made software associating medical images directly with the 3D printing process were employed. ResultsThree phantoms representing the hip bone were 3D printed utilizing two filaments under three different printing scenarios. The phantoms are based on a patient’s abdominal CT scan images. Histograms of CT scans of the printed hip bone phantoms were calculated and compared to the original patient’s hip bone histogram, demonstrating that a constant mixing composition of 30% Stonefil and 70% PLA with 0.0375 extrusion rate per voxel (93.75% flow for fulfilling a single voxel) for the cancellous bone, and using 100% Stonefil with 0.04 extrusion rate per voxel (100% flow) for the cortical bone results in a realistic anatomy replication of the hip bone. Reproduced HU varied between 700 and 800, which are close to those of the hip bone. ConclusionsThe study demonstrated that it is possible to mix two different filaments in real-time during the printing process to obtain phantoms with realistic and radiographically bone tissue equivalent attenuation. The results will be explored for manufacturing a CT-compatible abdominal phantom.

Cell-Laden Composite Hydrogel Bioinks with Human Bone Allograft Particles to Enhance Stem Cell Osteogenesis.

There is a growing demand for bone graft substitutes that mimic the extracellular matrix properties of the native bone tissue to enhance stem cell osteogenesis. Composite hydrogels containing human bone allograft particles are particularly interesting due to inherent bioactivity of the allograft tissue. Here, we report a novel photocurable composite hydrogel bioink for bone tissue engineering. Our composite bioink is formulated by incorporating human allograft bone particles in a methacrylated alginate formulation to enhance adult human mesenchymal stem cell (hMSC) osteogenesis. Detailed rheology and printability studies confirm suitability of our composite bioinks for extrusion-based 3D bioprinting technology. In vitro studies reveal high cell viability (~90%) for hMSCs up to 28 days of culture within 3D bioprinted composite scaffolds. When cultured within bioprinted composite scaffolds, hMSCs show significantly enhanced osteogenic differentiation as compared to neat scaffolds based on alkaline phosphatase activity, calcium deposition, and osteocalcin expression.

Quantifying how altered lacunar morphology and perilacunar tissue properties influence local mechanical environment of osteocyte lacunae using finite element modeling

Previous studies have demonstrated that osteocyte lacunar morphology and perilacunar bone tissue properties undergo alterations due to physiological and pathological processes such as aging, lactation, diseases, and treatments. However, the influence of these alterations on the apparent mechanical properties of the bone and the local mechanical environment of osteocyte lacunae has not been evaluated in detail. The goal of this study is to quantify the influence of osteocyte lacunar morphology and perilacunar tissue properties on local mechanical environment around lacunae and the apparent mechanical properties of the bone using three-dimensional FE models of lacunae networks with varying lacunar morphology and perilacunar properties based on previously reported experimental data. To attain this goal, a parametric study using models with different lacunar/perilacunar properties, including lacunar density (Lc.D), orientation (Lc.Φ), volume (Lc.V), and equancy (Lc.Eq), as well as perilacunar modulus (Pl.E), and size (Pl.S) was carried out. In addition, a specific case study using models derived from aged and young bone specimens was performed. Our results showed that the highly strained tissue around lacunae increased linearly with increasing Lc.D and Lc.V, reduced exponentially with decreasing angle of major axis of lacunae from the loading direction and with increasing Pl.E, and increased exponentially with increasing Pl.S. The change in apparent elastic modulus with modifications in lacunar morphology was very small whereas the change in perilacunar modulus had a more substantial influence on the apparent elastic modulus. Lacunar strain amplification was reduced by increasing Lc.Φ, and Pl.E and increased with increasing Lc.V within the range of 1.5 and 2.3. No significant difference was seen in the apparent elastic modulus of models derived from young and aged bone models. However, young bone showed substantially larger amount of highly strained tissue around lacunae compared to the aged bone. This difference was amplified when the perilacunar tissue property modifications were incorporated in the models. In summary, the results indicate that modifications in the osteocyte lacunar morphology and perilacunar tissue properties can significantly alter local tissue deformation around lacunae which may impact osteocyte mechanosensitivity.

Biomedical response of femurs in male Wistar rat in chronic hypergravity environments

Bone is sensitive to mechanical stimulation and plays a loading-bearing role in the human body. However, regulation of bone biomechanical properties in chronic hypergravity environments is still unclear. In this study, male Wistar rats exposed to chronic hypergravity environments (4×g, 8×g, 10×g, and 20×g) for 4 weeks were set as the hypergravity groups, and rats exposed to the normal gravity as the control group. Morphology parameters and bone remodeling factors were obtained by means of micro-CT, Western blot, and q-PCR. Mechanical properties of femurs were measured utilizing three points bending test and creep test and were fitted into a viscoelastic-viscoplastic constitutive equation. The results indicate osteoporosis occurred in femurs of hypergravity groups. Accordingly, the protein and gene expressions of bone remodeling factors (OPG, RANKL, runx2) in hypergravity groups were significantly different from that in the control group, demonstrating that bone formation level increased and bone resorption level decreased. Meanwhile, mechanical properties of femurs in hypergravity groups showed that Young's modulus of femurs in the 20×g group was significantly higher than that in the control group. The viscoelastic-viscoplastic properties of bone tissue were changed in hypergravity environments. Among them, the 8×g group was closest to the control group in morphology and mechanical properties. To sum up, the biomechanical response regulation of rat femur under 4-20×g chronic hypergravity environments was presented. Hypergravity environments could lead to osteoporosis. The balance between bone formation and bone resorption would be disrupted in hypergravity groups due to bone adaptation. 20×g environment has a significant effect on elastic modulus on femurs. Due to the difference in biomechanical response of femurs, the viscoelastic-viscoplastic characteristics of femurs have a nonlinear relationship with hypergravity values. Bone tissue was least affected by 8×g hypergravity in morphology and mechanical properties.

Additively manufactured lattice structures with controlled transverse isotropy for orthopedic porous implants

Additively manufactured lattice structures enable the design of tissue scaffolds with tailored mechanical properties, which can be implemented in porous biomaterials. The adaptation of bone to physiological loads results in anisotropic bone tissue properties which are optimized for site-specific loads; therefore, some bone sites are stiffer and stronger along the principal load direction compared to other orientations. In this work, a semi-analytical model was developed for the design of transversely isotropic lattice structures that can mimic the anisotropy characteristics of different types of bone tissue. Several design possibilities were explored, and a particular unit cell, which was best suited for additive manufacturing was further analyzed. The design of the unit cell was parameterized and in-silico analysis was performed via Finite Element Analysis. The structures were manufactured additively in metal and tested under compressive loads in different orientations. Finite element analysis showed good correlation with the semi-analytical model, especially for elastic constants with low relative densities. The anisotropy measured experimentally showed a variable accuracy, highlighting the deviations from designs to additively manufactured parts. Overall, the proposed model enables to exploit the anisotropy of lattice structures to design lighter scaffolds with higher porosity and increased permeability by aligning the scaffold with the principal direction of the load.

Deep adversarial data augmentation for biomedical spectroscopy: Application to modelling Raman spectra of bone

Deep learning algorithms have performed remarkably well to predict state of health. Nevertheless, they typically rely on ample training data to avoid overfitting. In the biomedical sector, sufficient data are not typically available due to low availability or accessibility. Data augmentation of physiological recordings can be achieved using Generative Adversarial Networks (GAN). GAN is a computational framework for approximating generative models within an adversarial process, where two neural networks compete against one other while being trained simultaneously. Despite the widespread use and adoption of deep learning algorithms in life sciences, concerns have been raised about the lack of biological context. Therefore, to assess a data augmentation workflow, both computational and physiological quality metrics must be considered. Raman spectroscopy can be effectively used to study the molecular properties of bone tissue. Both inorganic and organic phases can be analysed simultaneously as probes of bone health status. In this work, we describe an easy-to-follow GAN approach for generating synthetic Raman spectra from a small dataset of ex vivo healthy and osteoporotic bone samples. The model was applied to raw Raman spectra, while it can be modified accordingly to produce any one-dimensional biomedical signal. We also introduced a novel unsupervised methodology to evaluate the variability of the synthetic dataset, based on successive Principal Component Analysis (PCA) modelling. The properties of the synthetic spectra were scrutinized by Fréchet Distance and difference spectroscopy, as well as by bone quality metrics, like mineral-to-matrix ratio and crystallinity. Finally, classification studies demonstrated the increased discrimination accuracy of the augmented dataset.

A pilot study on the nanoscale properties of bone tissue near lacunae in fracturing women

The goal of this study is to investigate the causes of osteoporosis-related skeletal fragility in postmenopausal women. We hypothesize that bone fragility in these individuals is largely due to mineral, and/or intrinsic material properties in the osteocyte lacunar/peri-lacunar regions of bone tissue. Innovative measurements with nanoscale resolution, including scanning electron microscope (SEM), an atomic force microscope that is integrated with infrared spectroscopy (AFM-IR), and nanoindentation, were used to characterize osteocyte lacunar and peri-lacunar properties in bone biopsies from fracturing (Cases) and matched (Age, BMD), non-fracturing (Controls) postmenopausal healthy women. In the peri-lacunar space, the nanoindentation results show that the modulus and hardness of the Controls are lower than the Cases. The AFM-IR results conclusively show that the mineral matrix, maturity (peak) (except in outer/far regions in Controls) were greater in Controls than in Cases. Furthermore, these results indicate that while mineral-to-matrix area ratio tend to be greater, the mineral maturity and crystallinity peak ratio “near” lacunae is greater than at regions “far” or more distance from lacunae in the Controls only. Due to the heterogeneity of bone structure, additional measurements are needed to provide more convincing evidence of altered lacunar characteristics and changes in the peri-lacunar bone as mechanisms related to postmenopausal women and fragility. Such findings would motivate new osteocyte-targeted treatments to reduce fragility fracture risks in these groups.

Temporal and spatial changes in bone mineral content and mechanical properties during breast-cancer bone metastases

Cancer cells favour migration and metastasis to bone tissue for 70–80 % of advanced breast cancer patients and it has been proposed that bone tissue provides attractive physical properties that facilitate tumour invasion, resulting in osteolytic and or osteoblastic metastasis. However, it is not yet known how specific bone tissue composition is associated with tumour invasion. In particular, how compositional and nano-mechanical properties of bone tissue evolve during metastasis, and where in the bone they arise, may affect the overall aggressiveness of tumour invasion, but this is not well understood. The objective of this study is to develop an advanced understanding of temporal and spatial changes in nano-mechanical properties and composition of bone tissue during metastasis. Primary mammary tumours were induced by inoculation of immune-competent BALB/c mice with 4T1 breast cancer cells in the mammary fat pad local to the right femur. Microcomputed tomography and nanoindentation were conducted to quantify cortical and trabecular bone matrix mineralisation and nano-mechanical properties. Analysis was performed in proximal and distal femur regions (spatial analysis) of tumour-adjacent (ipsilateral) and contralateral femurs after 3 weeks and 6 weeks of tumour and metastasis development (temporal analysis). By 3 weeks post-inoculation there was no significant difference in bone volume fraction or nano-mechanical properties of bone tissue between the metastatic femora and healthy controls. However, early osteolysis was indicated by trabecular thinning in the distal and proximal trabecular compartment of tumour-bearing femora. Moreover, cortical thickness was significantly increased in the distal region, and the mean mineral density was significantly higher in cortical and trabecular bone tissue in both proximal and distal regions, of ipsilateral (tumour-bearing) femurs compared to healthy controls. By 6 weeks post-inoculation, overt osteolytic lesions were identified in all ipsilateral metastatic femora, but also in two of four contralateral femora of tumour-bearing mice. Bone volume fraction, cortical area, cortical and trabecular thickness were all significantly decreased in metastatic femora (both ipsilateral and contralateral). Trabecular bone tissue stiffness in the proximal femur decreased in the ipsilateral femurs compared to contralateral and control sites. Temporal and spatial analysis of bone nano-mechanical properties and mineralisation during breast cancer invasion reveals changes in bone tissue composition prior to and following overt metastatic osteolysis, local and distant from the primary tumour site. These changes may alter the mechanical environment of both the bone and tumour cells, and thereby play a role in perpetuating the cancer vicious cycle during breast cancer metastasis to bone tissue.

Influence of zoledronic acid in physicochemical and morphostructural parameters of bone and dental tissue of mice submitted to a jaw osteonecrosis model

Zoledronic acid (ZA) leads to structural and physicochemical changes in mineralized tissues. The aim was to an- alyze physicochemical and morphostructural properties of bone and dental tissue of mice submitted to a model of ZA-related osteonecrosis of the jaws (OJ). This is a 2 × 2 factorial design experimental study, considering sex (male/female) and treatment (ZA/Saline). Lower left 2nd molar (day 42) extraction was performed after three ad- ministrations (days 0, 7, 14) of ZA 1.0 mg / kg or saline (n=8/group), with another administration on 49^th and eu- thanasia on 70^th day. Histological analysis, computerized microtomography, three-point bending test and Raman spectroscopy were performed. ANOVA 2-way/Bonferroni test was applied (p<0.05). Treatment with ZA promoted histological alterations in femoral epiphysis and increased bone necrosis signs (p <0.05) at sites of exodontia. Be- sides, ZA groups presented a lower number and greater separation of bone trabeculae, and smaller ratio bone/tissue volume in alveolar trabecular bone. Females presented a lower value of these parameters. In femoral bone, sex and treatment factors exerted an independent influence in mechanical parameters, on the cross-sectional area, maximum load, moment of inertia and work to fracture (p <0.05), being lower in females and increased in treated animals, which also presented higher flexural stiffness. Yield stress and flexural modulus were higher in females and lower with ZA treatment (p <0.05). Spectroscopic analysis showed increased crystallinity with ZA in cortical and medullar of right and left hemimandible, respectively, as well as femoral cortical. There was an increase of crys- tallinity in dental enamel and dentin with treatment. It is concluded that treatment with ZA, although associated with occurrence of OJ, modifies bone and dental mineral matrix, contributing to tissue biomechanics' improvement. Females present differences in femoral biomechanical properties and have a lower density of trabecular bone in the post-dental extraction socket, when compared to males.

DYNAMICS OF BONE MINERAL COMPOSITION OF RABBIT LOWER JAW AFTER BONE-DESTRUCTIVE TRAUMA

The properties of bone tissue, in particular its strength and hardness, depend on the mineral component of the bone. The aim of our work was to study the content of four mineral macronutrients – calcium, phosphorus, magnesium and sodium in the bone tissue of the rabbit lower jaw and to analyze the posttraumatic dynamics. Research was done on 20 adult 6-7-month-old rabbits, having 2.5-3.0 kg weight, which were segregated into experimental (15 animals) and control (5 animals) groups. Animals of the experimental group under combined anesthesia were subjected to bilateral bone-destructive trauma with a dental drill, that disrupted the integrity of the bone tissue of the alveolar part of the lower jaw. 1, 2, and 3 weeks after the injury the animals were taken out of the experiment, and were subjected to lower jaw disarticulation. To determine the mineral composition of the bone tissue, we used the method of atomic absorption spectral analysis. The content of four mineral elements (Ca, P, Mg, Na) was determined. It was found that calcium content more than doubled by the end of the fi rst week after injury, slightly decreased by the end of the second week, and slightly increased again during the third week. Bone phosphorus content increases by the end of the fi rst week after injury, and decreases during the next two weeks. The amount of sodium decreases slightly at the end of the fi rst week after injury, but increases during the next two weeks and exceeds the norm at the end of the third week. The amount of magnesium in the bone tissue decreases during the two weeks after injury, and increases by the end of the third week, almost returning to normal levels. The results of the study allowed us to conclude that within three weeks after surgical bone-destructive trauma, the studied macronutrients in bone tissue have a pronounced dynamic, diff erent and specifi c for each element.

Does a suspensory lifestyle result in increased tensile strength? Organ-level material properties of sloth limb bones.

The material composition of vertebrate connective tissue is highly conserved across taxa. Existing data suggest that the compressive and tensile strength of limb bones are very similar despite marked variation in limb posture and locomotor patterns. However, the material properties of limb bone tissue from suspensory taxa have not been formally evaluated. Sloths are nearly obligatory in their use of below-branch suspensory locomotion and posture, thus placing their limb bones and associated soft tissue structures under routine tensile loading. It is possible that sloth limb bones are modified for enhanced tensile strength, perhaps at the expense of compressive strength. Forelimb and hindlimb bones of two-toed (Choloepus hoffmanni) and three-toed (Bradypus variegatus) sloths were tested in compression and bending to evaluate this hypothesis. Strength and elastic (Young's) modulus were similarly lower in sloth limb bones during both compression and bending, as compared with pronograde taxa. Ratios of peak bending strength to compressive strength additionally were elevated (sloths: 1.4-1.7; upright taxa: 0.6-1.2) for sloth limb bones. Overall, the material properties measured from the limb bones of tree sloths support our hypothesis of predicted function in a tensile limb system. Future studies should aim to directly test bones in tension to confirm indications of elevated axial tensile strength. Nevertheless, the results herein expand understanding of functional adaptation in mammalian tissue for a range of locomotor/postural behaviors that were previously unexplored.

A multiscale finite element investigation on the role of intra- and extra-fibrillar mineralisation on the elastic properties of bone tissue

Lamellar bone is one of the fundamental structural units of bone tissue and it consists of mineralised collagen fibrils (MCFs) embedded within an extra-fibrillar matrix comprised of hydroxyapatite minerals distributed throughout a matrix of non-collagenous proteins (NCPs). While both intra- and extra-fibrillar phases provide a critical contribution to tissue-level behaviour, the mechanical implications of their structural arrangement, and in particular the relative distribution of HA minerals between both phases, remains poorly understood. This study presents a multiscale finite element framework to investigate the role of intra- and extra-fibrillar mineralisation on the elastic properties of bone tissue by considering two levels of structural hierarchy. At the nanoscale, representative volume elements (RVEs) of both MCFs and the extra-fibrillar matrix were developed, and a homogenisation strategy was used to determine the effective elastic properties of each phase. At the sub-micron level, an RVE of lamellar bone that accounted for newly reported patterns of mineral platelets encircling collagen fibrils was used to predict the effective response of lamellar bone tissue, with material properties established from the previous length scale. The results demonstrated that the overall mineral content in the tissue is the biggest contributor to the effective elastic properties of lamellar bone. While this is perhaps unsurprising, importantly, it was demonstrated that the extra-fibrillar matrix (and mineral therein) is the phase that makes the primary contribution to the elastic response of the tissue. The two main reasons that the extra-fibrillar matrix dominated the load-bearing response are (i) the greater proportion of mineral content compared to the intra-fibrillar regions and (ii) the highly ordered arrangement of mineral platelets that are aligned to the longitudinal axis of MCFs. Both of these features resulted in extra-fibrillar mineral strain ratios that were consistently higher than intra-fibrillar mineral strain ratios under axial loading. As a result, the predicted elastic properties of MCFs were much lower than the extra-fibrillar matrix, indicating that intra-fibrillar mineralisation only provided a modest contribution to the stiffness of bone tissue. Collectively, the predicted results of the multiscale approach compared well to the range properties measured through various experimental testing methods, highlighting its potential to provide further insight into the role of sub-tissue features of tissue biomechanics.

Compressive Strength Characteristics of Long Tubular Bones after Hyperthermal Ablation

Thermoablation is used in the treatment of tumorous bones. However, little is known about the influence such thermal treatment has on the mechanical properties of bone tissue. The purpose of this work was to study the influence of thermal treatment in a range of 60–100 °C (in increments of 10 °C) on the structural properties of pig femurs using an original approach that involved a periosteal arrangement of heating elements providing gradual dry heating of the bone from its periphery to its center. Heating of freshly extracted bone tissue segments was performed ex vivo using surface heaters of a Phoenix-2 local hyperthermia hardware system. Mechanical testing followed the single-axis compression scheme (traverse velocity of 1 mm/min). In the 60–90 °C range of heating, no attributes of reduced structural characteristics were found in the samples subjected to thermoablation in comparison to the control samples taken from symmetric areas of adjacent cylinders of healthy bones and not subjected to heat treatment. The following statistically significant changes were found as a result of compressing the samples to 100 °C after the heat treatment: reduced modulus of elasticity and increased elastic strain (strain-to-failure), mainly due to increases in plastic deformation. This finding may serve as evidence of a critical ex vivo change in the biomechanical behavior of bone tissues at such temperatures. Thus, ex vivo treatment of bone tissue in the thermal range of 60–90 °C may be used in studies of thermoablation efficiency against tumor involvement of bones.

Properties of Additive-Manufactured Open Porous Titanium Structures for Patient-Specific Load-Bearing Implants

Additive manufacturing has been well established in many sectors, including the medical industry. For load-bearing bone implants, titanium and its alloys, such as Ti6Al4V, are widely used due to their high strength to weight ratio and osseointegrative properties. However, bone resorption and loosening of implants is related to the significantly higher stiffness of dense Ti6Al4V, leading to stress shielding. With the aging of population, there is an increasing need for orthopedic implants with a high success rate and a long implant life span. Besides that the treatment of non-healing segmental bone defects, where the self-repairing properties of bone tissue are not sufficient, is still a challenge. In both fields of application, patient-specific titanium implants combined with functionally graded porosity designed according to locally expected loads unlock new possibilities. Many studies underline the huge potential of the new design freedom to generate open porous structures and more personalized implants with enhanced mechanical properties that also integrate well with surrounding tissues. Integration of functionally graded open porosity into implants allows for the implant to more closely mimic the mechanical properties of human bone and its internal architecture. The results of this work represent the basis for developing complex porous titanium structures with various pore sizes and shapes to tailor structural mechanical properties and biological responses. Therefore, 3D porous structures with various pore sizes and shapes were designed and manufactured in Ti6Al4V using laser powder bed fusion (PBF-LB/M). Based on these structures, the correlation of pore size and shape with cell ingrowth, morphology, metabolic activity, and early markers for bone formation (ALP activity) was investigated in static cell cultures using the osteosarcoma cell line Saos-2. Mechanical properties, such as stiffness and compression strength, were investigated with compression testing. The present study concludes that cell morphology, metabolic activity, and ALP activity are widely independent of pore shape and size within the tested range of 400–700 µm pore size. Furthermore, the mechanical properties of the evaluated structures were in the range of cortical and trabecular bone. This opens the possibility to design mechanical properties with gradient porosity without decisively affecting biological responses.

Brillouin-Raman microspectroscopy for the morpho-mechanical imaging of human lamellar bone.

Bone has a sophisticated architecture characterized by a hierarchical organization, starting at the sub-micrometre level. Thus, the analysis of the mechanical and structural properties of bone at this scale is essential to understand the relationship between its physiology, physical properties and chemical composition. Here, we unveil the potential of Brillouin–Raman microspectroscopy (BRaMS), an emerging correlative optical approach that can simultaneously assess bone mechanics and chemistry with micrometric resolution. Correlative hyperspectral imaging, performed on a human diaphyseal ring, reveals a complex microarchitecture that is reflected in extremely rich and informative spectra. An innovative method for mechanical properties analysis is proposed, mapping the intermixing of soft and hard tissue areas and revealing the coexistence of regions involved in remodelling processes, nutrient transportation and structural support. The mineralized regions appear elastically inhomogeneous, resembling the pattern of the osteons' lamellae, while Raman and energy-dispersive X-ray images through scanning electron microscopy show an overall uniform distribution of the mineral content, suggesting that other structural factors are responsible for lamellar micromechanical heterogeneity. These results, besides giving an important insight into cortical bone tissue properties, highlight the potential of BRaMS to access the origin of anisotropic mechanical properties, which are almost ubiquitous in other biological tissues.

Integrated osteochondral differentiation of mesenchymal stem cells on biomimetic nanofibrous mats with cell adhesion-generated piezopotential gradients.

Biomimetic piezoelectric scaffolds provide a noninvasive method for in vivo cell regulation and tissue regeneration. Herein, considering the gradually varied piezoelectric properties of native cartilage and bone tissues, we fabricated biomimetic electrospun poly(L-lactic acid) (PLLA) nanofibrous mats with gradient piezoelectric properties to induce the integrated osteochondral differentiation of rat mesenchymal stem cells (MSCs). Nanofibrous mats are polarized under electric fields with linear variation of strength to generate gradient piezoelectricity, and cell adhesion-derived contraction forces could produce gradient piezoelectric potential on the scaffolds. Our results demonstrated that the piezoelectric potential could positively modulate cell adhesion, intracellular calcium transients, Ca2+ binding proteins, and differentiation-related genes. In addition, the differentiation of MSCs into osteogenic and chondrogenic lineages was integrated on a single scaffold at different areas with relatively high and low piezoelectricity values, respectively. The continuous gradient scaffold exhibited the potential to provide a smooth transition between the cartilage and bone, offering new insights to probe the regeneration mechanisms of the osteochondral tissue in a single scaffold and inspiring a future efficient and rational design of piezoelectric smart biomaterials for tissue engineering.

USE OF OSTEOPLASTIC MATERIALS TO RESTORE BONE DEFECTS FOLLOWING THE SURGICAL TREATMENT

In recent years, the number of dental surgical operations has been growing rapidly worldwide, and clinicians are facing pressing issue to select and apply osteoplastic materials, which would promote rapid repair of jaw bone defects and relieve symptoms during the post-operative period. With the advancements in the field of dentoalveolar reconstruction, it is of great importance to develop the material for bone restoration, which by its properties would be identical to autologous bone. The aim of this study is to analyze the effectiveness of osteoplastic materials used for the augmentation following sinus lift, tooth socket preservation, osteosynthesis of mandibular fractures and extraction of impacted third molars. 280 people aged from 18 to 55 with partial or complete adentia and atrophy of the alveolar arch of the jaws, with chronic periapical infection, chronic generalized periodontitis, fractures and impacted third molars were examined at the Department of Surgical Dentistry and Maxillofacial Surgery of the Chernivtsi Regional Clinical Hospital. All patients were planned to undergo prosthodontic treatment assisted by dental implants. The study has demonstrated that the patients of subgroups B of all groups of the study, where the augmentation of bone defects was performed using a combination of osteoplastic material «Colapan-L» containing multipotent mesenchymal stem cells of adipose tissue and platelet-rich plasma presented alleviating clinical symptoms including pain, collateral oedema, hyperaemia of the oral mucosa and better bone regeneration at the site of surgery, compared with subgroups A, where the augmentation was performed with osteoplastic material «Colapan-L», and sub-groups B, whose healing followed by blood clot forming. The use of osteoplastic materials containing multipotent mesenchymal stem cells of adipose tissue during dental operations improves the regenerative and reparative properties of bone tissue, facilitates the postoperative period and reduces the duration of inpatient treatment period.

Osteocytes Influence on Bone Matrix Integrity Affects Biomechanical Competence at Bone-Implant Interface of Bioactive-Coated Titanium Implants in Rat Tibiae.

Osseointegration is a prerequisite for the long-term success of implants. Titanium implants are preferred for their biocompatibility and mechanical properties. Nonetheless, the need for early and immediate loading requires enhancing these properties by adding bioactive coatings. In this preclinical study, extracellular matrix properties and cellular balance at the implant/bone interface was examined. Polyelectrolyte multilayers of chitosan and gelatin or with chitosan and Hyaluronic acid fabricated on titanium alloy using a layer-by-layer self-assembly process were compared with native titanium alloy. The study aimed to histologically evaluate bone parameters that correlate to the biomechanical anchorage enhancement resulted from bioactive coatings of titanium implants in a rat animal model. Superior collagen fiber arrangements and an increased number of active osteocytes reflected a significant improvement of bone matrix quality at the bone interface of the chitosan/gelatin-coated titan implants over chitosan/hyaluronic acid-coated and native implants. Furthermore, the numbers and localization of osteoblasts and osteoclasts in the reparative and remodeling phases suggested a better cellular balance in the chitosan/Gel-coated group over the other two groups. Investigating the micro-mechanical properties of bone tissue at the interface can elucidate detailed discrepancies between different promising bioactive coatings of titanium alloys to maximize their benefit in future medical applications.

Retrospective Evaluation and Framework Development of Bone Anisotropic Material Behavior Compared with Elastic, Elastic-Plastic, and Hyper-Elastic Properties.

The main motivation for studying damage in bone tissue is to better understand how damage develops in the bone tissue and how it progresses. Such knowledge may help in the surgical aspects of joint replacement, fracture fixation or establishing the fracture tolerance of bones to prevent injury. Currently, there are no standards that create a realistic bone model with anisotropic material properties, although several protocols have been suggested. This study seeks to retrospectively evaluate the damage of bone tissue with respect to patient demography including age, gender, race, body mass index (BMI), height, and weight, and their role in causing fracture. Investigators believe that properties derived from CT imaging data to estimate the material properties of bone tissue provides more realistic models. Quantifying and associating damage with in vivo conditions will provide the required information to develop mathematical equations and procedures to predict the premature failure and potentially mitigate problems before they begin. Creating a realistic model for bone tissue can predict the premature failure(s), provide preliminary results before getting the surgery, and optimize the design of orthopaedic implants. A comparison was performed between the proposed model and previous efforts, where they used elastic, hyper- elastic, or elastic-plastic properties. Results showed that there was a significant difference between the anisotropic material properties of bone when compared with unrealistic previous methods. The results showed that the density is 50% higher in male subjects than female subjects. Additionally, the results showed that the density is 47.91% higher in Black subjects than Mixed subjects, 53.27% higher than Caucasian subjects and 57.41% higher than Asian. In general, race should be considered during modeling implants or suggesting therapeutic techniques.