Trabecular Structures Research Articles

Fluid mechanics of the zebrafish embryonic heart trabeculation.

Embryonic heart development is a mechanosensitive process, where specific fluid forces are needed for the correct development, and abnormal mechanical stimuli can lead to malformations. It is thus important to understand the nature of embryonic heart fluid forces. However, the fluid dynamical behaviour close to the embryonic endocardial surface is very sensitive to the geometry and motion dynamics of fine-scale cardiac trabecular surface structures. Here, we conducted image-based computational fluid dynamics (CFD) simulations to quantify the fluid mechanics associated with the zebrafish embryonic heart trabeculae. To capture trabecular geometric and motion details, we used a fish line that expresses fluorescence at the endocardial cell membrane, and high resolution 3D confocal microscopy. Our endocardial wall shear stress (WSS) results were found to exceed those reported in existing literature, which were estimated using myocardial rather than endocardial boundaries. By conducting simulations of single intra-trabecular spaces under varied scenarios, where the translational or deformational motions (caused by contraction) were removed, we found that a squeeze flow effect was responsible for most of the WSS magnitude in the intra-trabecular spaces, rather than the shear interaction with the flow in the main ventricular chamber. We found that trabecular structures were responsible for the high spatial variability of the magnitude and oscillatory nature of WSS, and for reducing the endocardial deformational burden. We further found cells attached to the endocardium within the intra-trabecular spaces, which were likely embryonic hemogenic cells, whose presence increased endocardial WSS. Overall, our results suggested that a complex multi-component consideration of both anatomic features and motion dynamics were needed to quantify the trabeculated embryonic heart fluid mechanics.

Updating on dental implant osseointegration and survival rate in osteoporotic bone

Background: Systemic diseases may impact osseointegration of dental implants. Osteoporosis has become one of the concerning diseases since its prevalence reached 18.3% in the world and 10.3% in Indonesia. It is characterized by the decrease in bone thickness, alteration of trabecular structures, and increase in ratio of carbonate and phosphate, making the bone more fragile and prone to fracture. Consequently, the issue of bone quantity and quality will have a great impact on dental implant survival rate.Objectives: To know the effect of osteoporosis on survival rate and osseointegration of dental implants.Conclusion: Dentists should be more cautious if patients receiving dental implant treatment have a bone mineral density (BMD) score of -2.5 < T-Score < -1 and an estrogen deficiency, because both are directly related to osteoporosis. Consumption of bisphosphonates should also be asked because it could cause osteonecrosis of the jaw. Most studies show no significant differences between survival rate of implants placed on osteoporotic patients and healthy patients after a short time period (0-1 year). However, most studies show significant differences after a long time period (5-7 years) so evaluation of implants is recommended.

Investigation of the process intergrowth of bone tissue into the hole in titanium implants (Experimental research)

IntroductionDespite the use of modern implants, complications such as nonunion and avascular necrosis of the femoral head are observed in femoral neck fractures (FNF). We have created a new perforated I-beam implant for FNF osteosynthesis and developed a new osteosynthesis philosophy based not only on the mechanical and biomechanical interaction of the bone-implant system, but also on the interaction of the biological properties of the bone and the implant.The purpose of the work is to study the interaction of the biological process of the bone - its regeneration (germination) of bone tissue into the holes of the implant. Materials and methodsThe experiment was carried out on fourteen Chinchilla rabbits in accordance with all international standards. A perforated implant specially made of titanium (ChM, Poland) was surgically implanted into the proximal femur.The implant measurements were as follows: length – 6 mm, width – 3 mm, thickness – 2 mm, 2 holes with a diameter of 2 mm. The 14 rabbits were divided into 7 groups. After 1, 2, 3, 4, 5, 10 and 12 weeks the animals were withdrawn from the experiment according to the standard rules in sequential order. The preparations were placed in a formalin solution and sent to the pathomorphology laboratory (CITO, Russia) for histological studies. ResultsWeekly histopathological studies revealed a gradual transition from the organization of a hematoma to the formation of mature bone tissue in the holes of the implants. The titanium implant is bioinert and did not cause any visible reactions from the bone tissue. Simultaneous integration of vascular proliferation and newly formed bone tissue into the implant holes were revealed. On 10–12-week preparations, the formation of trabecular structures of mature bone tissue was revealed in the holes of the implants and elements of adipose and bone marrow tissue were observed. Macroscopic examination of 4–5-week preparations showed almost complete filling of the holes with bone tissue. On 10–12-week preparations, the bone tissue in the holes of the implants did not differ from the bone tissue surrounding the implant. The processes of formation of mature bone tissue in the holes of the implants were similar to the processes of physiological bone healing (regeneration) at the fracture site. ConclusionsThe obtained results show the following: 1.The titanium implant is bioinert and does not cause any visible reactions from the bone tissue; 2. There is a gradual process of formation of new vessels, and then the formation of new bone tissue in the holes of the implant instead of the one damaged during implantation.Thus, the results of this experiment indirectly confirm our assumption that a perforated implant for FNF osteosynthesis will participate not only in the mechanical and biomechanical interaction of the bone-implant system, but will also include the 3rd element in this system - the biological properties of the bone itself. We assume that these properties of the new implant will increase blood flow in the femoral neck and partially replenish the volume of bone tissue destroyed during osteosynthesis which does not occur with FNF osteosynthesis by any of the known implants.

A novel porous granular scaffold for the promotion of trabecular bone repair by time-dependent alteration of morphology.

Granular scaffolds have been extensively used in the clinic to repair irregular maxillofacial defects. There remain some challenges for the repair of trabecular structures in cancellous bone due to the reticular lamella-like morphology. In this study, we fabricated a novel granular scaffold by rational design of components with different degradation rates so that the morphology of the novel scaffold can evolve to match the growth period of bone cells. Here, polycaprolactone (PCL) was used to fabricate porous microspheres as a skeleton with slow degradation. The macropores were filled with quick degraded gelatin to form complete microspheres. Asynchronous degradation of the two components altered the morphology of the evolutive scaffold from compact to porous, gradually exposing the ridge-like skeletons. This scaffold reversed the decline of cellular adhesion to simple porous skeletons during the initial adhesion. Furthermore, the cells were able to grow into the pores and adhere onto the skeletons with an elongated cellular morphology, facilitating osteogenic differentiation. This novel scaffold was experimentally proven to promote the regeneration of alveolar bone along with a good percentage of bone volume and the formation of trabecular structures. We believe this morphology-evolved scaffold is highly promising for regenerative applications in the clinic.

3D printing of trabecular bone-mimetic structures by vat photopolymerization of bovine hydroxyapatite as a potential candidate for scaffolds

3D printing of trabecular bone-mimetic structures by vat photopolymerization of bovine hydroxyapatite as a potential candidate for scaffolds

Effective Spatial Resolution of Photon Counting CT for Imaging of Trabecular Structures is Superior to Conventional Clinical CT and Similar to High Resolution Peripheral CT.

Photon counting computed tomography (PCCT) might offer an effective spatial resolution that is significantly improved compared with conventional state-of-the-art computed tomography (CT) and even provide a microstructural level of detail similar to high-resolution peripheral CT (HR-pQCT). The aim of this study was to evaluate the volumetric effective spatial resolution of clinically approved PCCT as an alternative to HR-pQCT for ex vivo or preclinical high-resolution imaging of bone microstructure. The experiment contained 5 human vertebrae embedded in epoxy resin, which were scanned 3 times each, and on 3 different clinical CT scanners: a PCCT (Naeotom Alpha), a dual-energy CT (Somatom Force [SF]), and a single-energy CT (Somatom Sensation 40 [S40]), all manufactured by Siemens Healthineers (Erlangen, Germany). Scans were performed with a tube voltage of 120 kVp and, to provide maximum scan performance and minimum noise deterioration, with exposures of 1500 mAs (SF), 2400 mAs (S40), and 4500 mAs (PCCT) and low slice increments of 0.1 (PCCT) and 0.3 mm (SF, S40). Images were reconstructed with sharp and very sharp bone kernels, Br68 and Br76 (PCCT), Br64 (SF), and B65s and B75h (S40). Ground truth information was obtained from an XtremeCT scanner (Scanco, Brüttisellen, Switzerland). Voxel-wise comparison was performed after registration, calibration, and resampling of the volumes to isotropic voxel size of 0.164 mm. Three-dimensional point spread- and modulation-transfer functions were calculated with Wiener's deconvolution in the anatomical trabecular structure, allowing optimum estimation of device- and kernel-specific smoothing properties as well as specimen-related diffraction effects on the measurement. At high contrast (modulation transfer function [MTF] of 10%), radial effective resolutions of PCCT were 10.5 lp/cm (minimum resolvable object size 476 μm) for kernel Br68 and 16.9 lp/cm (295 μm) for kernel Br76. At low contrast (MTF 5%), radial effective spatial resolutions were 10.8 lp/cm (464 μm) for kernel Br68 and 30.5 lp/cm (164 μm) for kernel Br76. Axial effective resolutions of PCCT for both kernels were between 27.0 (185 μm) and 29.9 lp/cm (167 μm). Spatial resolutions with kernel Br76 might possibly be still higher but were technically limited by the isotropic voxel size of 164 μm. The effective volumetric resolutions of PCCT with kernel Br76 ranged between 61.9 (MTF 10%) and 222.4 (MTF 5%) elements per cubic mm. Photon counting CT improved the effective volumetric resolution by factor 5.5 (MTF 10%) and 18 (MTF 5%) compared with SF and by a factor of 8.7 (MTF 10%) and 20 (MTF 5%) compared with S40. Photon counting CT allowed obtaining similar structural information as HR-pQCT. The effective spatial resolution of PCCT in trabecular bone imaging was comparable with that of HR-pQCT and more than 5 times higher compared with conventional CT. For ex vivo samples and when patient radiation dose can be neglected, PCCT allows imaging bone microstructure at a preclinical level of detail.

Understanding the Role of Surface Modification of Randomized Trabecular Titanium Structures in Bone Tissue Regeneration: An Experimental Study.

Background and Objectives: Three-dimensional (3D) metallic trabecular structures made by additive manufacturing (AM) technologies promote new bone formation and osteointegration. Surface modifications by chemical treatments can improve the osteoconductive properties of metallic structures. An in vivo study in sheep was conducted to assess the bone response to randomized trabecular titanium structures that underwent a surface modification by chemical treatment compared to the bone response to the untreated specimens. Material and Methods: Sixteen specimens with a randomized trabecular titanium structure were implanted in the spongious bone of the distal femur and proximal tibia and the cortical bone of the tibial diaphysis of two sheep. Of them, eight implants had undergone a chemical treatment (treated) and were compared to eight implants with the same structure but native surfaces (native). The sheep were sacrificed at 6 weeks. Surface features of the lattice structures (native and treated) were analyzed using a 3D non-contact profilometer. Compression tests of 18 lattice cubes were performed to investigate the mechanical properties of the two structures. Excellent biocompatibility for the trabecular structures was demonstrated in vitro using a cell mouse fibroblast culture. Histomorphometric analysis was performed to evaluate bone implant contact and bone ingrowth. Results: A compression test of lattice cubic specimens revealed a comparable maximum compressive strength value between the two tested groups (5099 N for native surfaces; 5558 N for treated surfaces; p > 0.05). Compared to native surfaces, a homogenous formation of micropores was observed on the surface of most trabeculae that increased the surface roughness of the treated specimens (4.3 versus 3.2 µm). The cellular viability of cells seeded on three-dimensional structure surfaces increased over time compared to that on plastic surfaces. The histomorphometric data revealed a similar behavior and response in spongious and cortical bone formation. The percentage of the implant surface in direct contact with the regenerated bone matrix (BIC) was not significantly different between the two groups either in the spongious bone (BIC: 27% for treated specimens versus 30% for native samples) or in the cortical bone (BIC: 75% for treated specimens versus 77% for native samples). Conclusions: The results of this study reveal rapid osseointegration and excellent biocompatibility for the trabecular structure regardless of surface treatment using AM technologies. The application of implant surfaces can be optimized to achieve a strong press-fit and stability, overcoming the demand for additional chemical surface treatments.

Jawbone Segmentation with Trabecular Bone Preservation from Cone Beam CT Images

To segment jaw structures in both open and closed mouth states from cone beam CT images and to preserve the true structures of trabecular bones. Segmentation algorithms of the mandible and maxilla were designed based on their different structures. We detected edges in volume and segment edges of the mandible and maxilla whether the mouth of a patient was open or closed. The internal structures of the mandible and maxilla were preserved by a morphological method with different parameters, respectively. An axial plane corresponding to the bottom of the hard palate was identified so that the bone structures of the maxilla above this plane were removed. Finally, the mandibular surface was smoothed by a simple thresholding method, and the maxillary surface was optimized by a geodesic active contours method. The 3D jaw model was segmented automatically by our proposed procedure with high accuracy. The average dice coefficients of the mandible and maxilla were equal to 0.9709 and 0.9420, respectively. The proposed jaw segmentation algorithm is automatic and knowledge-driven. The segmented jaws truly demonstrate the cortical and trabecular bone structures. It may potentially assist doctors in diagnosis and surgical planning.

Mechanical simulation considering anisotropy of trabecular scaffolds for 3D-printed biomimetic bone implants

This work proposes the mechanical simulation of scaffold-type custom implants with a trabecular structure created by additive manufacturing. The primary purpose is to offer an alternative to currently used implants that overcomes stress shielding and creates a proper environment for bone resorption. Biomimetic implants were digitally designed from computed tomographies. A finite element analysis (FEA) simulation was performed, and trabecular scaffolds were compared to compact or solid scaffolds currently applied in the operative room. This study proved that compact structures have less resistance than trabecular scaffolds by identifying plastic compression properties. Finally, it was found that trabecular structures in bone implants increased the compression modulus by 49.74%.

Repair of Osteonecrosis of the Femoral Head with Adipose‐Derived Stem Cell Composite with New Nanomaterial

This study was aimed at researching the effect of adipose‐derived stem cell (ADSC) composite with new nanomaterials on repairing osteonecrosis of the femoral head (ONFH). Nanophase hydroxyapatite/collagen bone material was composited with ADSCs to form a new nanobone material. 24 bone defect rabbits were divided into S1 group (implanted with ADSC composite with nanophase hydroxyapatite/collagen bone material 14 days after modelling), S2 group (implanted with nanophase hydroxyapatite/collagen bone material), and S3 group (simple models). HE staining was used to measure the percentage area of trabecular bone and bone mineral density in rabbit femoral tissue, the load strength of femoral head was measured by orthopedic biomechanical tester, and the number of FVII‐Ag‐positive cells was detected by immunohistochemistry. There were 8 rabbit models in each group. ADSCs showed black nodules after alkaline phosphatase staining, which was a positive reaction. The OD value of ADSC cells showed a trend of increasing first and then decreasing. The growth rate of ADSC cells was relatively slow in 1‐4 days, the growth rate was significantly accelerated in 4‐6 days, and the growth inhibition period was entered after 6 days. After hematoxylin‐eosin (HE) staining, many scattered bone trabecular structures and bone marrow tissues were found in the rabbits in the S1 group. The nanomaterials were still observed in the rabbits in the S2 group after surgery, and large sheets of bone trabecula appeared with the formation of medullary cavity partially. The bone marrow tissues of the rabbits in the S3 group disappeared partially after surgery, and undifferentiated mesenchymal stem cells and capillaries appeared with many scattered bone trabeculae. The rabbits in the S1 group had significantly higher trabecular bone percentage area and bone mineral density (59.76 ± 6.23; 0.141 ± 0.015 g/cm2) than the S2 group (42.51 ± 7.03; 0.113 ± 0.008 g/cm2), and the differences were statistically significant (P < 0.05). The postoperative load strength of rabbits in group S1 was significantly higher than that in group S2, and the difference was statistically significant (P < 0.05). ADSC composite with the new nanomaterial had a good repairing effect on ONFH.

Topology Optimisation for Compliant Hip Implant Design and Reduced Strain Shielding.

Stiff total hip arthroplasty implants can lead to strain shielding, bone loss and complex revision surgery. The aim of this study was to develop topology optimisation techniques for more compliant hip implant design. The Solid Isotropic Material with Penalisation (SIMP) method was adapted, and two hip stems were designed and additive manufactured: (1) a stem based on a stochastic porous structure, and (2) a selectively hollowed approach. Finite element analyses and experimental measurements were conducted to measure stem stiffness and predict the reduction in stress shielding. The selectively hollowed implant increased peri-implanted femur surface strains by up to 25 percentage points compared to a solid implant without compromising predicted strength. Despite the stark differences in design, the experimentally measured stiffness results were near identical for the two optimised stems, with 39% and 40% reductions in the equivalent stiffness for the porous and selectively hollowed implants, respectively, compared to the solid implant. The selectively hollowed implant’s internal structure had a striking resemblance to the trabecular bone structures found in the femur, hinting at intrinsic congruency between nature’s design process and topology optimisation. The developed topology optimisation process enables compliant hip implant design for more natural load transfer, reduced strain shielding and improved implant survivorship.

Application of Fractal Analysis in Detecting Trabecular Bone Changes in Periapical Radiograph of Patients with Periodontitis.

Introduction Evaluation of detailed features of the supporting bone is an important step in diagnosis and treatment planning for teeth with clinical attachment loss. Fractal analysis can be used as a method for evaluating the complexity of trabecular bone structures. The aim of this study was to evaluate the trabecular bone changes in periapical radiographs of patients with different stages of periodontitis using fractal analysis. Methods This comparative cross-sectional study was performed on patients with and without clinical attachment loss in mandibular first molars. Teeth with clinical attachment loss were divided into mild, moderate, and severe periodontitis groups. Digital periapical radiographs were obtained from the mandibular first molars using the same exposure parameters. DICOM file of the radiographs was exported to ImageJ software for fractal analysis. Three regions of interest (ROIs) were considered in each radiograph: two proximal ROIs mesial and distal to the mandibular first molar and one apical ROI. Fractal dimension (FD) values were calculated using the fractal box counting approach. Statistical analysis was performed using the chi-square test, Mann–Whitney test, intraclass correlation coefficient, and ANOVA (α = 0.05). Results FD values were significantly different between moderate and severe periodontitis and healthy periodontal bone (P < 0.05), except for the distal ROI for moderate periodontitis cases (P=0.280). However, FD values of the supporting bone in periodontally healthy teeth and teeth with mild periodontitis did not show a statistically significant difference (P > 0.05). Conclusion Fractal analysis is a useful tool for evaluation of bone alterations in moderate and severe periodontitis, but was not able to detect the most initial radiographic bone signs of mild periodontitis.

Evaluation of porosity in 3D printed trabecular bone structures for prostheses

Hip prostheses require an external porous area in order to fix them by means of osseointegration. Different structures can be printed in order to favour bone fixation, such as octet-truss or trabecular, among others. In the present paper, bone-like structures are printed in cubic shapes, by means of fused filament fabrication (FFF). Three design parameters of the structures were varied: the number of joining points per unit volume, the area scale and the offset that is given to the different struts of the structure. Both the theoretical and the measured porosity of the samples is evaluated, from the drawing of the structures and by means of weight measurements respectively. As expected, the structures having fewer union points per unit volume are more porous than the structures having more points. When low number of points generating struts of the structure were employed, measured porosity is lower than the theoretical one, while when high number of points is considered, the opposite situation is found. The present work will help to obtain porous structures to be used in prostheses, by means of extrusion 3D printing processes.

3D-printing for the precision assessment of a new medical device

Additive manufacturing played a keyrole in investigating the precision of a recently-developed device that measures the elastic characteristics of the trabecular bone by simulating the application of loads on a virtual biopsy obtained from radiographic images of the proximal epiphyses in the patient’s hand fingers. The simulation results are combined in a Bone Structure Index (BSI), which has shown to be able to detect trabecular bone alterations due to osteoporosis or other pathological situations. In order to obtain a large number of measurements without having voluntary patients undergo unnecessary radiations, the precision assessment tests were carried out on a 3D-printed phantom hand, in which different mimicked trabecular structures (chips) were inserted. Each mimicked bone had a unique internal structure and density and was 3D-printed using radiopaque composite materials. Fifteen different chips were additively manufactured; 20 measurements were performed on each chip. BSI and BSI_T-score precision values were computed according to ISO 5725 and ISCD standards. For all the chips, no relationship was found between the mean [Formula: see text] and standard deviation [Formula: see text] of the measurements in each chip. The range of the 95% confidence interval ([Formula: see text]) was computed assuming the repeatability standard deviation [Formula: see text] as the known standard deviation of the measurement method (average of [Formula: see text] values): [Formula: see text], corresponding to [Formula: see text]. Least Significant Change was evaluated as well: [Formula: see text], corresponding to [Formula: see text]. The 95% confidence intervals are small when compared to the commonly-accepted diagnostic values, where a patient is classified as osteoporotic if T-score &lt; −2.5, non-osteoporotic if T-score &gt; -1 and osteopoenic if -2.5 &lt; T-score &lt; -1. The LSC results are in line with the requirements for the gold-standard osteoporosis diagnostic systems. Additive manufacturing made it possible to avoid irradiation of humans in this precision assessment.

Mechanical Properties of Porous Structures for Dental Implants: Experimental Study and Computational Homogenization.

A combined experimental and numerical study on titanium porous microstructures intended to interface the bone tissue and the solid homogeneous part of a modern dental implant is presented. A specific class of trabecular geometries is compared to a gyroid structure. Limitations associated with the application of the adopted selective laser melting technology to small microstructures with a pore size of 500 m are first examined experimentally. The measured effective elastic properties of trabecular structures made of Ti6Al4V material support the computational framework based on homogenization with the difference between the measured and predicted Young’s moduli of the Dode Thick structure being less than 5%. In this regard, the extended finite element method is promoted, particularly in light of the complex sheet gyroid studied next. While for plastic material-based structures a close match between experiments and simulations was observed, an order of magnitude difference was encountered for titanium specimens. This calls for further study and we expect to reconcile this inconsistency with the help of computational microtomography.

A novel compound bone articular repair material combining deproteinized osteoarticulation with calcium phosphate cement and BMP-9

The objective of this study was to combine bone morphogenetic protein-9 (BMP-9), a protein with good osteogenic and angiogenic activities, with deproteinized osteoarticulation (DPOA). Calcium phosphate cement (CPC) loaded with BMP-9 was coated on the surface and partially filled in the intramedullary cavity of DPOA. A canine femoral condylar defect model was established and implanted with DPOA/CPC/BMP-9 material. DPOA preserved the shape of the femoral condyle and the three-dimensional reticular bone matrix structure. CPC/BMP-9 persistently and slowly released BMP-9. The DPOA/CPC/BMP-9 group was superior to the DPOA/BMP-9 and DPOA groups in the number and maturity of newly formed blood vessels, the number and maturity of bone trabecular structures, and the integrated optical density of the type I collagen-positive area. At 16 weeks after the operation, the newly formed bone trabeculae in the DPOA/CPC/BMP-9 group were well shaped and orderly, forming a lamellar woven bone structure that was tightly connected to the boundary of the host bone, resulting in excellent osteoarticular repair. As a novel compound osteoarticular repair material, DPOA/CPC/BMP-9 has excellent biocompatibility, osteoconductivity, osteoinductivity, and angiogenicity, and it is expected to become an excellent alternative repair material for bone tissue engineering.

Biomimetic Zirconia with Cactus-Inspired Meso-Scale Spikes and Nano-Trabeculae for Enhanced Bone Integration.

Biomimetic design provides novel opportunities for enhancing and functionalizing biomaterials. Here we created a zirconia surface with cactus-inspired meso-scale spikes and bone-inspired nano-scale trabecular architecture and examined its biological activity in bone generation and integration. Crisscrossing laser etching successfully engraved 60 μm wide, cactus-inspired spikes on yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) with 200–300 nm trabecular bone-inspired interwoven structures on the entire surface. The height of the spikes was varied from 20 to 80 μm for optimization. Average roughness (Sa) increased from 0.10 μm (polished smooth surface) to 18.14 μm (80 μm-high spikes), while the surface area increased by up to 4.43 times. The measured dimensions of the spikes almost perfectly correlated with their estimated dimensions (R2 = 0.998). The dimensional error of forming the architecture was 1% as a coefficient of variation. Bone marrow-derived osteoblasts were cultured on a polished surface and on meso- and nano-scale hybrid textured surfaces with different spike heights. The osteoblastic differentiation was significantly promoted on the hybrid-textured surfaces compared with the polished surface, and among them the hybrid-textured surface with 40 μm-high spikes showed unparalleled performance. In vivo bone-implant integration also peaked when the hybrid-textured surface had 40 μm-high spikes. The relationships between the spike height and measures of osteoblast differentiation and the strength of bone and implant integration were non-linear. The controllable creation of meso- and nano-scale hybrid biomimetic surfaces established in this study may provide a novel technological platform and design strategy for future development of biomaterial surfaces to improve bone integration and regeneration.

Effects of hyperlipidemia on trabecular and cortical structures of the mandible.

To evaluate the mandibular bone structure of patients with hyperlipidemia by fractal dimension (FD) analysis and panoramic radiomorphometric indices including mandibular cortical thickness measurement, panoramic mandibular index (PMI), mandibular cortical index (MCI) and to compare with the healthy group. In total, 60 panoramic radiographs were included, including panoramic radiographs of 30 individuals with hyperlipidemia and 30 individuals with systemically healthy. FD analysis in the mandibular condyle, angle of the mandible, the distal side of the second premolar and anterior to mental foramen, PMI, MCI, and mandibular cortical thickness measurements were evaluated on radiographs. Independent samples t-test was used for differences between healthy and hyperlipidemia groups with regard to age and PMI. Repeated measurement of variance with one within and one between factors in the comparison of four regions and two groups in terms of FD and cortical thickness measurements. Following this analysis, significant differences were detected by post-hoc Sidak test. Fisher-Freeman-Halton analysis was applied to determine the relationship between categorical variables. FD values of the hyperlipidemic patients were found to be lower than the healthy group. Between the hyperlipidemic and healthy groups, there was a difference in the angle of the mandible FD values (p = 0.020). There were no differences in the cortical thickness measurements and PMI between the groups (p > 0.05). There was a difference in MCI values between the groups (p < 0.05). The trabecular structure of the angle of the mandible and the cortical bone structure of the mandible were found to be negatively affected by hyperlipidemia.

The Potential of Stereolithography for 3D Printing of Synthetic Trabecular Bone Structures.

Synthetic bone models are used to train surgeons as well as to test new medical devices. However, currently available models do not accurately mimic the complex structure of trabecular bone, which can provide erroneous results. This study aimed to investigate the suitability of stereolithography (SLA) to produce synthetic trabecular bone. Samples were printed based on synchrotron micro-computed tomography (micro-CT) images of human bone, with scaling factors from 1 to 4.3. Structure replicability was assessed with micro-CT, and mechanical properties were evaluated by compression and screw pull-out tests. The overall geometry was well-replicated at scale 1.8, with a volume difference to the original model of <10%. However, scaling factors below 1.8 gave major print artefacts, and a low accuracy in trabecular thickness distribution. A comparison of the model–print overlap showed printing inaccuracies of ~20% for the 1.8 scale, visible as a loss of smaller details. SLA-printed parts exhibited a higher pull-out strength compared to existing synthetic models (Sawbones ™), and a lower strength compared to cadaveric specimens and fused deposition modelling (FDM)-printed parts in poly (lactic acid). In conclusion, for the same 3D model, SLA enabled higher resolution and printing of smaller scales compared to results reported by FDM.

Lithium chloride prevents glucocorticoid-induced osteonecrosis of femoral heads and strengthens mesenchymal stem cell activity in rats.

Background:Accumulating evidence suggests that lithium influences mesenchymal stem cell (MSC) proliferation and osteogenic differentiation. As decreased bone formation in femoral heads is induced by glucocorticoids (GCs), we hypothesized that lithium has a protective effect on GC-induced osteonecrosis of femoral heads (ONFH).Methods:A rat ONFH model was induced by methylprednisolone (MP) and the effect of lithium chloride on the models was evaluated. Micro-computed tomography (CT)-based angiography and bone scanning were performed to analyze the vessels and bone structure in the femoral heads. Hematoxylin and eosin and immunohistochemical staining were performed to evaluate the trabecular structure and osteocalcin (OCN) expression, respectively. Bone marrow-derived MSCs were isolated from the models, and their proliferative and osteogenic ability was evaluated. Western blotting and quantitative real-time polymerase chain reaction were performed to detect osteogenic-related proteins including Runx2, alkaline phosphatase, and Collagen I.Results:Micro-CT analysis showed a high degree of osteonecrotic changes in the rats that received only MP injection. Treatment with lithium reduced this significantly in rats that received lithium (MP + Li group); while 18/20 of the femoral heads in the MP showed severe osteonecrosis, only 5/20 in the MP + Li showed mild osteonecrotic changes. The MP + Li group also displayed a higher vessel volume than the MP group (0.2193 mm3vs. 0.0811 mm3, P < 0.05), shown by micro-CT-based angiography. Furthermore, histological analysis showed better trabecular structures and more OCN expression in the femoral heads of the MP + Li group compared with the MP group. The ex vivo investigation indicated higher proliferative and osteogenic ability and upregulated osteogenic-related proteins in MSCs extracted from rats in the MP + Li group than that in the MP group.Conclusions:We concluded that lithium chloride has a significant protective effect on GC-induced ONFH in rats and that lithium also enhances MSC proliferation and osteogenic differentiation in rats after GC administration.