Stress In Bone Tissue Research Articles

Exogenous iron caused osteocyte apoptosis, increased RANKL production, and stimulated bone resorption through oxidative stress in a murine model

Iron overload is a risk factor for osteoporosis due to its oxidative toxicity. Previous studies have demonstrated that an excessive amount of iron increases osteocyte apoptosis and receptor activator of nuclear factor κ-B ligand (RANKL) production, which stimulates osteoclast differentiation in vitro. However, the effects of exogenous iron supplementation-induced iron overload on osteocytes in vivo and its role in iron overload-induced bone loss are unknown. This work aimed to develop an iron overloaded murine model of C57BL/6 mice by intraperitoneal administration of iron dextran for two months. The iron levels in various organs, bone, and serum, as well as the microstructure and strength of bone, apoptosis of osteocytes, oxidative stress in bone tissue, and bone formation and resorption, were assessed. The results showed that 2 months of exogenous iron supplementation significantly increased iron levels in the liver, spleen, kidney, bone tissue, and serum. Iron overload negatively affected bone microstructure and strength. Osteocyte apoptosis and empty lacunae rate were elevated by exogenous iron. Iron overload upregulated RANKL expression but had no significant impact on osteoprotegerin (OPG) and sclerostin levels. Static and dynamic histologic analyses and serum biochemical assay showed that iron overload increased bone resorption without significantly affecting bone formation. Exogenous iron promoted oxidative stress in osteocytes in vivo and in vitro. Additional supplementation of iron chelator (deferoxamine) or N-acetyl-l-cysteine (NAC) partially alleviated bone loss, osteocyte apoptosis, osteoclast formation, and oxidative stress due to iron overload. These findings, in line with prior in vitro studies, suggest that exogenous iron supplementation induces osteoclastogenesis and osteoporosis by promoting osteocyte apoptosis and RANKL production via oxidative stress.

Biomechanical Analysis of Palateless Splinted and Unsplinted Maxillary Implant-Supported Overdentures: A Three-Dimensional Finite Element Analysis.

The objective of this study was to compare the distribution of stress in the maxillary bone, dental implants, and prosthetic components supporting implant-supported maxillary overdentures with partial palatal coverage, in both splinted and unsplinted designs. Two models of maxillary overdentures were designed using the Exocad Dental CAD program, which included cancellous and cortical bone. The complete denture design and abutments (locator abutments in the unsplinted and Hader bar with Vertix attachments placed distally in the splinted variant) were also designed. The denture material was PEEK (Polyetheretherketone), and the method used to analyze patient-specific 3D X-ray scans was 3D QCT/FEA (three-dimensional quantitative computed tomography-based finite element analysis). Loading was divided into three load cases, in the frontal region (both incisors of the denture) and distal region (both molars and first premolar of the denture). The forces applied were 150 N with an oblique component with a buccal inclination of 35° in the frontal region, and 600 N with a buccal inclination of 5° (molars) or solely vertical (premolar) in the distal region. The model with locator abutments showed higher stresses in all load cases in both analyzed implant variants and in the maxilla. The differences in stress distribution between the splinted and unsplinted variants were more significant in the distal region. According to the results of the present study, the amount of stress in bone tissue and dental implant parts was smaller in the splinted, bar-retained variant. The findings of this study can be useful in selecting the appropriate prosthetic design for implant-supported maxillary overdentures with partial palatal coverage.

Stress concentration in bone tissues and screw dental implants

Analysis of stress concentration in bone tissues and screw dental implants was per-formed on a model of screw join of the implant and surrounding bone tissues under the action of normal and tangential loads. The computations were performed by the bounda-ry element method for the plane strain state. It was assumed that those hollows in the spongy bone, which had formed in the bone after the implant insertion, are conformed to the screw thread on the implant. Bone tissues are considered as an isotropic and homo-geneous linear-elastic materials. It has been found that with the increasing in the spongy bone tissue elastic modulus, the maximum equivalent stresses in this bone tissue in-crease. Stresses in the cortical bone tissue decrease with the increasing in the spongy bone elastic modulus due to the decreasing in the load transferred to this bone part. Stresses in the spongy bone decrease with the increasing of the cortical bone layer elas-ticity modulus. The level of maximum stress in the cortical layer of the bone increases with the increasing of this bone tissue elastic modulus. The maximum of stresses in the cortical bone tissue are observed near the implant neck.

In Silico Modeling the Impact of Cartilage Stiffness on Bone Tissue Stress

The knee joint is a complex biomechanical subsystem, modeling of which can reveal a deeper understanding of the processes occurring within it. The purpose of this study is to examine the stress alteration in bone based on mechanical properties of cartilage. To achieve this, a numerical model of the knee joint was developed and tested under different displacement values. The mechanical behavior of the model was represented by considering the hyperelastic properties of soft tissues, along with the verification of trabecular structure of bones, resulting in a more realistic mechanical depiction of the biological subsystem. The results showed that as the stiffness of the cartilage increased; the distribution of stresses in the bone became uneven; and stress concentrators dispersed over articular surface, while in the case of mild cartilage no stress concentrators were expressed. The proposed modeling approach allows the adaptation of patient-specific data in order to predict the outcomes of tissue diseases. The obtained results allow us to state that taking into account the non-linear properties of soft tissues is extremely important for assessing the stress state of the entire biological subsystem. The main difficulty, however, is the lack of data regarding the mechanical behavior of tissues in certain diseases.

Biomechanical Behavior of Different Miniplate Designs for Skeletal Anchorage in the Anterior Open Bite Treatment

This study aimed to evaluate the stress distribution and mechanical behavior of miniplate designs to skeletal anchorage for the treatment of anterior open bite in adult patients. A complete hemimaxilla, teeth, brackets, transpalatal bar, and three miniplates were virtually modeled. I-, Y-, and T-shaped miniplates were installed in the area of the alveolar zygomatic crest. The assembly was constricted and three intrusive forces (2, 4, and 6 N) were applied to the maxillary molars and anchorage according to the miniplates. All materials were considered homogeneous, elastic, and linear; the mesh was 1,800,000 hexahedrons with 2,800,000 nodes on average. Displacement, maximum principal stress, and von Mises stress were evaluated according to the shape of the anchorage device and intrusive force. The miniplate configurations resulted in different stress and displacement intensities in the bone tissue and plate; these stresses were always located in the same regions and were within physiological limits. The Y-plate showed the best performance since its application generated less stress in bone tissue with less displacement.

Influence of Different Restoring Materials on Stress Distribution in Prosthesis on Implants: A Review of Finite Element Studies.

The selection of material used on the occlusal surface of implant-supported prostheses is important, as these materials can transmit destructive forces to the interface between the alveolar bone and the implant. Different prosthetic materials are suggested for implant-supported prostheses. The choice of prosthetic material is a controversial issue, and there is a consensus that implant survival is not affected by the prosthetic material. Three-dimensional finite element studies are often used in dentistry to estimate the stress distribution that occurs in the implant system, peri-implant bone, and prosthetic components. To analyze the influence of the prosthetic restorative material on the stresses in bone tissue and peri-implant through a literature review of three-dimensional finite element studies. The search for articles was performed in the PubMed/Medline database up to November 2021. The selected articles were independently evaluated by two different reviewers. The information collected was author and year of publication, dimensions of implants used, the material used in the prosthetic crown, simulated force and direction, and conclusion and effect. After searching, 14 studies were selected for full reading, and based on the inclusion and exclusion criteria, all could be included in this review. The articles were based on evidence-based laboratory medicine. After analyzing these articles, it was concluded that the prosthetic materials used on the occlusal surface do not interfere with the destruction of stresses to the bone and peri-implant tissue, both in single prostheses and protocol-type prostheses, when three-dimensional finite element method is used.

Orcinol Glucoside Improves Senile Osteoporosis through Attenuating Oxidative Stress and Autophagy of Osteoclast via Activating Nrf2/Keap1 and mTOR Signaling Pathway.

Oxidative stress and autophagy play essential roles in the development of senile osteoporosis which is characterized by disrupted osteoclastic bone resorption and osteoblastic bone formation. Orcinol glucoside (OG), a phenolic glycoside isolated from Curculigo orchioides Gaertn, possesses antiosteoporotic properties. This study examined the protective effects of OG on bone loss in SAMP6 mice and explored the underlying mechanisms. The osteoporotic SAMP6 mice were treated with OG oral administration. RAW264.7 cells were induced to differentiate into osteoclast by RANKL and H2O2 in vitro and received OG treatment. The results demonstrated that OG attenuated bone loss in SAMP6 mice and inhibited the formation and bone resorption activities of osteoclast and reduced levels of oxidative stress in bone tissue of SAMP6 mice and osteoclast. Furthermore, OG activated Nrf2/Keap1 signaling pathway and enhanced the phosphorylation of mTOR and p70S6K which are consequently suppressing autophagy. Of note, the effect of OG on Nrf2/Keap1 signaling was neutralized by the mTOR inhibitor rapamycin. Meanwhile, the inhibitory effect of OG on autophagy was reversed by the Nrf2 inhibitor ML385.Conclusively, OG attenuated bone loss by inhibiting formation, differentiation, and bone resorption activities of osteoclast. Regulation of Nrf2/Keap1 and mTOR signals is a possible mechanism by which OG suppressed oxidative and autophagy of osteoclasts. Thus, OG prevented senile osteoporosis through attenuating oxidative stress and autophagy of osteoclast via activating Nrf2/Keap1 and mTOR signaling pathway.

Аналіз математичного моделювання біомеханічної моделі гало-гравітаційної тракції при деформаціях хребта в дітей

Halo-gravity traction (HGT) systems are widely used in leading clinics around the world as a staged method for correcting complex (>100°) scoliotic deformities of the spine in children. Today there is no single approach to the use of this technique, and each doctor makes a decision regarding the treatment regimen empirically, based on his clinical experience. Purpose – to investigate with the help of finite element method the stress-strain state of the spine of various degrees of deformation using HGT. Materials and methods. When constructing the computational model, geometric models of various parts of the spine, developed in the laboratory of biomechanics of the State Institution «IPPS named after I.P. Sitenko of the National Academy of Medical Sciences of Ukraine». The following changes were made to the model, in accordance with the purpose of the study: spinal deformity 70° and 100°; added skull model; added model of HGT and its fixation to the skull. Results. When using the HGT system with fixation, the most loaded part of the spine is the T2-T5 vertebrae. It should be noted that with an increase in the degree of deformity, the T4 and T5 vertebrae become loaded. The HGT system with fixation and load equal to half the body weight does not lead to critical values of bone tissue stress in terms of strength. Results. In the treatment of rigid spinal deformities in children with a deformity angle (>100°) using a HGT system, the first stage mathematically proved the effectiveness of this technique, but the maximum recommended load should not exceed 50% of the patient’s body weight. Modeling the correction of spinal deformities using mathematical models makes it possible to analyze the effect of various treatment methods in several versions without surgery. The maximum von Mises stress value of 40.1 MPa is not critical for bone tissue in terms of strength (ultimate strength for cortical bone is 70 MPa). However, when the load is doubled, i.e. with HGT to a load equal to the body weight, the level of stress will also double and exceed the ultimate strength of the bone tissue. The research was carried out in accordance with the principles of the Helsinki declaration. The study protocol was approved by the Local ethics committee of all participating institutions. The informed consent of the patient was obtained for conducting the studies. No conflict of interest was declared by the authors. Key words: final element method, spinal deformity, halo-gravity traction.

Bone Stress Evaluation with and without Cortical Bone Using Several Dental Restorative Materials Subjected to Impact Load: A Fully 3D Transient Finite-Element Study.

Statement of problem. Previous peri-implantitis, peri-implant bone regeneration, or immediate implant placement postextraction may be responsible for the absence of cortical bone. Single crown materials are then relevant when dynamic forces are transferred into bone tissue and, therefore, the presence (or absence) of cortical bone can affect the long-term survival of the implant. Purpose: the purpose of this study is to assess the biomechanical response of dental rehabilitation when selecting different crown materials in models with and without cortical bone. Methods: several crown materials were considered for modeling six types of crown rehabilitation: full metal (MET), metal-ceramic (MCER), metal-composite (MCOM), peek-composite (PKCOM), carbon fiber-composite (FCOM), and carbon fiber-ceramic (FCCER). An impact-load dynamic finite-element analysis was carried out on all the 3D models of crowns mentioned above to assess their mechanical behavior against dynamic excitation. Implant-crown rehabilitation models with and without cortical bone were analyzed to compare how the load-impact actions affect both type of models. Results: numerical simulation results showed important differences in bone tissue stresses. The results show that flexible restorative materials reduce the stress on the bone and would be especially recommendable in the absence of cortical bone. Conclusions: this study demonstrated that more stress is transferred to the bone when stiffer materials (metal and/or ceramic) are used in implant supported rehabilitations; conversely, more flexible materials transfer less stress to the implant connection. Also, in implant-supported rehabilitations, more stress is transferred to the bone by dynamic forces when cortical bone is absent.

Abstracts from the World Federation for Laser Dentistry—Asia Pacific Division Virtual Conference July 16–17, 2021

Abstracts from the World Federation for Laser Dentistry—Asia Pacific Division Virtual Conference July 16–17, 2021

Finite Element Analysis of Stress in Anterior Prosthetic Rehabilitation with Zirconia Implants with and without Cantilever.

Objectives The aim of this study was to evaluate using finite element analysis (FEA), the stress distribution in prostheses (lithium disilicate crowns) on monotype zirconia implants with and without cantilever in the anterior region of the maxilla. Materials and Methods From a virtual reconstruction of bone model of the toothed maxilla from a computed tomography, three models (groups) were created: Zr (11–21)—implants placed in the area of 11 and 21 with cantilever; Zr (12–22)—implants placed in the area of 12 and 22 without cantilever; and Zr (11–22)—implants intercalated placed in the area of 11 and 22. In all models, monotype zirconia implant (4.1 × 12.0 mm) was used in single-body configuration. Lithium disilicate crowns were designed on the implants and pontics for all groups. A 150-N load was applied to the prostheses. The materials used were considered isotropic, homogeneous, and linearly elastic. FEA was performed to evaluate the maximum (tensile) and minimum (compressive) principal stresses in the implant, crowns, and bone tissue. Data were analyzed qualitatively and quantitatively. Results For all groups, the highest maximum principal stress occurred in the palatal cervical area of the implant, with the high values for the Zr (12–22) group and the low values for the Zr (11–21) group. The maximum principal stress was concentrated in the cervical palatal area of the crown, with the Zr (11–21) group presented the highest values and the Zr (12–22) group showed the lowest values. In the bone tissue all the groups presented similar values of maximum and minimal principal stress, with the palatal (maximum principal) and vestibular (minimum principal) close to the cervical of the implants the area with the highest concentration of stresses. Conclusions The position of monotype zirconia implant did not interfere in the bone tissue stress, and the implants placed in the 11–21 present lower stress in implants and higher in the crown. The cantilever does not increase the stress in the implants, crown, and bone tissue.

Mechanical writing of electrical polarization in poly (L-lactic) acid

Stimuli responsive materials are found in a broad range of applications, from energy harvesters to biomolecular sensors. Here, we report the production of poly (L-lactic acid) (PLLA) thin films that exhibit a mechanical stress responsive behaviour. By simply applying a mechanical stress through an AFM tip, a local electrical polarization was generated and measured by Kelvin Probe Force Microscopy. We showed that the magnitude of the stress generated electrical polarization can be manipulated by varying the thickness or crystallization state of the PLLA thin films. Besides exhibiting a mechanical stress-response behaviour with potential for energy harvesting and sensor applications, we show by AFM that these platforms react to mechanical forces with physiological relevance: interaction forces as low as a cell sheet migrating over a substrate or larger ones as the fluid induced stresses in bone tissue. In living tissues, as most mechanical stimuli are transduced as strain gradients for the anatomical structures, these mechanically responsive substrates can be used as ex vivo platforms to study the protein and cells response over a large range of electrical stimuli amplitude. As a proof of concept, selective adsorption of a human fibronectin was demonstrated by local patterning of the stimuli responsive PLLA films. Statement of significanceBioelectricity is inherent to the formation and repair of living tissues and electrical stimulation has been recognized for promoting regeneration. Given the proven beneficial effects of electric fields and the absence of a suitable method of stimulation, there is a clinical need for smart substrates, which can generate a polarization (charges) to promote tissue regeneration without the need of external devices. In this work, we report the fabrication of poly(L-lactic) acid platforms that exhibit a mechanical stress responsive behaviour when subjected to physiologically relevant forces. This behaviour can be tailored by varying the thickness or crystallization state of the PLLA films. We further demonstrate the biofunctionality of such platforms by exploiting the mechanically-induced charge for adhesion protein adsorption.

Alleviative Effects of Exercise on Bone Remodeling in Fluorosis Mice.

Fluorine is widely present in nature in the form of fluoride. Prolonged high-dose fluoride exposure can cause skeletal fluorosis, resulting in osteosclerosis, osteoporosis or osteomalacia. It has been proved that exercise is one of the important factors affecting the health of the bone and promoting bone formation. To investigate the effects of exercise on bone remodeling in fluorosis mice, 120 male 3-week-old ICR mice were randomly divided into four groups: control group (C), exercise group (E), fluoride group (F), fluoride plus exercise group (F + E). After 8-week physical exercise and/or fluoride exposure, we evaluated the content of fluorine, the histopathological structure and microstructure of femur, bone metabolism biochemical indexes and oxidative stressrelated parameters, and the mRNA and protein levels of genes in BMP-2/Smads and OPG/RANKL/RANK signaling pathways. Our results showed that 100mg/L NaF exposure increased the accumulation of fluoride in bone, altered histology of bone, and enhanced the activities of ALP and TRACP. Meanwhile, excessive fluoride induced oxidative stress in bone tissue by increasing the content of ROS and MDA, and decreasing the activities of antioxidant enzymes. In addition, the results of qRT-PCR suggested that NaF significantly increased the mRNA expression of BMP-2, Smad-5, Col IA1, Col IA2, OPG, RANKL and RANK, as well as the elevated proteins of OPG, RANKL and RANK. However, these fluoride-induced changes were alleviated after moderate exercise. Taken together, these findings indicated that moderate exercise decreased the toxicity of fluoride by reducing the accumulation of fluorine in the body to relieve the bone damage caused by fluorosis.

The Role of Vertebral Porosity and Implant Loading Mode on Bone-Tissue Stress in the Human Vertebral Body Following Lumbar Total Disc Arthroplasty.

Micro-computed tomography- (micro-CT-) based finite element analysis of cadaveric human lumbar vertebrae virtually implanted with total disc arthroplasty (TDA) implants. (1) Assess the relationship between vertebral porosity and maximum levels of bone-tissue stress following TDA; (2) determine whether the implant's loading mode (axial compression vs. sagittal bending) alters the relationship between vertebral porosity and bone-tissue stress. Implant subsidence may be related to the bone biomechanics in the underlying vertebral body, which are poorly understood. For example, it remains unclear how the stresses that develop in the supporting bone tissue depend on the implant's loading mode or on typical inter-individual variations in vertebral morphology. Data from micro-CT scans from 12 human lumbar vertebrae (8 males, 4 females; 51-89 years of age; bone volume fraction [BV/TV] = 0.060-0.145) were used to construct high-resolution finite element models (37 μm element edge length) comprising disc-vertebra-implant motion segments. Implants were loaded to 800 N of force in axial compression, flexion-, and extension-induced impingement. For comparison, the same net loads were applied via an intact disc without an implant. Linear regression was used to assess the relationship between BV/TV, loading mode, and the specimen-specific change in stress caused by implantation. The increase in maximum bone-tissue stress caused by implantation depended on loading mode (P < 0.001), increasing more in bending-induced impingement than axial compression (for the same applied force). The change in maximum stress was significantly associated with BV/TV (P = 0.002): higher porosity vertebrae experienced a disproportionate increase in stress compared with lower porosity vertebrae. There was a significant interaction between loading mode and BV/TV (P = 0.002), indicating that loading mode altered the relationship between BV/TV and the change in maximum bone-tissue stress. Typically-sized TDA implants disproportionately increase the bone-tissue stress in more porous vertebrae; this affect is accentuated when the implant impinges in sagittal bending.Level of Evidence: N/A.

Insights into Oxidative Stress in Bone Tissue and Novel Challenges for Biomaterials

Reactive Oxygen Species (ROS) in the bone environment can affect the behaviour of resident cells as well as the composition and morphology of the extra-cellular matrix. These alterations may reduce bone tissue performances, leading to a consequent collapse. Furthermore, there is a need for the creation of innovative biomaterials capable to counteract the increase of ROS produced by the fracture, the implantation process and the material itself, as well as by an age-related accumulation.

Biomechanical Analysis of a Custom-Made Mouthguard Reinforced With Different Elastic Modulus Laminates During a Simulated Maxillofacial Trauma.

There is a lack of data regarding the influence of different laminates for mouthguard reinforcement in the mechanical response during an impact in the orofacial region. The aim of this study was to verify the influence of the laminate framework on the stresses and strains of the anterior teeth and displacement of ethylene-vinyl acetate (EVA) custom-made mouthguards during a simulated impact. The null hypotheses was that the different laminates reinforcement would present the similar effect in maxillary structures, regardless the elastic modulus. A finite element model of human maxillary central incisors with an antagonist contact was used. A linear quasi-static analysis was used to simulate the force exerted during an impact. A total of 5 different layers were simulated inside the mouthguard at the labial portion according to the Elastic Modulus 1 MPa (Extremely flexible), 9 GPa (Low modulus reinforcement), 18 GPa (Without reinforcement), 50 GPa (Flexible alloy), 100 GPa (Titanium alloy) and 200 GPa (Hard material). The results were evaluated by means of Maximum Principal Stress (in the tooth and bone), Microstrain (periodontal ligament) and Displacement (mouthguard) criteria. The elastic modulus of the material inside the MG influenced the stress distribution on the enamel buccal face. However, it did not affect the bone tissue stress, periodontal ligament strain or root dentin tissue stress. Conclusion: The use of reinforcement inside the custom-made mouthguard can modify the stress generated in the enamel buccal surface without improvement to the root dentin, periodontal ligament or bone tissue.

Biomechanical Comparison of a New Triple Cylindrical Implant Design and a Conventional Cylindrical Implant Design on the Mandible by Three-Dimensional Finite Element Analysis.

The aim of this study was to evaluate the effect of implant designs with different lengths and diameters on the stress distribution in abutments, implants, and cortical and trabecular bone of the edentulous mandible via three-dimensional finite element analysis. Eight different finite models (cylindrical 3.5 × 6; cylindrical 3.5 × 10.5; cylindrical 4.5 × 6; cylindrical 4.5 × 10.5; triple cylindrical 3.5 × 6; triple cylindrical 3.5 × 10.5; triple cylindrical 4.5 × 6; and triple cylindrical 4.5 × 10.5) were created. Abutments, abutment screws, and metal-retained porcelain crowns were modeled on the implants. A 200-N oblique load was applied on the buccal cusp of the crown. The highest maximum principal (Pmax) and minimum principal (Pmin) stresses were calculated for trabecular and cortical bone, and von Mises stress values were calculated for the implant and abutment. The triple cylindrical implant abutments showed lower stress values than cylindrical implant abutments. The highest von Mises stress values were observed in the cervical third of the abutments. The stress values on implants were found at the neck of the implants, and cylindrical implants showed higher stress values than triple cylindrical implants. The peak Pmax and Pmin values in cortical bone were detected around the implant neck. For implants with a 3.5-mm diameter, the triple cylindrical implant design showed lower stresses in cortical bone than the cylindrical implant design; however, similar stresses were observed in 4.5-mm implants for both designs. Implant length did not affect the stresses in cortical bone. Implants with a 10.5-mm length showed lower Pmax values than implants with a 6-mm length in trabecular bone. For Pmin values in trabecular bone, the triple cylindrical implant design had lower values than did the cylindrical implant design. Within the limitations of this study, the triple cylindrical implants, with a new implant design, showed appropriate results in terms of abutment, implant, and bone tissue stress.

Oxidative protein modification of the temporal bone tissue in chronic otitis media

Aim. To study the role of oxidative protein modification of bone tissue proteins in the formation of destruction of temporal bone structures in chronic otitis media. Methods. The study included 139 patients aged 16-75 years with a verified diagnosis of chronic otitis media, who are candidates for surgical treatment. Depending on the method of surgical treatment, patients are divided into four groups (by nosology and complications and reoperations): patients with tubotympanic otitis media and epitympanic antral otitis, without complications and with local or intracranial complications, after reconstructive sanitizing ear surgery. The state of the processes of oxidative modification of proteins was evaluated in the bone tissue of the middle ear cavities, obtained intraoperatively, by the content of carbonyl products with the use of spectrophotometry. The data were processed by descriptive statistics and were presented in the form of a median and a range between quartiles with an estimate of the reliability of the intergroup differences by the Mann-Whitney U-criterion. Results. A comparison of the indicators characterizing the oxidative modification of bone tissue proteins of the temporal bone in patients with complicated and recurrent forms of chronic otitis media demonstrates a greater degree of free radical destruction of proteins, primarily markers of early stages of protein damage and an increase of aldehyde products, both at the basal level and in response to induction in a complicated course of the disease. Conclusion. The obtained data allow drawing a conclusion about a high level of oxidative stress in bone tissue in destructive forms of chronic otitis media accompanied by relapses and complications, and about the perspectives of antioxidant pre-operative use taking into account the features of oxidative stress in bone tissue in patients with chronic otitis media.

Biomechanical analysis of iliac crest loading following cortico-cancellous bone harvesting

BackgroundIliac crest bone harvesting is a frequently performed surgical procedure widely used to treat bone defects. The objective of this study is to assess the biomechanical quantities related to risk for pelvic fracture after harvesting an autologous bone graft at the anterior iliac crest.MethodsFinite element models with a simulated harvest site (sized 15 × 20 mm, 15 × 35 mm, 30 × 20 mm and 30 × 35 mm) in the iliac wing are created. The relevant loading case is when the ipsilateral leg is lifted off the ground. Musculoskeletal analysis is utilized to compute the muscle and joint forces involved in this motion. These forces are used as boundary conditions for the finite element analyses. Bone tissue stress is analyzed.ResultsCritical stress peaks are located between the anterior superior iliac spine (ASIS) and the anterior edge of the harvest site. Irrespective of the graft size, the iliac wing does not show any significant stress peaks with the harvest site being 20 to 25 mm posterior to the ASIS. The harvest area itself inhibits the distribution of the forces applied on the ASIS to extend to the posterior iliac wing. This leads to a lack of stress posterior to the harvest site. A balanced stress distribution with no stress peaks appears when the bone graft is taken below the iliac crest.ConclusionA harvest site located at least 20 to 25 mm posterior to the ASIS should be preferred to minimize the risk of iliac fatigue fracture.

Biomechanics of implant retained fixed prosthesis in patient with edentulous upper jaw

The purpose of the study was to study the stress-strain state of bone tissue and a permanent prosthesis on implants installed in the frontal part of the upper jaw. The 150N load was applied to the frontal and 250N to the side of the non-removable prosthesis on six or four implants, including zygomatic and 'All-On-Four' technology. The values of stresses in bone tissue, implants and prosthesis are obtained, which show a large margin of strength in structural materials. At the same time, the bone strength is low, especially around the zygomatic implants and the extreme implants 'All-on-4' with the load of the lateral part of the prosthesis.