Search

In this work, composite filaments in the form of sticks and 3D-printed scaffolds were investigated as a future component of an osteochondral implant. The first part of the work focused on the development of a filament modified with bioglass (BG) and Zn-doped BG obtained by injection molding. The main outcome was the manufacture of bioactive, strong, and flexible filament sticks of the required length, diameter, and properties. Then, sticks were used for scaffold production. We investigated the effect of bioglass addition on the samples mechanical and biological properties. The samples were analyzed by scanning electron microscopy, optical microscopy, infrared spectroscopy, and microtomography. The effect of bioglass addition on changes in the SBF mineralization process and cell morphology was evaluated. The presence of a spatial microstructure within the scaffolds affects their mechanical properties by reducing them. The tensile strength of the scaffolds compared to filaments was lower by 58–61%. In vitro mineralization experiments showed that apatite formed on scaffolds modified with BG after 7 days of immersion in SBF. Scaffold with Zn-doped BG showed a retarded apatite formation. Innovative 3D-printing filaments containing bioglasses have been successfully applied to print bioactive scaffolds with the surface suitable for cell attachment and proliferation.

The main purpose of this study was to analyse the temperatures generated during the bone bed preparation, given the internal structure of the bone bed, the geometry of the hole, and the treatment parameters such as the type of cooling and the rotational speed of the drill. The investigated material was domestic pig ribs, in which holes were drilled three times using two drill bit systems used for Hiossen® and Paltop® dental implantation. The ThermaCAM® P640 thermal imaging camera was used for measurement of drilling temperatures. After the holes were drilled, each rib was examined using the 1172 SkyScan microtomograph, Bruker®, to compare the geometry of the machined holes. The presented study proved that larger diameter drill bits (Hiossen® drill bits) generate more heat during the machining process, as evidenced by higher temperatures obtained for the Hiossen system in each case. It was proved that rotational speed, drill bit diameter and cooling system have a significant effect on the amount of heat generated during bone tissue preparation. The density and type of bone tissue in which the hole is prepared are significant factors affecting the amount of heat generated.

Purpose: Bone fractures are one of the most commonly seen problems in veterinary traumatology. The authors of this study strive to find a new intramedullary nail, which is intended for treating femoral bone fractures for canine patients. The purpose of this study was to analyze biomechanical parameters of the intramedullary nails, which use a new bolt system concept. Methods: Dissected femoral bones of a large breed dog were cut in order to simulate interfragmentary gap, and then the bones were stabilized using intramedullary nail with locking bolts. Bone-nail systems were subjected to cyclic loading using force which corresponds to the load on the femoral bone in the first few days after surgery. Micro-CT scans were taken of the bone samples around implant in order to determine deformation and structural parameters of bone tissue. Results: The calculation of the bone-nail system stiffness was done through analysis of the force displacement curves recorded during experimental studies. Using monocortical locking bolts resulted in smaller stiffness of the bone-nail system than using bicortical locking bolts. Conclusions: The results obtained in this study can indicate that the intramedullary nail could work well when used for treatment of bone fractures in dogs. The authors focused on using monocortical bolts which provides good stability and adequate biomechanical environment. Described fixation method is easily adjustable to a particular patient individual parameters.

Preformed stainless steel crowns are used in pediatric dentistry to obtain full crown restoration of primary molar teeth. They are consider the best restoration in terms of durability and effectiveness. The purpose of this study is to evaluate microbial, cytological and physio-chemical properties to determine whereas stainless steel crown are biocompatible, safe for surrounding tissue and helpful in avoiding micro-organisms influence on the tooth tissue. Based on the results, it was determined that stainless steel crowns used in pediatric dentistry represent no cytotoxic risk to the surrounding tissues, have a low probability of developing hypersensitivity to the coronal material and also that their biological properties make them suitable to use in pediatric dentistry for the reconstruction of damaged primary molar tissue.

The studies conducted so far indicate a negative effect of dioxins on the structure of the alveolar bone and teeth, especially in the developmental period in rats. The research aimed to analyze the indirect effect of dioxins contained in the body of female rats on the structure of the dental organ in their offspring in the neonatal period and to determine the possibility of reducing potential dioxin disorders of the structure of hard tissues in the offspring of intoxicated mothers by simultaneous administration of vitamin E or acetylsalicylic acid (ASA). Another goal of the research was to determine the level of magnesium, calcium and phosphorus contained in bone tissue as indicators of the mineralization process of hard tissues in rats, in the case of using 2,3,7,8-tetrachlorodibenzo

Osteoporosis is a skeletal disease associated with excessive bone turnover. Among the compounds with antiresorptive activity, nitrogen-containing bisphosphonates play the most important role in antiosteoporotic treatment. In previous studies, we obtained two aminomethylidenebisphosphonates—benzene-1,4-bis[aminomethylidene(bisphosphonic)] (WG12399C) acid and naphthalene-1,5-bis[aminomethylidene(bisphosphonic)] (WG12592A) acid—which showed a significant antiproliferative activity toward J774E macrophages, a model of osteoclast precursors. The aim of these studies was to evaluate the antiresorptive activity of these aminobisphosphonates in ovariectomized (OVX) Balb/c mice. The influence of WG12399C and WG12592A administration on bone microstructure and bone strength was studied. Intravenous injections of WG12399C and WG12592A bisphosphonates remarkably prevented OVX-induced bone loss, for example, they sustained bone mineral density at control levels and restored other bone parameters such as trabecular separation. This was accompanied by a remarkable reduction in the number of TRAP-positive cells in bone tissue. However, a significant improvement in the quality of bone structure did not correlate with a parallel increase in bone strength. In ex vivo studies, WG12399C and WG12592A remarkably bisphosphonates reduced osteoclastogenesis and partially inhibited the resorptive activity of mature osteoclasts. Our results show interesting biological activity of two aminobisphosphonates, which may be of interest in the context of antiresorptive therapy.

The aim of the study was to investigate the effect of physical training on bone parameters of rats exposed to alcohol (Al) and/or cadmium (Cd). Young female rats were divided into one control group and six groups exposed to Cd and/or Al. Al (36% calories of diet) and Cd (20 mg Cd/kg feed) were administered with liquid diet. Half of the rats from the treated groups were subjected to treadmill training (20 m/min for 0.5 h, 4 days a week). The experiment was carried out for 5 months. Al decreased the concentration of calcium (Ca) and iron (Fe) in the femur, whereas Cd and Cd + Al intake reduced the contents of Ca, Fe and zinc. Al and/or Cd caused an increase in both C-terminal telopeptide of type I collagen (CTX1; bone resorption marker) and osteocalcin (OC; formation indicator) and enhanced the degree of porosity and flexural strength of the femur. Al partially prevented the loss of Fe from the bone caused by Cd, but intensified the inhibition of growth of body weight in comparison with separate exposure to Cd. In rats co-exposed to Cd + Al, the levels of CTX1 were greater compared with those treated with Al or Cd separately, and the density was less than that in rats exposed to Al separately. The training caused increases of magnesium and Ca contents, decreases in CTX1, as well as increases in OC and bone density, decreasing their porosity. The effect of training on the bone status, however, was limited (especially in rats co-exposed to Cd and Al) because of the increase in their mineralization, stimulated by exercises, was insufficient in relation to collagen production intensity. In conclusion, training had favourable effects on some bone parameters, but did not compensate for the negative effects of Al and/or Cd exposure on the poor mineralization and histopathological and morphological changes in the femur.

Bone structure abnormalities are increasingly observed in patients chronically treated with antiepileptic drugs (AEDs). The majority of the available data concern older conventional AEDs, while the amount of information regarding newer AEDs, including stiripentol, is limited. The aim of the study was to assess the effect of stiripentol on bones. For 24 weeks, male Wistar rats, received 0.9% sodium chloride (control group) or stiripentol (200 mg/kg/day) (STP group). In the 16th week of the study, we detected lower serum PINP levels in the STP group compared to the control group. In the 24th week, a statistically significant lower 1,25-dihydroxyvitamin D3 level, higher inorganic phosphate level and higher neutrophil gelatinase-associated lipocalin (NGAL) levels in serum were found in the STP group compared to the control. Micro X-ray computed tomography of the tibias demonstrated lower bone volume fraction, lower trabecular thickness, higher trabecular pattern factor and a higher structure model index in the stiripentol group. Considering the results of this experiment on rats which suggests that long-term administration of stiripentol may impair the cancellous bone microarchitecture, further prospective human studies seem to be justified. However, monitoring plasma vitamin D, calcium, inorganic phosphate and kidney function in patients on long-term stiripentol therapy may be suggested.

We sought to evaluate the effects of Er:YAG laser (LightTouch, LightInstruments, Israel) conditioning on enamel roughness and shear bond strength of orthodontic brackets on enamel. Eighteen human molars (n = 9) and premolars (n = 9), were divided into 3 groups depending on the enamel conditioning method, Er:YAG laser (G1, n = 6), conventional etching with 37% orthophosphoric acid (G2, n = 6), Er:YAG laser combined with conventional etching (G3, n = 6). Er:YAG laser parameters were as follows: energy: 100 mJ, frequency: 10 Hz, exposure time: 10 s, applicator diameter: 600 μm, fluence: 35.37 J/cm2, distance: 1 mm away from a tooth, cooling: 80%. An MTS 858 MiniBionix® machine was used to determine the shear bond strength (MTS System, Eden Prairie, MN, USA). The enamel structure was assessed using X-ray microtomography (SkyScan 1172, Bruker, Kontich, Belgium). The highest values of shear bond strength were obtained in the G3 group (9.23 ± 2.38 MPa) and the lowest values in the G2 group (6.44 ± 2.11 MPa) (p &lt, 0.05). A significant change in the enamel surface was noted after applying laser, reaching up to 9% of enamel thickness, which was not observed in the etched samples. Moreover, the Er:YAG laser-irradiated enamel surface was characterized by the greatest roughness. The combined use of an Er:YAG laser with a conventional etching improves the adhesion of composite materials to the tooth.

Highly active antiretroviral therapy (HAART) is used in HIV-infected patients. Alongside the prolongation of patients’ life, adverse side effects associated with long-term therapy are becoming an increasing problem. Therefore, optimizing of HAART is extremely important. The study is aimed at evaluating the toxicity of abacavir and etravirine in monotherapy on the reproductive system, liver, kidneys, and bones in young, sexually mature, male rats. Thirty-six 8-week-old male Wistar rats randomized into three 12-animal groups received either normal saline (control), abacavir 60 mg/kg (AB group), or etravirine 40 mg/kg (ET group) once daily for 16 weeks. Semen morphology, oxide–redox state parameters (MDA, SOD, catalase, GPx, glutathione, GSH/GSSG ratio) in tissue homogenates (testes, liver, kidneys), and serum samples were studied. In bones, microcomputed tomography and a four-point bending test were performed. Total sperm count, sperm concentration, motility, and sperm morphology did not differ significantly in AB or ET groups compared to the control. In the flow cytometry of semen, an increased percentage of cells with denatured DNA was noticed for both tested drugs. However, no significant changes of oxide–redox state in testicular homogenates were found, except of increased SOD activity in the AB-receiving group. Additionally, ET significantly altered catalase and GPx in the liver and SOD activity in kidneys. Abacavir decreased catalase in the liver and GSH levels in kidneys. AB caused significant changes to bone microarchitecture (bone volume fraction, trabecular number, connectivity density, total porosity) and increased Young’s modulus. Etravirine had a greater impact on macrometric parameters of bones (tibial index, mid-tibial diameter, femur length). After 4 weeks in the ET group, a lower 1,25-dihydroxyvitamin D3 serum concentration was found. The results showed that abacavir and etravirine disturb oxidative stress. An increase in the percentage of sperms with chromatin damage suggests decreased fertility in rats receiving the studied drugs. Both drugs affected bone formation in growing rats. Additionally, etravirine disturbed vitamin D metabolism.

Krzysztof Marycz,1,2 Agnieszka Śmieszek,1 Katarzyna Kornicka-Garbowska,1,2 Ariadna Pielok,1 Maciej Janeczek,3 Anna Lipińska,3 Anna Nikodem,4 Jarosław Filipiak,4 Paulina Sobierajska,5 Jean-Marie Nedelec,6 Rafał J Wiglusz2,5 1Department of Experimental Biology, Wroclaw University of Environmental and Life Sciences, Wroclaw, 50-375, Poland; 2International Institute of Translational Medicine, Malin, 55-124, Poland; 3Department of Biostructure and Animal Physiology, Wroclaw University of and Life Sciences, Wroclaw, 51-631, Poland; 4Department of Mechanics, Materials and Biomedical Engineering, Wroclaw University of Science and Technology, Wybrzeze Wyspianskiego 27, 50-370 Wrocław, Poland; 5Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Okolna 2, 50-422 Wroclaw, Poland; 6Universite Clermont Auvergne, Clermont Auvergne INP, CNRS, ICCF, Clermont-Ferrand, FranceCorrespondence: Krzysztof MaryczThe Department of Experimental Biology, The Faculty of Biology and Animal Science, University of Environmental and Life Sciences Wroclaw, Norwida 27B St, Wroclaw, 50– 375, PolandTel +48 71 320 5201Email krzysztof.marycz@upwr.edu.plPurpose: Healing of osteoporotic defects is challenging and requires innovative approaches to elicit molecular mechanisms promoting osteoblasts-osteoclasts coupling and bone homeostasis.Methods: Cytocompatibility and biocompatibility of previously characterised nanocomposites, i.e Ca5(PO4)3OH/Fe3O4 (later called nHAp/IO) functionalised with microRNAs (nHAp/IO@miR-21/124) was tested. In vitro studies were performed using a direct co-culture system of MC3T3-E1 pre-osteoblast and 4B12 pre-osteoclasts. The analysis included determination of nanocomposite influence on cultures morphology (confocal imaging), viability and metabolic activity (Alamar Blue assay). Pro-osteogenic signals were identified at mRNA, miRNA and protein level with RT-qPCR, Western blotting and immunocytochemistry. Biocompatibility of biomaterials was tested using bilateral cranial defect performed on a senescence-accelerated mouse model, ie SAM/P6 and Balb/c. The effect of biomaterial on the process of bone healing was monitored using microcomputed tomography.Results: The nanocomposites promoted survival and metabolism of bone cells, as well as enhanced functional differentiation of pre-osteoblasts MC3T3-E1 in co-cultures with pre-osteoclasts. Differentiation of MC3T3-E1 driven by nHAp/IO@miR-21/124 nanocomposite was manifested by improved extracellular matrix differentiation and up-regulation of pro-osteogenic transcripts, ie late osteogenesis markers. The nanocomposite triggered bone healing in a cranial defect model in SAM/P6 mice and was replaced by functional bone in Balb/c mice.Conclusion: This study demonstrates that the novel nanocomposite nHAp/IO can serve as a platform for therapeutic miRNA delivery. Obtained nanocomposite elicit pro-osteogenic signals, decreasing osteoclasts differentiation, simultaneously improving osteoblasts metabolism and their transition toward pre-osteocytes and bone mineralisation. The proposed scaffold can be an effective interface for in situ regeneration of osteoporotic bone, especially in elderly patients.Keywords: senile osteoporosis, osteoblasts, osteoclasts, nanohydroxyapatite, iron oxide nanoparticles, small non-coding RNA

BACKGROUND Clinical trials indicate an increased risk of osteoporosis and bone fractures in people infected with human immunodeficiency virus (HIV). The pathogenesis of bone disturbances in HIV-positive patients is unknown, but it is suggested that antiretroviral drugs may be involved. OBJECTIVES To assess the effects of efavirenz (EF) and tenofovir (T) on bone remodeling in rats. MATERIAL AND METHODS The study involved 36 male Wistar rats divided into 3 groups, receiving normal saline (control group - group C), efavirenz (group EF) or tenofovir disoproxil (group T). RESULTS After 24 weeks of the study, the following observations were made: In blood serum of the EF group compared to group C, there were increased levels of tartrate-resistant acid phosphatase form 5b (TRAP) and inorganic phosphorus. In the densitometric examination, group T showed a lower total body (TB) bone mineral density (BMD) than group C. In the immunohistochemical assessment, group EF showed a higher intensity and extension of anti-tartrate resistant acid phosphatase antibodies (abTRAP) compared to group C. In the histopathological examination of the second lumbar vertebra (L2), group EF showed a lower bone surface/volume ratio (BS/BV) and higher trabecular thickness (Tb.Th) than the control group. In the histopathological examination of the femur, a lower bone surface/tissue volume (BS/TV) and lower trabecular number (Tb.N) were found in group T compared to in group C. A lower value of the Young's modulus was observed in the four-point bending trial in groups EF and T compared to group C. CONCLUSIONS The results of this study indicate that EF affects bone microarchitecture and leads to impaired biomechanical properties of bones in rats. Additionally, the negative effect of T on bone tissue was confirmed.

Purpose The main goal of this article was the analysis of the changes of mechanical properties, thickness and histology of the cartilage in different regions of the femur head in advanced stage of the osteoarthritis. Methods The study material consisted of cylindrical specimens (9.7 mm) prepared form proximal epiphysis of the human femur bone after hip arthroplasty. The thickness was determined from the reconstruction of the specimen from microtomography (SkyScan 1172, Bruker®) images. Mechanical properties of the cartilage tissue were identified in static indentation test conducted the use of MTS® Synergie 100 testing machine. Histological study enabled us to determine cartilage total thickness as well as location and orientation of the collagen fibers. Results Depending on the region of the head, the cartilage tissue thickness was in the range (0.74-2.23 mm). The lowest thickness values were obtained for the R5 region and the lowest for R4. Samples from R1-R4 regions differ by 24%. Measurements of cartilage tissue indentation, determined with the help of Hayes' formula, showed that the values of mechanical parameters in regions R1, R2, R3 and R5 have similar values (the difference between them is about 5.5%). Region R4, which had the smallest thickness, also had the lowest values of mechanical parameters. Conclusions Using κ coefficients, proposed by Hayes, enabled us to obtain similar values of mechanical parameters in the regions R1, R2, R3 and R5, despite differences in cartilage tissue thickness. The R4 region, which had the weakest mechanical parameters, was characterized by the strongest reduction of the articular cartilage tissue, which was accompanied by an unformed mass of cartilage residue originating from the abraded surface and bursa fluid.

Postmenopausal osteoporosis and osteoporotic fractures constitute an increasing problem in developing countries. Kaempferol, isolated from seeds of Cuscuta chinensis, is an active flavonoid inhibiting in vitro osteoclast activity. The aim of the presented research was an assessment of kaempferol effect on estrogen-deficiency-induced bone structure disturbances in rats. The study was performed on 24 Wistar female rats divided into 3 groups: SHAM — rats undergoing a “sham” surgery, OVX-C — control group of animals that underwent ovariectomy, OVX-K — rats undergoing ovariectomy and receiving kaempferol for 8 weeks (from day 56 to day 112). In the OVX-K group, contrary to the OVX-C one, there was no significant decrease in femoral bone mineral density (BMD). A significant increase in Young’s modulus was observed in the OVX-K group compared to the OVX-C (15.33 ± 2.51 GPa vs. 11.14 ± 1.93 GPa, p < 0.05). A decreased bone turnover was detected in the OVX-K group. Tissue volume ratio (BV/TV) and trabecular bone perimeter were increased in the OVX-K group compared to the OVX-C one (0.241 ± 0.037 vs. 0.170 ± 0.022, p < 0.05 and 15.52 ± 2.78 mm vs. 9.67 ± 3.07 mm, p < 0.05, respectively). Kaempferol has a beneficial influence on estrogen-deficiency-induced disturbances of bone structure in rats.

Bone tissue is a biological system in which the dynamic processes of, among others, bone formation or internal reconstruction will determine the spatial structure of the tissue and its mechanical properties. The appearance of a factor disturbing the balance between biological processes, e.g. a disease, will cause changes in the spatial structure of bones, thus affecting its mechanical properties. One of the bone diseases most common in an increasingly ageing population is osteoarthritis, also referred to as degenerative joint disease. It is estimated that in 2050 about 1300 million people will show symptoms of OA. The appearance of a pathological stimulus disturbs the balance of the processes of degradation and synthesis of articular cartilage, chondrocytes and the extracellular matrix, and the subchondral bone layer. As osteoarthritis progresses, study of the epiphysis reveals increasingly widespread changes of the articular surface and the internal structure of bone tissue. In this paper, the authors point out the differences in the mechanical properties of cancellous bone tissue forming the proximal epiphysis of the femoral bone during the progressive stages of OA. In order to determine microproperties of bone trabeculae, specimens from different stages of the disease (N=9) were subjected to microindentation testing, which made it possible to determine the material properties of bone tissue, such as microhardness HV and Young׳s modulus E. In addition, mechanical tests were supplemented with Raman spectroscopy, which determine the degree of bone mineralization, and measurements of structural properties based on analysis using microCT. The conducted tests were used to establish both quantitative and quantitative description of changes in the structural and mechanical properties connected with reorganization of trabeculae making up the bone in the various stages of osteoarthritis. The proposed description will supplement existing knowledge in the literature about identification of the processes occurring during the development of this disease.

The implementation of new methods of osteoporotic therapy requires tests on animal model. The use of sheep as model has numerous advantages over other animals. The aim of this study was to describe the change in parameters in sheep with osteoporosis induced using steroids and ovariorectomy methods as opposed to the parameters in healthy sheep. The study was performed on female „merinos” breed sheep divided into the three groups: negative control (NC) - healthy animals, positive control (PC) - ovariorectomized animals and steroid control group (SC) - in which methylprednisolone was administered. This paper presents histological and ultrastructural examination with mechanical comparative tests for force/strength values as well as indentation tests of joint cartilage. The obtained results confirm the loss of bone mass associated with mineral composition content in bones, which has an influence on bone strength.

Purpose The purpose of this study was to investigate the influence of selective agonists of the retinoid receptor X (RXR) and the retinoid acid receptor (RAR) on bone metabolism in rats. Methods Thirty six male Wistar rats were divided into three groups: receiving bexarotene, or tazarotene, or to control group. Serum biochemical markers of bone turnover (osteocalcin – OC, tartrate resistant acid phosphatase 5 – TRACP5b and osteoprotegerin – OPG) and mechanical properties of bones were analyzed. Results There was a significant decrease in the femur index value in groups receiving tazarotene and bexarotene on Day 14 (8% and 20% respectively, p = 0.0039). On Day 28, 14 days after discontinuation of tazarotene and bexarotene, the difference in femur indexes was still significant (4% for T1–6 and B1–6, p = 0.0270). In the bexarotene group an increase in mean plasma osteocalcin level and mean plasma TRACP5b level was detected. In the tazarotene group the mean osteocalcin level remained unchanged and the mean plasma TRACP5b level decreased. An increased yield stress was detected in groups receiving retinoids comparing to controls after 14 days of tazarotene and bexarotene administration. Conclusion Although bexarotene and tazarotene administration caused decrease in the femur index, mechanisms responsible for that effect seem to be different. Our results suggest that bexaroten increases bone turnover. On the contrary, tazaroten seems to have inhibitory effect on bone turnover. A counter influence of selective RAR and RXR agonists on the bone turnover might be the reason for inconsistency in results from published research concerning the influence of retinoids on bone metabolism.

The aim of this study is to evaluate the influence of the swimming speed during diving on the biomechanical parameters describing the movement of selected measurement points of the lower limb in professional divers.The study involved a group of 4 professional divers whose movement was recorded during underwater swimming at slow (approx. 0.4 m·s-1), medium (approx. 0.5 m·s-1), and fast (approx. 0.8 m·s-1) pace.During swimming at medium speed, the divers made a smaller displacement (along the axes Y) of the midpoint of fin than during swimming at fast speed. The range of motion in the ankle joint increased in fast speed in comparison with low and medium swimming speed. The same relationship was noted for the obtained velocity and angular acceleration in the hip, knee and ankle joints. The authors observed that during swimming at slow pace the divers choose movement ensuring high swimming comfort while the efficiency of motion is a secondary factor. On the other hand, during swimming at higher pace, the applied movement pattern ensures far greater efficiency rather than swimming comfort.The conducted analysis showed that divers adjust the movement of their lower limbs to the swimming pace.

BACKGROUND Drug-induced osteoporosis is a significant health problem, as many drugs have deleterious effects on bone metabolism. Data from several studies concerning the influence of retinol on bone homeostasis are inconsistent. OBJECTIVES The purpose of this study was to investigate the influence of tazarotene, a selective agonist of the retinoic acid receptor (RAR), on bone metabolism and bone mechanical properties in rats. MATERIAL AND METHODS Sixteen male Wistar rats were assigned either to the group receiving tazarotene or to the control group. Serum biochemical markers of bone turnover (osteocalcin: OC, tartrate resistant acid phosphatase 5: TRACP5b, and osteoprotegerin: OPG) and the mechanical properties of bones were analyzed. RESULTS The mean Young's modulus was 24% higher (p < 0.05) in the control group than in the group receiving tazarotene. The stiffness of femur bones was 25% lower (p < 0.05) in rats receiving tazarotene. Flexural yield stress was slightly (2%) decreased in the tazarotene group, but the difference was not statistically significant. In the tazarotene group significantly lower serum concentration of bone turnover markers were obeserved (TRACP5b: 0.86 ± 0.30 ng/mL vs. 2.17 ± 0.67 ng/mL, OC: 7.77 ± 2.28 ng/mL vs. 13.04 ± 3.54 ng/mL and OPG: 0.09 ± 0.04 ng/mL vs. 0.27 ± 0.10) than in the control group. CONCLUSIONS Tazarotene worsened bone mechanical properties and inhibited bone turnover in rats. These results suggest that tazarotene has a negative impact on bone metabolism and that it exerts osteoporotic activity.

The implementation of new methods of oseoporotic therapy requires tests on an animal model. One of the best is the sheep, whose numerous advantages over other models are described in the literature. The aim of this study was induction of osteoporosis using steroids and ovariorectomy methods in sheep and description of the change in parameters with regard to healthy sheep. The study was performed on female „merino” breed sheep divided into three groups: Negative control (NC) healthy animals, positive control (PC) ovariorectomised animals and steroid group (SC) where methylprednisolone was implemented. Blood tests, diagnostic arthroscopy, quantitative computed tomography and X-Ray micro-tomography of bone were carried out. Blood tests revealed a decreased level of estrogens, progesterone and increased parathormone and cortisol levels in the SC group. A decrease in bone turnover markers and an increase in bone resorption markers in all groups were also noted. Diagnostic arthroscopy revealed osteoarthrosis in PC and SC groups. Radiological density tests showed a slight decrease in PC and NC groups whereas there was more than a triple decrease in SC. Results obtained from microCT showed quickly developing osteoporosis in the SC group, which is reflected in numerous parameters analysed in this study. The best effects for osteoporosis induction were obtained using ovariorectomised sheep with methylprednisolone injections.

In this article, the author presents mathematical relationships between the structural and mechanical properties of cancellous human bone tissue obtained by experimental analysis of specimens. Bone tissue material can adjust its internal structure to the existing loading conditions. The mechanical properties affect the structural properties but changes in structural properties likewise cause changes in the mechanical properties of the tissue. In normal tissue, the processes of tissue construction, destruction, and reconstruction are mutually balanced and complementary; if that balance is disturbed, lesions can occur. Therefore, normal bone tissue and pathologically changed tissue (osteoporosis and osteoarthrosis) coming from the area of human femoral head were examined. The structural properties of cancellous tissue specimens were determined non-destructively for three-dimensional reconstructions with the use of modern micro-CT methods. The mechanical properties of the specimens were determined by an uniaxial compression test in three orthogonal directions. Next, in order to specify the compressive strength, a failure test was conducted in the direction perpendicular to the neck-shaft angle of the hip joint.

In 1995 Kuttner and Goldberg defined osteoarthritis as a group of distinct simultaneous diseases, which may have different etiologies but have similar biologic, morphologic, and clinical outcomes. The disease processes does not only affect the articular cartilage, but involve the entire joint, including the subchondral bone, ligaments, capsule, synovial membrane, and periarticular muscles. Ultimately, the articular cartilage degenerates with fibrillation, fissures, ulceration, and full thickness loss of the joint surface (Kuttner & Golderg, 1995). Osteoarthritis (OA) is also characterised by chronic degradation of articular cartilage and hypertrophy of bone tissue in joint region. OA results from both biological and mechanical causes which lead to instability of bone degradation and remodeling processes of entire joint organ, including the chrondocytes, subchondral bone and synovium articular (Grynpas et al., 1991). Precise classification of joint degeneration is difficult. For example, American College of Rheumatology (ACR) classifies osteoarthritis as non inflammatory condition despite the fact, that clinical observation show frequent inflammatory reaction (Pelletier et al., 1999; Wang et al., 2002; Malcolm, 2002) although the latter may actually be a manifestation of a superimposed crystalline arthritis. To evaluate degradation of joint cartilage two methods are the most frequently used: Altman scale (Altman et al., 1986) and Kellegren-Lawrence scale. First method differentiates between primary and secondary effects of degradation without taking into account etiological factors which precise identification allows to prevent development of OA. Kellegen-Lawrence defined a five level scale that is used to evaluate changes in tissue structure based on its images. Unfortunately, if computer tomography images are used then only advanced stages of OA disease can be detected. Origins of OA are not well known but several hypothesis on its etiology were proposed. Hypothesis focus on changes in biochemical composition and physical properties of synovial fluid that debilitates cartilage nutrition, increased friction of joint surface, impaired blood supply as well as increased number of micro–cracks, especially in subchondral bone. When OA affects hip joint then those changes apply to the femoral head and acetabulum. Two, seemingly equivalent hypotheses about the origins and progress of osteoarthritis are presented in the literature (Radin, 1995). According to the first one changes in the articular cartilage cause

The aim of the study was to assess the influence of various feed phosphates on the structural and mechanical properties as well as on the chemical composition of femurs in adult pigs (weight approx. 110 kg). Three types of phosphates--monocalcium phosphate (MCP), dicalcium phosphate (n-DCP) and calcium-sodium phosphate (CSP)--were used alternatively in pigs fed with the standard feed mixture. The MCP and CSP phosphates were typical, imported products used traditionally in pig feeding. Dicalcium phosphate (n-DCP) was manufactured in Poland on the basis of phosphoric acid with the new pro-ecological method. The following parameters were determined: the mean physical density of the samples of the compact and spongy bone tissue, values of Young's modulus, strength and the energy of deformation, and Vickers microhardness (HV). Also the content of C, O, Na, Mg, Al, and Si, as well as Ca, P and Sr was determined. Significant differences in mean values of the mentioned parameters occurred between the studied groups. The best mechanical properties were shown by the bones from the n-DCP group, and the compact bone tissue (diaphysis) contained the most Ca, P, and Sr when compared to the MCP and CSP groups.

The knowledge of the mechanical characteristics of bone structures is a prerequisite for theoretical, numerical, and experimental analyses describing the functioning of bone, which is a living organ. The description of the mechanical properties of bone tissue, such as conventional Young's modulus or strength, will enable the assessment of the degree of tissue degeneration through a comparison of the material properties of the examined bones to the properties determined for physiologically normal bones. However, the mechanical parameters published by different research centres often differ from each other by up to several hundred percent. These discrepancies arise primarily from the differences in the research methodology applied, and thus from many additional factors having a direct impact on the values of the mechanical parameters obtained in experimental tests. Therefore, in order to standardize and improve the interpretation of the results of measurements, we should develop universal criteria for the measuring conditions and quantify the impact of the factors being related to sample and measurements on the values obtained. In this paper, the authors present the dependence of some factors, i.e. the site and direction of sample excision as well as the rate and type of loading, on the values of the mechanical parameters. Those values were determined in experimental tests and the additional correlation coefficients proposed enabled an easier comparison of the results obtained with the values presented in the literature.

Bone tissue can adjust internal structure to the existing loading condition. The mechanical properties affect the structural properties but changes in structural properties likewise cause changes in the mechanical properties of the tissue. In healthy tissue the remodelling processes: resorption and bone deposition, determined by the activities of two principle cell types, osteoclasts and osteoblasts which are mutually balanced and complementary. Capability to adapt bone’s structure to load condition may have adverse consequences and lead to pathological changes when balance between processes of bone remodeling is disturbed.

The function of the highly complex structure such as the human skeletal system is possible by the appropriate construction and properties of bone tissue. Bone tissue, due to its design, is a material that continuously adapts its mechanical properties and structural response to the smallest change in load condition. Bone should be viewed as a twophase composite material, consisting of a collagen matrix with low elasticity and HA crystals with high elasticity modulus. The main mineral components of these crystals are Ca and P. The degree of digestibility of P compounds is affected by many factors, which include, type of feed, breed and species of animals, amount of vitamins and probiotics, and the ratio of Ca vs. P. The primary feed used in swine feeding is grain, which is also the main source of P that has in the form of phytate. This form of phosphorus is very difficult absorb as molecules of phytic. Consequently, in neutral pH phytate forms sparingly soluble complexes with amino acids, sugars and divalent metal cations, thus reducing its absorption. Amount of P supplied with the feed, even when supplemented by microbial phytase, does not cover the requirements of extensively growing pigs. The most frequently commercial products which are intended to supplement deficiencies are 1, 2 and 3-calcium, calcium-sodium, sodium-calcium-magnesium. Studies in literature (Jongbloed, 2000) present that the best results in swine nutrition is obtained when one or disodium phosphate is used. The main goal of this study was to determine the mechanical properties and elemental content of bone tissue derived from pigs fed with forage with different amounts of Ca and P. In addition, the study was to determine the fodder value of the new dicalcium phosphate feed (n-DCP) produced by the Gda sk Phosphate Fertilizer Plants' Fosfory "Ltd. according to patent No. P-369805, when compared to monocalcium phosphate, calcium and sodium.

In a motorbike different types of shaft-hub couplings are used to join the handlebar to the suspension legs of the front wheel. Some papers were recently published with reference to the experimental determination of the starting friction coefficient of the fork-steering pin compression coupling [1], to the development of FEM assisted design strategies for the fork-pin [2], fork-leg [3] and leg-pin couplings [4]. On the other hand, another important joint, the clamping between the fork and the handlebar has been less investigated. The clamp (aluminium alloy, EN AW-6082, Fig. 1 A, B) consists of two parts, the lower one (connected to the fork by two screws), interfacing with the lower part of the handlebar, and the upper one, shaped to lodge the upper part of the handlebar. The assembly procedure consists in the insertion of the handlebar between the two clamp parts and in screw tightening, according to a particular procedure. Screws indicated as 1 and 2 are tightened first to create contact between mating surfaces of the two clamp parts, screws 3 and 4 are then applied to complete clamp closing. No information are available about stress trends during screw tightening, and about non symmetric effects in stress distribution, depending on the tightening order of screws 3 and 4. Moreover, no studies are available on the effects of yield strength overcome over a small region, and in case, on the safety of disassembling and reassembling the same clamp during maintenance procedures. Consequently, the main objects of this work were the followings: • Experimental determination of stress trends in the elastic field: discussion on non symmetric effects depending on tightening sequence. • Experimental stress analysis in the elasto-plastic field and discussion on the safety of the coupling, even in case of disassembling and reassembling of the same parts.

In a previous works [1] an innovative technological test has been presented developed by this research group. Analytical models available in the literature to describe the material behaviour in the creep-fatigue regime are currently under investigation to be validated against this experimental campaign. Aim of the present work is to present the first step of this investigation in which the thermal distribution of the specimen has been replicated by means of thermo-electrical simulations. Preliminary comparison between experimental and numerical results on the creep behaviour are also presented.