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ABSTRACT: Stress erythropoiesis (SE) can be defined as a state of increased red cell production in response to an enhanced secretion
of erythropoietin. Under normal conditions, erythropoiesis in the adult occurs in the erythropoietic tissue that is confined
to the bone marrow within the skeleton. Hypertrophy of the erythropoietic marrow that occurs during SE must be accommodated
in a larger space. The resulting expansion of the marrow space may induce bone resorption and could alter the biomechanical
performance of bone. The present study was designed to estimate the effect of sustained SE on diaphyseal structure and biomechanics
of rat femur by mechanically testing the diaphyseal stiffness and strength and calculating some indicators of bone material
properties. Female Sprague–Dawley rats weighing 100.0 ± 5.2g were divided in a control (C) and an experimental (E) group.
E rats were biweekly injected with 60mg/kg of phenylhydrazyne during 6weeks to induce a haemolytic state. SE, in response
to haemolysis, was estimated by reticulocyte count and erythrokinetic techniques, which were markedly increased. To assess
bone mechanical properties, the right femur was tested in three-point bending test. Sections of the left femur were stained
with haematoxylin–eosin. Body growth was not altered by treatment. Diaphyseal bone mass (CSA) was 13% lower in E than in C
rats, while the cross-sectional bending moment of inertia (xCSMI) was significantly higher. The “load capacity” extrinsic
properties of the femoral diaphysis were about 40% decreased in E rats when compared to C ones, while the bone material quality
indicators (elastic modulus and yield stress of cortical bone tissue) were 54 and 38% lower, respectively. The histologic
sections of E femora exhibited a marked thinning of cortical bone and the presence of woven bone in the medullary compartment.
The results obtained in this study indicate that SE caused the impairment of the diaphyseal bone material properties (elastic
modulus and elastic stress) but enhanced xCSMI over the control values. Neither this improvement in diaphyseal cross-sectional
design nor the formation of woven bone could offset the impairment in the bone material stiffness. It is thus proposed that
the biomechanical impact of SE upon the whole-bone stiffness should have been more determined by the negative effect on bone
material quality than by the negative changes in the cortical area.
Comparative Clinical Pathology 04/2012; 17(1):17-22.
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ABSTRACT: Trypanosoma cruzi (T cruzi) is an intracellular protozoan pathogen that causes American trypanosomiasis (Chagas disease). The aim of this study was to evaluate the histopathological effects of acute infection by T. cruzi on bone repair, Wistar rats were used throughout. The animals were assigned to two groups: Control Group (CG n =20) and Experimental Group (EG n = 20). All the animals were anesthetized, at to the first lower right molar was extracted. The EG animals were inoculated subcutaneously at to with 0.1 mL of 10 trypomastigotes of the virulent strain Tulahuen of T. cruzi. The CG animals were administered an equivalent volume ofsaline solution subcutaneously. The animals in both groups were euthanized at 15 days post-infection and tooth extraction. The mandibles were resected, fixed informalin solution, radiographed, decalcified and embedded in paraffin. Bucco-lingually oriented sections were obtained at the level of the mesial tooth socket of the first lower molar and stained with hematoxylin-eosin. Total alveolar volume (TV) and bone volume (TBV/TV) in the apical third of the tooth socket were evaluated histomorphometrically. The histological analysis revealed an alteration in post-extraction bone tissue repair in animals infected by T. cruzi. A reduction in osteogenic activity was observed concomitant with a rise in quiescent and eroded bone surfaces. Histomorphometric evaluation revealed a significant reduction (19%) in total alveolar volume (TV) and bone volume (TBV/TV) (24%) in the apical third of the tooth socket in animals infected with T. cruzi in comparison to non-infected animals (p<0.05). The results obtained using this experimental model showed decreased osteogenesis in bone tissue repair under acute Trypanosoma cruzi infection in rats.
Acta odontológica latinoamericana: AOL 01/2012; 25(2):193-200.
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ABSTRACT: Titanium is the most widely used metal in dental implantology. The release of particles from metal structures into the biologic milieu may be the result of electrochemical processes (corrosion) and/or mechanical disruption during insertion, abutment connection, or removal of failing implants. The aim of the present study is to evaluate tissue response of human oral mucosa adjacent to titanium cover screws.
One hundred fifty-three biopsies of the supra-implant oral mucosa adjacent to the cover screw of submerged dental implants were analyzed. Histologic studies were performed to analyze epithelial and connective tissue as well as the presence of metal particles, which were identified using microchemical analysis. Langerhans cells, macrophages, and T lymphocytes were studied using immunohistochemical techniques. The surface of the cover screws was evaluated by scanning electron microscopy (SEM).
Forty-one percent of mucosa biopsies exhibited metal particles in different layers of the section thickness. Particle number and size varied greatly among specimens. Immunohistochemical study confirmed the presence of macrophages and T lymphocytes associated with the metal particles. Microchemical analysis revealed the presence of titanium in the particles. On SEM analysis, the surface of the screws exhibited depressions and irregularities.
The biologic effects seen in the mucosa in contact with the cover screws might be associated with the presence of titanium or other elements, such as aluminum or vanadium. The potential long-term biologic effects of particles on soft tissues adjacent to metallic devices should be further investigated because these effects might affect the clinical outcome of the implant.
Journal of Periodontology 12/2011; 83(8):973-80. · 2.60 Impact Factor
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ABSTRACT: Titanium and zirconium are biomaterials that present a layer of titanium dioxide (TiO2) or zirconium dioxide (ZrO2). As a result of corrosion, microparticles can be released into the bioenvironment, and their effect on tissues is seemingly associated with differences in the physicochemical properties of these metals. The aim of this study was to perform a long-term evaluation of the distribution, destination, and potential risk of TiO2 and ZrO2 microparticles that might result from the corrosion process. Wistar rats were i.p. injected with an equal dose of either TiO2 or ZrO2 suspension. The following end-points were evaluated at 3, 6, and 18 months: (a) the presence of particles in blood cells and liver and lung tissue, (b) Ti and Zr deposit quantitation, (c) oxidant–antioxidant balance in tissues, and (d) O2− generation in alveolar macrophages. Ti and Zr particles were detected in blood mononuclear cells and in organ parenchyma. At equal doses and times postadministration, Ti content in organs was consistently higher than Zr content. Ti elicited a significant increase in O2− generation in the lung compared to Zr. The consumption of antioxidant enzymes was greater in the Ti than in the Zr group. The present study shows that the biokinetics of TiO2 and ZrO2 depends on particle size, shape, and/or crystal structure. © 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A:, 2011.
Journal of Biomedical Materials Research Part A 06/2011; 98A(4):604 - 613. · 2.63 Impact Factor
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ABSTRACT: Emerging evidence indicates that boron (B) plays a role in bone formation and maintenance. Thus, a study was performed to determine whether dietary B-deficiency affects periodontal alveolar bone modelling and remodelling.
Weanling Swiss mice (n=30) were divided into three groups: control diet (GI, 3mg B/kg); B-deficient diet (GII, 0.07 mg B/kg); and pair-fed with GII (GIII). The animals were maintained on their respective diets for 9 weeks and then sacrificed. The guidelines of the NIH for the care and use of laboratory animals were observed. The mandibles were resected, fixed, decalcified in 10% EDTA and embedded in paraffin. Buccolingually oriented sections were obtained at the level of the mesial root of the first lower molar and stained with H-E. Histomorphometric studies were performed separately on the buccal and lingual sides of the periodontal alveolar bone. Percentages of osteoblast surfaces (ObSs), eroded surfaces (ESs), and quiescent surfaces (QSs) were determined.
No statistically significant differences in food intake and body weight were observed between the groups. When compared with GI and GIII mice, GII mice (B-deficient) had 63% and 48% reductions in ObS and 58% and 73% increases in QS in buccal and lingual plates, respectively. ES were not affected by B nutriture.
The results are evidence that dietary boron deprivation in mice alters periodontal alveolar bone modelling and remodelling by inhibiting bone formation.
Archives of Oral Biology 08/2008; 53(7):677-82. · 1.60 Impact Factor
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ABSTRACT: Bone healing after tooth extraction in rats is a suitable experimental model to study bone formation. Thus, we performed a study to determine the effects of boron (B) deficiency on bone healing by using this model. The first lower right molar of weanling Wistar rats was extracted under anesthesia. The animals were divided into two groups: +B (adequate; 3 mg B/kg diet), and -B (boron-deficient; 0.07 mg/kg diet). The animals in both groups were killed in groups of 10 at 7 and 14 days after surgery. The guidelines of the NIH for the care and use of laboratory animals were observed. The mandibles were resected, fixed, decalcified, and embedded in paraffin. Buccolingually oriented sections were obtained at the level of the mesial alveolus and used for histometric evaluations. Total alveolar volume (TAV) and trabecular bone volume per total volume (BV/TV) in the apical third of the alveolus were determined. Percentages of osteoblast surface (ObS), eroded surface (ES), and quiescent surface (QS) were determined. No statistical significant differences in food intake and body weight were observed. Histomorphometric evaluation found -B rats had 36% and 63% reductions in BV/TV at 7 and 14 days, respectively. When compared with +B rats, -B rats had significant reductions (57% and 87%) in ObS concomitantly with increases (120% and 126%) in QS at 7 and 14 days, respectively. The findings show that boron deficiency results in altered bone healing because of a marked reduction in osteogenesis.
The Anatomical Record Advances in Integrative Anatomy and Evolutionary Biology 05/2008; 291(4):441-7. · 1.47 Impact Factor
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ABSTRACT: The titanium dioxide layer is composed mainly of anatase and rutile. This layer is prone to break, releasing particles to the milieu. Therefore, corrosion may cause implant failure and body contamination. We have previously shown that commercial anatase-titanium dioxide (TiO(2)-anatase) is deposited in organs with macrophagic activity, transported in the blood by phagocytic-mononuclear cells, and induces an increase in the production of reactive oxygen species (ROS). In this study, we evaluated the effects of rutile-titanium dioxide (TiO(2)-rutile). Male Wistar rats were injected i.p. with a suspension of TiO(2)-rutile powder at a dose of 1.60 g/100 g b.w. Six months postinjection, the presence of Ti was assessed in serum, blood cells, liver, spleen, and lung. Titanium was found in phagocytic mononuclear cells, serum, and in the parenchyma of all the organs tested. TiO(2)-rutile generated a rise in the percentage of reactive cells, which was smaller than that observed when TiO(2)-anatase was employed in a previous study. Although TiO(2)-rutile provoked an augmentation of ROS, it failed to induce damage to membrane lipids, possibly due to an adaptive response. The present study reveals that TiO(2)-rutile is less bioreactive than TiO(2)-anatase.
Journal of Biomedical Materials Research Part A 04/2008; 84(4):1087-93. · 2.63 Impact Factor
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ABSTRACT: In this study, Frost's bulk-staining in combination with confocal laser scanning microscopy (CLSM) was used to image and characterize ground sections of undecalcified rat bone tissue with in situ bioceramic implants. This was addressed by bulk staining specimens in alcohol-soluble basic fuchsin dye. The ground sections were imaged using CLSM in the confocal fluorescence mode. Confocal images revealed that the newly formed bone could be clearly distinguished from bone marrow and cortical bone, as well as from the implant material.
Journal of Biomedical Materials Research Part A 06/2007; 81(2):443-5. · 2.63 Impact Factor
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ABSTRACT: The aim of the present study was to characterize the neoformed bone tissue around boron-modified bioactive glass particles implanted in rat tibia bone marrow by histologic, histomorphometric and microchemical evaluation. Melt-derived glasses were prepared from a base 45S5 bioactive glass of nominal composition (45% SiO(2), 24.5% CaO, 24.5% Na(2)O and 6% P(2)O(5) in wt%). The glass composition was modified by adding 2% wt of boron oxide (45S5.2B). Histological and histomorphometric analyses using undecalcified sections showed that at 15 days post-implantation the area of neoformed bone tissue around the 45S5.2B particles was significantly higher than control 45S5 glass. No statistically significant differences were observed at 30 days post-implantation. The thickness of osseointegrated tissue on 45S5.2B BG particles was significantly greater than on the control at all experimental time-points evaluated. A statistically significant increase in the Ca:P ratio was observed in the neoformed bone around 45S5.2B particles 15 days post-implantation. The results of the present study provide evidence that particles of boron-modified 45S5 BG (45S5.2B) enhance bone formation more than 45S5 glass when implanted into the intramedullary canal of rat tibiae.
Biomedical Materials 10/2006; 1(3):100-5. · 2.16 Impact Factor
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ABSTRACT: Alveolar bone is the least stable of the periodontal tissues, because it is subjected to continuous modeling and remodeling.
To perform a histological and histomorphometric evaluation of bone modeling and remodeling of periodontal alveolar bone under experimental anaemia and polycythaemia.
Thirty Wistar rats were divided into three groups: control (C), animals were i.p. injected with 0.5 mL of saline solution; anaemia (A), animals were injected with 6 mg/100 b.w. of phenylhydrazine every 48 h; polycythaemia (P), animals were transfused with 2.5 mL/100 b.w. of 80% suspension of homologous erythrocytes. All the animals were sacrificed 14 days after the onset of the experiment. The mandibles were resected, fixed in formalin, radiographed, processed and embedded in paraffin. Bucco-lingually oriented sections were obtained at the level of the mesial root of the first lower molar, and stained with hematoxylin-eosin. Histological and histomorphometric studies were performed on the buccal and lingual plates of periodontal alveolar bone.
Histological and histomorphometric studies showed a statistically significant decrease in bone formation both in buccal and lingual plates in group A (anaemia) as compared to group C (control). An increase in active bone formation was found in the lingual plate in group P (polycythaemia) as compared to group C (control).
The results obtained using this experimental model evidenced alterations in bone modeling and remodeling under conditions of anaemia and polycythaemia and/or associated factors.
Archives of Oral Biology 04/2006; 51(3):246-51. · 1.60 Impact Factor
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ABSTRACT: Metallic implants of titanium are used therapeutically in biomedicine because of its excellent biocompatibility. However, no metal or alloy is completely inert. We have previously shown that titanium oxide (TiO(2)) is transported in blood by phagocytic monocytes and deposited in organs such as liver, spleen, and lung 6 months after intraperitoneal injection (ip). Furthermore, it is well known that exposure to metal traces alters the cellular redox status. Thus, the aim of the present study was to determine the presence of titanium in target organs after chronic exposure, assess the potential structural alterations, and evaluate the oxidative metabolism of alveolar macrophages (AM) in the lung. Rats were ip injected with 1.60 g/100 g body wt of TiO(2) in saline solution. Organs (liver, spleen, lung) were processed for histological evaluation. Reactive oxygen species (ROS) in AM obtained by bronchoalveolar lavage (BAL) were evaluated using the nitroblue tetrazolium test and quantitative evaluation by digital image analysis. The histological analysis of organs revealed the presence of titanium in the parenchyma of these organs with no associated tissue damage. Although in lung alveolar macrophages TiO(2) induced a significant rise in ROS generation, it failed to cause tissue alteration. This finding may be attributed to an adaptive response.
Journal of Biomedical Materials Research Part A 06/2005; 73(2):142-9. · 2.63 Impact Factor
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ABSTRACT: Collagen materials have been utilized in medicine and dentistry because of their proven biocompatibility and capability of promoting wound healing. The aim of the present experimental study was to perform a histomorphometric evaluation of the effect of bovine collagen granules on post-extraction alveolar wound healing in rats. Twenty male Wistar rats were submitted to bilateral extraction of the first lower molars under ketamine/xylazine anesthesia according to the technique previously described by Guglielmotti and Cabrini. Sterile Bovine collagen granules of approximately 80 +/- 10 microm (Membracel G, Lab. Celina, Buenos Aires) were hydrated with saline solution and placed into the right mesial socket (experimental side) with gentle pressure, completely filling the site. The contralateral sockets were considered as the control side. Sutures were not performed. After surgery neither special diet nor antibiotics were given. The rats were fed rat chow and water ad libitum. All the animals were killed on the 30th day following surgery by ether overdose. The jaws were dissected, radiographed, decalcified, and embedded in paraffin. Sections were obtained at the level of the first molar mesial socket in a buccolingual orientation and stained with hematoxylin-eosin. The trabecular area and volume density of trabecular bone were measured histomorphometrically. The trabecular area was greater in alveoli treated with collagen granules than in control alveoli (P<0.05). Values of volume density of trabecular bone were greater in experimental than in control sockets (P<0.05). This experimental study provides evidence for the use of bovine collagen granules as bone grafting material, as a therapeutic alternative to fill postextraction sockets.
Acta odontológica latinoamericana: AOL 02/2004; 17(1-2):9-13.
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ABSTRACT: Different metals are increasingly being used to manufacture implants, especially in the fields of dentistry and orthopedics. No metal or alloy is completely inert in vivo. The metal and the organic fluids interact releasing, for example, metallic products. Several hypotheses regarding the probable dissemination routes of titanium have been postulated, but its valence, the organic nature of its ligands and its potential toxicity have yet to be established. In a previous experimental study we demonstrated that i.p. injected titanium and zirconium oxides disseminate and deposit in organs such as liver and lung. The aim of this work was to study the eventual participation of blood cells in the transport mechanism of titanium employing the intraperitoneal injection of titanium oxide in rats as the experimental model. Twenty male Wistar rats, x: 100 g body weight, were intraperitoneally injected with 16x10(3) mg/kg b.w. of TiO(2) in saline solution. Blood samples were taken by heart puncture at 3 and 6 months; blood smears were performed and stained with safranin evidencing monocytes containing titanium particles. The results obtained in this study would indicate that one of the ways in which titanium is disseminated is through the blood stream, via blood cells.
Journal of Materials Science Materials in Medicine 01/2004; 14(12):1099-103. · 2.32 Impact Factor
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ABSTRACT: A deficiency of lipotropic factors in the rat induces renal, hepatic, and/or hematic damage. The aim of the present study was to evaluate the effect of a choline-deficient diet and refeeding on mandibular bone remodeling.
Fifty Wistar rats were divided into 5 groups: group 1 (G1): control diet for 15 days; group 2 (G2): choline-deficient diet for 15 days; group 3 (G3): control diet for 30 days; group 4 (G4): choline-deficient diet for 30 days; and group 5 (G5): choline-deficient diet for 15 days and control diet for 15 days. All animals were sacrificed by ether overdose. The mandibles were resected, radiographed, decalcified, processed, and embedded in paraffin. Bucco-lingually oriented sections were obtained at the level of the interradicular bone of the medial roots of the left first molar, and stained with hematoxylin and eosin (H & E). Bone tissue density and bone remodeling were determined histomorphometrically. Body weight, food intake, hematocrit, and hemoglobinemia were also recorded.
Microscopic observation revealed that osteogenesis was lower in rats fed a choline-deficient diet, at both 15 and 30 days, and that this decrease did not revert with a control diet. Histomorphometric evaluation showed 37% and 27% reduction in bone tissue density at 15 and 30 days, respectively, and a 30% decrease in bone formation at 30 days, compared to controls.
In this experimental model, a choline-deficient diet led to altered bone remodeling as observed by a marked reduction in osteogenesis.
Journal of Periodontology 06/2003; 74(6):831-7. · 2.60 Impact Factor
