Tissue response to a membrane of demineralized bovine cortical bone implanted in the subcutaneous tissue of rats

Valuation of angiogenesis in bovine xenografts implanted in intracorporal sites of rabbits as models of in-vivo bioreactors

ABSTRACT The aim of this study was to evaluate neovascularization of bovine xenografts implanted in intracorporeal sites of rabbits (bioreactors). 30 rabbits were used, divided into 6 groups, according to the evaluation time (7, 15, 30, 45, and 60 days); each animal received xenogenic implants in 3 different intracorporeal sites (A1 - omentum bag; A2 - intermuscular space of quadriceps femoris; A3 - subperiosteal of ilium bone). Histological assessments graded the presence of angiogenesis, the number of inflammatory cells, newly formed bone tissue, and the presence of giant cells. Histological analyses showed intense angiogenesis in all implanted xenografts. Presence of inflammatory infiltrate and giant cells at the A1 implant site and presence of bone neoformation at the A3 implant site were noted. Degeneration of implants and formation of a fibrous capsule were noted. When comparing the interaction of the site with the days of evaluation, statistical analysis showed a significant difference (p≤0.05) in any time of neovascularization analysis. The vascular endothelial growth factor (VEGF) and inflammatory cells of the omentum in its structure, may have contributed to the greater presence of neovessels and inflammatory cells, a fact that may indicate functionality as a possible bone substitute.

In Vitro Physico-Chemical Characterization and Standardized In Vivo Evaluation of Biocompatibility of a New Synthetic Membrane for Guided Bone Regeneration

This study’s aim was to evaluate the biocompatibility and bioabsorption of a new membrane for guided bone regeneration (polylactic-co-glycolic acid associated with hydroxyapatite and β-tricalcium phosphate) with three thicknesses (200, 500, and 700 µm) implanted in mice subcutaneously. Scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and the quantification of carbon, hydrogen and nitrogen were used to characterize the physico-chemical properties. One hundred Balb-C mice were divided into 5 experimental groups: Group 1—Sham (without implantation); Group 2—200 μm; Group 3—500 μm; Group 4—700 μm; and Group 5—Pratix^®. Each group was subdivided into four experimental periods (7, 30, 60 and 90 days). Samples were collected and processed for histological and histomorphometrical evaluation. The membranes showed no moderate or severe tissue reactions during the experimental periods studied. The 500-μm membrane showed no tissue reaction during any experimental period. The 200-μm membrane began to exhibit fragmentation after 30 days, while the 500-μm and 700-µm membranes began fragmentation at 90 days. All membranes studied were biocompatible and the 500 µm membrane showed the best results for absorption and tissue reaction, indicating its potential for clinical guided bone regeneration.

Demineralized Freeze-Dried Bovine Cortical Bone: Its Potential for Guided Bone Regeneration Membrane

BACKGROUND

Bovine pericardium collagen membrane (BPCM) had been widely used in guided bone regeneration (GBR) whose manufacturing process usually required chemical cross-linking to prolong its biodegradation. However, cross-linking of collagen fibrils was associated with poorer tissue integration and delayed vascular invasion.

OBJECTIVE

This study evaluated the potential of bovine cortical bone collagen membrane for GBR by evaluating its antigenicity potential, cytotoxicity, immune and tissue response, and biodegradation behaviors.

MATERIAL AND METHODS

Antigenicity potential of demineralized freeze-dried bovine cortical bone membrane (DFDBCBM) was done with histology-based anticellularity evaluation, while cytotoxicity was analyzed using MTT Assay. Evaluation of immune response, tissue response, and biodegradation was done by randomly implanting DFDBCBM and BPCM in rat's subcutaneous dorsum. Samples were collected at 2, 5, and 7 days and 7, 14, 21, and 28 days for biocompatibility and tissue response-biodegradation study, respectively.

RESULT

DFDBCBM, histologically, showed no retained cells; however, it showed some level of in vitro cytotoxicity. In vivo study exhibited increased immune response to DFDBCBM in early healing phase; however, normal tissue response and degradation rate were observed up to 4 weeks after DFDBCBM implantation.

CONCLUSION

Demineralized freeze-dried bovine cortical bone membrane showed potential for clinical application; however, it needs to be optimized in its biocompatibility to fulfill all requirements for GBR membrane.

Influence of dentin thickness on intrapulpal temperature under simulated pulpal pressure during Nd:YAG laser irradiation

The aim of this study was to evaluate the effects of dentin thickness and pulpal pressure simulation (PPS) on the variation of intrapulpal temperature (∆T) when submitted to an adhesive technique using laser irradiation. Sixty sound human molars were sectioned and randomly divided into two groups (n = 30): group 1-1 mm of dentin thickness; group 2-2 mm of dentin thickness. Each group was divided into two subgroups (n = 15): subgroup A-absence of PPS; subgroup P-presence of PPS (15 cm H₂O), sequentially treated with the following: 37 % phosphoric acid, adhesive system (Adper Single Bond), irradiation with Nd:YAG laser (1064 nm, 10 Hz, 60 s) using 60, 80, and 100 mJ/pulse energy parameters and light-curing (10 s). The ∆T was evaluated during the laser irradiation with a digital thermometer. Data were analyzed by three-way ANOVA and Tukey tests (p < 0.05). Three-way ANOVA revealed no significant differences for dentin thickness (p = 0.6512) on ∆T. PPS significantly reduced ∆T (p = 0.0001). The laser energy parameters (p = 0.0027) indicated that 100 mJ presented with significantly greater ∆T when compared to the groups irradiated with 80 and 60 mJ. Dentin thickness did not affect ∆T. The presence of PPS reduced the mean temperature values. The Nd:YAG laser energy parameters had a negative influence on the variation of temperature in the absence of PPS. In the presence of PPS, there was no risk to the pulp, since this study obtained temperature increases below 5.5 °C for all energy parameters, showing the technical viability for in vivo conditions.

Laser teeth bleaching: evaluation of eventual side effects on enamel and the pulp and the efficiency in vitro and in vivo

Light and heat increase the reactivity of hydrogen peroxide. There is no evidence that light activation (power bleaching with high-intensity light) results in a more effective bleaching with a longer lasting effect with high concentrated hydrogen peroxide bleaching gels. Laser light differs from conventional light as it requires a laser-target interaction. The interaction takes place in the first instance in the bleaching gel. The second interaction has to be induced in the tooth, more specifically in the dentine. There is evidence that interaction exists with the bleaching gel: photothermal, photocatalytical, and photochemical interactions are described. The reactivity of the gel is increased by adding photocatalyst of photosensitizers. Direct and effective photobleaching, that is, a direct interaction with the colour molecules in the dentine, however, is only possible with the argon (488 and 415 nm) and KTP laser (532 nm). A number of risks have been described such as heat generation. Nd:YAG and especially high power diode lasers present a risk with intrapulpal temperature elevation up to 22°C. Hypersensitivity is regularly encountered, being it of temporary occurrence except for a number of diode wavelengths and the Nd:YAG. The tooth surface remains intact after laser bleaching. At present, KTP laser is the most efficient dental bleaching wavelength.

Guided bone regeneration following surgical treatment of a rare variant of Pindborg tumor: a case report

Calcifying epithelial odontogenic tumor is a benign neoplasm, but its local destructive potential may lead to the formation of major bone defects. Microscopically, there are some histological variants. Among them, we highlight the clear cell variant due to its more aggressive behavior and a higher incidence of relapse. In this context, it is pertinent to describe the clear cell variant of calcifying epithelial odontogenic tumor. Despite the large bone defect formed in the posterior region of the mandible, conservative treatment associated with guided bone regeneration assured complete bone formation and the absence of recurrence in an 8-year follow-up period.

Comparative In Vivo Study of Biocompatibility of Apatites Incorporated with 1% Zinc or Lead Ions versus Stoichiometric Hydroxyapatite

Hydroxyapatite is the main ceramic material that has being used in bone repair, although its physico-chemical and in vivo behavior should be better understood. A method to improve the biocompatibility of HA is the substitution of calcium with divalent cations which enhance mechanic resistance and can modulate inflammatory response against implanted material. In this study we analyzed the biocompatibility of HA doped with one per cent of Zn2+ or Pb2+. The first one has being described as an inflammation modulator and the second would be a model for chronic toxicity assay. Biocompatibility of the both materials was studied in vivo following the ISO 10993-6 standard. HA cylinders (ZnHA, PbHA and stoichiometric HA as positive control) were implanted into subcutaneous tissue of 45 Balb-c mice and after 1, 3 and 9 weeks the animals were euthanized (5 for each experimental condition). Necropsies of the skin containing reactional tissue were removed, fixed in 10% formaldehyde and followed the histological processing for paraffin embedding and staining with Hematoxylin-Eosine and Picrosirius red. Microscopic analysis showed for all groups moderate inflammatory response, decreasing throughout the experimental periods, with ZnHA group showing more intense response. Similar presence of macrophages, fibrosis and angiogenesis were observed among the groups. Thereby, we can conclude that ZnHA and PbHA are biocompatible and not bioresorbable, being the ZnHA potentially indicated as bone graft. Detailed studies are required to better understand the role of PbHA as chronic model for lead toxicity.

Osteoconduction and Bioresorption of Bone Allograft versus Anorganic Bovine Bone Xenograft: A Histomorphometric Study in Humans

This clinical study evaluated the tissue repair process using different bone grafts. Nine dental patients with indication for posterior implantodontic treatment were submitted to maxillary sinus lifting procedures associated to grafting. After 6 months, bone biopsies (6 sites with allogenous bone grafting and 13 sites with bovine xenogenous bone grafting/OsseusTM) were removed and processed for histopathological and histomorphometric analyses (ANOVA and Tukey's test). Both groups had tissue biocompatibility without significant inflammatory response, only punctual presence of multinucleated giant cells in xenograft group. Osteoconductive potential was evidenced by new bone tissue surrounding and in direct contact with the granules of both grafts. Volume density of connective tissue was similar between groups, although there were significant differences in allograft group in comparison to xenograft as the presence of new bone formation (48.50%±13.93 versus 29.83±9.56, respectively, p<0.05) and remnant biomaterial (1.57±2.39 versus 22.23±12.41, respectively, p<0.001), suggesting a greater osteoconductivity and faster bioresorption in the allograft group. These results demonstrate that allogenous bone and OsseusTM can be satisfactorily used as grafts in minor oral surgeries for bone augmentation in humans.

Exploring anorganic bovine bone granules as osteoblast carriers for bone bioengineering: a study in rat critical-size calvarial defects

It is known that current trends on bone bioengineering seek ideal scaffolds and explore innovative methods to restore tissue function. In this way, the objective of this study was to evaluate the behavior of anorganic bovine bone as osteoblast carrier in critical-size calvarial defects. MC3T3-E1 osteoblast cells (1x10(5) cells/well) were cultured on granules of anorganic bovine bone in 24-well plates and after 24 h these granules were implanted into rat critical-size calvarial defects (group Biomaterial + Cells). In addition, other groups were established with different fillings of the defect: Blood Clot (negative control); Autogenous Bone (positive control); Biomaterial (only granules) and Cells (only MC3T3-E1 cells). After 30 days, the animals were euthanized and the calvaria were technically processed in order to allow histological and morphometric analysis. It was possible to detect blood vessels, connective tissue and newly formed bone in all groups. Particularly in the Biomaterial + Cells group, it was possible to observe a profile of biological events between the positive control group (autogenous bone) and the group in which only anorganic bovine granules were implanted. Altogether, the results of the present study showed that granules of anorganic bovine bone can be used as carrier to osteoblasts and that adding growth factors at the moment of implantation should maximize these results.

Natural Bovine Anorganic Apatite and Collagen Presents Osteoconductivity and Contribute to Bone Repair of Rat Calvaria Critical Size Defect

The aim of this study was verify the biological efficacy of the use of a xenograft for bone loss therapy. Blood clot, particulate autogenous bone or anorganic bovine xenograft filled critical size defects (CSD) in rat calvaria (8mm diameter). After 0, 7, 30 and 90 days the animals were killed and macroscopic, radiographic and histopathological analysis were conducted. Although no treatment promoted the total closure of bone defect, autogenous bone group had better bone repair after 90 days, followed by xenograft group that exhibited direct bone neoformation onto, and around, the particles confirming its osteoconductivity. In conclusion, the xenograft tested in vivo showed biocompatibility, biodegradability and osteoconductive properties in rat calvaria CSD.

Biocompatibility of Bovine Anorganic Xenograft

Porous granules without organic residues were produced from bovine medular anorganic bone. Sample showed carbonate content and crystalline order similar to natural bone. The cytotoxicity of anorganic bovine xenograft (Ossĕus®) was valuated from fibroblasts (1.5x104/cm2) cultured in serial diluted extract (0 – 100%) of Ossĕus plus 10% of fetal bovine serum (FBS). Pure extract (100%) reduced in 15% the number of viable cells (p<0.05, ANOVA, Tukey test) indicating very low cytotoxicity. Samples were implanted in the subcutaneous tissue of mice in order to evaluate tissue reaction. An organized connective tissue in contact to the granules was observed nine weeks after implantation. The anorganic bovine xenograft (Ossĕus®) was biocompatible and its behavior and osteoconduction potential should be evaluated in bony defects.

Evaluation of the cytocompatibility of mixed bovine bone

Treatment of bovine bone with peroxides and chaotropic agents aims to obtain an acellular bone matrix that is able to maintain the collagen-apatite complex and a higher mechanical resistance, a mixed biomaterial hereby named mixed bovine bone (MBB). The purpose of this study was to evaluate the cytocompatibility of MBB and cell-MBB interaction. Cell morphology, number of viable cells, ability to reduce methyltetrazolium and to incorporate neutral red upon exposure to different concentrations of the hydrosoluble extract of MBB were assessed in Balb-c 3T3 cells according to ISO 10993-5 standard. The interaction between cells and MBB surface was evaluated by scanning electron microscopy. The water-soluble MBB extracts were cytotoxic and led to cell death possibly due to its effect on mitochondrial function and membrane permeability. Cells plated directly onto the MBB did not survive, although after dialysis and material conditioning in DMEM + 10% FCS, the cells adhered and proliferated onto the material. It may be concluded that, in vitro, water-soluble MBB extracts were cytotoxic. Nevertheless, MBB cytotoxic effect was reverted by dialysis resulting in a material that is suitable for cell based-therapy in the bioengineering field.

Dynamics of Subcutaneous Tissue Response to the Implantation of Tetracycline-Treated or Untreated Membrane of Demineralized Bovine Cortical Bone in Rats

This study aims to conduct a histological evaluation of tissue response to a membrane obtained from demineralized bovine cortical bone, associated or not, to tetracycline (TTC). TTC treated and untreated bovine membranes were implanted in the subcutaneous tissue of rats ( n = 120). The animals were killed 1, 3, 7, 15, 30, and 60 days after surgery. The tissue around the material was fixed in 10% buffered formalin for 24 h. Sections of 6 mm were stained with hematoxylin and eosin. In general, moderate to intense inflammatory response was observed in the initial periods (1 and 3 days), moderate response in the 7- and 15-day periods, and that was remarkably reduced at 30 and 60 days. Resorptions of the membranes by mononuclear cells (fibroblasts and macrophages) and multinucleated giant cells were observed 15 days after implantation. Only the remnants of the material could be detected in some animals in 60 days. Both membranes were tolerated by the tissue and were completely resorbed after 30-60 days. While the association of TTC apparently accelerated the biodegradability of the membrane substrate, no significant differences were found in the tissue response behavior between the two groups tested.

Rat subcutaneous tissue response to macrogranular porous anorganic bovine bone graft

The ideal bone graft must present biocompatibility, osteoconductive and osteoinductive properties, resistance and plasticity. Xenogenic grafts of bovine cancellous bone origin are particularly interesting due to their biologically designed porous structure that enhance both cellular and vascular invasion. The purpose of this study was to evaluate the tissue response induced by bovine macrogranular porous anorganic bone implanted in rat subcutaneous tissue. Forty rats were assigned to 2 groups, as follows: the control group received empty collagen capsules and the test group received subcutaneous implants of the test material. Samples were collected after 10, 20, 30 and 60 days and processed histologically. Histological analysis showed at 10 days a granulomatous inflammatory infiltrate, rich in multinucleated giant cells and free of lymphocytes or plasma cells, similarly to mineralized allograft implanted in rat subcutaneous. In later periods, there was a significant decrease in the inflammatory infiltrate and an increase in fibrosis around graft particles. In conclusion, the test material induced a foreign body-type granuloma with subsequent fibrosis around the graft particles implanted in rat subcutaneous and did not elicit any immune response, thus being considered biocompatible.