Bone Healing Response Research Articles

Impact of Release Kinetics on Efficacy of Locally Delivered Parathyroid Hormone for Bone Regeneration Applications.

Characterizing the release profile for materials-directed local delivery of bioactive molecules and its effect on bone regeneration is an important step to improve our understanding of, and ability to optimize, the bone healing response. This study examined the local delivery of parathyroid hormone (PTH) using a thiol-ene hydrogel embedded in a porous poly(propylene fumarate) (PPF) scaffold for bone regeneration applications. The aim of this study was to characterize the degradation-controlled in vitro release kinetics of PTH from the thiol-ene hydrogels, in vivo hydrogel degradation in a subcutaneous implant model, and bone healing in a rat critical size bone defect. Tethering PTH to the hydrogel matrix eliminated the early timepoint burst release that was observed in previous in vitro work where PTH was free to diffuse out of the matrix. Only 8% of the tethered PTH was released from the hydrogel during the first 2 weeks, but by day 21, 80% of the PTH was released, and complete release was achieved by day 28. In vivo implantation revealed that complete degradation of the hydrogel alone occurred by day 21; however, when incorporated in a three-dimensional printed osteoconductive PPF scaffold, the hydrogel persisted for >56 days. Treatment of bone defects with the composite thiol-ene hydrogel-PPF scaffold, delivering either 3 or 10 μg of tethered PTH 1-84, was found to increase bridging of critical size bone defects, whereas treatment with 30 μg of tethered PTH resulted in less bone ingrowth into the defect area. Continued development of this biomaterial delivery system for PTH could lead to improved therapies for treatment of nonunion fractures and critical size bone defects.

A therapeutic oxygen carrier isolated from Arenicola marina decreased P. gingivalis induced inflammation and tissue destruction

The control of inflammation and infection is crucial for periodontal wound healing and regeneration. M101, an oxygen carrier derived from Arenicola marina, was tested for its anti-inflammatory and anti-infectious potential based on its anti-oxidative and tissue oxygenation properties. In vitro, no cytotoxicity was observed in oral epithelial cells (EC) treated with M101. M101 (1 g/L) reduced significantly the gene expression of pro-inflammatory markers such as TNF-α, NF-κΒ and RANKL in P. gingivalis-LPS stimulated and P. gingivalis-infected EC. The proteome array revealed significant down-regulation of pro-inflammatory cytokines (IL-1β and IL-8) and chemokine ligands (RANTES and IP-10), and upregulation of pro-healing mediators (PDGF-BB, TGF-β1, IL-10, IL-2, IL-4, IL-11 and IL-15) and, extracellular and immune modulators (TIMP-2, M-CSF and ICAM-1). M101 significantly increased the gene expression of Resolvin-E1 receptor. Furthermore, M101 treatment reduced P. gingivalis biofilm growth over glass surface, observed with live/dead analysis and by decreased P. gingivalis 16 s rRNA expression (51.7%) (p < 0.05). In mice, M101 reduced the clinical abscess size (50.2%) in P. gingivalis-induced calvarial lesion concomitant with a decreased inflammatory score evaluated through histomorphometric analysis, thus, improving soft tissue and bone healing response. Therefore, M101 may be a novel therapeutic agent that could be beneficial in the management of P. gingivalis associated diseases.

Mechanical performance and implications on bone healing of different screw configurations for plate fixation of diaphyseal tibia fractures: a computational study

Diaphyseal tibia fractures may require plate fixation for proper healing to occur. Currently, there is no consensus on the number of screws required for proper fixation or the optimal placement of the screws within the plate. Mechanical stability of the construct is a leading criterion for choosing plate and screws configuration. However, number and location of screws have implications on the mechanical environment at the fracture site and, consequently, on bone healing response: The interfragmentary motion attained with a specific plate and screw construct may elicit mechano-transduction signals influencing cell-type differentiation, which in turn affects how well the fracture heals. This study investigated how different screw configurations affect mechanical performance of a tibia plate fixation construct. Three configurations of an eight-hole plate were considered with the fracture in the center of the plate: eight screws-screws at first, fourth, fifth and eighth hole and screws at first, third, sixth and eighth hole. Constructs' stiffness was compared through biomechanical tests on bone surrogates. A finite element model of tibia diaphyseal fracture was used to conduct a stress analysis on the implanted hardware. Finally, the potential for bone regeneration of each screw configuration was assessed via the computational model through the evaluation of the magnitude of mechano-transduction signals at the bone callus. The results of this study indicate that having screws at fourth and fifth holes represents a preferable configuration since it provides mechanical properties similar to those attained by the stiffest construct (eight screws), and elicits an ideal bone regenerative response.

THE CLINICAL AND RADIOLOGICAL OUTCOME OF BOVINE HYDROXYAPATITE (BIO HYDROX) AS BONE GRAFT

Background: A Bone graft is a transplanted material to enhance the bone healing response through the osteogenic, osteoconductive, and osteoinductive process on the tissue. Bone autograft has long been the gold standard with the susceptibility of limited supply from the donor and the morbidity risk. The limitation presented by both autograft and allograft has led to the development of bovine hydroxyapatite (BHA). This research was conducted to evaluate the clinical and radiological outcomes of bovine hydroxyapatite as a bone graft.Methods: This research is a descriptive study using a consecutive sampling design of all trauma patients who received bovine hydroxyapatite in our hospital institution between the period of 2016 to 2018 as the samples. The bovine hydroxyapatite was obtained from the tissue bank in our hospital institution. The results were evaluated clinically and radiologically. The data was tabulated and analyzed descriptively.Results: From the 56 patients who underwent surgery and were given the bovine hydroxyapatite, most of the results were 80.36% excellent, 12.5% good, 3.57% fair, and 3.57 % poor. Conclusion: Bovine hydroxyapatite can be considered as an alternative for bone graft in supporting the bone healing process.

Targeted Deletion of CD11b+ Macrophage Subtypes alter the Acute Inflammatory Cytokine Response In Bone Healing

Abstract Any immunological or inflammatory dysregulation can impair the bone healing process. Macrophages (MØ) are immune cells specialized for phagocytosis and assist in all stages of bone repair. MØs are often divided into two main subsets, MØ1, pro-inflammatory M1 macrophages and MØ2, anti-inflammatory or resolving M2 macrophages. Our preliminary data demonstrates that MØ1 to MØ2 polarization occurs following femur fracture during the first 7 days post-fracture and is associated with a specific cytokine expression profile over time. Other studies have demonstrated that dysregulated inflammation can impair fracture healing outcomes in normal mice. We hypothesize that targeted depletion of CD11b+ MØ cells will reduce the acute inflammatory response, alter the normal cytokine expression profile, and interfere with the bone healing response. Therefore, the bone marrow of mice depleted of CD11b+ MØ cells were compared to normal mice following femur fracture at days 0, 1, 2, and 4 using established methods. MØ subtypes were identified using flow cytometry and cytokine expression was quantified using Luminex. The data demonstrated that after fracture, the CD11b+ MØ depleted group had significantly less MØ1s, F480+/CD86+/MHC classII+/CD11b+ cells when compared to controls at all timepoints. MØ cytokine expression profiles were found to be altered in the control fractures when compared to the CD11b+ MØ depleted fractures. Our results demonstrate that MØ subsets contribute substantially to the signaling mechanisms that guide the acute inflammatory phase of bone healing. Proper modulation of macrophage polarization may be useful to develop novel treatment strategies to improve healing when the immune system or inflammation is dysregulated.

Mesenchymal stem cell transplantation in polytrauma: Evaluation of bone and liver healing response in an experimental rat model.

Trauma is the most common cause of death of young people in the world. As known, mesenchymal stem cells (MSCs) accelerate tissue regeneration mechanisms. In our study, we aimed to investigate the effects of MSCs transplantation on the healing of liver and bone tissue by considering trauma secondary inflammatory responses. 56 adult Wistar-albino rats were divided into two groups: the polytrauma (liver and bone) (n = 28), and the liver trauma group (n = 28). At 36h and 5th day after surgery, both rats with polytrauma and with isolated liver injury received either intravenous (IV) or intraperitoneal (IP) injections of MSCs (one million cells per kg body weight). Untreated groups received IV and IP saline injections. At day 21 after surgery, liver, tibia and fibula of the subjects were excised and evaluated for histopathologic and histomorphometric examination. Additionally, whole blood count (white blood cells, hemoglobin and platelets), C-reactive protein (CRP), glucose, alanine aminotransferase (ALT), aspartate aminotransferase (AST), albumin, blood gas, and trauma markers interleukin-1B (IL-1B), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF alpha) levels were investigated. In general, MSC transplantations were well tolerated by the subjects. It was found that ALT, CRP, albumin were significantly lower in rats which received MSCs (p < 0.001). Inflammation of the liver and bone tissue in the MSC-injected rats were significantly lower than that of the untreated groups. Herewith we have shown that MSC infusion in posttraumatic rats leads to less aggressive and more effective consequences on liver and bone tissue healing. Human MSC treatment for trauma is still in early stages of development; thus standard protocols, and patient inclusion criteria should be established beforehand clinical trials.

Biomimetic Surfaces Coated with Covalently Immobilized Collagen Type I: An X-Ray Photoelectron Spectroscopy, Atomic Force Microscopy, Micro-CT and Histomorphometrical Study in Rabbits.

Background: The process of osseointegration of dental implants is characterized by healing phenomena at the level of the interface between the surface and the bone. Implant surface modification has been introduced in order to increase the level of osseointegration. The purpose of this study is to evaluate the influence of biofunctional coatings for dental implants and the bone healing response in a rabbit model. The implant surface coated with collagen type I was analyzed through X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM), micro-CT and histologically. Methods: The sandblasted and double acid etched surface coated with collagen type I, and uncoated sandblasted and double acid etched surface were evaluated by X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM) analysis in order evaluate the different morphology. In vivo, a total of 36 implants were positioned in rabbit articular femoral knee-joint, 18 fixtures for each surface. Micro-CT scans, histological and histomorphometrical analysis were conducted at 15, 30 and 60 days. Results: A histological statistical differences were evident at 15, 30 and 60 days (p < 0.001). Both implant surfaces showed a close interaction with newly formed bone. Mature bone appeared in close contact with the surface of the fixture. The AFM outcome showed a similar roughness for both surfaces. Conclusion: However, the final results showed that a coating of collagen type I on the implant surface represents a promising procedure able to improve osseointegration, especially in regions with a low bone quality.

Influence of the Thermal Treatment to Address a Better Osseointegration of Ti6Al4V Dental Implants: Histological and Histomorphometrical Study in a Rabbit Model.

Background Pure titanium continues to be the first choice for dental implants and represents the gold standard for their biocompatibility and physical and mechanical characteristics, while the titanium alloy (Ti6Al4V) has good mechanical properties. The surface structure of the titanium oxide layer formation on the surface influences and improves the bone response around dental implants. Purpose The purpose of this study is to evaluate the influence of a thermal treatment of Ti6Al4V implant surfaces and the bone healing response in a rabbit model. Methods Altogether sixteen implants with same design were inserted into the distal femoral metaphysis. A screw (13 mm long, 4 mm in diameter) was inserted in an implant bed. Each rabbit received two implants, one in the left femur and one in the right femur. The samples were histologically and histomorphometrically evaluated at 8 weeks. Results A statistically significant difference (p = 0.000034) was present histologically in the percentages of bone-implant contact (BIC) between the test group (BIC = 69.25±4.49%.) and control group (BIC = 56.25 ± 4.8%) by one-way analysis of variance (ANOVA). Significance was set at p ≤ 0.05. Conclusions The outcome of the present study indicates a novel approach to improving bone healing around titanium implants.

The roles of cellular and molecular components of a hematoma at early stage of bone healing.

Bone healing is a complex repair process that commences with the formation of a blood clot at the injured bone, termed hematoma. It has evidenced that a lack of a stable hematoma causes delayed bone healing or non-union. The hematoma at the injured bone constitutes the early healing microenvironment. It appears to dictate healing pathways that ends in a regenerative bone. However, the hematoma is often clinically removed from the damaged site. Conversely, blood-derived products have been used in bone tissue engineering for treating critical sized defects, including fibrin gels and platelet-rich plasma. A second generation of platelet concentrate that is based on leukocyte and fibrin content has also been developed and introduced in market. Conflicting effect of these products in bone repair are reported. We propose that the bone healing response becomes dysregulated if the blood response and subsequent formation and properties of a hematoma are altered. This review focuses on the central structural, cellular, and molecular components of a fracture hematoma, with a major emphasis on their roles in regulating bone healing mechanism, and their interactions with mesenchymal stem cells. New angles towards a better understanding of these factors and relevant mechanisms involved at the beginning of bone healing may help to clarify limited or adverse effects of blood-derived products on bone repair. We emphasize that the recreation of an early hematoma niche with critical compositions might emerge as a viable therapeutic strategy for enhanced skeletal tissue engineering.

TLR4 Inactivation in Myeloid Cells Accelerates Bone Healing of a Calvarial Defect Model in Mice.

Toll-like receptor 4 (TLR4) has been implicated in inflammation-induced bone destruction in various chronic bone diseases; however, its direct influence on bone healing is not well understood. The authors' previous study showed accelerated bone healing with higher osteoclastogenesis gene expression in toll-like receptor 4 knockout mice (TLR4). This study aimed to further elucidate the underlying cellular mechanisms during fracture healing by generating a myeloid cell-specific toll-like receptor 4 knockout model (Lyz-TLR4 mice). Calvarial defects, 1.8 mm in diameter, were created in wild-type, TLR4, and Lyz-TLR4 mice. Bone healing was investigated using micro-computed tomography and histologic, histomorphometric, and immunohistochemistry analyses. Primary bone marrow-derived cells were also isolated from wild-type, TLR4, and Lyz-TLR4 mice to measure their osteoclast differentiation and resorption properties. A similar faster bone healing response, with active intramembranous bone formation, intense osteopontin staining, and more osteoblast infiltration, was observed in TLR4 and Lyz-TLR4 mice. Tartrate-resistant acid phosphatase staining showed more osteoclast infiltration in Lyz-TLR4 mice than in wild-type mice at day 7. Primary bone marrow-derived cells isolated from TLR4 and Lyz-TLR4 mice presented enhanced osteoclastogenesis and resorption activity compared with those from wild-type mice. Comparable M0, M1, and M2 macrophage infiltration was found among all groups at days 1, 4, and 7. This study revealed that inactivation of toll-like receptor 4 in myeloid cells enhanced osteoclastogenesis and accelerated healing response during skull repair. Together with the role of toll-like receptor 4 in inflammation-mediated bone destruction, it suggests that toll-like receptor 4 might regulate inflammation-induced osteoclastogenesis under different clinical settings.

In vivo study of microarc oxidation coated biodegradable magnesium plate to heal bone fracture defect of 3 mm width

Microarc oxidation (MAO) coated magnesium (Mg) with improved corrosion resistance appeal increasing interests as a revolutionary biodegradable metal for fractured bone fixing implants application. However, the in vivo corrosion degradation of the implants and bone healing response are not well understood, which is highly required in clinic. In the present work, 10μm and 20μm thick biocompatible MAO coatings mainly composed of MgO, Mg2SiO4, CaSiO3 and Mg3(PO4)2 phases were fabricated on AZ31 magnesium alloy. The electrochemical tests indicated an improved corrosion resistance of magnesium by the MAO coatings. The 10μm and 20μm coated and uncoated magnesium plates were separately implanted into the radius bone fracture site of adult New Zealand white rabbits using a 3mm width bone fracture defect model to investigate the magnesium implants degradation and uninhibited bone healing. Taking advantage of the good biocompatibility of the MAO coatings, no adverse effects were detected through the blood test and histological examination. The implantation groups of coated and uncoated magnesium plates were both observed the promoting effect of bone fracture healing compared with the simple fracture group without implant. The releasing Mg2+ by the degradation of implants into the fracture site improved the bone fracture healing, which is attributed to the magnesium promoting CGRP-mediated osteogenic differentiation. Mg degradation and bone fracture healing promoting must be tailored by microarc oxidation coating with different thickness for potential clinic application.

Efficacy comparison of Accell Evo3 and Grafton demineralized bone matrix putties against autologous bone in a rat posterolateral spine fusion model

Background ContextSpinal fusion procedures are intended to stabilize the spinal column for a multitude of disorders including abnormal curvature, traumatic instability, degenerative instability, and damage from infections or tumors. As an aid in the bone healing response, bone graft materials are used to bridge joints for arthrodesis and promote unions in pseudoarthrosis. Currently, the gold standard for stabilizing fusion masses in spinal procedures involves using the osteogenic, osteoinductive, and osteoconductive properties of autologous iliac crest corticocancellous bone. However, considerable morbidity is associated with harvesting the autologous graft. Donor site complications including infection, large hematomas, and pain have been reported at rates as high as 50% (Boden and Jeffrey, 1995). Biologically, the rate of bone repair dictates the rate at which the fusion mass will unite under autologous graft conditions. PurposeThe purpose of this study is to compare the quality and rate of fusion between Accell Evo3 and Grafton demineralized bone matrix (DBM), with the gold standard iliac crest bone graft (ICBG) as the control, in athymic rat posterolateral fusion. Study DesignThis study was a randomized, controlled study in a laboratory setting at the Hospital for Special Surgery in New York City. Blinded observations were made, which created an assessment of outcomes for successful fusions between each method. Patient SampleForty-eight (48) athymic rats were used in this study and underwent posterolateral lumbar fusion. They were assessed at either 3 weeks or 9 weeks to see the rate and efficacy of fusion. Outcome MeasuresOutcome measures will be the efficacy of the different bone grafts and their success rates of fusion in the rats. MethodsA comparison of the quality and rate of fusion between Accell Evo3® (DBM A) and Grafton (DBM B), with the gold standard iliac crest bone graft (ICBG) as the control, was performed using the established posterolateral intertransverse process on an athymic rat model. Materials were evaluated for fusion by several criteria, including manual palpation, standard and high-resolution radiographic imaging, micro-computed topography, and histologic analysis. Forty-eight (48) athymic rats received a bilateral intertransverse process fusion, using either bone from the iliac crest (control group), Accell Evo3, or Grafton. Twelve (12) rats (four from each group) were sacrificed at 3 weeks postoperatively, whereas the remaining thirty-six (36) were sacrificed at 9 weeks postoperatively. Three blinded observers examined the spines after the rats were euthanized, and they blindly assessed each rat for fusion success. ResultsManual palpation of the three different groups at 3 weeks postoperatively found successful fusion in 1 of 4 (25%) of the autologous bone graft (ABG) group and 4 of 4 (100%) of both DBM A and B groups. Manual palpation of the remaining animals that were sacrificed at 9 weeks postoperatively showed successful fusion in 4 of 12 (33%) of the ABG group, 8 of 12 (66%) of the DBM A group, and 12 of 12 (100%) of the DBM B group. Radiography found that 9 of 16 (56%) of the ABG group and 16 of 16 (100%) of both DBM Putty A and B groups had fused. Histologic analysis of the ABG group demonstrated less mature and less organized osteoid at both 3 and 9 weeks than the DBM Putty A and B groups. Nondestructive mechanical testing demonstrated increased stiffness in 4-point bending of both DBM A and B compared with ABG. ConclusionsBoth DBM-treated groups achieved a significantly higher rate of fusion than the ABG-treated group at 9 weeks in this model. Successful fusion was also demonstrated in the DBM-treated groups at 3 weeks.

Soft tissues and bone healing response in impacted third molar osteotomies

Objective: To determine differences between bone healing and soft tissues in the lower jaw of patients subjected to impacted third molar extraction after using a high and low speed rotary devices. Material and methods: Crossed clinical assay-type intervention study. Under local anesthsesia, forty tooth extractions were performed (right and left) from 20 healthy patients. Two groups were thus formed: in group 1 high speed hand-piece was used, in group 2, low speed hand-piece was employed. Index cards were used to record time devoted to each patient as well as preoperative and postoperative clinical data related to inflammation, pain, opening limitations, bone healing and periodontal changes in the adjacent teeth. Results: When comparing high and low speed hand-pieces, statistically significant differences were found between pain, surgical time and probing depth; it was observed that low speed hand-piece generated lesser aggression to soft tissues. Conclusions: Accurate use of low speed hand-pieces allows a decrease of surgical time thus providing the patients with more suitable postoperative evolution.

Effect of Butyrate on Collagen Expression, Cell Viability, Cell Cycle Progression and Related Proteins Expression of MG-63 Osteoblastic Cells.

AimsButyric acid is one major metabolic product generated by anaerobic Gram-negative bacteria of periodontal and root canal infection. Butyric acid affects the activity of periodontal cells such as osteoblasts. The purposes of this study were to investigate the effects of butyrate on MG-63 osteoblasts.MethodsMG-63 cells were exposed to butyrate and cell viability was estimated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The mRNA and protein expression of type I collagen and cell cycle-related proteins were measured by reverse-transcriptase polymerase chain reaction (RT-PCR), western blotting or immunofluorescent staining. Cellular production of reactive oxygen species (ROS) was analyzed by 2',7'-dichlorofluorescein (DCF) fluorescence flow cytometry.ResultsExposure to butyrate suppressed cell proliferation, and induced G2/M (8 and 16 mM) cell cycle arrest of MG-63 cells. Some cell apoptosis was noted. The mRNA expression of cdc2 and cyclin-B1 decreased after exposure to butyrate. The protein expression of type I collagen, cdc2 and cyclin B1 were decreased, whereas the expression of p21, p27 and p57 was stimulated. Under the treatment of butyrate, ROS production in MG-63 cells markedly increased.ConclusionsThe secretion of butyric acid by periodontal and root canal microorganisms may inhibit bone cell growth and matrix turnover. This is possibly due to induction of cell cycle arrest and ROS generation and inhibition of collagen expression. These results suggest the involvement of butyric acid in the pathogenesis of periodontal and periapical tissue destruction by impairing bone healing responses.

The role of peptides in bone healing and regeneration: a systematic review.

BackgroundBone tissue engineering and the research surrounding peptides has expanded significantly over the last few decades. Several peptides have been shown to support and stimulate the bone healing response and have been proposed as therapeutic vehicles for clinical use. The aim of this comprehensive review is to present the clinical and experimental studies analysing the potential role of peptides for bone healing and bone regeneration.MethodsA systematic review according to PRISMA guidelines was conducted. Articles presenting peptides capable of exerting an upregulatory effect on osteoprogenitor cells and bone healing were included in the study.ResultsBased on the available literature, a significant amount of experimental in vitro and in vivo evidence exists. Several peptides were found to upregulate the bone healing response in experimental models and could act as potential candidates for future clinical applications. However, from the available peptides that reached the level of clinical trials, the presented results are limited.ConclusionFurther research is desirable to shed more light into the processes governing the osteoprogenitor cellular responses. With further advances in the field of biomimetic materials and scaffolds, new treatment modalities for bone repair will emerge.

Influence of Additives to Bovine Bone Material in Osseous Regeneration of Mandibular Defect: An Animal Study using DXA

ABSTRACTIntroductionIncreasing bone quality and quantity in the areas with insufficient bone volume is a major concern among scientists. Ideal bone substitute materials should have osteogenicity, osteoconductivity, and osteoinductivity. Clinoptilolite offers bovine deorganified crystalline bone materials, the advantage of being very similar to human bone with regard to its pore morphology and crystalline structure. This study evaluated the effect of adding Clinoptilolite to Bio-Oss on the osseous regeneration and bone healing process using serial dual-energy X-ray absorptiometry (DXA).Materials and methodsA total of 64 rabbits were anesthetized and a bone defect was created on both semi-mandibles. The rabbits were divided into four equal groups: A (Bio-Oss®); B (Bio-Oss® with 2% Clinoptilolite mixture); C (allograft); and D receiving no treatment. The bone healing response of animals was tested after 2, 14, 30, and 60 days.ResultsStatistical analysis showed significant differences at time intervals before 14 days between allograft and other groups (p &lt; 0.05). In all the defects filled with the tested materials, bone formation was observed subjectively. At 30-and 60-day intervals, there were no significant differences between allograft and Bio-Oss with 2% Clinoptilolite group (p = 0.052 and p = 0.260 respectively) although it was significant in 2-and 14-day intervals.ConclusionClinoptilolite (2%) can be used to improve the osteoinduction property of bovine deorganified crystalline bone material. Clinoptilolite can be suggested as a potential material added to bone substitute materials due to its porous structure and buffering capacity and adsorption of a number of serum components which aids the osseous regeneration and healing process.How to cite this articleSaghiri MA, Orangi J, Tanideh N, Asatourian A, Garcia-Godoy F, Sheibani N. Influence of Additives to Bovine Bone Material in Osseous Regeneration of Mandibular Defect: An Animal Study using DXA. Int J Experiment Dent Sci 2016;5(2):104-108.

Alteration of Masquelet's induced membrane characteristics by different kinds of antibiotic enriched bone cement in a critical size defect model in the rat's femur

The Masquelet technique for the treatment of large bone defects consists of a 2-stage procedure. In the first stage, a polymethylmethacrylate (PMMA) cement spacer is inserted into the bony defect of a rat's femur and over a period of 2–4 weeks a membrane forms that encapsulates the defect/spacer. In a second operation the membrane is opened, the PMMA spacer is removed and the resulting cavity is filled with autologous bone. Different kinds of bone cements are available, with or without supplemental antibiotics. Both might influence the development and the characteristics of the induced membrane which might affect the bone healing response. Hence, this comparative study was performed to elucidate the effect of different bone cements with or without supplemental antibiotics on the development of an induced membrane in a critical size femur defect model in rats.A total of 72 male SD rats received a 10mm critical size defect of the femur which was stabilised by a plate osteosynthesis and filled with either Palacos+Gentamycin, Copal Gentamycin+Vancomycin, Copal+Gentamycin+Clindamycin or Copal Spacem. The induced membranes were analysed after two, four and six weeks (wks) after insertion of the cement spacers (n=6/group). Paraffin embedded histological sections of the membrane were microscopically analysed for membrane thickness, elastic fibres, vascularisation and proliferation by an independent observer blinded to the group setup.The thickness of the induced membrane increased significantly from 2 wks (553μm) to 6 wks (774μm) in group Palacos+Gentamycin whereas membrane thickness decreased significantly in groups Copal+Gentamycin+Clindamycin (682–329μm) and Copal Spacem (916μm to 371μm). The comparison between the groups revealed significantly increased membrane thickness in group Palacos+Gentamycin and Copal Gentamycin+Vancomycin in comparison to group Copal+Gentamycin+Clindamycin six weeks after induction. However, the fraction of elastic fibres was significantly increased in groups Copal+Gentamycin+Clindamycin (71%, 80%) and Copal Spacem (82%, 81%) after 2 and 4 weeks in comparison to the groups Palacos+Gentamycin (56%, 57%) and Copal Gentamycin+Vancomycin (63%, 69%). Those differences however were partly diminished after 6 wks. The ratio of immature (vWF+) to more mature (CD31+) blood vessels increased significantly in groups Palacos+Gentamycin and Copal Gentamycin+Vancomycin whereas no significant alterations were noted in groups Copal+Gentamycin+Clindamycin and Copal Spacem.For the first time we demonstrated that thickness and proportion of elastic fibres in induced membranes were influenced by the type of cement and the kind of supplemental antibiotics being used. Whether these alterations of the induced membrane have an effect on bone healing remains to be proven in future studies.

Impaired Fracture Healing after Hemorrhagic Shock.

Impaired fracture healing can occur in severely injured patients with hemorrhagic shock due to decreased soft tissue perfusion after trauma. We investigated the effects of fracture healing in a standardized pressure controlled hemorrhagic shock model in mice, to test the hypothesis that bleeding is relevant in the bone healing response. Male C57/BL6 mice were subjected to a closed femoral shaft fracture stabilized by intramedullary nailing. One group was additionally subjected to pressure controlled hemorrhagic shock (HS, mean arterial pressure (MAP) of 35 mmHg for 90 minutes). Serum cytokines (IL-6, KC, MCP-1, and TNF-α) were analyzed 6 hours after shock. Fracture healing was assessed 21 days after fracture. Hemorrhagic shock is associated with a significant increase in serum inflammatory cytokines in the early phase. Histologic analysis demonstrated a significantly decreased number of osteoclasts, a decrease in bone quality, and more cartilage islands after hemorrhagic shock. μCT analysis showed a trend towards decreased bone tissue mineral density in the HS group. Mechanical testing revealed no difference in tensile failure. Our results suggest a delay in fracture healing after hemorrhagic shock. This may be due to significantly diminished osteoclast recruitment. The exact mechanisms should be studied further, particularly during earlier stages of fracture healing.

A comparative study of calcium sulfate artificial bone graft versus allograft in the reconstruction of bone defect after tumor curettage

Background Cavity reconstruction after benign bone tumor removal is varied and controversial. Allograft is widely used but is associated with complications. New bone substitutes, such as calcium sulfate artificial bone, have been introduced for bone tumor operation. However, the bone healing response of artificial bone has not been compared with allograft bone. We therefore compared calcium sulfate grafts (study group) with bone allografts (control group) for the treatment of benign bone tumors. Methods We retrospectively reviewed 50 patients who underwent calcium sulfate reconstruction and 50 patients who underwent allograft cancellous bone reconstruction. The two groups were well matched. The mean follow-up time of the study group was 19.9 (12–55) months. We investigated bone healing response, complications, and factors affecting bone healing. Results At the last follow-up, 84% (42/50) of cases in the study group and 62% (31/50) of cases in the control group had achieved clinical healing (P=0.013). The initial healing rate showed no significant difference between the two groups (100% vs. 96%, P=0.153). The mean healing times for calcium sulfate and allograft bone were 9.6 (3–42) months and 13.8 (3–36) months, respectively (P &lt;0.01). Complications in the study group were minor and resolved. Implant volume was a significant factor affecting bone healing. Conclusion The calcium sulfate bone substitute showed a satisfactory healing outcome and safety profile in reconstruction of bone defects after benign bone tumor curettage, especially in smaller cavities.

High-frequency loading positively impacts titanium implant osseointegration in impaired bone

High-frequency loading via whole body vibration promotes bone formation and increases bone strength. Whether this translates to positive titanium implant osseointegration in osteoporotic bone was explored in this animal study. An anabolic effect of not only bisphosphonate treatment but also high-frequency loading on implant osseointegration in osteoporotic bone was observed. The present study investigated the impact of high-frequency (HF) loading, applied via whole body vibration (WBV), on titanium implant osseointegration in healthy versus ovariectomy-induced compromised versus pharmacologically treated compromised bone. A custom-made Ti implant was inserted into the metaphyseal tibia of 59 rats and left to heal for either 4 or 14 days. Rats were divided into six groups according to their hormonal and mechanical status. WBV, consisting of 10 consecutive frequency steps at an acceleration of 0.3 g, was applied daily for either 4 or 14 days. Tissue samples were processed for quantitative histology at the tibial cortical and medullar level. Data were analyzed by three-way ANOVA and by post hoc pairwise comparisons. The bone healing response at the interface and surrounding titanium implants was negatively influenced by osteoporotic bone conditions, mainly at the trabecular bone level. Furthermore, the administration of bisphosphonates for preventing the ovariectomy-induced impaired peri-implant response was successful. Finally, the effect of HF WBV loading on the peri-implant bone healing was dependent on the bone condition and was anabolic solely in untreated osteoporotic trabecular bone when applied for an extended period of time. The bone healing response to implant installation is compromised in osteoporotic bone conditions, in particular at the trabecular bone compartment. Meanwhile, not only pharmacological treatment but also mechanical loading via HF WBV can exert a positive effect on implant osseointegration in this specific bone micro-environment. The peri-implant cortical bone, however, seems to be less sensitive to HF WBV loading influences.