Porosity and surface curvature effects on the permeability and wall shear stress of trabecular bone: Guidelines for biomimetic scaffolds for bone repair.

Scaffolds are an essential component of bone tissue engineering to provide support and create a physiological environment for cells. Biomimetic scaffolds are a promising approach to fulfill the requirements. Bone allografts are widely used scaffolds due to their mechanical and structural characteristics. The scaffold geometry is well known to be an important determinant of induced mechanical stimulation felt by the cells. However, the impact of allograft geometry on permeability and wall shear stress distribution is not well understood. This information is essential for designing biomimetic scaffolds that provide a suitable environment for cells to proliferate and differentiate. The present study investigates the effect of geometry on the permeability and wall shear stress of bone allografts at both macroscopic and microscopic scales. Our results concluded that the wall shear stress was strongly correlated with the porosity of the allograft. The level of wall shear stress at a local scale was also determined by the surface curvature characteristics. The results of this study can serve as a guideline for future biomimetic scaffold designs that provide a mechanical environment favorable for osteogenesis and bone repair.

The survey of bone allograft transplantation in a Japanese regional bone bank.

BACKGROUND: In reconstructive surgery for large bone defects, the demand for bone allografts has increased over the years; however, it is unclear how the supply and demand in Japanese regional bone banks have evolved over time. This study investigated the 15-year supply and demand of bone allografts stored in a regional bone bank, along with assessing the screening process's effectiveness. METHODS: The target period was 15 years from April 2005 to March 2020. The period was subdivided into three 5-year periods: first, second, and third. The study items included the number of bone allografts donated, the number of bone allografts used, donor and user facilities, surgical methods using bone allografts, and the number of bone allografts discarded. We used the Cochran-Armitage test for statistical analysis. RESULTS: A total of 1852 bone allografts were donated to the bone bank, and a total of 1721 were used. A total of 677 bone allografts grafts were provided in the first period, 738 in the second period, and 525 in the third period, indicating a decreasing trend. The average number of allografts per surgery was 2.8 in the first, 3.1 in the second, and 1.7 in the third, showing a decreasing trend. Concerning the percentage of each surgery using bone allografts, spine fusion decreased in the third period but not significantly, whereas primary hip arthroplasty increased significantly in the third period. The total number of discarded bone allografts was 4.8% of the total number of donated bone allografts, largely because of a lack of screening tests. CONCLUSION: Although the number of allogeneic bone surgeries has been increasing over time, the number of allogeneic bone donations has shown a decreasing trend, and there is a need to develop a system that can provide surgeons with sufficient bone allografts.

Use of Injectable Platelet-Rich Fibrin Accompanied by Bone Graft in Socket Endurance: A Radiographic and Histological Study.

Background Ridge preservation became a crucial dental health issue and strategy to keep away from ridge defacement after post-tooth loss. The recent scientific evolution of platelet-rich fibrin (PRF) comprises a parenteral formulation of PRF. The combined allograft for socket preservation gives benefits. In this study, bone allografts, demineralized freeze-dried bone allografts (DFDBA) and freeze-dried bone allografts (FDBA) are used in a 30:70 ratio alone or in combination with injectable PRF (I-PRF) for socket preservation. Methods This study is a radiographic and histological examination conducted on 60 participants aged between 19-65 years. Participating patients agreed voluntarily that they would not bear any fixed prosthesis for the next nine months and plan for implanted teeth placement, including multi-rooted mandibular molars denticles. Both groups received atraumatic extraction; then, the socket was preserved with bone allograft alone in the control group and bone allograft mixed with I-PRF, forming sticky bone, in the experimental group. Clinical, radiological, and histological assessments were taken at the inception stage, three months, six months, and nine months. A multivariate regression model and a generalized estimating equation (GEE) model were used to analyse the effects of these changes on outcomes. Results In all the parameters, the test group indicated a good amount of bone growth with increasing intervals of time for bone height radiographically with statistically significant difference present (p<0.05) and histologically after nine months when socket site grafted with bone graft in combination with I-PRF. Conclusion This study's results demonstrated that I-PRF possesses the potential to regenerate and heal in the tooth-extracted socket. This study further recommends the implementation of I-PRF in safeguarding and conserving the raised rim of the tooth. Future research should take place on the osteogenic capability of I-PRF in more comprehensive ridge accession surgical procedures and additional expanding and improving capacities in periodontal reconstruction.

A New Microarchitecture-Based Parameter to Predict the Micromechanical Properties of Bone Allografts.

Scaffolds are an essential component of bone tissue engineering. They provide support and create a physiological environment for cells to proliferate and differentiate. Bone allografts extracted from human donors are promising scaffolds due to their mechanical and structural characteristics. Bone microarchitecture is well known to be an important determinant of macroscopic mechanical properties, but its role at the microscopic, i.e., the trabeculae level is still poorly understood. The present study investigated linear correlations between microarchitectural parameters obtained from X-ray computed tomography (micro-CT) images of bone allografts, such as bone volume fraction (BV/TV), degree of anisotropy (DA), or ellipsoid factor (EF), and micromechanical parameters derived from micro-finite element calculations, such as mean axial strain (εz) and strain energy density (We). DAEF, a new parameter based on a linear combination of the two microarchitectural parameters DA and EF, showed a strong linear correlation with the bone mechanical characteristics at the microscopic scale. Our results concluded that the spatial distribution and the plate-and-rod structure of trabecular bone are the main determinants of the mechanical properties of bone at the microscopic level. The DAEF parameter could, therefore, be used as a tool to predict the level of mechanical stimulation at the local scale, a key parameter to better understand and optimize the mechanism of osteogenesis in bone tissue engineering.

Osteogenic differentiation of mesenchymal stem cells cultured on allogenic trabecular bone grafts treated with high hydrostatic pressure.

The requirements for bone substitute materials are multifaceted. Beside biomechanical stability, these materials should provide osteoconductive and osteoinductive properties to promote integration into the host tissue. So far, autologous bone is the only material, which combines all properties, but is naturally limited. Allogenic bone grafts have to be decellularized prior to implantation. This causes the reduction of biomechanical properties and the loss of osteoinductive qualities. High hydrostatic pressure (HHP) offers a gentle alternative for processing and supply of allogenic bone substitute materials while preserving biomechanical integrity. To determine whether osteogenic properties are retained by HHP treatment, mesenchymal stem cells (MSCs) were cultured with HHP-treated and untreated allogenic trabecular bone blocks up to 28 days. Both, gene expression and protein analysis showed that HHP-treated bone positively influenced differentiation of MSCs into osteoblasts and mineralization of bone matrix. This effect was greater in samples cultivated with HHP-treated bone blocks. The present study shows that HHP treatment does not result in the reduction of osteoinductivity, thus serving as an alternative approach for processing allogeneic bone substitute materials.

Effect of gamma rays and accelerated electron beam on medullary lipids decomposition: influence of dose and irradiation temperature.

Ionizing radiation sterilization of non-defatted bone grafts has been found to deteriorate their quality and biocompatibility due to induction of lipid peroxidation products toxic for osteoblast-like cells. Therefore, the purpose of our study was to evaluate the effect of two types of ionizing radiation-gamma rays (G) or accelerated electron beam (EB) applied with two doses at different temperature conditions on hydrocarbons production, resulting from decomposition of palmitic and oleic acids-most abundant fatty acids in medullary lipids. Bone marrow samples isolated from femoral shafts of 6 male donors (aged 46-67 years) were irradiated with G or EB with doses of 25 or 35 kGy at different temperature conditions (ambient or deep freezing temperature). Fresh-frozen, non-irradiated samples served as control. Marrow lipids were extracted with n-hexane (Soxhlet's method), hydrocarbons fraction isolated on Florisil column chromatography, separated by gas chromatography and detected by mass spectrometry. Irradiation of bone marrow with sterilization doses of ionizing radiation (G and EB) was found to induce lipid radiolysis as measured by resulting hydrocarbons production. The effect was dose-dependent, whereas no marked influence of radiation type was observed. In contrast, irradiation temperature had a profound effect on lipids decomposition which was partially prevented while irradiation was performed in deep frozen state. Defatting of bone grafts prior to ionizing radiation sterilization seems essential for their biocompatibility, whereas irradiation in a deep-frozen state might compromise the effectiveness of sterilization and needs further studies.

Decellularized vascularized bone grafts: A preliminary in vitro porcine model for bioengineered transplantable bone shafts.

Introduction: Durable reconstruction of critical size bone defects is still a surgical challenge despite the availability of numerous autologous and substitute bone options. In this paper, we have investigated the possibility of creating a living bone allograft, using the perfusion/decellularization/recellularization (PDR) technique, which was applied to an original model of vascularized porcine bone graft. Materials and Methods: 11 porcine bone forelimbs, including radius and ulna, were harvested along with their vasculature including the interosseous artery and then decellularized using a sequential detergent perfusion protocol. Cellular clearance, vasculature, extracellular matrix (ECM), and preservation of biomechanical properties were evaluated. The cytocompatibility and in vitro osteoinductive potential of acellular extracellular matrix were studied by static seeding of NIH-3T3 cells and porcine adipose mesenchymal stem cells (pAMSC), respectively. Results: The vascularized bone grafts were successfully decellularized, with an excellent preservation of the 3D morphology and ECM microarchitecture. Measurements of DNA and ECM components revealed complete cellular clearance and preservation of ECM's major proteins. Bone mineral density (BMD) acquisitions revealed a slight, yet non-significant, decrease after decellularization, while biomechanical testing was unmodified. Cone beam computed tomography (CBCT) acquisitions after vascular injection of barium sulphate confirmed the preservation of the vascular network throughout the whole graft. The non-toxicity of the scaffold was proven by the very low amount of residual sodium dodecyl sulfate (SDS) in the ECM and confirmed by the high live/dead ratio of fibroblasts seeded on periosteum and bone ECM-grafts after 3, 7, and 16 days of culture. Moreover, cell proliferation tests showed a significant multiplication of seeded cell populations at the same endpoints. Lastly, the differentiation study using pAMSC confirmed the ECM graft's potential to promote osteogenic differentiation. An osteoid-like deposition occurred when pAMSC were cultured on bone ECM in both proliferative and osteogenic differentiation media. Conclusion: Fully decellularized bone grafts can be obtained by perfusion decellularization, thereby preserving ECM architecture and their vascular network, while promoting cell growth and differentiation. These vascularized decellularized bone shaft allografts thus present a true potential for future in vivo reimplantation. Therefore, they may offer new perspectives for repairing large bone defects and for bone tissue engineering.

The potential of radiation sterilized and banked tissue allografts for management of nuclear casualties.

Processed and radiation sterilized allograft tissues that can be banked for use on demand are a precious therapeutic resource for the repair or reconstruction of damaged or injured tissues. Skin dressings or skin substitutes like allograft skin, amniotic membrane and bioengineered skin can be used for the treatment of thermal burns and radiation induced skin injuries. Bone grafts can be employed for repairing fracture defects, filling in destroyed regions of bone, and treatment of spinal and joint injuries. A nuclear scenario would result in a large number of casualties due to the heat, blast and radiation effects of the weapon. Perspective of radiation sterilized biological tissues provided by the tissue banks for management of casualties in a nuclear disaster scenario is presented.

Commercial Bone Grafts Claimed as an Alternative to Autografts: Current Trends for Clinical Applications in Orthopaedics.

In the last twenty years, due to an increasing medical and market demand for orthopaedic implants, several grafting options have been developed. However, when alternative bone augmentation materials mimicking autografts are searched on the market, commercially available products may be grouped into three main categories: cellular bone matrices, growth factor enhanced bone grafts, and peptide enhanced xeno-hybrid bone grafts. Firstly, to obtain data for this review, the search engines Google and Bing were employed to acquire information from reports or website portfolios of important competitors in the global bone graft market. Secondly, bibliographic databases such as Medline/PubMed, Web of Science, and Scopus were also employed to analyse data from preclinical/clinical studies performed to evaluate the safety and efficacy of each product released on the market. Here, we discuss several products in terms of osteogenic/osteoinductive/osteoconductive properties, safety, efficacy, and side effects, as well as regulatory issues and costs. Although both positive and negative results were reported in clinical applications for each class of products, to date, peptide enhanced xeno-hybrid bone grafts may represent the best choice in terms of risk/benefit ratio. Nevertheless, more prospective and controlled studies are needed before approval for routine clinical use.

Barriers to the Development and Sustainability of Bone Banking Programs in Low- and Middle-Income Countries: A Systematic Review.

Purpose: The number of bone allograft transplantations required in low- and middle-income countries (LMICs) is growing very quickly. No previous study has investigated the challenges clinical banks face to sustain operations or meet this demand. The purpose of this study was to conduct a systematic review of the barriers to implementation and sustainability of clinical bone tissue banks in LMICs. Barriers identified in clinical bone banking can shed light on strategies for overcoming obstacles in other biobanking programs. Methods: A systematic review protocol was registered with PROSPERO under identification number CRD42019136045. LMIC was defined using World Bank criteria. A search strategy targeting PubMed, Cumulative Index of Nursing and Allied Health Literature (CINAHL), and the World Health Organization (WHO) Global Health Library was used. Studies from the inception of bone banking until June 4, 2019, that discussed an identifiable barrier to bone banking were included. Study quality was assessed using The Critical Appraisals Skills Programme (CASP) Qualitative Checklist. Results: Of studies identified, 33 studies were included in the final analysis. Based on the full-text review, the primary barriers identified were lack of regulation, low donor rates, and insufficient training and staffing. CASP analysis performed on the 24 qualitative articles showed an average of 3.6 qualitative measurements met. Conclusions: As international organizations such as the International Atomic Energy Agency (IAEA) restructure their participation in global bone banking regulation, these barriers such as lack of regulation, low donor rates, and insufficient training and staffing could pose a challenge to meeting the rising demand for bone transplantation in LMICs. Articles with higher quality evidence are needed to better define barriers and propose evidence-based solutions.

Biomechanical properties enhancement of gamma radiation-sterilized cortical bone using antioxidants.

Gamma radiation sterilization is the method used by the majority of tissue banks to reduce disease transmission from infected donors to recipients through bone allografts. However, many studies have reported that gamma radiation impairs the structural and mechanical properties of bone via formation of free radicals, the effect of which could be reduced using free radical scavengers. The aim of this study is to examine the radioprotective role of hydroxytyrosol (HT) and alpha lipoic acid (ALA) on the mechanical properties of gamma-sterilized cortical bone of bovine femur, using three-point bending and microhardness tests. Specimens of bovine femurs were soaked in ALA and HT for 3 and 7 days, respectively, before being exposed to 35-kGy gamma radiation. In unirradiated samples, both HT and ALA pre-treatment improved the cortical bone bending plastic properties (maximum bending stress, maximum bending strain, and toughness) without affecting microhardness. Irradiation resulted in a drastic reduction of the plastic properties and an increased microhardness. ALA treatment before irradiation alleviated the aforementioned reductions in maximum bending stress, maximum bending strain, and toughness. In addition, under ALA treatment, the microhardness was not increased after irradiation. For HT treatment, similar effects were found. In conclusion, the results indicate that HT and ALA can be used before irradiation to enhance the mechanical properties of gamma-sterilized bone allografts.

Human bone and amniotic membrane banking in Bangladesh for grafting: the impact of the international atomic energy agency (IAEA) programme.

The idea of establishing a human tissue bank in Bangladesh was started in 1985. However, in 2003, with the active cooperation of international atomic energy agency (IAEA) and Bangladesh Atomic Energy Commission, a tissue bank laboratory was upgraded as a unit for tissue banking and research. Due to increasing demand of allograft, this unit was transformed as an independent institute "Institute of Tissue Banking and Biomaterial Research (ITBBR)" in 2016. This is the only human tissue bank in Bangladesh, which processes human bone and amniotic membrane to provide safe and cost-effective allografts for transplantation. Importantly, banking of human cranial bone as autograft has also started at ITBBR. These processed grafts are sterilized using gamma radiation according to the IAEA Code of Practice for the radiation sterilization of tissues allografts. The amount of grafts produced by the ITBBR from 2007 to 2018 were 120,800 cc of bone chips, 45,420 cm2 of amniotic membranes, 277 vials of de-mineralized bone granules (DMB), 95 pieces of massive bones, and 134 pieces of cranial bones. Overall, 112,748 cc of bone chips, 40,339 cm2 of amniotic membranes, 174 vials of DMB, 44 pieces of massive bones, and 64 pieces of cranial bones were transplanted successfully. Nevertheless, to cope up with the modern advanced concepts of cell and tissue banking for therapeutic purpose, ITBBR is working to set up facilities for skin banking, stem cells banking including amniotic and cord blood derived stem cells and scaffold designing. To ensure the quality, safety, ethical and regulatory issues are sustainable in cell and tissue banking practices, ITBBR always works with the Government of Bangladesh for enhancing the national tissue transplantation programme within the contemporary facilities.

Calvarial bone defects in ovariectomised rats treated with mesenchymal stem cells and demineralised freeze-dried bone allografts.

BACKGROUND: The aim of the study was to investigate the ability of a combination of bone marrow mesenchymal stem cells (BM-MSCs) with and without demineralised freeze-dried bone allografts (DFDBAs) to induce bone regeneration in calvarial defects in ovariectomised rats. MATERIALS AND METHODS: Critical size defects were filled with a combination of DFDBAs and BM-MSCs or BM-MSCs alone. Eight weeks after calvarial surgery, the rats were sacrificed. The samples were analysed histologically and immunohistochemically. RESULTS: No difference was observed in vascularisation between groups C1 (animals with cranial defect only, control group) and O1 (animals with cranial defect only, ovariectomy group). Intramembranous ossification was observed at a limited level in groups C2 (animals with cranial defect with MSCs, control group) and O2 (animals with cranial defect with MSCs, ovariectomy group) compared to C1 and O1. In group C3 (animals with DFDBAs with MSCs, control group), the fibrous structures of the matrix became compact as a result of a bone graft having been placed in the cavity, but in group O3 (animals with DFDBAs with MSCs, ovariectomy group), the fibrous tissue was poorly distributed between the bone grafts for the most parts. CONCLUSIONS: We conclude that the insertion of BM-MSCs enhances bone healing; however, the DFDBA/BM-MSC combination has little effect on overcoming impaired bone formation in ovariectomised rats.

Bone Augmentation and Simultaneous Implant Placement with Allogenic Bone Rings and Analysis of Its Purification Success.

The main objective of this manuscript was to demonstrate the use of freeze-dried bone allografts (FDBA) by means of a technique of simultaneous bone augmentation and implant placement ("Bone Ring Technique") in different indications, i.e., ridge reconstruction and sinus floor elevation procedure with a maxillary bone height of less than 4 mm. Moreover, cases with an up to 3-year follow-up were chosen to analyze the techniques of mid-term clinical success. Finally, the purification success of the FDBA was analyzed by means of established scanning electron microscopic (SEM) and histological methods. The FBDA bone ring was applied in three different patients and indications and presented; the healing success was analyzed on the basis of radiographical and clinical images. For analysis of the purification of the allogeneic bone, previously established histological methods and scanning electron microscopy (SEM) were applied. All analyzed patient cases showed that the FDBA-based bone ring was fully integrated into newly built alveolar bone. Furthermore, the observations revealed that the three-dimensional bone reconstructions in maxilla and mandible were stable within the observational period of up to 3 years. Altogether, the present data show that the application of the Bone Ring Technique using the FDBA rings allows for successful regeneration of alveolar bone with a predictable clinical outcome, functionality and esthetics. Moreover, the material analyses showed that the allogeneic bone tissue was free of cells or cell remnants, while the (ultra-) structure of the bone matrix has been retained. Thus, the biological safety of the FDBA has been confirmed.

Pre-clinical evaluation of bone allograft toughened with a novel sterilization method: An in vivo rabbit study.

Bone allografts often undergo γ-irradiation sterilization to decrease infection risk. However this consequently degrades bone collagen and makes the allograft brittle. Our laboratory has previously found that pre-treatment with ribose ex vivo protects the bone. However, it remains unclear whether or not ribose-treated γ-irradiated allografts are able to unite and remodel in vivo. Using New Zealand White rabbits (NZWr), we aimed to evaluate if ribose-treated allografts can unite with host bone (compared to untreated (fresh-frozen) and conventionally-irradiated allografts). A critically-sized defect was created in the radii of NZWr and reconstructed with allografts fixed with an intramedullary Kirschner wire. Healing and union were assessed at 2, 6, and 12 weeks post operation, with radiographs, µCT, static and dynamic histomorphometry, backscatter electron microscopy, and torsion testing. Intramedullary fixation achieved stable reconstructions and bony union in all groups and no differences were found in the radiographic and biomechanical parameters tested. Interestingly, γ-irradiated allografts had significantly less bone volume due to evident resorption of the grafts. In contrast, ribose pre-treatment protected γ-irradiated allografts from this bone loss, with results similar to the fresh frozen controls. In conclusion, ribose-pretreated γ-irradiated allografts were able to unite in vivo. In addition to achieving bony union with host bone, ribose pre-treatment may protect against allograft resorption. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

The role of biologic in foot and ankle trauma-a review of the literature.

PURPOSE OF REVIEW: The use of biologics in orthopedics is becoming increasingly popular as an adjuvant in healing musculoskeletal injuries. Though many biologics involved in the management of foot and ankle injuries are used based on physician preference, reports of improved outcomes when combined with standard operative treatment has led to further clinical interest especially in foot and ankle trauma. RECENT FINDINGS: The most recent studies have shown benefits for biologic use in patients predisposed to poor bone and soft tissue healing. Biologics have shown benefit in treating soft tissue injuries such as Achilles ruptures as well as the complications of trauma such as non-unions and osteoarthritis. Biologics have shown some benefit in improving functional and pain scores, as well as reducing time to heal in foot and ankle traumatic injuries, with particular success shown with patients that have risk factors for poor healing. As the use of biologics continues to increase, there is a need for high-level studies to confirm early findings of lower level reports.

Performance of cooling materials and their composites in maintaining freezing temperature during irradiation and transportation of bone allografts.

PURPOSE: Bone allografts supplied by University Malaya Medical Centre Bone Bank are sterilized by gamma radiation at 25 kGy in dry ice (DI) to minimize radiation effects. Use of cheaper and easily available cooling materials, gel ice (GI) and ice pack (IP), was explored. Composites of DI and GI were also studied for the use in routine transportations and radiation process. METHODS: (a) Five dummy bones were packed with DI, GI, or IP in a polystyrene box. The bone temperatures were monitored while the boxes were placed at room temperature over 96 h. Durations for each cooling material maintaining freezing temperatures below -40°C, -20°C, and 0°C were obtained from the bone temperature over time profiles. (b) Composites of DI (20, 15, 10, 5, and 0 kg) and GI were used to pack five dummy bones in a polystyrene box. The durations maintaining varying levels of freezing temperature were compared. RESULTS: DI (20 kg) maintained temperature below -40°C for 76.4 h as compared to 6.3 h in GI (20 bags) and 4.0 h in IP (15 packs). Composites of 15DI (15 kg DI and 9 GI bags) and 10DI (10 kg DI and 17 GI bags) maintained the temperature below -40°C for 61 and 35.5 h, respectively. CONCLUSION: Composites of DI and GI can be used to maintain bones in deep frozen state during irradiation, thus avoiding radiation effects on biomechanical properties. Sterile frozen bone allograft with preserved functional properties is required in clinical applications.

Recombinant human bone morphogenetic protein (rhBMP)9 induces osteoblast differentiation when combined with demineralized freeze-dried bone allografts (DFDBAs) or biphasic calcium phosphate (BCP).

OBJECTIVES: Recently, recombinant human bone morphogenetic protein 9 (rhBMP9) has been characterized as one of the most osteogenic growth factors among the 15 human BMPs. The aim of the present study was to investigate the effects of rhBMP9 in comparison to the clinically utilized rhBMP2 on in vitro cell behavior when combined with two bone graft materials including demineralized freeze-dried bone allografts (DFDBAs) and biphasic calcium phosphate (BCP). MATERIALS AND METHODS: The absorption and release kinetics of rhBMPs from DFDBA and BCP were investigated by ELISA. Moreover, murine bone stromal ST2 cell behavior was investigated on DFDBA or BCP seeded on (1) graft only, (2) rhBMP2 (10 ng/ml), (3) rhBMP2 (100 ng/ml), (4) rhBMP9 (10 ng/ml), and (5) rhBMP9 (100 ng/ml). The effects of rhBMPs on DFDBA and BCP were assessed for cell adhesion, proliferation, and osteoblast differentiation by alkaline phosphatase (ALP) activity, alizarin red staining, and real-time PCR for genes encoding Runx2, ALP, and bone sialoprotein (BSP). RESULTS: While both BMPs were gradually released from DFDBA and BCP over time, significantly higher adsorption was observed on BCP when compared to DFDBA. Cell attachment and proliferation was higher on BCP with little influence of either rhBMP2/9. Despite rhBMPs having relatively no effect on cell attachment/proliferation, a pronounced and marked effect was observed on osteoblast differentiation for both rhBMP2/9. Interestingly, it was observed that rhBMP9 induced significantly higher ALP activity, alizarin red staining, and messenger RNA (mRNA) levels of ALP and BSP when compared to rhBMP2. Our results also revealed higher differentiation for rhBMP2/9 with BCP when compared to DFDBA most likely as a result of higher growth factor adsorption. CONCLUSION: While both rhBMP2/9 combined with DFDBA or BCP induced osteoblast differentiation, rhBMP9 induced greater osteoblast differentiation when compared to rhBMP2. CLINICAL RELEVANCE: rhBMP9 may be a recombinant growth factor with higher potential to induce new bone formation when compared to rhBMP2. Further in vivo studies are necessary to characterize its regenerative potential in various animal models.

Histologic and Tomographic Findings of Bone Block Allografts in a 4 Years Follow-up: A Case Series

Abstract The aim of this paper is to report histologic and tomographic findings of fresh frozen bone block allografts bearing dental implants in functional occlusion in a long-term follow-up. Four patients with implants functionally loaded for 4 years on augmented ridges requiring additional mucogingival surgery or implant placement were included in this case series. Cone-beam tomography scans were compared volumetrically between the baseline (first implant placement) and current images. Biopsies of the grafts were retrieved and sent to histological analysis. Volumetric reduction of the grafts varied from 2.1 to 7.7%. Histological evaluation demonstrated well-incorporated grafts with different degrees of remodeling. While data presented in this report are from a small sample size and do not allow definitive conclusions, the biopsies of the grafted sites were very similar to the host's native bone. Remodeling of the cortical portion of the allografts seems to take longer than the cancellous portion. The presence of unincorporated graft remains did not impair the implant success or the health of the surrounding tissues. This is the first time histologic and tomographic long term data of bone allograft have been made available in dentistry.

Resumo O objetivo deste artigo é relatar achados histológicos e tomográficos de aloenxertos ósseos em bloco com implantes dentários em oclusão funcional em um acompanhamento de longo prazo. Quatro pacientes com implantes funcionalmente carregados por 4 anos em rebordos alveolares enxertados, que necessitaram de cirurgia mucogengival ou instalação de implantes adicionais foram incluídos nesta série de casos. Imagens de tomografia cone-beam foram comparados volumetricamente entre o momento inicial (instalação do implante original) e imagens atuais. Biópsias dos enxertos foram coletadas e enviadas para análise histológica. A redução volumétrica dos enxertos variou entre 2,1-7,7%. A avaliação histológica demonstrou enxertos bem incorporados com diferentes graus de remodelação. Embora os dados apresentados neste relato sejam de uma amostra pequena e não permitam conclusões definitivas, as biópsias dos sítios enxertados apresentaram características muito similares ao osso nativo. A remodelação da porção cortical dos aloenxertos parece levar mais tempo do que a porção esponjosa. A presença de remanescentes do enxerto não incorporado não demonstrou impacto no sucesso dos implantes ou na saúde dos tecidos circunjacentes. Este é o primeiro relato com dados histológicos e tomográficos em longo prazo de enxertos ósseos alógenos disponível na odontologia.