Review of bone substitutes

Incorporating strontium enriched amorphous calcium phosphate granules in collagen/collagen-magnesium-hydroxyapatite osteochondral scaffolds improves subchondral bone repair

Osteochondral defect repair with a collagen/collagen-magnesium-hydroxyapatite (Col/Col-Mg-HAp) scaffold has demonstrated good clinical results. However, subchondral bone repair remained suboptimal, potentially leading to damage to the regenerated overlying neocartilage. This study aimed to improve the bone repair potential of this scaffold by incorporating newly developed strontium (Sr) ion enriched amorphous calcium phosphate (Sr-ACP) granules (100-150 μm). Sr concentration of Sr-ACP was determined with ICP-MS at 2.49 ± 0.04 wt%. Then 30 wt% ACP or Sr-ACP granules were integrated into the scaffold prototypes. The ACP or Sr-ACP granules were well embedded and distributed in the collagen matrix demonstrated by micro-CT and scanning electron microscopy/energy dispersive x-ray spectrometry. Good cytocompatibility of ACP/Sr-ACP granules and ACP/Sr-ACP enriched scaffolds was confirmed with in vitro cytotoxicity assays. An overall promising early tissue response and good biocompatibility of ACP and Sr-ACP enriched scaffolds were demonstrated in a subcutaneous mouse model. In a goat osteochondral defect model, significantly more bone was observed at 6 months with the treatment of Sr-ACP enriched scaffolds compared to scaffold-only, in particular in the weight-bearing femoral condyle subchondral bone defect. Overall, the incorporation of osteogenic Sr-ACP granules in Col/Col-Mg-HAp scaffolds showed to be a feasible and promising strategy to improve subchondral bone repair.

Bone Graft Substitutes and Enhancement in Craniomaxillofacial Surgery

Critical-sized bone defects are a reconstructive challenge, particularly in the craniomaxillofacial (CMF) skeleton. The "gold standard" of autologous bone grafting has been the work horse of reconstruction in both congenital and acquired defects of CMF skeleton. Autologous bone has the proper balance of the protein (or organic) matrix and mineral components with no immune response. Organic and mineral adjuncts exist that offer varying degrees of osteogenic, osteoconductive, osteoinductive, and osteostimulative properties needed for treatment of critical-sized defects. In this review, we discuss the various mostly organic and mostly mineral bone graft substitutes available for autologous bone grafting. Primarily organic bone graft substitutes/enhancers, including bone morphogenic protein, platelet-rich plasma, and other growth factors, have been utilized to support de novo bone growth in setting of critical-sized bone defects. Primarily mineral options, including various calcium salt formulation (calcium sulfate/phosphate/apatite) and bioactive glasses have been long utilized for their similar composition to bone. Yet, a bone graft substitute that can supplant autologous bone grafting is still elusive. However, case-specific utilization of bone graft substitutes offers a wider array of reconstructive options.

Three-Dimensional Scaffolds for Bone Tissue Engineering

Immobilization using external or internal splints is a standard and effective procedure to treat minor skeletal fractures. In the case of major skeletal defects caused by extreme trauma, infectious diseases or tumors, the surgical implantation of a bone graft from external sources is required for a complete cure. Practical disadvantages, such as the risk of immune rejection and infection at the implant site, are high in xenografts and allografts. Currently, an autograft from the iliac crest of a patient is considered the "gold standard" method for treating large-scale skeletal defects. However, this method is not an ideal solution due to its limited availability and significant reports of morbidity in the harvest site (30%) as well as the implanted site (5-35%). Tissue-engineered bone grafts aim to create a mechanically strong, biologically viable and degradable bone graft by combining a three-dimensional porous scaffold with osteoblast or progenitor cells. The materials used for such tissue-engineered bone grafts can be broadly divided into ceramic materials (calcium phosphates) and biocompatible/bioactive synthetic polymers. This review summarizes the types of materials used to make scaffolds for cryo-preservable tissue-engineered bone grafts as well as the distinct methods adopted to create the scaffolds, including traditional scaffold fabrication methods (solvent-casting, gas-foaming, electrospinning, thermally induced phase separation) and more recent fabrication methods (fused deposition molding, stereolithography, selective laser sintering, Inkjet 3D printing, laser-assisted bioprinting and 3D bioprinting). This is followed by a short summation of the current osteochondrogenic models along with the required scaffold mechanical properties for in vivo applications. We then present a few results of the effects of freezing and thawing on the structural and mechanical integrity of PLLA scaffolds prepared by the thermally induced phase separation method and conclude this review article by summarizing the current regulatory requirements for tissue-engineered products.

Calcium Phosphate Delivery Systems for Regeneration and Biomineralization of Mineralized Tissues of the Craniofacial Complex

Calcium phosphate (CaP)-based materials have been extensively used for mineralized tissues in the craniofacial complex. Owing to their excellent biocompatibility, biodegradability, and inherent osteoconductive nature, their use as delivery systems for drugs and bioactive factors has several advantages. Of the three mineralized tissues in the craniofacial complex (bone, dentin, and enamel), only bone and dentin have some regenerative properties that can diminish due to disease and severe injuries. Therefore, targeting these regenerative tissues with CaP delivery systems carrying relevant drugs, morphogenic factors, and ions is imperative to improve tissue health in the mineralized tissue engineering field. In this review, the use of CaP-based microparticles, nanoparticles, and polymer-induced liquid precursor (PILPs) amorphous CaP nanodroplets for delivery to craniofacial bone and dentin are discussed. The use of these various form factors to obtain either a high local concentration of cargo at the macroscale and/or to deliver cargos precisely to nanoscale structures is also described. Finally, perspectives on the field using these CaP materials and next steps for the future delivery to the craniofacial complex are presented.

Bone Morphogenetic Protein as Bone Additive around Dental Implant and its Impact on Osseointegration: a Systematic Review

Statement of the Problem

Bone morphogenetic protein (BMP), a potential osteoinductive agent, was systematically reviewed for merits and demerits when used as a bone additive that was intervened during the surgical phase of dental implant placement; and suitable drug carriers that could withstand the functional load and deliver BMP at its lowest concentration.

Purpose

To identify the carriers and concentration of BMP acceptable during surgical phase of implant placement and evaluate its efficacy in bone gain and osseointegration.

Materials and Method

The study design was systematic review. Literature search as per PICO format was carried out within a time range from 2000 to July 2021. The review fol-lowed PRISMA guidelines and registered with the PROSPERO (CRD42020171667). The focus question included the population with an intra-oral implant placed in both animal and human models that were intervened with BMP-2 as an external additive biomaterial during the surgical phase. 2631 articles selected from the initial search were systematically filtered and yielded 16 articles that were qualitatively analysed.

Results

The inter-rater reliability and level of agreement were 93.71%, κ(Kappa)>0.81 re-spectively. Results revealed the collagen carrier was commonly used for BMP delivery but lacked the property to withstand functional load and sustained release. BMP concentration varied in the range of 0.215μg to 0.8mg and the study revealed significantly indifferent out-come with low dose compared to the highest dose. BMP supplement showed better osseointe-gration in comparison with non-supplemented sites during the early period (within 6 months).

Conclusion

BMP at lower concentrations and with appropriate carriers, collagen sponge, hydroxyapatite/tricalcium phosphate (HA/TCP) with a bio ceramic bulking agent, and poly (D, L-lactide-co-glycolic acid) (PLGA) reinforced with gelatin/HA/TCP accelerated bone growth during the initial stages of healing. Further long-term clinical trials for dental implant, analysing the sustained release of BMP with biodegradable and load-bearing carriers should be considered.

Laser Sintering Approaches for Bone Tissue Engineering

The adoption of additive manufacturing (AM) techniques into the medical space has revolutionised tissue engineering. Depending upon the tissue type, specific AM approaches are capable of closely matching the physical and biological tissue attributes, to guide tissue regeneration. For hard tissue such as bone, powder bed fusion (PBF) techniques have significant potential, as they are capable of fabricating materials that can match the mechanical requirements necessary to maintain bone functionality and support regeneration. This review focuses on the PBF techniques that utilize laser sintering for creating scaffolds for bone tissue engineering (BTE) applications. Optimal scaffold requirements are explained, ranging from material biocompatibility and bioactivity, to generating specific architectures to recapitulate the porosity, interconnectivity, and mechanical properties of native human bone. The main objective of the review is to outline the most common materials processed using PBF in the context of BTE; initially outlining the most common polymers, including polyamide, polycaprolactone, polyethylene, and polyetheretherketone. Subsequent sections investigate the use of metals and ceramics in similar systems for BTE applications. The last section explores how composite materials can be used. Within each material section, the benefits and shortcomings are outlined, including their mechanical and biological performance, as well as associated printing parameters. The framework provided can be applied to the development of new, novel materials or laser-based approaches to ultimately generate bone tissue analogues or for guiding bone regeneration.

Cranioplasty: A Multidisciplinary Approach

Decompressive craniectomy (DC) is an operation where a large section of the skull is removed to accommodate brain swelling. Patients who survive will usually require subsequent reconstruction of the skull using either their own bone or an artificial prosthesis, known as cranioplasty. Cranioplasty restores skull integrity but can also improve neurological function. Standard care following DC consists of the performance of cranioplasty several months later as historically, there was a concern that earlier cranioplasty may increase the risk of infection. However, recent systematic reviews have challenged this and have demonstrated that an early cranioplasty (within three months after DC) may enhance neurological recovery. However, patients are often transferred to a rehabilitation unit following their acute index admission and before their cranioplasty. A better understanding of the pathophysiological effects of cranioplasty and the relationship of timing and complications would enable more focused patient tailored rehabilitation programs, thus maximizing the benefit following cranioplasty. This may maximise recovery potential, possibly resulting in improved functional and cognitive gains, enhancement of quality of life and potentially reducing longer-term care needs. This narrative review aims to update multi-disciplinary team regarding cranioplasty, including its history, pathophysiological consequences on recovery, complications, and important clinical considerations both in the acute and rehabilitation settings.

Cellular Response of Human Osteoblasts to Different Presentations of Deproteinized Bovine Bone

Objectives: This study evaluated the cellular response of primary osteoblasts exposed to two different presentations of a low-temperature non-sintered deproteinized bovine bone matrix (DBBM). Materials and methods: Six different baths of a commercially available DBBM block (Bonefill^® Porous Block) and one of DBBM granule (Bonefill^® Porous) were evaluated to identify the mineral structure and organic or cellular remnants. Samples of the same baths were processed in TRIZOL for RNA extraction and quantification. For the immunologic cell reaction assay, primary human osteoblasts (pOB) were exposed to DBMM block (pOB + B) or granules (pOB + G), or none (control) for 1, 3, or 7 days of cell cultivation. Expression of proinflammatory cytokines by pOB was evaluated by crosslinked ELISA assay. In addition, total DNA amount, as well as cell viability via LDH evaluation, was assessed. Results: Organic remnants were present in DBBM blocks; 45.55% (±7.12) of osteocytes lacunae presented cellular remnants in blocks compared to 17.31% (±1.31) in granules. In three of five batches of blocks, it was possible to isolate bovine RNA. The highest concentration of TGF-β1 was found in supernatants of pOB + G on day 7 (218.85 ± 234.62 pg/mL) (p < 0.05), whereas pOB + B presented the lowest amount of TGF-β1 secretion at the end of evaluation (30.22 ± 14.94 pg/mL, p < 0.05). For IL-6 and OPG, there was no statistical difference between groups, while pOB + G induced more IL-8 secretion than the control (3.03 ± 3.38 ng/mL, p < 0.05). Considering the kinetics of cytokine release during the study period, all groups presented a similar pattern of cytokines, estimated as an increasing concentration for IL-6, IL-8, and OPG during cultivation. Adherent cells were observed on both material surfaces on day 7, according to H&E and OPN staining. Conclusion: Neither tested material induced a pronounced inflammatory response upon osteoblast cultivation. However, further studies are needed to elucidate the potential influence of organic remnants in bone substitute materials on the regeneration process.

Transforming the Degradation Rate of β-tricalcium Phosphate Bone Replacement Using 3-Dimensional Printing

BACKGROUND

β-Tricalcium phosphate (β-TCP) is one of the most common synthetic bone grafting materials utilized in craniofacial reconstruction; however, it is limited by a slow degradation rate. The aim of this study was to leverage 3-dimensional (3D) printing in an effort to accelerate the degradation kinetics of β-TCP.

METHODS

Twenty-two 1-month-old New Zealand white rabbits underwent creation of calvarial and alveolar defects, repaired with 3D-printed β-TCP scaffolds coated with 1000 μM of osteogenic agent dipyridamole. Rabbits were euthanized after 2, 6, and 18 months after surgical intervention. Bone regeneration, scaffold degradation, and bone mechanical properties were quantified.

RESULTS

Histological analysis confirmed the generation of vascularized and organized bone. Microcomputed tomography analysis from 2 to 18 months demonstrated decreased scaffold volume within calvarial (23.6% ± 2.5%, 5.1% ± 2.2%; P < 0.001) and alveolar (21.5% ± 2.2%, 0.2% ± 1.9%; P < 0.001) defects, with degradation rates of 54.6%/year and 90.5%/year, respectively. Scaffold-inducted bone generation within the defect was volumetrically similar to native bone in the calvarium (55.7% ± 6.9% vs 46.7% ± 6.8%; P = 0.064) and alveolus (31.4% ± 7.1% vs 33.8% ± 3.7%; P = 0.337). Mechanical properties between regenerated and native bone were similar.

CONCLUSIONS

Our study demonstrates an improved degradation profile and replacement of absorbed β-TCP with vascularized, organized bone through 3D printing and addition of an osteogenic agent. This novel additive manufacturing and tissue engineering protocol has implications to the future of craniofacial skeletal reconstruction as a safe and efficacious bone tissue engineering method.

Evaluation of a self-fitting, shape memory polymer scaffold in a rabbit calvarial defect model

Self-fitting scaffolds prepared from biodegradable poly(ε-caprolactone)-diacrylate (PCL-DA) have been developed for the treatment of craniomaxillofacial (CMF) bone defects. As a thermoresponsive shape memory polymer (SMP), with the mere exposure to warm saline, these porous scaffolds achieve a conformal fit in defects. This behavior was expected to be advantageous to osseointegration and thus bone healing. Herein, for an initial assessment of their regenerative potential, a pilot in vivo study was performed using a rabbit calvarial defect model. Exogenous growth factors and cells were excluded from the scaffolds. Key scaffold material properties were confirmed to be maintained following gamma sterilization. To assess scaffold integration and neotissue infiltration along the defect perimeter, non-critically sized (d = 8 mm) bilateral calvarial defects were created in 12 New Zealand white rabbits. Bone formation was assessed at 4 and 16 weeks using histological analysis and micro-CT, comparing defects treated with an SMP scaffold (d = 9 mm x t = 1 or 2 mm) to untreated defects (i.e. defects able to heal without intervention). To further assess osseointegration, push-out tests were performed at 16 weeks and compared to defects treated with poly(ether ether ketone) (PEEK) discs (d = 8.5 mm x t = 2 mm). The results of this study confirmed that the SMP scaffolds were biocompatible and highly conducive to bone formation and ingrowth at the perimeter. Ultimately, this resulted in similar bone volume and surface area versus untreated defects and superior performance in push-out testing versus defects treated with PEEK discs. STATEMENT OF SIGNIFICANCE: Current treatments of craniomaxillofacial (CMF) bone defects include biologic and synthetic grafts but they are limited in their ability to form good contact with adjacent tissue. A regenerative engineering approach using a biologic-free scaffold able to achieve conformal fitting represents a potential "off-the-shelf" surgical product to heal CMF bone defects. Having not yet been evaluated in vivo, this study provided the preliminary assessment of the bone healing potential of self-fitting PCL scaffolds using a rabbit calvarial defect model. The study was designed to assess scaffold biocompatibility as well as bone formation and ingrowth using histology, micro-CT, and biomechanical push-out tests. The favorable results provide a basis to pursue establishing self-fitting scaffolds as a treatment option for CMF defects.

FDA-approved bone grafts and bone graft substitute devices in bone regeneration

To induce bone regeneration there is a complex cascade of growth factors. Growth factors such as recombinant BMP-2, BMP-7, and PDGF are FDA-approved therapies in bone regeneration. Although, BMP shows promising results as being an alternative to autograft, it also has its own downfalls. BMP-2 has many adverse effects such as inflammatory complications such as massive soft-tissue swelling that can compromise a patient's airway, ectopic bone formation, and tumor formation. BMP-2 may also be advantageous for patients not willing to give up smoking as it shows bone regeneration success with smokers. BMP-7 is no longer an option for bone regeneration as it has withdrawn off the market. PDGF-BB grafts in studies have shown PDGF had similar fusion rates to autologous grafts and fewer adverse effects. There is also an FDA-approved bioactive molecule for bone regeneration, a peptide P-15. P-15 was found to be effective, safe, and have similar outcomes to autograft at 2 years post-op for cervical radiculopathy due to cervical degenerative disc disease. Growth factors and bioactive molecules show some promising results in bone regeneration, although more research is needed to avoid their adverse effects and learn about the long-term effects of these therapies. There is a need of a bone regeneration method of similar quality of an autograft that is osteoconductive, osteoinductive, and osteogenic. This review covers all FDA-approved bone regeneration therapies such as the "gold standard" autografts, allografts, synthetic bone grafts, and the newer growth factors/bioactive molecules. It also covers international bone grafts not yet approved in the United States and upcoming technologies in bone grafts.

3D-printed Poly-Lactic Co-Glycolic Acid (PLGA) scaffolds in non-critical bone defects impede bone regeneration in rabbit tibia bone

BACKGROUND

An increasing number of bone graft materials are commercially available and vary in their composition, mechanism of action, costs, and indications.

OBJECTIVE

A commercially available PLGA scaffold produced using 3D printing technology has been used to promote the preservation of the alveolar socket after tooth extraction. We examined its influence on bone regeneration in long bones of New Zealand White rabbits.

METHODS

5.0-mm-diameter circular defects were created on the tibia bones of eight rabbits. Two groups were studied: (1) control group, in which the bone defects were left empty; (2) scaffold group, in which the PLGA scaffolds were implanted into the bone defect. Radiography was performed every two weeks postoperatively. After sacrifice, bone specimens were isolated and examined by micro-computed tomography and histology.

RESULTS

Scaffolds were not degraded by eight weeks after surgery. Micro-computed tomography and histology showed that in the region of bone defects that was occupied by scaffolds, bone regeneration was compromised and the total bone volume/total volume ratio (BV/TV) was significantly lower.

CONCLUSION

The implantation of this scaffold impedes bone regeneration in a non-critical bone defect. Implantation of bone scaffolds, if unnecessary, lead to a slower rate of fracture healing.

Mechanistic Illustration: How Newly-Formed Blood Vessels Stopped by the Mineral Blocks of Bone Substitutes Can Be Avoided by Using Innovative Combined Therapeutics

One major limitation for the vascularization of bone substitutes used for filling is the presence of mineral blocks. The newly-formed blood vessels are stopped or have to circumvent the mineral blocks, resulting in inefficient delivery of oxygen and nutrients to the implant. This leads to necrosis within the implant and to poor engraftment of the bone substitute. The aim of the present study is to provide a bone substitute currently used in the clinic with suitably guided vascularization properties. This therapeutic hybrid bone filling, containing a mineral and a polymeric component, is fortified with pro-angiogenic smart nano-therapeutics that allow the release of angiogenic molecules. Our data showed that the improved vasculature within the implant promoted new bone formation and that the newly-formed bone swapped the mineral blocks of the bone substitutes much more efficiently than in non-functionalized bone substitutes. Therefore, we demonstrated that our therapeutic bone substitute is an advanced therapeutical medicinal product, with great potential to recuperate and guide vascularization that is stopped by mineral blocks, and can improve the regeneration of critical-sized bone defects. We have also elucidated the mechanism to understand how the newly-formed vessels can no longer encounter mineral blocks and pursue their course of vasculature, giving our advanced therapeutical bone filling great potential to be used in many applications, by combining filling and nano-regenerative medicine that currently fall short because of problems related to the lack of oxygen and nutrients.

Solution blow spinning of PLLA/hydroxyapatite composite scaffolds for bone tissue engineering

Composite poly-L-lactide acid-based scaffolds with hydroxyapatite (HAp) content up to 75 wt.% were fabricated via solution blow spinning. The influence of HAp concentration on structure, wettability, mechanical properties and chemical and phase composition of the produced materials was examined. It was found that with an increase of HAp content the average fiber diameter was increased, the uniaxial strength and relative elongation were reduced, while the phase composition and surface wettability did not change. The performance of the scaffolds during implantation in the parietal bone of a rat skull for a period from 15 to 90 days was studied. The materials have shown high ability to integrate with both soft and hard tissues. It was found that scaffolds with 25 wt.% HAp content significantly enhance osteogenesis during scarification (damage) of the periosteum. Overall, the fabricated scaffolds proved to be highly efficient for replacing bone defects in long tubular bones.

Translucent Customized Cranial Implants Made of Clear Polymethylmethacrylate: An Early Outcome Analysis of 55 Consecutive Cranioplasty Cases

BACKGROUND

Large skull reconstruction, with the use of customized cranial implants, restores cerebral protection, physiologic homeostasis, and one's preoperative appearance. Cranial implants may be composed of either bone or a myriad of alloplastic biomaterials. Recently, patient-specific cranial implants have been fabricated using clear polymethylmethacrylate (PMMA), a visually transparent and sonolucent variant of standard opaque PMMA. Given the new enhanced diagnostic and therapeutic applications of clear PMMA, we present here a study evaluating all outcomes and complications in a consecutive patient series.

METHODS

A single-surgeon, retrospective, 3-year study was conducted on all consecutive patients undergoing large cranioplasty with clear PMMA implants (2016-2019). Patients who received clear PMMA implants with embedded neurotechnologies were excluded due to confounding variables. All outcomes were analyzed in detail and compared with previous studies utilizing similar alloplastic implant materials.

RESULTS

Fifty-five patients underwent cranioplasty with customized clear PMMA implants. Twenty-one (38%) were performed using a single-stage cranioplasty method (ie, craniectomy and cranioplasty performed during the same operation utilizing a prefabricated, oversized design and labor-intense, manual modification), whereas the remaining 34 (62%) underwent a standard, 2-stage reconstruction (craniectomy with a delayed surgery for cranioplasty and minimal-to-no implant modification necessary). The mean cranial defect size was 101.8 cm. The mean follow-up time was 9 months (range, 1.5-39). Major complications requiring additional surgery occurred in 7 patients (13%) consisting of 2 (4%) cerebrospinal fluid leaks, 2 (4%) epidural hematomas, and 3 (4%) infections. In addition, 3 patients developed self-limiting or nonoperative complications including 2 (4%) with new onset seizures and 1 (2%) with delayed scalp healing.

CONCLUSIONS

This is the first reported consecutive case series of cranioplasty reconstruction using customized clear PMMA implants, demonstrating excellent results with regard to ease of use, safety, and complication rates well below published rates when compared with other alloplastic materials. Clear PMMA also provides additional benefits, such as visual transparency and sonolucency, which is material specific and unavailable with autologous bone. Although these early results are promising, further studies with multicenter investigations are well justified to evaluate long-term outcomes.

Development and Characterization of 3D Printed Multifunctional Bioscaffolds Based on PLA/PCL/HAp/BaTiO3 Composites

Bone substitute materials are placed in bone defects and play an important role in bone regeneration and fracture healing. The main objective of the present research is fabrication through the technique of 3D printing and the characterization of innovative composite bone scaffolds composed of polylactic acid (PLA), poly (ε-caprolactone) (PCL) while hydroxyapatite (HAp), and/or barium titanate (BaTiO3—BT) used as fillers. Composite filaments were prepared using a single screw melt extruder, and finally, 3D composite scaffolds were fabricated using the fused deposition modeling (FDM) technique. Scanning electron microscopy (SEM) images showed a satisfactory distribution of the fillers into the filaments and the printed objects. Furthermore, differential scanning calorimetry (DSC) measurements revealed that PLA/PCL filaments exhibit lower glass transition and melting point temperatures than the pure PLA filaments. Finally, piezoelectric and dielectric measurements of the 3D objects showed that composite PLA/PCL scaffolds containing HAp and BT exhibited piezoelectric coefficient (d33) values close to the human bone and high dielectric permittivity values.

Physicochemical changes of the chitosan/β-1,3-glucan/hydroxyapatite biocomposite caused by mesenchymal stem cells cultured on its surface in vitro

In the present study structural characteristics and physicochemical properties of tri-component biomaterial (consisting of chitosan, β-1,3-glucan and hydroxyapatite) seeded with mesenchymal stem cells were investigated with the use of diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). In this study we use non-conventional approach of DRIFT spectroscopy for investigating biomaterial changes under simulated physiological conditions. Particular cell-induced changes were intended to be properly evaluated with analytical methods. Abovementioned techniques allowed to precisely assess the changes on the surface of the biomaterial caused by two kinds of stem cells (ADSCs - Adipose tissue-Derived Stem Cells and BMDSCs - Bone Marrow-Derived Stem Cells) cultured directly on the surface of bioceramic-based biomaterial. The bioactivity and biocompatibility of designed bone biomaterial were demonstrated and hence it seems to be a promising scaffold used in tissue engineering. Designed chitosan, β-1,3-glucan, and hydroxyapatite biomaterial was proven to be non-toxic, surgically handy with cellular compatibility. The obtained results are interesting and promising in terms of spectroscopic methods suitability for qualitative assessment of material-cell interactions.

How is Biodegradable Scaffold Effective in Gap Non-union? Insights from an Experiment

OBJECTIVE

To evaluate the role of composite (Chitosan/Chondroitin sulphate/gelatin/nano-bioglass) scaffold in the union of critical size bone defect created in the rabbit's ulna.

METHODS

The composite (Chitosan/Chondroitin sulphate/gelatin/nano-bioglass) scaffold was fabricated using the freeze-drying technique under standard laboratory conditions. The scaffold was cut into the appropriate size and transferred into the defect created (critical bone size defect 1 cm) over the right ulna in the rabbit. The scaffold was not implanted on the left side thus the left side ulna served as control. Results were assessed on serial radiological examination. Rabbits were sacrificed at 20 weeks for histopathological examination (Haematoxylin-Eosin staining and Mason's trichrome staining) and scanning electron microscope observation. Radiological scoring was done by Lane and Sandhu's scoring.

RESULTS

Among 12 rabbits, 10 could complete the follow-up. Among those 10 rabbits, 8 among the test group showed good evidence of bone formation at the gap non-union scaffold implanted site. Histological evidence of new bone formation, collagen synthesis, scaffold resorption, minimal chondrogenesis was evident by 20 weeks in the test group. Two rabbits had poor bone formation.

CONCLUSION

The chitosan-chondroitin sulphate-gelatin-nano-bioglass composite scaffold is efficient in osteoconduction and osteoinduction in the gap non-union model as it is biocompatible, bioactive, and non-immunogenic as well.

Synthetic Polymeric Materials for Bone Replacement

Some treatment options available to repair bone defects are the use of autogenous and allogeneic bone grafts. The drawback of the first one is the donor site’s limitation and the need for a second operation on the same patient. In the allograft method, the problems are associated with transmitted diseases and high susceptibility to rejection. As an alternative to biological grafts, polymers can be used in bone repair. Some polymers used in the orthopedic field are poly(methyl methacrylate), poly(ether-ether-ketone), and ultra-high molecular weight polyethylene (UHMWPE). UHMWPE has drawn much attention since it combines low friction coefficient and high wear and impact resistance. However, UHMWPE is a bioinert material, which means that it does not interact with the bone tissue. UHMWPE composites and nanocomposites with hydroxyapatite (HA) are widely studied in the literature to mitigate these issues. HA is the main component of the inorganic phase in the natural bone, and the addition of this bioactive filler to the polymeric matrix aims to mimic bone composition. This brief review discusses some polymers used in orthopedic applications, focusing on the UHMWPE/HA composites as a potential bone substitute.

Are recent available blended collagen-calcium phosphate better than collagen alone or crystalline calcium phosphate? Radiotextural analysis of a 1-year clinical trial

OBJECTIVES

The purpose of this study is to compare bone regeneration properties of recently available collagen-calcium phosphate (C-CP) blend as bone substitute (BS) material in oral surgery with calcium phosphate (CP) as well as collagen material (Collagen). Is C-CP better than the classic loose CP, or is it at least equally effective in the jawbone regeneration with the superiority of a coherent consistency?

MATERIALS AND METHODS

This study included 102 patients during 12-month follow-up. All patients underwent the following surgical procedures: sinus lift (52patients) and tooth extraction (50patients). Patients were divided into 3 groups which are as follows: experimental group with C-CP, CP and pure Collagen as control groups. Texture analysis was performed in intra-oral radiographs. Analyses were performed in the MaZda 4.6 software. Average 2444-pixel ROIs were established in the image of BS materials and normal trabecular bone for texture comparison to evaluate the jawbone regeneration process. Four features were calculated and investigated.

RESULTS

Texture analyses revealed that all 4 features described the healing process well. Reference textural value of feature SumOfSqrs < 102.37 was soft tissue, DifEntr < 1.1 was not the bone, Entr < 2.62 was not a bone and LngREmph > 1.8 was soft tissue. For 12 months, bone regeneration was proved by 3 of 4 investigated features. Only Entr indicated to CP remnants in the ROI (p < 0.05).

CONCLUSIONS

This study proves that blended collagen-calcium phosphate as a BS material can bring satisfactory and predictable outcomes in jawbone regeneration.

CLINICAL RELEVANCE

Clinicians can choose a satisfactory and predictable material for bone regeneration treatment.

An Antibiotic-Releasing Bone Void Filling (ABVF) Putty for the Treatment of Osteomyelitis

The number of total joint replacements (TJR) is on the rise with a corresponding increase in the number of infected TJR, which necessitates revision surgeries. Current treatments with either non-biodegradable, antibiotic-releasing polymethylmethacrylate (PMMA) based bone cement, or systemic antibiotic after surgical debridement do not provide effective treatment due to fluctuating antibiotic levels at the site of infection. Here, we report a biodegradable, easy-to-use "press-fitting" antibiotic-releasing bone void filling (ABVF) putty that not only provides efficient antibiotic release kinetics at the site of infection but also allows efficient osseointegration. The ABVF formulation was prepared using poly (D,L-lactide-co-glycolide) (PLGA), polyethylene glycol (PEG), and polycaprolactone (PCL) as the polymer matrix, antibiotic vancomycin, and osseointegrating synthetic bone PRO OSTEON for bone-growth support. ABVF was homogenous, had a porous structure, was moldable, and showed putty-like mechanical properties. The ABVF putty released vancomycin for 6 weeks at therapeutic level. Furthermore, the released vancomycin showed in vitro antibacterial activity against Staphylococcus aureus for 6 weeks. Vancomycin was not toxic to osteoblasts. Finally, ABVF was biodegradable in vivo and showed an effective infection control with the treatment group showing significantly higher bone growth (p < 0.001) compared to the control group. The potential of infection treatment and osseointegration makes the ABVF putty a promising treatment option for osteomyelitis after TJR.

Long-term Effect of Cranioplasty on Overlying Scalp Atrophy

Scalp thinning over a cranioplasty can lead to complex wound problems, such as extrusion and infection. However, the details of this process remain unknown. The aim of this study was to describe long-term soft-tissue changes over various cranioplasty materials and to examine risk factors associated with accelerated scalp thinning.

Correlation between Surface Properties of Polystyrene and Polylactide Materials and Fibroblast and Osteoblast Cell Line Behavior: A Critical Overview of the Literature

Bone reconstruction remains an important challenge today in several clinical situations, notably regarding the control of the competition occurring during proliferation of osteoblasts and fibroblasts. Polystyrene and polylactide are reference materials in the biomedical field. Therefore, it could be expected from the literature that clear correlations have been already established between the behavior of fibroblasts or osteoblasts and the surface characteristics of these materials. After an extensive analysis of the literature, although general trends could be established, our critical review has highlighted the need to develop a more in-depth analysis of the surface properties of these materials. Moreover, the large variation noticed in the experimental conditions used for in vitro animal cell studies impairs comparison between studies. From our comprehensive review on this topic, we have suggested several parameters that would be valuable to standardize to integrate the data from the literature and improve our knowledge on the cell-material interactions.

In vitro and in vivo proves of concept for the use of a chemically cross-linked poly(ester-urethane-urea) scaffold as an easy handling elastomeric biomaterial for bone regeneration

Bone loss can occur as a result of various pathologies, traumas and injuries and poor bone healing leads to functionally debilitating condition, loss of self-sufficiency and deterioration in life quality. Given the increasing incidence of facial trauma and the emergence of new procedural techniques, advanced scaffolds are currently developed as substitutes for bone tissue engineering. In this study, we investigated the capability of a chemically cross-linked ε-caprolactone-based poly(ester-urethane-urea) (PCLU) scaffold to support bone regeneration. In vitro assays demonstrated that PCLU scaffolds could be colonized by cells through direct cell seeding and cell migration from outside to scaffold inside. Moreover, PCLU scaffolds could provide a suitable environment for stem cells proliferation in a 3D spatial arrangement, and allowed osteogenic differentiation under appropriate induction. In vivo results revealed the osteogenic properties of PCLU scaffolds through a drilled-hole femoral bone defect repair improvement in rats. Using histology and microtomography analysis, we showed that PCLU scaffolds fit well the bone cavity and were eventually entrapped between the newly formed trabeculae. Finally, no sign of inflammation or rejection was noticed. We envision that PCLU scaffolds can provide the clinicians with a substitute having appropriate characteristics for the treatment of bone defects.

Bread-Derived Bioactive Porous Scaffolds: An Innovative and Sustainable Approach to Bone Tissue Engineering

In recent years, bioactive glasses gained increasing scientific interest in bone tissue engineering due to their capability to chemically bond with the host tissue and to induce osteogenesis. As a result, several efforts have been addressed to use bioactive glasses in the production of three-dimensional (3D) porous scaffolds for bone regeneration. In this work, we creatively combine typical concepts of porous glass processing with those of waste management and propose, for the first time, the use of bread as a new sacrificial template for the fabrication of bioactive scaffolds. Preliminary SEM investigations performed on stale bread from industrial wastes revealed a suitable morphology characterized by an open-cell 3D architecture, which is potentially able to allow tissue ingrowth and vascularization. Morphological features, mechanical performances and in vitro bioactivity tests were performed in order to evaluate the properties of these new “sustainable” scaffolds for bone replacement and regeneration. Scaffolds with total porosity ranging from 70 to 85 vol% and mechanical strength comparable to cancellous bone were obtained. Globular hydroxyapatite was observed to form on the surface of the scaffolds after just 48-h immersion in simulated body fluid. The results show great promise and suggest the possibility to use bread as an innovative and inexpensive template for the development of highly-sustainable bone tissue engineering approaches.

Sonolucent Cranial Implants: Cadaveric Study and Clinical Findings Supporting Diagnostic and Therapeutic Transcranioplasty Ultrasound

BACKGROUND

Previously, sonographic evaluation of the intracranial contents was limited to intraoperative use following bone flap removal, with placement of the probe directly on the cortical surface or through a transsulcal tubular retractor. Cranioplasty with sonolucent implants may represent a postoperative window into the brain by allowing ultrasound to serve as a novel bedside imaging modality. The potential sonolucency of various commonly used cranial implant types was examined in this study.

METHODS

A 3-phase study was comprised of cadaveric evaluation of transcranioplasty ultrasound (TCU) with cranioplasty implants of varying materials, intraoperative TCU during right-sided cranioplasty with clear implant made of poly-methyl-methacrylate (PMMA), and bedside TCU on postoperative day 5 after cranioplasty.

RESULTS

The TCU through clear PMMA, polyether-ether-ketone, and opaque PMMA cranial implants revealed implant sonoluceny, in contrast to autologous bone and porous-polyethylene. Intraoperative ultrasound via the clear PMMA implant in a single patient revealed recognizable ventricular anatomy. Furthermore, postoperative bedside ultrasound in the same patient revealed comparable ventricular anatomy and a small epidural fluid collection corresponding to that visualized on an axial computed tomography scan.

CONCLUSION

Sonolucent cranial implants, such as those made of clear PMMA, hold great promise for enhanced diagnostic and therapeutic applications previously limited by cranial bone. Furthermore, as functional cranial implants are manufactured with implantable devices housed within clear PMMA, the possibility of utilizing ultrasound for real-time surveillance of intracranial pathology becomes much more feasible.

Porous Phosphate-Based Glass Microspheres Show Biocompatibility, Tissue Infiltration, and Osteogenic Onset in an Ovine Bone Defect Model

Phosphate-based glasses (PBGs) are bioactive and fully degradable materials with tailorable degradation rates. PBGs can be produced as porous microspheres through a single-step process, using changes in their formulation and geometry to produce varying pore sizes and interconnectivity for use in a range of applications, including biomedical use. Calcium phosphate PBGs have recently been proposed as orthobiologics, based on their in vitro cytocompatibility and ion release profile. In this study, porous microspheres made of two PBG formulations either containing TiO₂ (P40Ti) or without (P40) were implanted in vivo in a large animal model of bone defect. The biocompatibility and osteogenic potential of these porous materials were assessed 13 weeks postimplantation in sheep and compared to empty defects and autologous bone grafts used as negative and positive controls. Histological analysis showed marked differences between the two formulations, as lower trabeculae-like interconnection and higher fatty bone marrow content were observed in the faster degrading P40-implanted defects, while the slower degrading P40Ti material promoted dense interconnected tissue. Autologous bone marrow concentrate (BMC) was also incorporated within the P40 and P40Ti microspheres in some defects; however, no significant differences were observed in comparison to microspheres implanted alone. Both formulations induced the formation of a collagen-enriched matrix, from 20 to 40% for P40 and P40Ti2.5 groups, suggesting commitment toward the bone lineage. With the faster degrading P40 formulation, mineralization of the tissue matrix was observed both with and without BMC. Some lymphocyte-like cells and foreign body multinucleated giant cells were observed with P40Ti2.5, suggesting that this more durable formulation might be linked to an inflammatory response. In conclusion, these first in vivo results indicate that PBG microspheres could be useful candidates for bone repair and regenerative medicine strategies and highlight the role of material degradation in the process of tissue formation and maturation.

The Timing of Alloplastic Cranioplasty in the Setting of Previous Osteomyelitis

BACKGROUND

Management of cranial osteomyelitis is challenging and often includes débridement of infected bone and delayed alloplastic cranioplasty. However, the optimal interval between the removal of infected bone and definitive reconstruction remains controversial. The authors investigated the optimal time for definitive reconstruction and factors influencing cranioplasty reinfection.

METHODS

A retrospective review of 111 alloplastic cranioplasties for osteomyelitis between 2002 and 2015 was performed. Patients were divided into four subgroups based on timing of reconstruction: group 1, less than 3 months; group 2, 3 to 6 months; group 3, 6 to 12 months; and group 4, more than 12 months. Multivariate logistic regression was used to calculate the probability of cranioplasty reinfection based on risk factors. Median follow-up was 45.9 months (range, 12.4 to 136.9 months).

RESULTS

The combined reinfection rate was 23.4 percent. The reinfection rate in group 1 was 39.6 percent; group 2, 12.5 percent; group 3, 8.0 percent; and group 4, 0.0 percent (p < 0.001). The mean interval between the infected bone removal and cranioplasty was shorter in patients with reinfection than in patients without reinfection (2.2 ± 3.9 months versus 6.1 ± 8.3 months; p < 0.001). The strongest independent predictors of reinfection were chemotherapy (OR, 10.1; 95 percent CI, 2.9 to 35.2), composite defect requiring scalp reconstruction at the time of cranioplasty (OR, 3.3; 95 percent CI, 1.2 to 8.9), and early reconstruction. Each month of delay in reconstruction reduced the reinfection rate by 10 percent (OR, 0.9 per each month of delay; 95 percent CI, 0.8 to 1.0). Cranioplasty material was not significant.

CONCLUSIONS

Early alloplastic cranioplasty following osteomyelitis carries an unacceptably high risk of reinfection. This risk decreases by 10 percent with each month of delay. The authors' regression model can be used to predict the probability of reinfection for all time periods.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

The Biological Evaluation of Conventional and Nano-Hydroxyapatite-Silica Glass Ionomer Cement on Dental Pulp Stem Cells: A Comparative Study

BACKGROUND

Despite their lower strength, glass ionomer cements (GICs) are widely used as restorative materials because of their anti-cariogenic properties, direct adhesion to tooth structure and good biocompatibility. Recently, the addition of nano-hydroxyapatite (nano-HA)-silica to conventional GIC (cGIC) has been shown to improve the strength of cGIC. However, the biocompatibility and cell attachment properties of this material are unknown.

AIMS

This study aims to evaluate and compare the cytotoxicity and cell attachment properties of cGIC and nano-HA-silica-GIC on dental pulp stem cells (DPSCs).

METHODS AND MATERIALS

Material extracts of nano-HA-silica-GIC and cGIC were prepared into seven serial dilutions and applied to 96 well plates seeded with DPSCs. After 72 h, the cell viability was determined using MTT assay. The DPSCs cell attachment properties were examined under scanning electron microscope (SEM) after 24 and 72 h. Kruskal-Wallis test was used to analyse the data for MTT assay (P < 0.05). SEM images of cell attachment properties were also described.

RESULTS

Nano-HA-silica-GIC and cGIC was shown to be slight to non-cytotoxic at all concentrations, except 200 mg/ml. Moderate cytotoxicity has been observed at 200 mg/ml concentration where nano-HA-silica-GIC and cGIC revealed cell viability values of 44.38 and 42.15%, respectively. Nano-HA-silica-GIC demonstrated better cell viability values than cGIC at all concentrations except for 6.25 and 12.5 mg/ml. Nevertheless, the results were not statistically significant (P > 0.05). SEM examination revealed the increasing numbers of DPSCs attached to both groups with prominent filopodia, especially after 72 h.

CONCLUSIONS

Nano-HA-silica-GIC exhibited good biocompatibility which is comparable to cGIC and favoured the attachment of DPSCs.

Fabrication of carbonate apatite honeycomb and its tissue response

Carbonate apatite (CO₃ Ap) block can be used as a bone substitute because it can be remodeled to new natural bone in a manner conforming with the bone remodeling process. Among the many porous structures available, honeycomb (HC) structure is advantageous for rapid replacement of CO₃ Ap to bone. In this study, the feasibility to fabricate a CO₃ Ap HC was studied, along with its initial tissue response in rabbit femur bone defect. First, a mixture of Ca(OH)₂ and a wax-based binder was extruded from a HC mold. Then the fabricated HC was heated for binder removal and carbonation at 450°C in a mixed O₂ -CO₂ atmosphere, forming a CaCO₃ HC. When the CaCO₃ HC was immersed in 1 mol/L Na₃ PO₄ solution at 80°C for 7 days, its composition changed from CaCO₃ to CO₃ Ap, maintaining the structure of the original CaCO₃ HC. Compressive strengths of the CaCO₃ and CO₃ Ap HCs were 65.2 ± 7.4 MPa and 88.7 ± 4.7 MPa, respectively. When the rabbit femur bone defect was reconstructed with the CO₃ Ap HC, new bone penetrated the CO₃ Ap HC completely. Osteoclasts and osteoblasts were found on the surface of the newly formed bone and osteocytes were also found in the newly formed bone, indicating ongoing bone remodeling. Furthermore, blood vessels were formed inside the pores of CO₃ Ap HC. Therefore, CO₃ Ap HC has good potential as an ideal bone substitute. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1014-1020, 2019.

Activin A/BMP2 Chimera (AB204) Exhibits Better Spinal Bone Fusion Properties than rhBMP2

Objective

To compare the spinal bone fusion properties of activin A/BMP2 chimera (AB204) with recombinant human bone morphogenetic protein (rhBMP2) using a rat posterolateral spinal fusion model.

Methods

The study was designed to compare the effects and property at different dosages of AB204 and rhBMP2 on spinal bone fusion. Sixty-one male Sprague-Dawley rats underwent posterolateral lumbar spinal fusion using one of nine treatments during the study, that is, sham; osteon only; 3.0 μg, 6.0 μg, or 10.0 μg of rhBMP2 with osteon; and 1.0 μg, 3.0 μg, 6.0 μg, or 10.0 μg of AB204 with osteon. The effects and property on spinal bone fusion was calculated at 4 and 8 weeks after treatment using the scores of physical palpation, simple radiograph, micro-computed tomography, and immunohistochemistry.

Results

Bone fusion scores were significantly higher for 10.0 μg AB204 and 10.0 μg rhBMP2 than for osteon only or 1.0 μg AB204. AB204 exhibited more prolonged osteoblastic activity than rhBMP2. Bone fusion properties of AB204 were similar with the properties of rhBMP2 at doses of 6.0 and 10.0 μg, but, the properties of AB204 at doses of 3.0 μg exhibited better than the properties of rhBMP2 at doses of 3.0 μg.

Conclusion

AB204 chimeras could to be more potent for treating spinal bone fusion than rhBMP2 substitutes with increased osteoblastic activity for over a longer period.

Bone Healing in Rabbit Calvaria Defects Using a Synthetic Bone Substitute: A Histological and Micro-CT Comparative Study

Bioactive alloplastic materials, like beta-tricalcium phosphate (β-TCP) and calcium sulfate (CS), have been extensively researched and are currently used in orthopedic and dental bone regenerative procedures. The purpose of this study was to compare the performance of EthOss versus a bovine xenograft and spontaneous healing. The grafting materials were implanted in standardized 8 mm circular bicortical bone defects in rabbit calvariae. A third similar defect in each animal was left empty for natural healing. Six male rabbits were used. After eight weeks of healing, the animals were euthanized and the bone tissue was analyzed using histology and micro-computed tomography (micro-CT). Defects treated with β-TCP/CS showed the greatest bone regeneration and graft resorption, although differences between groups were not statistically significant. At sites that healed spontaneously, the trabecular number was lower (p < 0.05) and trabecular separation was higher (p < 0.05), compared to sites treated with β-TCP/CS or xenograft. Trabecular thickness was higher at sites treated with the bovine xenograft (p < 0.05) compared to sites filled with β-TCP/CS or sites that healed spontaneously. In conclusion, the novel β-TCP/CS grafting material performed well as a bioactive and biomimetic alloplastic bone substitute when used in cranial defects in this animal model.

Adult Cranioplasty Reconstruction With Customized Cranial Implants: Preferred Technique, Timing, and Biomaterials

INTRODUCTION

Complex cranial defects requiring delayed reconstruction present numerous challenges. Delayed cranioplasties accompany frequent complications approaching an incidence of 35 to 40%. Therefore, the authors sought to collate their experience in hopes of sharing their perspective on several topics including technique, timing, and preferred biomaterials.

METHODS

The authors' 5-year consecutive experience over 430 customized cranial implants is described herein. Since its inception in 2012, the authors' team has employed the pericranial-onlay cranioplasty technique instead of the standard epidural approach. Optimal timing for cranioplasty is determined using objective criteria such as scalp healing and parenchymal edema, close collaboration with neuroplastic surgery, conversion from autologous bone to sterile implant in instances of questionable viability/storage, and the first-line use of solid poly(methylmethacrylate) implants for uncomplicated, delayed cases, first-line porous polyethylene (MEDPOR) implants for single-stage cranioplasty, and first-line polyether-ether-ketone implants for cases with short notice. Furthermore, the use of the pterional design algorithm with temporal bulking for all customized implants has helped to correct and/or prevent temporal hollowing deformities.

RESULTS

The authors' team has observed a three-fold reduction in reported complications as compared with the existing literature, with a major complication rate of 11%. The multidisciplinary center has provided an optimal stage for synergy and improved outcomes versus standard cranioplasty techniques.

CONCLUSION

Secondary cranial reconstruction, or cranioplasty, can be challenging due to numerous reasons. These best practices, developed in collaboration with neuroplastic surgery and neurosurgery, appear to encompass the largest published experience to date. The authors find this approach to be both safe and reliable.

Alternatives to Autologous Bone Graft in Alveolar Cleft Reconstruction: The State of Alveolar Tissue Engineering

Alveolar cleft reconstruction has historically relied on autologous iliac crest bone grafting (ICBG), but donor site morbidity, pain, and prolonged hospitalization have prompted the search for bone graft substitutes. The authors evaluated bone graft substitutes with the highest levels of evidence, and highlight the products that show promise in alveolar cleft repair and in maxillary augmentation. This comprehensive review guides the craniofacial surgeon toward safe and informed utilization of biomaterials in the alveolar cleft.A literature search was performed to identify in vitro human studies that fulfilled the following criteria: Level I or Level II of evidence, ≥30 subjects, and a direct comparison between a autologous bone graft and a bone graft substitute. A second literature search was performed that captured all studies, regardless of level of evidence, which evaluated bone graft substitutes for alveolar cleft repair or alveolar augmentation for dental implants. Adverse events for each of these products were tabulated as well.Sixteen studies featuring 6 bone graft substitutes: hydroxyapatite, demineralized bone matrix (DBM), β-tricalcium phosphate (TCP), calcium phosphate, recombinant human bone morphogenic protein-2 (rhBMP-2), and rhBMP7 fit the inclusion criteria for the first search. Through our second search, the authors found that DBM, TCP, rhBMP-2, and rhBMP7 have been studied most extensively in the alveolar cleft literature, though frequently in studies using less rigorous methodology (Level III evidence or below). rhBMP-2 was the best studied and showed comparable efficacy to ICBG in terms of volume of bone regeneration, bone density, and capacity to accommodate tooth eruption within the graft site. Pricing for products ranged from $290 to $3110 per 5 mL.The balance between innovation and safety is a complex process requiring constant vigilance and evaluation. Here, the authors profile several bone graft substitutes that demonstrate the most promise in alveolar cleft reconstruction.

Bone substitutes: a review of their characteristics, clinical use, and perspectives for large bone defects management

Bone replacement might have been practiced for centuries with various materials of natural origin, but had rarely met success until the late 19th century. Nowadays, many different bone substitutes can be used. They can be either derived from biological products such as demineralized bone matrix, platelet-rich plasma, hydroxyapatite, adjunction of growth factors (like bone morphogenetic protein) or synthetic such as calcium sulfate, tri-calcium phosphate ceramics, bioactive glasses, or polymer-based substitutes. All these substitutes are not suitable for every clinical use, and they have to be chosen selectively depending on their purpose. Thus, this review aims to highlight the principal characteristics of the most commonly used bone substitutes and to give some directions concerning their clinical use, as spine fusion, open-wedge tibial osteotomy, long bone fracture, oral and maxillofacial surgery, or periodontal treatments. However, the main limitations to bone substitutes use remain the management of large defects and the lack of vascularization in their central part, which is likely to appear following their utilization. In the field of bone tissue engineering, developing porous synthetic substitutes able to support a faster and a wider vascularization within their structure seems to be a promising way of research.

Loss of mechanosensitive sclerostin may accelerate cranial bone growth and regeneration

OBJECTIVE

Cranial defects can result from trauma, infection, congenital malformations, and iatrogenic causes and represent a surgical challenge. The current standard of care is cranioplasty, with either autologous or allogeneic material. In either case, the intrinsic vascularity of the surrounding tissues allows for bone healing. The objective of this study was to determine if mechanotransductive gene manipulation would yield non-weight-bearing bone regeneration in a critical size calvarial defect in mice.

METHODS

A mouse model of Sost deletion in Sost knockout (KO) mice was created in which the osteocytes do not express sclerostin. A critical size calvarial defect (4 mm in diameter) was surgically created in the parietal bone in 8-week-old wild-type (n = 8) and Sost KO (n = 8) male mice. The defects were left undisturbed (no implant or scaffold) to simulate a traumatic calvariectomy model. Eight weeks later, the animals were examined at necropsy by planimetry, histological analysis of new bone growth, and micro-CT scanning of bone thickness.

RESULTS

Defects created in wild-type mice did not fill with bone over the study period of 2 months. Genetic downregulation of sclerostin yielded animals that were able to regenerate 40% of the initial critical size defect area 8 weeks after surgery. A thin layer of bone covered a significant portion of the original defect in all Sost KO animals. A statistically significant increase in bone volume (p < 0.05) was measured in Sost KO mice using radiodensitometric analysis. Immunohistochemical analysis also confirmed that this bone regeneration occurred through the Wnt pathway and originated from the edge of the defect; BMP signaling did not appear to be affected by sclerostin.

CONCLUSIONS

Mechanical loading is an important mechanism of bone formation in the cranial skeleton and is poorly understood. This is partially due to the fact that it is difficult to load bone in the craniomaxillofacial skeleton. This study suggests that modulation of the Wnt pathway, as is able to be done with monoclonal antibodies, is a potentially efficacious method for bone regeneration that requires further study.

Application of Materials as Medical Devices with Localized Drug Delivery Capabilities for Enhanced Wound Repair

The plentiful assortment of natural and synthetic materials can be leveraged to accommodate diverse wound types, as well as different stages of the healing process. An ideal material is envisioned to promote tissue repair with minimal inconvenience for patients. Traditional materials employed in the clinical setting often invoke secondary complications, such as infection, pain, foreign body reaction, and chronic inflammation. This review surveys the repertoire of surgical sutures, wound dressings, surgical glues, orthopedic fixation devices and bone fillers with drug eluting capabilities. It highlights the various techniques developed to effectively incorporate drugs into the selected material or blend of materials for both soft and hard tissue repair. The mechanical and chemical attributes of the resultant materials are also discussed, along with their biological outcomes in vitro and/or in vivo. Perspectives and challenges regarding future research endeavors are also delineated for next-generation wound repair materials.

Calcium Phosphate Bioceramics: A Review of Their History, Structure, Properties, Coating Technologies and Biomedical Applications

Calcium phosphate (CaP) bioceramics are widely used in the field of bone regeneration, both in orthopedics and in dentistry, due to their good biocompatibility, osseointegration and osteoconduction. The aim of this article is to review the history, structure, properties and clinical applications of these materials, whether they are in the form of bone cements, paste, scaffolds, or coatings. Major analytical techniques for characterization of CaPs, in vitro and in vivo tests, and the requirements of the US Food and Drug Administration (FDA) and international standards from CaP coatings on orthopedic and dental endosseous implants, are also summarized, along with the possible effect of sterilization on these materials. CaP coating technologies are summarized, with a focus on electrochemical processes. Theories on the formation of transient precursor phases in biomineralization, the dissolution and reprecipitation as bone of CaPs are discussed. A wide variety of CaPs are presented, from the individual phases to nano-CaP, biphasic and triphasic CaP formulations, composite CaP coatings and cements, functionally graded materials (FGMs), and antibacterial CaPs. We conclude by foreseeing the future of CaPs.

Hydroxyapatite cement cranioplasty following translabyrinthine approach: Long-term study of 369 cases

OBJECTIVE

To report the authors' experience with hydroxyapatite cement (HAC) cranioplasty and analyze the material's long-term safety and efficacy in repairing translabyrinthine skull-base defects by examining adverse events, specifically cerebrospinal fluid (CSF) leaks and surgical site infections.

STUDY DESIGN

Retrospective case-control study (primary study arm); prospective cross-sectional study of patients not examined within the last 5 years (secondary arm).

SETTING

tertiary-care neurotology private practice and academic practice (two centers).

METHODS

Hydroxyapatite cement implanted following translabyrinthine approach, with or without fat graft, was included. Combined approaches were excluded. Implant-associated adverse events were defined as 1) CSF leaks requiring reoperation or spinal drainage, and (2) infections requiring reoperation. Patients not examined within 5 years were interviewed by telephone to update their condition. Incidence of adverse events was compared to published data for translabyrinthine cranioplasty using fat graft alone. Implant survival analysis was performed.

RESULTS

The study cohort included 369 HAC implants in the same number of patients. There were seven CSF leaks and seven infections. Combined (n = 14) incidence of adverse events was 3.8% (2.09%, 6.28%). Compared to fat graft alone, the adverse events associated with HAC were fewer (P < 0.001). Up to 15 years (5,475 days), HAC cement maintained 95% adverse event-free survival. There were no cases of meningitis.

CONCLUSION

Cranioplasty using HAC with autologous fat following translabyrinthine skull-base surgery is safer and more effective than fat graft alone, up to 15 years after surgery.

LEVEL OF EVIDENCE

4. Laryngoscope, 127:2120-2125, 2017.