The safety and efficacy of an injectable bone substitute in dental sockets demonstrated in a human clinical trial

Calcium Orthophosphate (CaPO4) Containing Composites for Biomedical Applications: Formulations, Properties, and Applications

The goal of this review is to present a wide range of hybrid formulations and composites containing calcium orthophosphates (abbreviated as CaPO4) that are suitable for use in biomedical applications and currently on the market. The bioactive, biocompatible, and osteoconductive properties of various CaPO4-based formulations make them valuable in the rapidly developing field of biomedical research, both in vitro and in vivo. Due to the brittleness of CaPO4, it is essential to combine the desired osteologic properties of ceramic CaPO4 with those of other compounds to create novel, multifunctional bone graft biomaterials. Consequently, this analysis offers a thorough overview of the hybrid formulations and CaPO4-based composites that are currently known. To do this, a comprehensive search of the literature on the subject was carried out in all significant databases to extract pertinent papers. There have been many formulations found with different material compositions, production methods, structural and bioactive features, and in vitro and in vivo properties. When these formulations contain additional biofunctional ingredients, such as drugs, proteins, enzymes, or antibacterial agents, they offer improved biomedical applications. Moreover, a lot of these formulations allow cell loading and promote the development of smart formulations based on CaPO4. This evaluation also discusses basic problems and scientific difficulties that call for more investigation and advancements. It also indicates perspectives for the future.

Enhanced mechanical properties, anti-biofilm activity, and cytocompatibility of a methacrylate-based polymer loaded with native multiwalled carbon nanotubes

OBJECTIVES

We aimed to optimize the mechanical and biological properties of a conventional methacrylate-based dental polymer by loading it with double- and triple-walled carbon nanotubes as growth (DTWCNTG).

METHODS

A formulation of bisphenol A-glycidyl methacrylate and triethylene glycol dimethacrylate (mass ratio = 2:1) was mixed with DTWCNTG at concentrations of 0.0% (control), 0.001%, 0.005%, and 0.010%. The concentrations were physicochemical and morphologically evaluated, and antibacterial activity was assessed by seeding a Streptococcus mutans strain (ATCC 25175) on the experimental polymeric surfaces. Cellular survival and osteodifferentiation were evaluated in epithelial (HaCat) and preosteoblast cells (MC3T3-E1).

RESULTS

The 0.001% DTWCNTG concentration yielded higher compressive strength, elastic modulus, flexural strength, flexural modulus, water sorption, and solubility than the control. The degree of conversion and color did not significantly change with a low amount of DTWCNTG incorporated into the polymer. Antibacterial activity significantly improved when tested on the 0.001% DTWCNTG discs. No groups showed cytotoxicity in a short-term analysis and adding DTWCNTG favored MC3T3-E1 mineralization over the control, particularly in the 0.001% formulation.

SIGNIFICANCE

The micro-addition of 0.001% DTWCNTG confers mechanical resistance, antimicrobial properties, and bioactivity to methacrylate-based polymers without significantly compromising color. Incorporating DTWCNTG improved dental composite properties and could be a biomodified material for minimally invasive procedures.

Design Strategies and Biomimetic Approaches for Calcium Phosphate Scaffolds in Bone Tissue Regeneration

Bone is a complex biologic tissue, which is extremely relevant for various physiological functions, in addition to movement, organ protection, and weight bearing. The repair of critical size bone defects is a still unmet clinical need, and over the past decades, material scientists have been expending efforts to find effective technological solutions, based on the use of scaffolds. In this context, biomimetics which is intended as the ability of a scaffold to reproduce compositional and structural features of the host tissues, is increasingly considered as a guide for this purpose. However, the achievement of implants that mimic the very complex bone composition, multi-scale structure, and mechanics is still an open challenge. Indeed, despite the fact that calcium phosphates are widely recognized as elective biomaterials to fabricate regenerative bone scaffolds, their processing into 3D devices with suitable cell-instructing features is still prevented by insurmountable drawbacks. With respect to biomaterials science, new approaches maybe conceived to gain ground and promise for a substantial leap forward in this field. The present review provides an overview of physicochemical and structural features of bone tissue that are responsible for its biologic behavior. Moreover, relevant and recent technological approaches, also inspired by natural processes and structures, are described, which can be considered as a leverage for future development of next generation bioactive medical devices.

Comparison of Injectable Biphasic Calcium Phosphate and a Bovine Xenograft in Socket Preservation: Qualitative and Quantitative Histologic Study in Humans

This study is the first histologic evaluation of an injectable biphasic calcium phosphate (IBCP) in humans six months after socket preservation according to the principles of guided bone regeneration. After tooth extraction, the alveolar ridge of 21 patients was augmented with IBCP (maxresorb® inject) in the test group, while 20 patients in the control group received a bovine xenograft (BX) (cerabone®). Six months after augmentation, a reentry procedure was performed to collect biopsies of regenerated bone for qualitative and quantitative histologic analysis. A total of 20 biopsies were taken for analysis. Qualitative histologic analysis showed complete integration of the biomaterial and no inflammatory tissue reaction, indicating the biocompatibility of the bone grafts and the surrounding tissue in both groups. Histomorphometric analysis showed comparable results in terms of newly formed bone (IBCP: 26.47 ± 14.71%, BX: 30.47 ± 16.39%) and residual biomaterial (IBCP: 13.1 ± 14.07%, BX: 17.89 ± 11.81%), with no significant difference found across groups (p > 0.05, Mann—Whitney U test). Statistical significance between groups was found in the result of soft tissue percentage (IBCP: 60.43 ± 12.73%, BX: 51.64 ± 14.63%, p = 0.046, Mann—Whitney U test). To conclude, IBCP and BX showed good osteoconductivity and biocompatibility with comparable new bone formation six months after alveolar ridge preservation.

In Vivo Biocompatibility Investigation of an Injectable Calcium Carbonate (Vaterite) as a Bone Substitute including Compositional Analysis via SEM-EDX Technology

Injectable bone substitutes (IBS) are increasingly being used in the fields of orthopedics and maxillofacial/oral surgery. The rheological properties of IBS allow for proper and less invasive filling of bony defects. Vaterite is the most unstable crystalline polymorph of calcium carbonate and is known to be able to transform into hydroxyapatite upon contact with an organic fluid (e.g., interstitial body fluid). Two different concentrations of hydrogels based on poly(ethylene glycol)-acetal-dimethacrylat (PEG-a-DMA), i.e., 8% (w/v) (VH-A) or 10% (w/v) (VH-B), were combined with vaterite nanoparticles and implanted in subcutaneous pockets of BALB/c mice for 15 and 30 days. Explants were prepared for histochemical staining and immunohistochemical detection methods to determine macrophage polarization, and energy-dispersive X-ray analysis (EDX) to analyze elemental composition was used for the analysis. The histopathological analysis revealed a comparable moderate tissue reaction to the hydrogels mainly involving macrophages. Moreover, the hydrogels underwent a slow cellular infiltration, revealing a different degradation behavior compared to other IBS. The immunohistochemical detection showed that M1 macrophages were mainly found at the material surfaces being involved in the cell-mediated degradation and tissue integration, while M2 macrophages were predominantly found within the reactive connective tissue. Furthermore, the histomorphometrical analysis revealed balanced numbers of pro- and anti-inflammatory macrophages, demonstrating that both hydrogels are favorable materials for bone tissue regeneration. Finally, the EDX analysis showed a stepwise transformation of the vaterite particle into hydroxyapatite. Overall, the results of the present study demonstrate that hydrogels including nano-vaterite particles are biocompatible and suitable for bone tissue regeneration applications.

Injectable silanized hyaluronic acid hydrogel/biphasic calcium phosphate granule composites with improved handling and biodegradability promote bone regeneration in rabbits

Biphasic calcium phosphate (BCP) granules are osteoconductive biomaterials used in clinics to favor bone reconstruction. Yet, poor cohesivity, injectability and mechanical properties restrain their use as bone fillers. In this study, we incorporated BCP granules into in situ forming silanized hyaluronic acid (Si-HA) and hydroxypropylmethylcellulose (Si-HPMC) hydrogels. Hydrogel composites were shown to be easily injectable (F < 30 N), with fast hardening properties (<5 min), and similar mechanical properties (E∼ 60 kPa). In vivo, both hydrogels were well tolerated by the host, but showed different biodegradability with Si-HA gels being partially degraded after 21d, while Si-HPMC gels remained stable. Both composites were easily injected into critical size rabbit defects and remained cohesive. After 4 weeks, Si-HPMC/BCP led to poor bone healing due to a lack of degradation. Conversely, Si-HA/BCP composites were fully degraded and beneficially influenced bone regeneration by increasing the space available for bone ingrowth, and by accelerating BCP granules turnover. Our study demonstrates that the degradation rate is key to control bone regeneration and that Si-HA/BCP composites are promising biomaterials to regenerate bone defects.

Synthetic Injectable Biomaterials for Alveolar Bone Regeneration in Animal and Human Studies

After tooth extraction, the alveolar ridge undergoes dimensional changes. Different bone regeneration biomaterials are used to reduce bone loss. The aim of this article was to systematically review the literature on the effect of injectable synthetic biomaterials and their advantages and disadvantages for new bone formation in the maxilla and mandible in animals and humans. A literature search was conducted in November 2020 via MEDLINE PubMed, Cochrane, and Embase. Of the 501 records screened, abstract analysis was performed on 49 articles, resulting in 21 studies that met the inclusion criteria. Animal studies have shown heterogeneity in terms of animal models, follow-up time, composition of the injectable biomaterial, and different outcome variables such as bone–implant contact, newly formed bone, and peri-implant bone density. Heterogeneity has also been demonstrated by human studies. The following outcomes were observed: newly formed bone, connective tissue, residual injectable bone graft substitute, radiographic density, residual bone height, and different follow-up periods. Further studies, especially in humans, based on the histological and biomechanical properties of the injectable delivery form, are needed to draw more concrete conclusions that will contribute to a better understanding of the benefits of this type of biomaterials and their role in bone regeneration.

Inhibition of osteoclast activities by SCPC bioceramic promotes osteoblast-mediated graft resorption and osteogenic differentiation

Maximizing vital bone in a grafted site is dependent on a number of factors. These include resorption or turnover of the graft material, stimulation of bone formation pathway without a need for biological molecules added to the site and inhibition of cellular activities that compromise the mineralization of new bone matrix. In the present study, the dissolution profile of silica-calcium phosphate composite (SCPC) in physiological solution was measured and the data were fed to (ANN-NARX) prediction model to predict the time required for complete dissolution. The inductively coupled plasma-optical emission spectrometer ionic composition analysis of the culture medium incubated for 3 days with SCPC showed 57% decrease in Ca concentration and a significant increase in the concentration of Si (13.5 ± 1.8 μg/ml), P (249.4 ± 22 μg/ml), and Na (9.3 ± 0.52 μg/ml). In conjunction with the release of Si, P, and Na ions, the bone resorptive activity of osteoclasts was inhibited as indicated by the significant decrease in multinucleated tartrate resistant acidic phosphate stained cells and the volume of resorption pits on bone slices. In contrast, addition of SCPC to hBMSC cultured in conventional medium promoted higher Runt-related transcription factor 2 (p < .05), osteocalcin (p < .01), and bone sialo protein (p < .01) than that expressed by control cells grown in the absence of SCPC. The predicted dissolution time of 200 mg of porous SCPC particles in 10 ml phosphate buffered saline is 6.9 months. An important byproduct of the dissolution is inhibition of osteoclastic activity and promotion of osteoblastic differentiation and hence bone formation.

Evaluation of Poly Lactic-co-Glycolic Acid-Coated β-Tricalcium Phosphate Bone Substitute as a Graft Material for Ridge Preservation after Tooth Extraction in Dog Mandible: A Comparative Study with Conventional β-Tricalcium Phosphate Granules

This study aims to evaluate the safety and efficacy of a poly lactic-co-glycolic acid (PLGA)-coated β-tricalcium phosphate (β-TCP) with N-methyl-2-pyrrolidone (NMP) liquid activator (PLGA/β-TCP) on alveolar ridge preservation after tooth extraction in dog mandible. Thirty-two extraction sites were prepared in eight dog mandibles. A distal root of the mandibular premolar was extracted and randomly grafted with one of the following bone substitutes: (1) PLGA/β-TCP, (2) β-TCP, or (3) left empty as a control, and wounds were closed with keratinized mucosa graft. Post-operative wound healing was observed and scored to evaluate safety. After 12 and 24 weeks, the bone regeneration was evaluated with micro-computed tomography (CT) images and histomorphometric analyses. Gingival epithelization progressed over time without complication or infection. Micro-CT images and histological observation revealed that both PLGA/β-TCP and β-TCP granules supported sufficient new bone formation. Although bone formation and substrate resorption were delayed slightly with the PLGA and the NMP-containing plasticizer as compared to those treated with conventional β-TCP, it can be concluded that the PLGA and the NMP-containing plasticizer that facilitated the in situ hardening properties of the material had no negative influence on the biocompatibility of the material.

Bone Regeneration Capability of 3D Printed Ceramic Scaffolds

In this study, we evaluated the bone regenerative capability of a customizable hydroxyapatite (HA) and tricalcium phosphate (TCP) scaffold using a digital light processing (DLP)-type 3D printing system. Twelve healthy adult male beagle dogs were the study subjects. A total of 48 defects were created, with two defects on each side of the mandible in all the dogs. The defect sites in the negative control group (sixteen defects) were left untreated (the NS group), whereas those in the positive control group (sixteen defects) were filled with a particle-type substitute (the PS group). The defect sites in the experimental groups (sixteen defects) were filled with a 3D printed substitute (the 3DS group). Six dogs each were exterminated after healing periods of 4 and 8 weeks. Radiological and histomorphometrical evaluations were then performed. None of the groups showed any specific problems. In radiological evaluation, there was a significant difference in the amount of new bone formation after 4 weeks (p < 0.05) between the PS and 3DS groups. For both of the evaluations, the difference in the total amount of bone after 8 weeks was statistically significant (p < 0.05). There was no statistically significant difference in new bone between the PS and 3DS groups in both evaluations after 8 weeks (p > 0.05). The proposed HA/TCP scaffold without polymers, obtained using the DLP-type 3D printing system, can be applied for bone regeneration. The 3D printing of a HA/TCP scaffold without polymers can be used for fabricating customized bone grafting substitutes.

Clinical study of octacalcium phosphate and collagen composite in oral and maxillofacial surgery

Octacalcium phosphate and its collagen composite have been recognized as bone substitute materials possessing osteoconductivity and biodegradation properties. We evaluated the effectiveness of octacalcium phosphate and its collagen composite used for bone augmentation in major oral and maxillofacial surgeries in a clinical trial. Octacalcium phosphate and its collagen composite were used in cases of sinus floor elevation in 1- and 2-stage, socket preservation, cyst, and alveolar cleft procedures. A total of 60 patients were evaluated for effectiveness after the implantation of octacalcium phosphate and its collagen composite. Although sinus floor elevation in 1-stage, cyst, and alveolar cleft cases met the criteria for the judgment of success, sinus floor elevation in 2-stage and socket preservation groups did not meet the criteria in the initial evaluation. However, an additional evaluation for reconfirmation revealed the effectiveness of octacalcium phosphate and its collagen composite in those groups, and all evaluation results ultimately indicated the success of this clinical trial. Therefore, this clinical trial suggested that application of octacalcium phosphate and its collagen composite for oral and maxillofacial surgery was safe and effective and that octacalcium phosphate and its collagen composite could be a bone substitute candidate instead of autologous bone.

Bone regeneration and graft material resorption in extraction sockets grafted with bioactive silica-calcium phosphate composite (SCPC) versus non-grafted sockets: clinical, radiographic, and histological findings

Purpose

The purpose of the present study was to evaluate the effect of silica-calcium phosphate composite (SCPC) granules on bone regeneration in extraction sockets.

Methods

Ten patients were selected for a split-model study. In each patient, bone healing in SCPC-grafted and control ungrafted sockets was analyzed through clinical, radiographic, histomorphometric, and immunohistochemical assessments 6 months postoperatively.

Results

A radiographic assessment using cone-beam computed tomography showed minimal ridge dimension changes in SCPC-grafted sockets, with 0.39 mm and 1.79 mm decreases in height and width, respectively. Core bone biopsy samples were obtained 6 months post-extraction during implant placement and analyzed. The average percent areas occupied by mature bone, woven bone, and remnant particles in the SCPC-grafted sockets were 41.3%±12%, 20.1%±9.5%, and 5.3%±4.4%, respectively. The percent areas of mature bone and woven bone formed in the control ungrafted sockets at the same time point were 31%±14% and 24.1%±9.4%, respectively. Histochemical and immunohistochemical analyses showed dense mineralized bundles of type I collagen with high osteopontin expression intensity in the grafted sockets. The newly formed bone was well vascularized, with numerous active osteoblasts, Haversian systems, and osteocytes indicating maturation. In contrast, the new bone in the control ungrafted sockets was immature, rich in type III collagen, and had a low osteocyte density.

Conclusions

The resorption of SCPC granules in 6 months was coordinated with better new bone formation than was observed in untreated sockets. SCPC is a resorbable bone graft material that enhances bone formation and maturation through its stimulatory effect on bone cell function.

Trial Registration

ClinicalTrials.gov Identifier: NCT03897010

Synthesis and Characterization of Nanohydroxyapatite-Gelatin Composite with Streptomycin as Antituberculosis Injectable Bone Substitute

The most effective treatment for spinal tuberculosis was by eliminating the tuberculosis bacteria and replacing the infected bone with the bone graft to induce the healing process. This study aims to synthesize and characterize nanohydroxyapatite-gelatin-based injectable bone substitute (IBS) with addition of streptomycin. The IBS was synthesized by mixing nanohydroxyapatite and 20 w/v% gelatin with ratio of 40:60, 45:55, 50:50, 55:45, 60:40, 65:35, 70:30, and 75:25 ratio and streptomycin addition as antibiotic agent. The mixture was added by hydroxypropyl methylcellulose as suspending agent. FTIR test showed that there was a chemical reaction occurring in the mixture, between the gelatin and streptomycin. The result of injectability test showed that the highest injectability of the IBS sample was 98.64% with the setting time between 30 minutes and four hours after injection on the HA scaffold that represents the bone cavity and coat the pore scaffold. The cytotoxicity test result showed that the IBS samples were nontoxic towards BHK-21 fibroblast cells and human hepatocyte cells since the viability cell was more than 50% with significant difference (p-value<0.05). The acidity of the IBS was stable and it was sensitive towards Staphylococcus aureus with significantly difference (p-value<0.05). The streptomycin release test showed that the streptomycin could be released from the IBS-injected bone scaffold with release of 2.5% after 4 hours. All the results mentioned showed that IBS was suitable as a candidate to be used in spinal tuberculosis case.

Low-intensity pulsed ultrasound promotes alveolar bone regeneration in a periodontal injury model

Periodontitis is a common oral disease characterized by progressive destruction of periodontal tissue and loss of teeth. However, regeneration of periodontal tissue is a time-consuming process. Low-intensity pulsed ultrasound (LIPUS) is a widely used non-invasive intervention for enhancing bone healing in fractures and non-unions. With the hypothesis that LIPUS may accelerate periodontal regeneration, the effects of LIPUS on periodontal tissue regeneration were investigated both in vitro and in vivo. LIPUS (90 mw/cm², 20 min/d, 1.5 MHz) was applied to stimulate dog periodontal ligament cells (dPDLCS). The mRNA expression of BSP (P < 0.05), OPN (P < 0.05) and COL3 (P < 0.05) was increased significantly in the LIPUS group. The positive stained mineralized nodules by alizarin red in the LIPUS group were greater than in the control group (P < 0.05). Eight male beagle dogs were divided into 4 groups: guided tissue regeneration (GTR) group (G1), LIPUS + GTR group (G2), LIPUS group (G3), and control group (G4, no treatment). A 4 × 5 mm² defect was created in the buccal alveolar bone. The modeling areas in the G2 and G3 groups were then exposed to LIPUS. Eight weeks after surgery, histological assessment indicated increased periodontal tissue in the LIPUS + GTR group. Micro computed tomography (micro-CT) showed that the regenerated bone volume (BV) in the G2 was significantly higher than that in the G1, G3 and G4 groups (P < 0.05). The bone surface (BS) trabecular number (Tb.N) and trabecular thickness (Tb.Th) in G2 were markedly higher than in G4 (P < 0.05). It is concluded that LIPUS + GTR can accelerate new alveolar bone formation, with a prospective for promoting periodontal tissue repair.

Evaluation of a hydrogel membrane on bone regeneration in furcation periodontal defects in dogs

The aim of the study was to evaluate bone regeneration using a canine model with surgically created periodontal defects filled for 12 weeks using a stratified biomaterial consisting in a biphasic calcium phosphate (BCP) covered with a crosslinking hydrogel acting as polymer membrane of silated hydroxypropyl methylcellulose (Si-HPMC) as the tested new concept. Bilateral, critical-sized, defects were surgically created at the mandibular premolar teeth of six adult beagle dogs. The defects were randomly allocated and: (i) left empty for spontaneous healing or filled with: (ii) BCP and a collagen membrane; (iii) BCP and hydrogel Si-HPMC membrane. At 12 weeks, the experimental conditions resulted in significantly enhanced bone regeneration in the test BCP/Si-HPMC group. Within the limits of this study, we suggest that the hydrogel Si-HPMC may act as an occlusive barrier to protect bone area from soft connective tissue invasion and then effectively contribute to enhance bone regeneration.

Inorganic Self-Assembled Bioactive Artificial Proto-Osteocells Inducing Bone Regeneration

Since the discovery of osteoinduction in the early 20th century, innovative biomaterials with osteoinductive potential have emerged as candidates for bone repair. Recently, artificial protocell models have demonstrated great potential for tissue regeneration. Herein, we developed artificial bioactive proto-osteocells by self-assembly of biodegradable biphasic-phosphate particles in the form of aqueous bone morphogenetic protein 2 (BMP2)-containing Pickering emulsions in corn oil to fulfill the release of BMP2 with controlled and local efficacy. These artificial proto-osteocells have the advantage of (1) being directly injected into the target location to avert reported side effects of BMP2, minimizing surgical complications, (2) exhibiting the capability of osteoinduction as shown in both in vitro and in vivo models, and (3) demonstrating calcific deposition locally by utilizing the biodegradable calcium phosphate shell. The efficiency of BMP2 within the artificial proto-osteocells showed 25 times greater bone-inducing potential when compared to the control. This study demonstrates for the first time a new strategy toward utilizing material-based artificial proto-osteocells to tackle medical issues in bone tissue repair and regeneration.

Bone regeneration using a porcine bone substitute collagen composite in vitro and in vivo

The biocharacteristics of xenogeneic grafts make them a possible substitute for autogenous bone grafts in dental bone graft procedures. This study aimed to develop a novel porcine graft with collagen capable of generating new bone in bone defects via osteoconduction over 8 weeks of healing and to compare it with a porcine graft. The porcine collagen graft was made to undergo a cell viability test (MTT) and alkaline phosphatase assay (ALP). The surgical procedure was performed in 20 male adult New Zealand white rabbits. Four calvarial critical-size defects of 6 mm in diameter were prepared in each rabbit. The upper left defect was filled with a porcine graft of 500–1000 μm, the upper right with a porcine collagen graft, the lower left with hydroxyapatite/beta-tricalcium phosphate and the lower right served as the control without any filling material. The rabbits were divided and sacrificed at 2, 4, 6 and 8 weeks after surgery. Histological and micro-CT scan results showed that the performance of the porcine collagen graft is superior for regenerating new bone. Porcine collagen graft showed cell viability and osteoblast-like cell differentiation in vitro. The results indicate that porcine collagen graft is a potential bone substitute for clinical application.

Biological properties of calcium phosphate biomaterials for bone repair: a review

This article reviews the recent advances and various factors affecting the improvement of the biological properties of calcium phosphate for bone repair.

Hydoxyapatite/beta-tricalcium phosphate biphasic ceramics as regenerative material for the repair of complex bone defects

Bone is a composite material composed of collagen and calcium phosphate (CaP) mineral. The collagen gives bone its flexibility while the inorganic material gives bone its resilience. The CaP in bone is similar in composition and structure to the mineral hydroxyapatite (HA) and is bioactive, osteoinductive and osteoconductive. Therefore synthetic versions of bone apatite (BA) have been developed to address the demand for autologous bone graft substitutes. Synthetic HA (s-HA) are stiff and strong, but brittle. These lack of physical attributes limit the use of synthetic apatites in situations where no physical loading of the apatite occurs. s-HA chemical properties differ from BA and thus change the physical and mechanical properties of the material. Consequently, s-HA is more chemically stable than BA and thus its resorption rate is slower than the rate of bone regeneration. One solution to this problem is to introduce a faster resorbing CaP, such as β-tricalcium phosphate (β-TCP), when synthesizing the material creating a biphasic (s-HA and β-TCP) formulation of calcium phosphate (BCP). The focus of this review is to introduce the major differences between BCP and biological apatites and how material scientists have overcome the inadequacies of the synthetic counterparts. Examples of BCP performance in vitro and in vivo following structural and chemical modifications are provided as well as novel ultrastructural data. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2493-2512, 2018.

Enhancement of Osteoblastic-Like Cell Activity by Glow Discharge Plasma Surface Modified Hydroxyapatite/β-Tricalcium Phosphate Bone Substitute

Glow discharge plasma (GDP) treatments of biomaterials, such as hydroxyapatite/β-tricalcium phosphate (HA/β-TCP) composites, produce surfaces with fewer contaminants and may facilitate cell attachment and enhance bone regeneration. Thus, in this study we used argon glow discharge plasma (Ar-GDP) treatments to modify HA/β-TCP particle surfaces and investigated the physical and chemical properties of the resulting particles (HA/β-TCP + Ar-GDP). The HA/β-TCP particles were treated with GDP for 15 min in argon gas at room temperature under the following conditions: power: 80 W; frequency: 13.56 MHz; pressure: 100 mTorr. Scanning electron microscope (SEM) observations showed similar rough surfaces of HA/β-TCP + Ar-GDP HA/β-TCP particles, and energy dispersive spectrometry analyses showed that HA/β-TCP surfaces had more contaminants than HA/β-TCP + Ar-GDP surfaces. Ca/P mole ratios in HA/β-TCP and HA/β-TCP + Ar-GDP were 1.34 and 1.58, respectively. Both biomaterials presented maximal intensities of X-ray diffraction patterns at 27° with 600 a.u. At 25° and 40°, HA/β-TCP + Ar-GDP and HA/β-TCP particles had peaks of 200 a.u., which are similar to XRD intensities of human bone. In subsequent comparisons, MG-63 cell viability and differentiation into osteoblast-like cells were assessed on HA/β-TCP and HA/β-TCP + Ar-GDP surfaces, and Ar-GDP treatments led to improved cell growth and alkaline phosphatase activities. The present data indicate that GDP surface treatment modified HA/β-TCP surfaces by eliminating contaminants, and the resulting graft material enhanced bone regeneration.

Potential Applications of Nanocellulose-Containing Materials in the Biomedical Field

Because of its high biocompatibility, bio-degradability, low-cost and easy availability, cellulose finds application in disparate areas of research. Here we focus our attention on the most recent and attractive potential applications of cellulose in the biomedical field. We first describe the chemical/structural composition of cellulose fibers, the cellulose sources/features and cellulose chemical modifications employed to improve its properties. We then move to the description of cellulose potential applications in biomedicine. In this field, cellulose is most considered in recent research in the form of nano-sized particle, i.e., nanofiber cellulose (NFC) or cellulose nanocrystal (CNC). NFC is obtained from cellulose via chemical and mechanical methods. CNC can be obtained from macroscopic or microscopic forms of cellulose following strong acid hydrolysis. NFC and CNC are used for several reasons including the mechanical properties, the extended surface area and the low toxicity. Here we present some potential applications of nano-sized cellulose in the fields of wound healing, bone-cartilage regeneration, dental application and different human diseases including cancer. To witness the close proximity of nano-sized cellulose to the practical biomedical use, examples of recent clinical trials are also reported. Altogether, the described examples strongly support the enormous application potential of nano-sized cellulose in the biomedical field.

A doxycycline inducible, adenoviral bone morphogenetic protein-2 gene delivery system to bone

We report the novel use of a tuneable, non-integrating viral gene delivery system to bone that can be combined with clinically approved biomaterials in an 'off-the-shelf' manner. Specifically, a doxycycline inducible Tet-on adenoviral vector (AdTetBMP-2) in combination with mesenchymal stromal cells (MSCs), fibrin and a biphasic calcium phosphate ceramic (MBCP®) was used to repair large bone defects in nude rats. Bone morphogenetic protein-2 (BMP-2) transgene expression could be effectively tuned by modification of the doxycycline concentration. The effect of adenoviral BMP-2 gene delivery upon bone healing was investigated in vivo in 4 mm critically sized, internally fixated, femoral defects. MSCs were transduced either by direct application of AdTetBMP-2 or by pre-coating MBCP granules with the virus. Radiological assessment scores post-mortem were significantly improved upon delivery of AdTetBMP-2. In AdTetBMP-2 groups, histological analysis revealed significantly more newly formed bone at the defect site compared with controls. Newly formed bone was vascularized and fully integrated with nascent tissue and implanted biomaterial. Improvement in healing outcome was achieved using both methods of vector delivery (direct application vs. pre-coating MCBP). Adenoviral delivery of BMP-2 enhanced bone regeneration achieved by the transplantation of MSCs, fibrin and MBCP in vivo. Importantly, our in vitro and in vivo data suggest that this can be achieved with relatively low (ng/ml) levels of the growth factor. Our model and novel gene delivery system may provide a powerful standardized tool for the optimization of growth factor delivery and release for the healing of large bone defects. Copyright © 2016 John Wiley & Sons, Ltd.

Maxillary Sinus Grafting With Biphasic Bone Ceramic or Autogenous Bone: Clinical, Histologic, and Histomorphometric Results From a Randomized Controlled Clinical Trial

PURPOSE

The present, randomized, controlled clinical trial compared the histologic and histomorphometric results from maxillary sinus augmentation with either biphasic calcium phosphate (BCP) (60% hydroxyapatite and 40% β-tricalcium phosphate) or autogenous bone (AB) as bone-grafting materials.

MATERIAL AND METHODS

Ten patients received bilateral sinus elevation surgery with intraoral AB chips (control group) on one side and BCP (test group) on the contralateral side. After a healing period of 6 to 8 months, implant sites were created and trephine cores were harvested for histological and histomorphometric analysis of the grafted areas.

RESULTS

The histological examination of biopsies showed BCP particles interconnected by bridges of a vital newly formed bone. Histomorphometry demonstrated that the amount of newly formed bone in the control group (36.8%) was significantly greater than that in the BCP (28.2%) group (P = 0.0032). BCP and AB cores revealed an average of residual graft particles of 32.9% and 4.8%, respectively. The average percentage of soft tissue components was 38.9% in the BCP cores and 58.4% in the AB cores.

CONCLUSIONS

Based on our findings, the amount of vital bone formation was significantly higher for AB than that for BCP. However, BCP seemed to be a biocompatible and osteoconductive material that can be used with success as a bone substitute in maxillary sinus procedures.

The proangiogenic potential of a novel calcium releasing composite biomaterial: Orthotopic in vivo evaluation

Insufficient angiogenesis remains a major hurdle in current bone tissue engineering strategies. An extensive body of work has focused on the use of angiogenic factors or endothelial progenitor cells. However, these approaches are inherently complex, in terms of regulatory and methodologic implementation, and present a high cost. We have recently demonstrate the potential of electrospun poly(lactic acid) (PLA) fiber-based membranes, containing calcium phosphate (CaP) ormoglass particles, to elicit angiogenesis in vivo, in a subcutaneous model in mice. Here we have devised an injectable composite, containing CaP glass-ceramic particles, dispersed within a (Hydroxypropyl)methyl cellulose (HPMC) matrix, with the capacity to release calcium in a more sustained fashion. We show that by tuning the release of calcium in vivo, in a rat bone defect model, we could improve both bone formation and increase angiogenesis. The bone regeneration kinetics was dependent on the Ca²⁺ release rate, with the faster Ca²⁺ release composite gel showing improved bone repair at 3weeks, in relation to control. In the same line, improved angiogenesis could be observed for the same gel formulation at 6weeks post implantation. This methodology allows to integrate two fundamental processes for bone tissue regeneration while using a simple, cost effective, and safe approach.

STATEMENT OF SIGNIFICANCE

In current bone tissue engineering approaches the achievement of sufficient angiogenesis, during tissue regeneration, is a major limitation in order to attain full tissue functionality. Recently, we have shown that calcium ions, released by the degradation of calcium phosphate ormoglasses (CaP), are effective angiogenic promoters, in both in vitro and in a subcutaneous implantation model. Here, we devised an injectable composite, containing CaP glass-ceramic particles, dispersed within a HPMC matrix, enabling the release of calcium in a more sustained fashion. We show that by tuning the release of calcium in vivo, in a rat bone defect model, we could improve both bone formation and increase angiogenesis. This simple and cost effective approach holds great promise to translate to the clinics.

Biphasic calcium phosphate ceramics for bone reconstruction: A review of biological response

Autologous bone graft is considered as the gold standard in bone reconstructive surgery. However, the quantity of bone available is limited and the harvesting procedure requires a second surgical site resulting in severe complications. Due to these limits, scientists and clinicians have considered alternatives to autologous bone graft. Calcium phosphates (CaPs) biomaterials including biphasic calcium phosphate (BCP) ceramics have proven efficacy in numerous clinical indications. Their specific physico-chemical properties (HA/TCP ratio, dual porosity and subsequent interconnected architecture) control (regulate/condition) the progressive resorption and the bone substitution process. By describing the most significant biological responses reported in the last 30years, we review the main events that made their clinical success. We also discuss about their exciting future applications as osteoconductive scaffold for delivering various bioactive molecules or bone cells in bone tissue engineering and regenerative medicine.

STATEMENT OF SIGNIFICANCE

Nowadays, BCPs are definitely considered as the gold standard of bone substitutes in bone reconstructive surgery. Among the numerous clinical studies in literature demonstrating the performance of BCP, Passuti et al. and Randsford et al. studies largely contributed to the emergence of the BCPs. It could be interesting to come back to the main events that made their success and could explain their large adhesion from scientists to clinicians. This paper aims to review the most significant biological responses reported in the last 30years, of these BCP-based materials. We also discuss about their exciting future applications as osteoconductive scaffold for delivering various bioactive molecules or bone cells in bone tissue engineering and regenerative medicine.

Clinical safety and efficacy of implantation of octacalcium phosphate collagen composites in tooth extraction sockets and cyst holes

It was demonstrated that octacalcium phosphate collagen composite achieved notable bone regeneration in bone defects in preclinical studies. On the basis of the research results, an investigator-initiated exploratory clinical trial was conducted after approval from a local Institutional Review Board. This clinical study was performed as a single-arm non-randomized intervention study. Octacalcium phosphate collagen composite was implanted into a total of 10 cases of alveolar bone defects after tooth extractions and cystectomy. Safety assessment was performed in terms of the clinical course and several consecutive laboratory examinations, and sequential radiographs were used for efficacy assessment. All participants uneventfully completed the clinical trial without major problems in their general condition. Postoperative wound swelling was observed, as also commonly seen in tooth extraction or cystectomy. Although no serious liver dysfunction, renal dysfunction, electrolyte imbalance, or abnormal urinalysis results were recognized, the number of white blood cells and C-reactive protein level temporarily increased after the operation. An increase in radiopacity in the octacalcium phosphate collagen composite–implanted site was observed in all cases. Finally, the border between the original bone and the octacalcium phosphate collagen composite–implanted site became indistinguishable. These results suggest that octacalcium phosphate collagen composite could be utilized safely in clinical situations in the future.

Clinical Performance of Moldable Bioceramics for Bone Regeneration in Maxillofacial Surgery

There are numerous clinical indications for bone grafts. The ideal graft material should favor bone apposition and growth while simultaneously being degraded by body fluids and cells. Ultimately, the material should be replaced by mature bone tissue within a healing period of weeks. Because autologous and allogenic bone grafts fulfill some of these requirements, these biological materials are routinely used by clinicians. However, biological materials have intrinsic limitations. Harvesting autologous bone requires a second surgical site, which can cause complications, the material is limited in quantity, and it may lead to immunogenic rejection or transfer certain pathogens and viruses [1-3]. For these reasons, researchers and clinicians have developed synthetic bone substitutes. Our approach has focused on composite biomaterials that combine bioceramics with hydrogels to replace and regenerate bone tissue in osseous defects.

Injectable Bone Substitute Based on β-TCP Combined With a Hyaluronan-Containing Hydrogel Contributes to Regeneration of a Critical Bone Size Defect Towards Restitutio ad Integrum

In the present in vivo study, the regenerative potential of a new injectable bone substitute (IBS) composed of beta-tricalcium phosphate (β-TCP) and hyaluronan was tested in a rabbit distal femoral condyle model. To achieve this, 2 defects of 6 mm in diameter and 10 mm in length were drilled into each femur condyle in a total of 12 animals. For each animal, 1 hole was filled with the substitute material, and the other was left empty to serve as the control. After 1, 3, and 6 months, the regenerative process was analyzed by radiography as well as by histological and histomorphometrical analysis. The results revealed that bone tissue formation took place through osteoconductive processes over time, starting from the defect borders to the center. Both the β-TCP content and the hydrogel support bone tissue growth. The histomorphometrical measurements showed that the amount of bone formation in the experimental group was significantly higher compared with that found in the control group after 3 months (19.51 ± 5.08% vs. 1.96 ± 0.77%, P < .05) and 6 months (4.57 ± 1.56% vs. 0.23 ± 0.21%, P < .05). The application of the IBS gave a restitutio ad integrum result after 6 months and was associated with its nearly complete degradation, in contrast to the results found in the control group. In conclusion, the results of the present study demonstrate that the IBS contributes to sufficient bone regeneration by serving as a scaffold-like structure, combined with its degradation within 6 months.

Calcium Orthophosphate-Containing Biocomposites and Hybrid Biomaterials for Biomedical Applications

The state-of-the-art on calcium orthophosphate (CaPO4)-containing biocomposites and hybrid biomaterials suitable for biomedical applications is presented. Since these types of biomaterials offer many significant and exciting possibilities for hard tissue regeneration, this subject belongs to a rapidly expanding area of biomedical research. Through the successful combinations of the desired properties of matrix materials with those of fillers (in such systems, CaPO4 might play either role), innovative bone graft biomaterials can be designed. Various types of CaPO4-based biocomposites and hybrid biomaterials those are either already in use or being investigated for biomedical applications are extensively discussed. Many different formulations in terms of the material constituents, fabrication technologies, structural and bioactive properties, as well as both in vitro and in vivo characteristics have been already proposed. Among the others, the nano-structurally controlled biocomposites, those containing nanodimensional compounds, biomimetically fabricated formulations with collagen, chitin and/or gelatin, as well as various functionally graded structures seem to be the most promising candidates for clinical applications. The specific advantages of using CaPO4-based biocomposites and hybrid biomaterials in the selected applications are highlighted. As the way from a laboratory to a hospital is a long one and the prospective biomedical candidates have to meet many different necessities, the critical issues and scientific challenges that require further research and development are also examined.

A Novel Porcine Graft for Regeneration of Bone Defects

Bone regeneration procedures require alternative graft biomaterials to those for autogenous bone. Therefore, we developed a novel porcine graft using particle sizes of 250–500 μm and 500–1000 μm in rabbit calvarial bone defects and compared the graft properties with those of commercial hydroxyapatite (HA)/beta-tricalcium phosphate (β-TCP) over eight weeks. Surgery was performed in 20 adult male New Zealand white rabbits. During a standardized surgical procedure, four calvarial critical-size defects of 5 mm diameter and 3 mm depth were prepared. The defects were filled with HA/β-TCP, 250–500 μm or 500–1000 μm porcine graft, and control defects were not filled. The animals were grouped for sacrifice at 1, 2, 4, and 8 weeks post-surgery. Subsequently, sample blocks were prepared for micro-computed tomography (micro-CT) scanning and histological sectioning. Similar bone formations were observed in all three treatment groups, although the 250–500 μm porcine graft performed slightly better. Rabbit calvarial bone tissue positively responded to porcine grafts and commercial HA/β-TCP, structural analyses showed similar crystallinity and porosity of the porcine and HA/β-TCP grafts, which facilitated bone formation through osteoconduction. These porcine grafts can be considered as graft substitutes, although further development is required for clinical applications.

Histopathological, histomorphometrical, and radiographical evaluation of injectable glass-ceramic-chitosan nanocomposite in bone reconstruction of rat

Background. Bone defects following tumor resection and osteolysis due to bone lesions, periodontal tissue disorders, and bone reconstruction are challenges that surgeons face. Gass-ceramic-chitosan nanocomposite contains chitosan, a derivative of crustaceans' exoskeleton. Methods. Thirty-two 6–8-week-old male Wistar rats were chosen. One hole on each right and left tibia was made. The right tibia holes were filled with injectable glass-ceramic-chitosan nanocomposite, and the left tibia holes were left empty. After 7, 14, 28, and 60 days, histopathological, histomorphometrical, and radiographical assessments were performed. Results. Radiographic density on days 7 and 14 was significantly higher in the right tibias than in the left tibias. Trabecular bone thickness, which was higher in the right tibias, increased from day 7 to day 60 in both right and left tibias, although not significantly. Conclusions. Glass-ceramic-chitosan nanocomposite is suggested for use in bone repair in cases of bone loss. More histopathological, histomorphometrical, and radiographical assessments are also recommended.

45S5 Bioglass analogue reinforced akermanite ceramic favorable for additive manufacturing mechanically strong scaffolds

Mechanically strong akermanite-based porous bioceramic scaffolds with appreciable bioactivity and biodegradation were developedviaextrusion 3D-printing followed by a low-melt bioactive glass-assisted pressureless sintering process.

Pullulan/dextran/nHA macroporous composite beads for bone repair in a femoral condyle defect in rats

The repair of bone defects is of particular interest for orthopedic, oral, maxillofacial, and dental surgery. Bone loss requiring reconstruction is conventionally addressed through bone grafting. Depending on the size and the location of the defect, this method has limits and risks. Biomaterials can offer an alternative and have features supporting bone repair. Here, we propose to evaluate the cellular penetration and bone formation of new macroporous beads based on pullulan/dextran that has been supplemented with nanocrystalline hydroxyapatite in a rat model. Cross-linked beads of 300–500 µm diameters were used in a lateral femoral condyle defect and analyzed by magnetic resonance imaging, micro-computed tomography, and histology in comparison to the empty defects 15, 30, and 70 days after implantation. Inflammation was absent for both conditions. For empty defects, cellularisation and mineralization started from the periphery of the defect. For the defects containing beads, cellular structures filling out the spaces between the scaffolds with increasing interconnectivity and trabecular-like organization were observed over time. The analysis of calcified sections showed increased mineralization over time for both conditions, but was more pronounced for the samples containing beads. Bone Mineral Density and Bone Mineral Content were both significantly higher at day 70 for the beads in comparison to empty defects as well as compared with earlier time points. Analysis of newly formed tissue around the beads showed an increase of osteoid tissue, measured as percentage of the defect surface. This study suggests that the use of beads for the repair of small size defects in bone may be expanded on to meet the clinical need for a ready-to-use fill-up material that can favor bone formation and mineralization, as well as promote vessel ingrowth into the defect site.

Influence of low-intensity pulsed ultrasound on osteogenic tissue regeneration in a periodontal injury model: X-ray image alterations assessed by micro-computed tomography

OBJECTIVE

This study was conducted to evaluate, with micro-computed tomography, the influence of low-intensity pulsed ultrasound on wound-healing in periodontal tissues.

METHODS

Periodontal disease with Class II furcation involvement was surgically produced at the bilateral mandibular premolars in 8 adult male beagle dogs. Twenty-four teeth were randomly assigned among 4 groups (G): G1, periodontal flap surgery; G2, periodontal flap surgery+low-intensity pulsed ultrasound (LIPUS); G3, guided tissue regeneration (GTR) surgery; G4, GTR surgery plus LIPUS. The affected area in the experimental group was exposed to LIPUS. At 6 and 8weeks, the X-ray images of regenerated teeth were referred to micro-CT scanning for 3-D measurement.

RESULTS

Bone volume (BV), bone surface (BS), and number of trabeculae (Tb) in G2 and G4 were higher than in G1 and G3 (p<0.05). BV, BS, and Tb.N of the GTR+LIPUS group were higher than in the GTR group. BV, BS, and Tb.N of the LIPUS group were higher than in the periodontal flap surgery group.

CONCLUSION

LIPUS irradiation increased the number, volume, and area of new alveolar bone trabeculae. LIPUS has the potential to promote the repair of periodontal tissue, and may work effectively if combined with GTR.

Osteotome sinus floor elevation with and without grafting: an animal study in Labrador dogs

AIM

To evaluate implant stability and histological outcomes after osteotome sinus floor elevation (OSFE) procedure, and to compare new bone formation and implant osseointegration with and without grafting.

MATERIAL AND METHODS

OSFE with simultaneous implant placement was conducted bilaterally on 6 Labrador dogs. Twenty-four implants were placed. The right side sinus (Group 1) was grafted with biphasic calcium phosphate (BCP), whereas the left side (Group 2) was left without any grafting materials. The animals were euthanized 8 and 24 weeks after surgery for histological and histomorphometric assessment. Bone-to-implant contact (BIC%), alveolar bone height (ABH), bone density (BD) and grafting material density (GMD) were measured. The implant stability (ISQ) was assessed using resonance frequency analysis (RFA) at implant placement and 1, 2, 4, 8, 12, 24 weeks after surgery.

RESULTS

Endo-sinus new bone with direct contact to implant surface were observed in two groups at both time points. ABH showed no difference between groups at both time points. BIC% and BD in Group 2 (40.05%, 35.90%) was higher than those in Group 1 (23.30%,25.59%) at 24 weeks. Significant shrinkage of grafting material was seen in Group 1. The GMD in Group 1 at 8 weeks was 24.35%, while it dropped to 19.90% at 24 weeks. The changing pattern of ISQ for both groups were similar.

CONCLUSIONS

Spontaneous new bone formation and better bone-to-implant contact were found for OSFE without grafting. The grafting material application during OSFE procedure showed no advantages in histological results.

The association of hydrogel and biphasic calcium phosphate in the treatment of dehiscence-type peri-implant defects: an experimental study in dogs

Hydrogel polymers have many applications in regenerative medicine. The aim of this study in dogs was to investigate bone regeneration in dehiscence-type peri-implant defects created surgically and treated with (i) biphasic calcium phosphate (BCP) granules alone; (ii) a composite putty hydroxypropyl methylcellulose (HPMC)/BCP (MBCP/putty); and (iii) a polymer crosslinked membrane of silanized-HPMC (Si-HPMC/BCP) compared with empty controls. At 3 months, new bone formation was significantly more important in defects filled with HPMC/BCP or Si-HPMC/BCP compared with spontaneous healing in control (P = 0.032 and P = 0.046 respectively) and more substantial compared with BCP alone. Furthermore, new bone formation in direct contact with the implant surface was observed in all three groups treated with BCP. The addition of HPMC to the BCP granules may have enhanced the initial stability of the material within the blood clot in these large and complex osseous defects. The Si-HPMC hydrogel may also act as an occlusive membrane covering the BCP, which could improve the stability of the granules in the defect area. However, the crosslinking time of the Si-HPMC is too long for easy handling and the mechanical properties remain to be improved. The composite MBCP/putty appears to be a valuable bone-graft material in complex defects in periodontology and implantology. These encouraging results should now be confirmed in clinical studies.

Calcium orthophosphates in dentistry

Dental caries, also known as tooth decay or a cavity, remains a major public health problem in the most communities even though the prevalence of disease has decreased since the introduction of fluorides for dental care. Therefore, biomaterials to fill dental defects appear to be necessary to fulfill customers' needs regarding the properties and the processing of the products. Bioceramics and glass-ceramics are widely used for these purposes, as dental inlays, onlays, veneers, crowns or bridges. Calcium orthophosphates belong to bioceramics but they have some specific advantages over other types of bioceramics due to a chemical similarity to the inorganic part of both human and mammalian bones and teeth. Therefore, calcium orthophosphates (both alone and as components of various formulations) are used in dentistry as both dental fillers and implantable scaffolds. This review provides brief information on calcium orthophosphates and describes in details current state-of-the-art on their applications in dentistry and dentistry-related fields. Among the recognized dental specialties, calcium orthophosphates are most frequently used in periodontics; however, the majority of the publications on calcium orthophosphates in dentistry are devoted to unspecified "dental" fields.

Carbon Nanotubes

One of the main goals of bone tissue engineering is to identify and develop new biomaterials and scaffolds for structural support and controlled cell growth, which allow for formation or replacement of bone tissue. Recently, carbon nanotubes (CNT) have emerged as a potential candidate for bone tissue engineering. CNT present remarkable mechanical, thermal, and electrical properties with easy functionalization capability and biocompatibility. In oral regenerative medicine, bone reconstruction is an essential requirement for functional rehabilitation of the stomatognathic system. Autologous bone still represents the gold standard graft material for bone reconstruction. However, the small amounts of bone available in donor regions, together with the high costs of surgeries, are critical aspects that hinder the selection of this procedure. Thus, CNT alone or combined with biopolymers have promise to be used as novel potential biomaterials for the restoration of bone defects. Indeed, recent evidence demonstrates CNT to be a feasible material that can increase the formation of bone in tooth sockets of rats. The purpose of this review is to summarize the recent developments in bone repair/regeneration with CNT or CNT-based composites. We further provide an overview of bone tissue engineering and current applications of biomaterials, especially of CNT, to enhance bone regeneration.

Synthesis of spherical calcium phosphate particles for dental and orthopedic applications

Calcium phosphate materials have been used increasingly in the past 40 years as bone graft substitutes in the dental and orthopedic fields. Accordingly, numerous fabrication methods have been proposed and used. However, the controlled production of spherical calcium phosphate particles remains a challenge. Since such particles are essential for the synthesis of pastes and cements delivered into the host bone by minimally-invasive approaches, the aim of the present document is to review their synthesis and applications. For that purpose, production methods were classified according to the used reagents (solutions, slurries, pastes, powders), dispersion media (gas, liquid, solid), dispersion tools (nozzle, propeller, sieve, mold), particle diameters of the end product (from 10 nm to 10 mm), and calcium phosphate phases. Low-temperature calcium phosphates such as monetite, brushite or octacalcium phosphate, as well as high-temperature calcium phosphates, such as hydroxyapatite, β-tricalcium phosphate or tetracalcium phosphate, were considered. More than a dozen production methods and over hundred scientific publications were discussed.

IN VIVO EVALUATION OF A NEW BIPHASIC CALCIUM PHOSPHATE BONE SUBSTITUTE IN RABBIT FEMUR DEFECTS MODEL

Calcium phosphate ceramic has been known for its properties of bioactivity and osteoconductivity and has been widely used in orthopedic, plastic and craniofacial surgeries. The biocompatibility, unlimited availability, lower morbidity for the patient and cost-effectiveness of calcium phosphate ceramics represent important advantages over other biological bone graft, such as autografts and allografts. A new synthetic biphasic calcium phosphate (BCP), Bicera™ (60% HA and 40% β-TCP), is manufactured by Wiltrom Co., Ltd., as a new bone graft substitute. It shows good biocompatibility without cytotoxicity in in vitro test. To evaluate the possible application for clinical use, we used New Zealand white rabbit femur defect model to compare the osteoconductivity of this new bone substitute to another commercially available bone substitute (Triosite®) which was used as the control material.

According to the macroscopic observation, both bone substitutes show good biocompatibility and no abnormal inflammation either infection was seen at the implantation sites. X-rays image of implant sites at one month, three months and six months showed all implanted materials were well incorporated with host bone. All of them were not fully absorbed and replaced after six months implantation. In the histological and hitomorphometric data, new bone grew into the surface of the peripheral pores in both bone substitutes and increased over time. Moreover, the degree of bone regeneration appeared to be relatively greater in the specimens with Bicera™ when compared with Triosite®. We concluded that this new synthetic BCP (Bicera™) showed similar biocompatibility and osteoconductive characteristic comparing with commercial product Triosite® in rabbit femur defects model.

Physicochemical modification of kafirin microparticles and their ability to bind bone morphogenetic protein-2 (BMP-2), for application as a biomaterial

Vacuolated spherical kafirin microparticles with a mean diameter of 5 μm can be formed from an acidic solution with water addition. Three-dimensional scaffolds for hard tissue repair require large structures with a high degree of interconnected porosity. Cross-linking the formed kafirin microparticles using wet heat or glutaraldehyde treatment resulted in larger structures (approximately 20 μm), which, while similar in size and external morphology, were apparently formed by further assisted assembly by two significantly different mechanisms. Heat treatment, which increased the vacuole size, involved kafirin polymerization by disulfide bonding with the microparticles being formed from round, coalesced nanostructures, as shown by atomic force microscopy (AFM). Kafirin polymerization of glutaraldehyde-treated microparticles was not by disulfide bonding, and the nanostructures, as revealed by AFM, were spindle shaped. Both treatments enhanced BMP-2 binding to the microparticles, probably due to their increased size. Thus, these modified kafirin microparticles have potential as natural, nonanimal protein bioactive scaffolds.