An Organic-Inorganic Hydrogel with Exceptional Mechanical Properties via Anion-Induced Synergistic Toughening for Accelerating Osteogenic Differentiation.

Mineralized bio-tissues achieve exceptional mechanical properties through the assembly of rigid inorganic minerals and soft organic matrices, providing abundant inspiration for synthetic materials. Hydrogels, serving as an ideal candidate to mimic the organic matrix in bio-tissues, can be strengthened by the direct introduction of minerals. However, this enhancement often comes at the expense of toughness due to interfacial mismatch. This study reveals that extreme toughening of hydrogels can be realized through simultaneous in situ mineralization and salting-out, without the need for special chemical modification or additional reinforcements. The key to this strategy lies in harnessing the kosmotropic and precipitation behavior of specific anions as they penetrate a hydrogel system containing both anion-sensitive polymers and multivalent cations. The resulting mineralized hydrogels demonstrate significant improvements in fracture stress, fracture energy, and fatigue threshold due to a multiscale energy dissipation mechanism, with optimal values reaching 12 MPa, 49 kJ m-2, and 2.98 kJ m-2. This simple strategy also proves to be generalizable to other anions, resulting in tough hydrogels with osteoconductivity for promoting in vitro mineralization of human adipose-derived mesenchymal stem cells. This work introduces a universal route to toughen hydrogels without compromising other parameters, holding promise for biological applications demanding integrated mechanical properties.

Improvement of absorbability, osteoconductivity, and strength of a ß-tricalcium phosphate spacer for opening wedge high tibial osteotomy: clinical evaluations with 106 patients.

BACKGROUND: An ideal synthetic spacer for medial opening wedge high tibial osteotomy (MOWHTO) has not yet been developed. The authors have developed a new ß-tricalcium phosphate (ß-TCP) spacer with 60% porosity (N-CP60) by modifying the micro- and macro-pore structures of a conventional ß-TCP spacer (CP60) that is widely used in clinical practice. The purpose of this study was to compare the absorbability, osteoconductivity, and in vivo strength of the N-CP60 spacer with those of the CP60 spacer, when used in MOWHTO. METHODS: First, the porosity, diameter distribution of macro- and micropores, and compressive strength of each ß-TCP block were examined using methodology of biomaterial science. Secondly, a clinical study was performed using a total of 106 patients (106 knees) with MOWHTO, who were followed up for 18 months after surgery. In these knees, the N-CP60 and CP-60 spacers were implanted into 49 tibias and 57 tibias, respectively. The absorbability and osteoconductivity were radiologically evaluated by measuring the area of the implanted spacer remaining unabsorbed and assessing with the Hemert's score, respectively. The incidence of cracking in the implanted spacers was determined using computed radiography. Statistical comparisons were made with non-parametric tests. The significance level was set at p = 0.05. RESULTS: The N-CP60 and CP60 blocks had almost the same porosity (mean, 61.0% and 58.7%, respectively). The diameter of macropores was significantly larger (p < 0.0001) in the N-CP60 block than in the CP60 block, while the diameter of micropores was significantly smaller (p = 0.019) in the N-CP60 block. The ultimate strength of the N-CP60 block (median, 36.8 MPa) was significantly greater (p < 0.01) than that of the CP60 block (31.6 MPa). As for the clinical evaluations, the absorption rate of the N-CP60 spacer at 18 months after implantation (mean, 48.0%) was significantly greater (p < 0.001) than that of the CP60 spacer (29.0%). The osteoconductivity of the N-CP60 spacer was slightly but significantly higher (p = 0.0408) than that of the CP60 spacer only in zone 1. The incidence of in vivo cracking of the posteriorly located N-CP60 spacer at one month (mean, 75.5%) was significantly lower (p = 0.0035) than that of the CP60 spacer (91.2%). CONCLUSIONS: The absorbability, osteoconductivity, and compressive strength of the new N-CP60 spacer were significantly improved by modifying the macro- and micro-pore structures, compared with the conventional CP60 spacer. The N-CP60 spacer is more clinically useful than the CP60 spacer. TRIAL REGISTRATION NUMBER: H29-0002.

A Water-Based Biocoating to Increase the Infection Resistance and Osteoconductivity of Titanium Surfaces.

As the population ages, the number of patients undergoing total hip arthroplasty (THA) and total knee arthroplasty (TKA) continues to increase. Infections after primary arthroplasty are rare but have high rates of morbidity and mortality, as well as enormous financial implications for healthcare systems. Numerous methods including the use of superhydrophobic coatings, the incorporation of antibacterial agents, and the application of topographical treatments have been developed to reduce bacterial attachment to medical devices. However, most of these methods require complex manufacturing processes. Thus, the main purpose of this study was to apply biocoatings to titanium (Ti) surfaces to increase their infection resistance and osteoconductivity via simple processes, without organic reagents. We modified titanium surfaces with a combination of aminomalononitrile (AMN) and an antibiotic-loaded mesoporous bioactive glass (MBG) and evaluated both the antibacterial effects of the coating layer and its effect on osteoblast proliferation and differentiation. The properties of the modified surface, such as the hydrophilicity, roughness, and surface morphology, were characterized via contact angle measurements, atomic force microscopy, and scanning electron microscopy. The cell proliferation reagent WST-1 assay and the alkaline phosphatase (ALP) assay were used to determine the degrees of adhesion and differentiation, respectively, of the MG-63 osteoblast-like cells on the surface. Antimicrobial activity was evaluated by examining the survival rate and inhibition zone of Escherichia coli (E. coli). The AMN coating layer reduced the water contact angle (WCA) of the titanium surface from 87° ± 2.5° to 53° ± 2.3° and this change was retained even after immersion in deionized water for five weeks, demonstrating the stability of the AMN coating. Compared with nontreated titanium and polydopamine (PDA) coating layers, the AMN surface coating increased MG-63 cell attachment, spreading, and early ALP expression; reduced E. coli adhesion; and increased the percentage of dead bacteria. In addition, the AMN coating served as an adhesion layer for the subsequent deposition of MBG-containing antibiotic nanoparticles. The synergistic effects of the AMN layer and antibiotics released from the MBG resulted in an obvious E. coli inhibition zone that was not observed in the nontreated titanium group.

Calcium-to-phosphorus releasing ratio affects osteoinductivity and osteoconductivity of calcium phosphate bioceramics in bone tissue engineering.

Calcium phosphate (Ca-P) bioceramics, including hydroxyapatite (HA), biphasic calcium phosphate (BCP), and beta-tricalcium phosphate (ß-TCP), have been widely used in bone reconstruction. Many studies have focused on the osteoconductivity or osteoinductivity of Ca-P bioceramics, but the association between osteoconductivity and osteoinductivity is not well understood. In our study, the osteoconductivity of HA, BCP, and ß-TCP was investigated based on the osteoblastic differentiation in vitro and in situ as well as calvarial defect repair in vivo, and osteoinductivity was evaluated by using pluripotent mesenchymal stem cells (MSCs) in vitro and heterotopic ossification in muscles in vivo. Our results showed that the cell viability, alkaline phosphatase activity, and expression of osteogenesis-related genes, including osteocalcin (Ocn), bone sialoprotein (Bsp), alpha-1 type I collagen (Col1a1), and runt-related transcription factor 2 (Runx2), of osteoblasts each ranked as BCP > ß-TCP > HA, but the alkaline phosphatase activity and expression of osteogenic differentiation genes of MSCs each ranked as ß-TCP > BCP > HA. Calvarial defect implantation of Ca-P bioceramics ranked as BCP > ß-TCP ≥ HA, but intramuscular implantation ranked as ß-TCP ≥ BCP > HA in vivo. Further investigation indicated that osteoconductivity and osteoinductivity are affected by the Ca/P ratio surrounding the Ca-P bioceramics. Thus, manipulating the appropriate calcium-to-phosphorus releasing ratio is a critical factor for determining the osteoinductivity of Ca-P bioceramics in bone tissue engineering.

Mesh Ti6Al4V Material Manufactured by Selective Laser Melting (SLM) as a Promising Intervertebral Fusion Cage.

Intervertebral cages made of Ti6Al4V alloy show excellent osteoconductivity, but also higher stiffness, compared to commonly used polyether-ether-ketone (PEEK) materials, that may lead to a stress-shielding effect and implant subsidence. In this study, a metallic intervertebral fusion cage, with improved mechanical behavior, was manufactured by the introduction of a three-dimensional (3D) mesh structure to Ti6Al4V material, using an additive manufacturing method. Then, the mechanical and biological properties of the following were compared: (1) PEEK, with a solid structure, (2) 3D-printed Ti6Al4V, with a solid structure, and (3) 3D-printed Ti6Al4V, with a mesh structure. A load-induced subsidence test demonstrated that the 3D-printed mesh Ti6Al4V cage had significantly lower tendency (by 15%) to subside compared to the PEEK implant. Biological assessment of the samples proved that all tested materials were biocompatible. However, both titanium samples (solid and mesh) were characterized by significantly higher bioactivity, osteoconductivity, and mineralization ability, compared to PEEK. Moreover, osteoblasts revealed stronger adhesion to the surface of the Ti6Al4V samples compared to PEEK material. Thus, it was clearly shown that the 3D-printed mesh Ti6Al4V cage possesses all the features for optimal spinal implant, since it carries low risk of implant subsidence and provides good osseointegration at the bone-implant interface.

Development of Silver-Containing Hydroxyapatite-Coated Antimicrobial Implants for Orthopaedic and Spinal Surgery.

The prevention of surgical site infections is directly related to the minimization of surgical invasiveness, and is in line with the concept of minimally invasive spine therapy (MIST). In recent years, the incidence of postoperative infections has been increasing due to the increased use of spinal implant surgery in patients at high risk of infection, including the elderly and easily infected hosts, the limitations of poor bone marrow transfer of antibiotics, and the potential for contamination of surgical gloves and instruments. Thus, the development of antimicrobial implants in orthopedic and spinal surgery is becoming more and more popular, and implants with proven antimicrobial, safety, and osteoconductive properties (i.e., silver, iodine, antibiotics) in vitro, in vivo, and in clinical trials have become available for clinical use. We have developed silver-containing hydroxyapatite (Ag-HA)-coated implants to prevent post-operative infection, and increase bone fusion capacity, and have successfully commercialized antibacterial implants for hip prostheses and spinal interbody cages. This narrative review overviews the present status of available surface coating technologies and materials; describes how the antimicrobial, safety, and biocompatibility (osteoconductivity) of Ag-HA-coated implants have been demonstrated for commercialization; and reviews the clinical use of antimicrobial implants in orthopedic and spinal surgery, including Ag-HA-coated implants that we have developed.

Effects of argon plasma treatment on the osteoconductivity of bone grafting materials.

BACKGROUND: The osteoconductive properties of bone grafting materials represent one area of research for the management of bony defects found in the fields of periodontology and oral surgery. From a physico-chemical aspect, the wettability of the graft has been demonstrated to be one of the most important factors for new bone formation. It is also well-known that argon plasma treatment (PAT) and ultraviolet irradiation (UV) may increase the surface wettability and, consequently, improve the regenerative potential of the bone grafts. Therefore, the aim of the present in vitro study was to evaluate the effect of PAT and UV treatment on the osteoconductive potential of various bone grafts. MATERIALS AND METHODS: The following four frequently used bone grafts were selected for this study: synthetic hydroxyapatite (Mg-HA), biphasic calcium phosphate (BCP), cancellous and cortical xenogenic bone matrices (CaBM, CoBM). Sixty-six serially numbered disks 10 mm in diameter were used for each graft material and randomly assigned to the following three groups: test 1 (PAT), test 2 (UV), and control (no treatment). Six samples underwent topographic analysis using SEM pre- and post-treatments to evaluate changes in surface topography/characteristics. Additionally, cell adhesion and cell proliferation were evaluated at 2 and 72 h respectively following incubation in a three-dimensional culture system utilizing a bioreactor. Furthermore, the effects of PAT and UV on immune cells were assessed by measuring the viability of human macrophages at 24 h. RESULTS: The topographic analysis showed different initial morphologies of the commercial biomaterials (e.g., Mg-HA and BCP showed flat morphology; BM samples were extremely porous with high roughness). The surface analysis following experimental treatments did not demonstrate topographical difference when compared with controls. Investigation of cells demonstrated that PAT treatment significantly increased cell adhesion of all 4 evaluated bone substitutes, whereas UV failed to show any statistically significant differences. The viability test revealed no differences in terms of macrophage adhesion on any of the tested surfaces. CONCLUSION: Within their limitations, the present results suggest that treatment of various bone grafting materials with PAT appears to enhance the osteoconductivity of bone substitutes in the early stage by improving osteoblast adhesion without concomitantly affecting macrophage viability. CLINICAL RELEVANCE: Treatment of bone grafts with PAT appears to result in faster osseointegration of the bone grafting materials and may thus favorably influence bone regeneration.

UV-Pre-Treated and Protein-Adsorbed Titanium Implants Exhibit Enhanced Osteoconductivity.

Titanium materials are essential treatment modalities in the medical field and serve as a tissue engineering scaffold and coating material for medical devices. Thus, there is a significant demand to improve the bioactivity of titanium for therapeutic and experimental purposes. We showed that ultraviolet light (UV)-pre-treatment changed the protein-adsorption ability and subsequent osteoconductivity of titanium. Fibronectin (FN) adsorption on UV-treated titanium was 20% and 30% greater after 1-min and 1-h incubation, respectively, than that of control titanium. After 3-h incubation, FN adsorption on UV-treated titanium remained 30% higher than that on the control. Osteoblasts were cultured on titanium disks after 1-h FN adsorption with or without UV-pre-treatment and on titanium disks without FN adsorption. The number of attached osteoblasts during the early stage of culture was 80% greater on UV-treated and FN-adsorbed (UV/FN) titanium than on FN-adsorbed (FN) titanium; osteoblasts attachment on UV/FN titanium was 2.6- and 2.1-fold greater than that on control- and UV-treated titanium, respectively. The alkaline phosphatase activity of osteoblasts on UV/FN titanium was increased 1.8-, 1.8-, and 2.4-fold compared with that on FN-adsorbed, UV-treated, and control titanium, respectively. The UV/FN implants exhibited 25% and 150% greater in vivo biomechanical strength of bone integration than the FN- and control implants, respectively. Bone morphogenetic protein-2 (BMP-2) adsorption on UV-treated titanium was 4.5-fold greater than that on control titanium after 1-min incubation, resulting in a 4-fold increase in osteoblast attachment. Thus, UV-pre-treatment of titanium accelerated its protein adsorptivity and osteoconductivity, providing a novel strategy for enhancing its bioactivity.

Frame Coating of Single-Walled Carbon Nanotubes in Collagen on PET Fibers for Artificial Joint Ligaments.

The coating formation technique for artificial knee ligaments was proposed, which provided tight fixation of ligaments of polyethylene terephthalate (PET) fibers as a result of the healing of the bone channel in the short-term period after implantation. The coating is a frame structure of single-walled carbon nanotubes (SWCNT) in a collagen matrix, which is formed by layer-by-layer solidification of an aqueous dispersion of SWCNT with collagen during spin coating and controlled irradiation with IR radiation. Quantum mechanical method SCC DFTB, with a self-consistent charge, was used. It is based on the density functional theory and the tight-binding approximation. The method established the optimal temperature and time for the formation of the equilibrium configurations of the SWCNT/collagen type II complexes to ensure maximum binding energies between the nanotube and the collagen. The highest binding energies were observed in complexes with SWCNT nanometer diameter in comparison with subnanometer SWCNT. The coating had a porous structure-pore size was 0.5-6 µm. The process of reducing the mass and volume of the coating with the initial biodegradation of collagen after contact with blood plasma was demonstrated. This is proved by exceeding the intensity of the SWCNT peaks G and D after contact with the blood serum in the Raman spectrum and by decreasing the intensity of the main collagen bands in the SWCNT/collagen complex frame coating. The number of pores and their size increased to 20 µm. The modification of the PET tape with the SWCNT/collagen coating allowed to increase its hydrophilicity by 1.7 times compared to the original PET fibers and by 1.3 times compared to the collagen coating. A reduced hemolysis level of the PET tape coated with SWCNT/collagen was achieved. The SWCNT/collagen coating provided 2.2 times less hemolysis than an uncoated PET implant. MicroCT showed the effective formation of new bone and dense connective tissue around the implant. A decrease in channel diameter from 2.5 to 1.7 mm was detected at three and, especially, six months after implantation of a PET tape with SWCNT/collagen coating. MicroCT allowed us to identify areas for histological sections, which demonstrated the favorable interaction of the PET tape with the surrounding tissues. In the case of using the PET tape coated with SWCNT/collagen, more active growth of connective tissue with mature collagen fibers in the area of implantation was observed than in the case of only collagen coating. The stimulating effect of SWCNT/collagen on the formation of bone trabeculae around and inside the PET tape was evident in three and six months after implantation. Thus, a PET tape with SWCNT/collagen coating has osteoconductivity as well as a high level of hydrophilicity and hemocompatibility.

Feasible Advantage of Bioactive/Bioresorbable Devices Made of Forged Composites of Hydroxyapatite Particles and Poly-L-lactide in Alveolar Bone Augmentation: A Preliminary Study.

Purpose: We aimed to document the clinical usefulness of uncalcined and unsintered hydroxyapatite (u-HA) particles and poly-L-lactide (PLLA) composite materials and their advantageous properties. Methods: Between April 2016 and March 2018, five patients required anterior maxillary alveolar ridge augmentation using fixation with u-HA/PLLA screws for an onlay block bone graft harvested from the mandibular ramus at our institute. Bone biopsies were obtained from the dental implantation site following bone healing for histomorphometric and immunohistochemical (IHC) measurements. Results: Many stromal cells were positive for Osterix, RUNX2, and SOX9 but were negative for CD68. On cell counting, based on IHC staining for Osterix, RUNX2, SOX9 and CD68 from peripheral u-HA/PLLA screw or bone areas, both areas consistently showed no significant difference in terms of Osterix, RUNX2, and SOX9. Hematoxylin-eosin staining revealed direct bone connection to the biomaterials, and no inflammatory cells infiltrated the areas surrounding the bone or artificial material. Area between the bone and u-HA/PLLA screw was seamless with no boundary. Round small cells and immature fibroblasts were noted. The new bone showed the presence of bone lamellae, normal osteocytes, and osteoblasts. Conclusion: The u-HA/PLLA materials showed excellent biodegradability and bioactive osteoconductivity. In addition, this material induced no apparent inflammatory or foreign body reactions following implantation, and it directly bonded to the human bone. Therefore, this u-HA/PLLA material seems ideal and most suitable for use as a substitute for osteosynthesis.

Bone-conditioned medium modulates the osteoconductive properties of collagen membranes in a rat calvaria defect model.

OBJECTIVES: Collagen membranes are not limited to be occlusive barriers as they actively support bone regeneration. However, the impact of bone-derived growth factors on their osteoconductive competence has not been examined. METHODS: Twenty adult Sprague Dawley rats were included in the study. Calvaria defects with a diameter of five millimeter were created. The defect was covered with one layer of a collagen membrane previously soaked in conditioned medium of porcine bone chips or in culture medium alone. After 4 weeks, microcomputed tomography was performed. Undecalcified thin-ground sections were subjected to light and scanning electron microscopy. Primary outcome parameter was the bone volume in the defect. Unit of analysis was the bone-conditioned medium (BCM). RESULTS: In the central defect area of the control and the BCM group, median new bone connected to the host bone was 0.54 and 0.32 mm³, respectively (p = .10). In the ectocranial defect area, the control group showed significantly more bone than the BCM group (0.90 and 0.26 mm³; p = .02). Based on an exploratory interpretation, the control group had smaller bony islands than the BCM group. Scanning electron microscopy and histology indicate the formation of bone but also the collagen membrane to be mineralized in the defect site. CONCLUSIONS: These results demonstrate that the commercial collagen membrane holds an osteoconductive competence in a rat calvaria defect model. Soaking collagen membranes with BCM shifts bone formation toward the formation of bony islands rather than new bone connected to the host bone.

Reposition of the bone plate over the antrostomy in maxillary sinus augmentation: A histomorphometric study in rabbits.

OBJECTIVE: To test if repositioning the bony plate secured with a cyanoacrylate over the antrostomy in maxillary sinus augmentation was superior to covering the antrostomy with a collagen membrane in terms of the bone augmentation area and the bone density. MATERIAL AND METHODS: After the exposure of the nasal bone in eighteen rabbits, a rectangular access window was prepared with a sonic instrument, and the bony plate was removed. A bilateral sinus mucosa elevation was performed, and the space was filled with a resorbable xenograft. On the test side, the bone plate was repositioned over the antrostomy and fixed with a cyanoacrylate. On the control side, a collagen membrane was placed over the opening. Per group, six animals were sacrificed after 2, 4, and 8 weeks of healing, respectively. Histological ground sections were prepared. RESULTS: The augmented area after elevation decreased between 2 and 8 weeks from 9.4 ± 1.8 to 4.8 ± 2.8 mm2 at the test and from 9.5 ± 2.6 and 5.1 ± 1.6 mm2 at the control sites. Small amounts of new bone were seen after 2 weeks in both groups (~1.6%-2.5%) forming from the bony sinus walls. New bone density increased over time in both groups reaching ~ 10%-11% and ~ 23%-25% after 4 and 8 weeks, respectively. No statistically significant differences were found. Small residual defects were present both at the test sites in the margin of the bone plate, and at the control sites in the center of the antrostomy. CONCLUSIONS: The bone healing in the elevated sinus space was similar irrespective of the coverage of the antrostomy. After 8 weeks, the bone plate repositioned on the antrostomy was incorporated while at the control sites the healing was still incomplete. Residual defects were still present in both groups.

Influence of a collagen membrane positioned subjacent the sinus mucosa following the elevation of the maxillary sinus. A histomorphometric study in rabbits.

OBJECTIVE: To evaluate the healing after elevation of the sinus mucosa when a collagen membrane was placed between the sinus mucosa and a xenograft used as filler. MATERIALS AND METHODS: Eighteen rabbits were used. Sinus mucosa elevation was performed bilaterally, and a collagen membrane was applied subjacent to the sinus mucosa only at a randomly selected test site. At both sites, a collagenated corticocancellous porcine bone was placed within the elevated space and the access window was covered with a collagen membrane. The animals were sacrificed after 2, 4, and 8 weeks of healing, six animals for group. Ground sections were prepared. RESULTS: At the histomorphometric evaluation, the elevated area after 2 and 8 weeks was 11.8 and 8.8 mm2 at the test, and 10.0 and 5.3 mm2 at the control sites, respectively. The available area was obtained subtracting the remaining area occupied by the membrane from the elevated area and, after 8 weeks, was 6.7 ± 0.9 mm2 . After 8 weeks of healing, the mineralized new bone within the elevated space was 18.2 ± 5.5% at the test and 26.7 ± 7.7% at the control sites. Within the available space at the test site, the percentage was 27.3 ± 7.0% after 8 weeks of healing. At 2 and 8 weeks of healing, within the elevated space, the xenograft proportion was 30.9 ± 4.4% and 6.9 ± 2.8% at the test, and 35.2 ± 7.3% and 9.6 ± 4.9% at the control sites, respectively. CONCLUSIONS: The placement of a collagen membrane subjacent the sinus mucosa did not reveal any major morphometric difference. The collagen membrane was not completely resorbed after 8 weeks.

Osteoconductivity of Binary Titanium Alloys with Different Micro/Nanoporous Surfaces.

The surface characteristics and osteoconductivity were evaluated for the micro/nanoporous surfaces of titanium (Ti) alloys prepared by micro-arc oxidation (MAO) and hydrothermal treatment (HT) of binary Ti-5 wt% A alloys (A = Au, Mn, Nb, and Pd). Surface properties were analyzed using X-ray diffractometry, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The osteoconductivity was evaluated by measuring the total protein, ALPase activity, and osteocalcin production. The surface morphologies of MAO/HT specimens mainly affected on their osteoconductivity. Total proteins on Ti alloys (MAO/HT) were slightly lower than that on commercially pure Ti (MAO/HT) after incubation of MG-63 osteoblast-like cells for 14 days. However, better ALPase activity and osteocalcin production were observed on MAO/HT-treated Ti­5Mn, Ti­5Nb, and Ti­5Pd than that on cp-Ti (MAO/HT) after 14 days. Especially, Ti­5Mn (MAO/HT) showed a significant increase of ALPase activity due to its well grown micro/nano structure. Meanwhile, very small nanorods on Ti­5Au (MAO/HT) affected negatively to ALPase activity and osteocalcin production.

Effects of Pore Size on the Osteoconductivity and Mechanical Properties of Calcium Phosphate Cement in a Rabbit Model.

Calcium phosphate cement (CPC) porous scaffold is widely used as a suitable bone substitute to repair bone defect, but the optimal pore size is unclear yet. The current study aimed to evaluate the effect of different pore sizes on the processing of bone formation in repairing segmental bone defect of rabbits using CPC porous scaffolds. Three kinds of CPC porous scaffolds with 5 mm diameters and 12 mm length were prepared with the same porosity but different pore sizes (Group A: 200-300 µm, Group B: 300-450 µm, Group C: 450-600 µm, respectively). Twelve millimeter segmental bone defects were created in the middle of the radius bone and filled with different kinds of CPC cylindrical scaffolds. After 4, 12, and 24 weeks, alkaline phosphatase (ALP), histological assessment, and mechanical properties evaluation were performed in all three groups. After 4 weeks, ALP activity increased in all groups but was highest in Group A with smallest pore size. The new bone formation within the scaffolds was not obvious in all groups. After 12 weeks, the new bone formation within the scaffolds was obvious in each group and highest in Group A. At 24 weeks, no significant difference in new bone formation was observed among different groups. Besides the osteoconductive effect, Group A with smallest pore size also had the best mechanical properties in vivo at 12 weeks. We demonstrate that pore size has a significant effect on the osteoconductivity and mechanical properties of calcium phosphate cement porous scaffold in vivo. Small pore size favors the bone formation in the early stage and may be more suitable for repairing segmental bone defect in vivo.

Evaluation of Poly(Lactic-co-glycolic) Acid Alone or in Combination with Hydroxyapatite on Human-Periosteal Cells Bone Differentiation and in Sinus Lift Treatment.

Most recent advances in tissue engineering in the fields of oral surgery and dentistry have aimed to restore hard and soft tissues. Further improvement of these therapies may involve more biological approaches and the use of dental tissue stem cells in combination with inorganic/organic scaffolds. In this study, we analyzed the osteoconductivity of two different inorganic scaffolds based on poly (lactic-co-glycolic) acid alone (PLGA-Fisiograft) or in combination with hydroxyapatite (PLGA/HA-Alos) in comparison with an organic material based on equine collagen (PARASORB Sombrero) both in vitro and in vivo. We developed a simple in vitro model in which periosteum-derived stem cells were grown in contact with chips of these scaffolds to mimic bone mineralization. The viability of cells and material osteoconductivity were evaluated by osteogenic gene expression and histological analyses at different time points. In addition, the capacity of scaffolds to improve bone healing in sinus lift was examined. Our results demonstrated that the osteoconductivity of PLGA/HA-Alos and the efficacy of scaffolds in promoting bone healing in the sinus lift were increased. Thus, new clinical approaches in sinus lift follow-up should be considered to elucidate the clinical potential of these two PLGA-based materials in dentistry.

Effects of a collagen membrane positioned between augmentation material and the sinus mucosa in the elevation of the maxillary sinus floor. An experimental study in sheep.

OBJECTIVE: To assess the influence of a collagen membrane placed subjacent to a pristine sinus mucosa on the healing outcome of a sinus floor elevation procedure. MATERIALS AND METHODS: Eight Pelibuey sheep (Cubano rojo) underwent sinus floor elevation on both sides of the maxilla. At a randomly selected side (test), a collagen membrane was placed subjacent to the sinus mucosa, while the contralateral side (control) was left without the placement of a membrane. Deproteinized bovine bone mineral (DBBM) was used to fill the space created. A collagen membrane was placed bilaterally to cover the access osteotomy. After 4 months, biopsies were harvested and ground sections prepared. Morphometric analysis was performed in four different regions, three within the elevated area and one at the site of the osteotomy. RESULTS: The total percentages of mineralized new bone within the elevated area were 29.4 ± 16.2% and 30.9 ± 9.2% and of marrow spaces 44.0 ± 23.0% and 45.6 ± 14.1%, at the Non-membrane and at the Membrane sites, respectively. A low content of connective tissue within the elevated area was noticed. A higher content of connective tissue was found in the osteotomy region, however. Remnants of DBBM granules were found at a percentage of 17-19%. No statistically significant differences were observed between test and control sites. CONCLUSION: The application of a collagen membrane subjacent to the Schneiderian mucosa in a sinus floor elevation procedure did not influence the healing outcomes at all.

[State and perspectives of studies on osteoplastic materials]. / Sovremennoe sostoianie i osnovnye napravleniia razvitiia issledovanii, posviashchennykh razrabotke osteoplasticheskikh materialov.

Article highlights the state and the main directions of researches on osteoplastic materials used for filling of bone defects, types of these materials, effects and mechanisms of their interaction with the recipient tissues, defines objectives and prospects for further researches on the issue.

Vertical osteoconductivity and early bone formation of titanium-zirconium and titanium implants in a subperiosteal rabbit animal model.

OBJECTIVES: The aim of this pilot study was to evaluate the vertical osteoconductive and osteointegrative dynamics around titanium-zirconium (TiZr) implants compared to titanium (Ti) implants. MATERIALS AND METHODS: In a split-leg design, 12 TiZr-SLActive and 12 Ti-SLActive implants were inserted 3 mm above bone level in the proximal tibia of 12 rabbits. Full periosteal flaps were repositioned to cover the site. Specimens were obtained after 10, 20 and 30 days (each n = 4 per group). Histomorphometric measurements included percentage of linear bone fill (PLF; %), new marginal vertical bone height (VBH; mm) and vertical bone-to-implant contact (vBIC; %). Statistical analysis was performed with the nonparametric F1_LD_F1 model to compare the two groups at the different time points. RESULTS: After 10 days, mean PLF was 7.7% (standard deviation (SD): 5.3) for TiZr and 17.6 (SD: 8.3) for Ti. Mean VBH was 0.35 mm (SD: 0.15) and 0.78 mm (SD: 0.4) for TiZr and Ti, respectively; mean vBIC was 24.4% (SD: 41) for TiZr and 53% (SD: 28.9) for Ti samples. The differences were significant for all parameters (PLF: P = 0.021; VBH: P = 0.009; vBIC: P = 0.011). After 20 days, mean PLF was 44.3% (SD: 26.3) for TIZr and 46.2% (SD: 21.3) for Ti implants. TiZr showed a mean VBH of 1.73 mm (SD: 1) and 1.8 mm (SD: 0.6) for Ti samples. Mean vBIC had values of 48.3% (SD: 23.7) and 68.7% (SD: 35.5) for TiZr and Ti, respectively (PLF: P = 0.78; VBH: P = 0.58; vBIC: P = 0.47). At the point of 30 days, mean PLF values were 23.7% (SD: 3.8) for TiZr and 28.9% (SD: 21.7) for Ti samples; mean for VBH in TiZr samples was 0.65 mm (SD: 0.39) and 1.7 mm (SD: 1.1) for Ti ones. Finally, mean vBIC was 28.3% (SD: 19.3) and 54.4% (SD: 26.5) for TiZr and Ti samples, respectively (PLF: P = 0.1; VBH: P = 0.088; vBIC: P = 0.089). CONCLUSIONS: A significant delay in vertical osteoconductivity at the earliest time point under examination was seen for TiZr implants when compared to their Ti counterparts. For the later points, TiZr as well as Ti implants demonstrated comparable values in this animal model. The long-term osteogenic surface properties of equally pretreated TiZr dental implants are therefore similar to those of Ti implants in vivo.

3D chitosan/hydroxyapatite scaffolds containing mesoporous SiO2-HA particles: A new step to healing bone defects.

Biocompatible scaffolds with high mechanical strengths that contain biodegradable components could boost bone regeneration compared with nondegradable bone repair materials. In this study, porous chitosan (CS)/hydroxyapatite (HA) scaffolds containing mesoporous SiO2-HA particles were fabricated through the freeze-drying process. According to field emission scanning electron microscopy (FESEM) results, combining mesoporous SiO2-HA particles in CS/HA scaffolds led to a uniform porous structure. It decreased pore sizes from 320 ± 1.1 µm to 145 ± 1.4 µm. Moreover, the compressive strength value of this scaffold was 25 ± 1.2 MPa. The in-vitro approaches exhibited good sarcoma osteogenic cell line (SAOS-2) adhesion, spreading, and proliferation, indicating that the scaffolds provided a suitable environment for cell cultivation. Also, in-vivo analyses in implanted defect sites of rats proved that the CS/HA/mesoporous SiO2-HA scaffolds could promote bone regeneration via enhancing osteoconduction and meliorating the expression of osteogenesis gene to 19.31 (about 5-fold higher compared to the control group) by exposing them to the bone-like precursors. Further, this scaffold's new bone formation percentage was equal to 90 % after 21 days post-surgery. Therefore, incorporating mesoporous SiO2-HA particles into CS/HA scaffolds can suggest a new future tissue engineering and regeneration strategy.