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    18 February 2024, Volume 28 Issue 5 Previous Issue    Next Issue
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    Biomechanical difference between resin ceramic crown and zirconia all-ceramic crown implant restorations in three occlusal relationships
    Dai Huijuan, Wang Zhaoxin, Baibujiafu·Yelisi, Sun Jiangwei, Gulizainu·Yibulayin, Nijiati·Tuerxun
    2024, 28 (5):  657-663.  doi: 10.12307/2023.984
    Abstract ( 177 )   PDF (2441KB) ( 31 )   Save
    BACKGROUND: In implant restoration in the aesthetic area, zirconium dioxide is gradually becoming the most commonly used upper restorative material and has achieved better clinical results. Resin-ceramic composite, a new type of dental restorative material, begins to try to be used as an upper restorative material in implant restoration, but there is less research on the application of this material in implant restoration.
    OBJECTIVE: To compare the biomechanical differences between resin ceramic crowns and zirconia all-ceramic crown implant restorations in three occlusal relationships for restoring maxillary central incisors.
    METHODS: The cone-beam CT image data of a patient with single-crown implant restoration of maxillary central incisor were selected, and the maxillary bone model was extracted by using Mimics 21.0 software, and the model was imported into Solidworks 2020 software. The crown, adhesive, abutment, central screw, and implant were modeled, and the model of single-crown implant restoration of maxillary central incisor was assembled. After giving the model material property parameters (resin-ceramic composite and zirconia for the upper restoration materials) in ANSYS Workbench 2021 R1 software, three occlusal relationships (edge-to-edge occlusion, normal overjet and deep overbite) were simulated and loaded to analyze the stress distribution of the resin-ceramic crown and zirconia all-ceramic crown implant restoration models.
    RESULTS AND CONCLUSION: (1) The stress concentration areas in the implant restoration models of the resin-ceramic crown group and the zirconia all-ceramic crown group in different occlusal relationships were distributed in the upper restoration loading point, the abutment-implant connection, the implant neck and the surrounding bone tissue. As the occlusal relationship changed from the edge-to-edge to normal and deep overbite, the peak equivalent forces of the restorative abutment, central screw, implant, and bone tissue in both the resin-ceramic and zirconia all-ceramic crown groups gradually decreased. The highest peak equivalent forces were observed for the upper restorations in deep overbite. The zirconia all-ceramic crown group had the highest peak equivalent force in the adhesive layer in the edge-to-edge relationship, and the resin-ceramic crown group had the highest peak equivalent force in the adhesive layer in the deep overbite. (2) In the edge-to-edge occlusion, the peak equivalent force of the adhesive layer and central screw in the resin-ceramic crown group was slightly smaller than that in the zirconia all-ceramic crown group, and there was no significant difference between the two groups in the peak equivalent force at the upper restoration, restoration abutment, implant, and bone tissue. The peak stresses in the upper restoration, adhesive layer, and central screw of the resin-ceramic crown group were slightly less than those of the zirconia all-ceramic crown group at normal fit, and there were no significant differences between the two groups in the peak equivalent forces at the restoration abutment, implant, and bone tissue. In deep overbite, the peak adhesive, abutment, and central screw stresses were greater in the resin-ceramic crown group than in the zirconia all-ceramic crown group, with no significant differences in the upper restorations, implants, or bone tissue. (3) The results showed that the upper restorative material had no significant effect on the stress distribution of the implant and bone tissue, and had some effects on the stress distribution of the upper restoration, adhesive, restoration abutment, and central screw, but the difference was not significant. The occlusal relationship has a significant influence on the stress distribution in all structures and bone tissue of the implant restoration. The resin-ceramic crowns have a buffering effect on the stresses in the case of edge-to-edge and normal occlusion.
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    Preparation and properties of selective laser melting of porous titanium at a low energy density
    Cheng Jinhui, Wu Quan, Peng Min, Huang Changli, Tian Huimin, Li Yang
    2024, 28 (5):  664-668.  doi: 10.12307/2024.251
    Abstract ( 180 )   PDF (1893KB) ( 17 )   Save
    BACKGROUND: At present, the traditional powder sintering method is easy to introduce impurities in the process of preparing porous titanium, and the manufacturing of porous titanium still faces two major problems: impurity pollution and difficult control of the material forming process.
    OBJECTIVE: To prepare pure porous titanium with certain porosity, and analyze the microstructure evolution and properties of the porous titanium. 
    METHODS: Porous titanium was prepared at a low energy density by selective laser melting technology. The parameter range of porous titanium with large porosity was obtained by measuring the porosity of the formed specimen, and the evolution of the microstructure and mechanical properties of the specimen in the range were analyzed.
    RESULTS AND CONCLUSION: (1) With the increase in energy density, the porosity of the porous titanium specimen decreased gradually. When the energy density was between 10.61 and 27.78 J/mm3, porous titanium with a porosity of 11.23%-33.67% could be formed. When the energy density was between 27.78-37.88 J/mm3, the forming parts were relatively dense. (2) The phase composition of porous titanium formed was mainly α titanium. With the increase in energy density, the porosity gradually decreased, and the pore morphology changed from irregularly connected pores to closed nearly spherical pores. The powder particles changed from a slightly sintered neck to a continuous fuse. The CT scan results revealed that there were a large number of connected pores in the forming specimen with a large specific surface area and the pore radius was roughly distributed between 2-6 μm at the energy density of 10.61 J/mm3. Simultaneously, porous titanium with compressive strength of 188-1 000 MPa could be obtained at the energy density of 10.61-27.78 J/mm3, which could meet the requirements of biomedical applications. (3) These results have confirmed that the selective laser melting technology can overcome the problems of impurity pollution and long manufacturing cycle caused by the traditional preparation process, and provide an effective solution for the preparation of porous titanium with excellent mechanical properties.
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    Preparation of a near-infrared photoresponsive biomimetic nanoprobe and its application in photothermal detection and treatment of breast cancer
    Li Wenlan, Wang Wenyuan, Ren Wenxiu, Zhang Yupei, Yang Xiaoyan, Wang Zhigang, Xia Jizhu
    2024, 28 (5):  669-675.  doi: 10.12307/2023.983
    Abstract ( 190 )   PDF (1841KB) ( 30 )   Save
    BACKGROUND: Photothermal therapy is a novel tumor treatment strategy that uses photothermal agents to transform light energy into heat energy to accomplish non-invasive tumor ablation. The rise of photothermal therapy and nanotechnology has provided a new perspective on breast cancer treatment.
    OBJECTIVE: To prepare a new type of near-infrared biomimetic nanoprobe that has been modified by breast cancer cell membrane, to investigate the effect of near-infrared fluorescence/ultrasound imaging in vitro, and to observe its targeting ability and photothermal therapy effect on homologous tumor cells in vitro.
    METHODS: Organic small molecule ITIC-4CI with A-D-A structure was used as photothermal agents; polylactic acid/glycolic acid copolymer as nanocarrier; 4T1 cell membrane of mouse breast cancer cells as a surface modifier of nanoparticles; perfluorohexane (PFH) was loaded. A novel near-infrared biomimetic nanoprobe (4T1m/ITIC-4CI/PFH) was prepared by the double emulsion evaporation method and sonication method. The basic characterization of the nanoprobe and the homologous targeting ability were detected. The photothermal properties and photothermal stability of the probe were investigated, and the near-infrared fluorescence/ultrasound imaging effect of the probe under laser irradiation was observed. The CCK-8 assay and calcein/propidium iodide staining were used to assess the efficacy of photothermal therapy.
    RESULTS AND CONCLUSION: (1) The prepared 4T1m/ITIC-4CI/PFH nanoprobes had uniform size, high stability, and an average particle size of (92.7±2.3) nm. The probe’s protein composition was identical to that of the 4T1 cell membrane. The nanoprobe’s ability to target homologous 4T1 cells was validated by an in vitro cell uptake assay. (2) The nanoprobe had a red-shift absorption spectrum and tail emission extending to the near-infrared-II, which emitted a bright near-infrared-II fluorescence signal under laser irradiation. (3) After laser irradiation, the nanoprobe 4T1m/ITIC-4CI/PFH could be turned into microbubbles and enhanced ultrasound imaging. The results of CCK-8 assay and calcein/propidium iodide staining showed that the nanoprobe 4T1m/ITIC-4CI/PFH had an obvious photothermal killing effect on 4T1 cells. (4) The results show that the nanoprobe 4T1m/ITIC-4CI/PFH has the ability to target homologous tumors and enhance near-infrared-II fluorescence imaging/ultrasound imaging and photothermal therapy effects. 
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    Melatonin-loaded gelatin methacryloyl microspheres delay nucleus pulposus degeneration
    Li Yangfeng, Tian Xin, He Fan, Yang Huilin
    2024, 28 (5):  676-681.  doi: 10.12307/2024.213
    Abstract ( 195 )   PDF (1156KB) ( 43 )   Save
    BACKGROUND: Nucleus pulposus degeneration is an important pathological link of intervertebral disc degeneration. Melatonin has a protective effect on cells through anti-inflammatory and antioxidant pathways, but the effect of melatonin on the nucleus pulposus has been less studied. At present, the emergence of various biological scaffolders provides a new idea for the study of drug-material combinations.
    OBJECTIVE: To explore whether melatonin can improve the metabolic state of the nucleus pulposus by reducing oxidative stress damage as well as the effect of gelatin methacryloyl (GelMA) microspheres loaded with melatonin on intervertebral disc degeneration in vivo.
    METHODS: In vitro, melatonin was combined with GelMA solution, and GelMA hydrogel was prepared into microspheres by microfluidic technology to co-culture with nucleus pulposus cells. The cell proliferation activity was detected by cell counting kit-8 assay, the surface morphology of the microspheres was observed under scanning electron microscopy, and the rate of drug release was detected by ultraviolet spectrophotometer. Then, interleukin-1β was used to induce degeneration of the nucleus pulposus. After treatment, the expression levels of aggrecan, type II collagen α1, matrix metalloproteinase 13 and a disintegrin and metalloproteinase with thrombospondin motifs-5 (ADAMTS5) in the nucleus pulposus were detected by qRT-PCR. In vivo, nucleus pulposus degeneration was induced by puncture. Subsequently, GelMA and GelMA@MT microspheres were injected. After 6 weeks, the specimens were taken for tissue staining, and the changes in tissue morphology were observed under the microscope for histological analysis and scoring.
    RESULTS AND CONCLUSION: (1) When the GelMA and GelMA@MT microspheres were observed under electron scanning microscope, melatonin binding did not change the morphology and external appearance of the microspheres. Drug release experiments showed that the drug release reached about 80% after 40 days. (2) Cell counting kit-8 assay results showed that both GelMA and GelMA@MT microspheres had no obvious cytotoxicity and promoted the proliferation of nucleus pulposus cells. (3) qRT-PCR results revealed that GelMA@MT microspheres increased the expression of aggrecan and type I collagen α1 in the interleukin 1β environment by 42.1% and 27.1%, respectively, and decreased the expression of matrix metalloproteinase 13 and ADAMTS5 by 70.7% and 109.3%, respectively. (4) The level of reactive oxygen species was significantly lower in the interleukin 1β+GelMA@MT group than in the interleukin 1β and interleukin 1β+GelMA groups. (5) Histological staining of the sections showed that melatonin-loaded GelMA microspheres significantly delayed disc degeneration in vivo. (6) These findings indicate that GelMA@MT microspheres made by combining melatonin with GelMA hydrogel have good cytocompatibility in vitro and significantly delay nucleus pulposus degeneration in vitro and in vivo.
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    Hydroxyapatite-polyvinyl alcohol/collagen-chitosan-gelatin composite hydrogel for repairing rabbit osteochondral defect
    Wang Wu, Fan Xiaolei, Xie Jie, Hu Yihe, Zeng Min
    2024, 28 (5):  682-689.  doi: 10.12307/2024.252
    Abstract ( 222 )   PDF (3004KB) ( 67 )   Save
    BACKGROUND: Osteochondral defect of the joint is a difficult problem faced by orthopedic surgeons, and traditional repair methods are difficult to obtain satisfactory curative effects. Hydroxyapatite-polyvinyl alcohol-based composite hydrogel material is a direction of current research. 
    OBJECTIVE: To prepare hydroxyapatite-polyvinyl alcohol/collagen-chitosan-gelatin composite hydrogel material and characterize its physical characteristics, to verify its histocompatibility and cell adhesion and proliferation ability after implantation in vivo, and explore its repair effect on rabbit osteochondral defects.
    METHODS: The cylindrical porous poly(lactic acid) scaffold was prepared by 3D printing technology (the pore sizes were 1.2, 1.4, 1.6 and 1.8 mm, respectively). The poly(lactic acid) scaffold was injected with polyvinyl alcohol and hydroxyapatite mixed emulsion. After freezing thawing and dichloromethane dissolution, hydroxyapatite-polyvinyl alcohol hydrogel was prepared. Then, the collagen-chitosan-gelatin mixture was injected into the hydroxyapatite-polyvinyl alcohol hydrogel and crosslinked with genipin. Finally, the hydroxyapatite-polyvinyl alcohol/collagen-chitosan-gelatin composite hydrogel was prepared by alcohol cleaning and freeze-drying. The physical characteristics of the four groups of hydrogels were characterized, and the hydrogels with the best performance were screened for follow-up experiments. Hydroxyapatite-polyvinyl alcohol hydrogel and collagen-chitosan-gelatin composite hydrogel were implanted subcutaneously in SD rats. Hematoxylin-eosin staining and Masson staining were used to observe the adhesion growth of cells on the material surface. Osteochondral defect (diameter: 5 mm, depth: 6 mm) models were made in the femoral trochlea of bilateral knee joints of 15 rabbits. The composite hydrogel was implanted on the left side (experimental group), while no material was implanted on the right side (control group). Micro-CT and histology were used to evaluate the repair effect of osteochondral defects.
    RESULTS AND CONCLUSION: (1) Based on the results of porosity, water content, mechanical testing and scanning electron microscopy, it was concluded that the hydroxyapatite-polyvinyl alcohol/collagen-chitosan-gelatin composite hydrogel with a pore size of 1.2 mm was more consistent with the general characteristics of natural cartilage, which was used for subsequent experiments. (2) Hematoxylin-eosin staining and Masson staining exhibited that with the extension of subcutaneous implantation time of the materials, the adhesion of cells around the two materials increased significantly, and the proliferation of cells after the implantation of collagen-chitosan-gelatin was better, a large number of cells could be seen growing into the formed network structure, and the network structure was gradually degraded. (3) In the rabbit osteochondral defect experiment, 8 weeks after surgery, Micro-CT examination demonstrated that the material implanted in the experimental group had good integration with the surrounding bone-cartilage, with some bone growth on the surface and inside, while the cartilage and subcartilage in the control group still had obvious defects, without effective repair. Hematoxylin-eosin staining and toluidine blue staining displayed that the composite hydrogel in the experimental group integrated with the surrounding articular cartilage 4-8 weeks after implantation. With the extension of time, new cartilage gradually formed on the surface of the material. At 12 weeks, most of the defect was covered by new cartilage, and good bone growth was also observed in the subcartilage. In the control group, the deep bone defects were mostly repaired and the superficial cartilage and subchondral bone defects were also repaired to a certain extent, but they were mainly replaced by fibrous tissue and part of fibrocartilage 12 weeks after surgery. (4) In conclusion, hydroxyapatite-polyvinyl alcohol/collagen-chitosan-gelatin composite hydrogel material can mimic the structure and function of natural cartilage, and can effectively repair osteochondral defects in animal experiments. 
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    Hydrogel loaded with platelet-rich plasma promotes wound healing in diabetic rats
    Zhang Ya, Mu Qiuju, Wang Zilin, Liu Hongjie, Zhu Lili
    2024, 28 (5):  690-696.  doi: 10.12307/2023.976
    Abstract ( 235 )   PDF (2080KB) ( 79 )   Save
    BACKGROUND: Diabetic wounds have complicated conditions such as infection, ischemia, peripheral neuropathy, and vascular disease. Ordinary hydrogel dressings with single structure and function cannot meet the needs of diabetic wound healing. 
    OBJECTIVE: To explore the effect of a hydrogel loaded with platelet-rich plasma on wound healing of full-thickness skin defects in diabetic rats.
    METHODS: The blood of SD rats was extracted to prepare platelet-rich plasma. Carboxymethyl chitosan/oxychondroitin sulfate hydrogel and carboxymethyl chitosan/oxychondroitin sulfate hydrogel loaded with platelet-rich plasma were prepared separately. Streptozotocin was used to induce diabetes model in adult male SD rats. A round full-thickness skin wound with a diameter of 2 cm was made on the back of diabetic rats. The rats were randomly divided into four groups (n=10 per group). The blank group was applied with gauze on the wound. The hydrogel group, platelet-rich plasma group, and composite hydrogel group were respectively applied with the corresponding hydrogel, platelet-rich plasma and hydrogel loaded with platelet-rich plasma. The wound healing was observed within 20 days after treatment. 
    RESULTS AND CONCLUSION: (1) On day 20 after treatment, the wound healing rate of the hydrogel group, platelet-rich plasma group and composite hydrogel group was significantly higher than that of the blank group (P < 0.05). The wound healing rate of the composite hydrogel group was significantly higher than that of the platelet-rich plasma group (P < 0.05). (2) The results of hematoxylin-eosin staining on day 5 after treatment showed that compared with the blank group, hydrogel group and platelet-rich plasma group, there were a large number of inflammatory cell infiltration, new granulation tissue and capillary formation in the wound tissue of the composite hydrogel group. (3) On day 5 after treatment, the results of immunohistochemical staining and western blot assay showed that the expression levels of tumor necrosis factor α and interleukin 1β in wound tissue in the composite hydrogel group were significantly lower than those in the blank group, hydrogel group and platelet-rich plasma group (P < 0.05). (4) Masson staining results on day 15 after treatment showed that compared with the blank group, hydrogel group and platelet-rich plasma group, there were more collagen fibers in the wound tissue of the composite hydrogel group, which were orderly, evenly distributed and dense. (5) CD31 immunofluorescence staining showed that on day 15 after treatment, the expression of CD31 in wound tissue of the composite hydrogel group was significantly higher than that of the blank group, hydrogel group and platelet-rich plasma group (P < 0.05). (6) These results suggest that the hydrogel loaded with platelet-rich plasma can promote the healing of full-thickness skin defect wounds in diabetic rats by promoting granulation tissue, collagen fiber and angiogenesis, and reducing the inflammatory response.
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    Vascularized tracheal substitutes constructed by exosome-load hydrogel-modified 3D printed scaffolds
    Shen Ziqing, Xia Tian, Shan Yibo, Zhu Ruijun, Wan Haoxin, Ding Hao, Pan Shu, Zhao Jun
    2024, 28 (5):  697-705.  doi: 10.12307/2023.885
    Abstract ( 233 )   PDF (2393KB) ( 69 )   Save
    BACKGROUND: For the replacement treatment of long-segment tracheal defects, although tissue engineering research has made some progress in recent years, it is still not perfect, and one of the biggest difficulties is that the hemodynamic reconstruction of the tracheal replacement cannot be achieved rapidly. 
    OBJECTIVE: To preliminarily explore the potential of polycaprolactone scaffolds modified with exosome-loaded hydrogels to construct a rapidly vascularized tracheal substitute. 
    METHODS: Exosomes were extracted from bone marrow mesenchymal stem cells of SD rats. After preparation of hyaluronic acid methacrylate solution, the exosome solution was mixed with hyaluronic acid methacrylate solution at a volume ratio of 1:1. Hyaluronic acid methacrylate hydrogels loaded with exosomes were prepared under ultraviolet irradiation for 5 minutes. The degradation of exosome-unloaded hydrogels and the controlled release of exosome-loaded hydrogels were detected. Polycaprolactone scaffolds were prepared by 3D printing. The pure hyaluronic acid methacrylate solution and the exosome-loaded hyaluronic acid methacrylate solution were respectively added to the surface of the scaffold. Hydrogel-modified scaffolds and exosome-modified scaffolds were obtained after ultraviolet irradiation. Thirty SD rats were randomly divided into three groups with 10 rats in each group and subcutaneously implanted with simple scaffolds, hydrogel-modified scaffolds and exosome-modified scaffolds, respectively. At 30 days after surgery, the scaffolds and surrounding tissues of each group were removed. Neovascularization was observed by hematoxylin-eosin staining and Masson staining and the expression of CD31 was detected by immunofluorescence. 
    RESULTS AND CONCLUSION: (1) As time went by, the hydrogel degraded gradually, and the exosomes enclosed in the hydrogel were gradually released, which could be sustained for more than 30 days. The exosome release rate was faster than the degradation rate of the hydrogel itself, and nearly 20% of the exosomes were still not released after 30 days of soaking. (2) Under a scanning electron microscope, the surface of the simple polycaprolactone scaffold was rough. After hydrogel modification, a layer of gel was covered between the pores of the scaffold, and the scaffold surface became smooth and dense. (3) After 30 days of subcutaneous embedding, hematoxylin-eosin staining and Masson staining showed that more neovascularization was observed inside the scaffolds of the exosome-modified scaffold group compared with the hydrogel-modified scaffold group. The hydrogels on the scaffolds of the two groups were not completely degraded. Immunofluorescence staining showed that CD31 expression in the exosome-modified scaffold group was higher than that in the hydrogel-modified scaffold group (P < 0.000 1). (4) These results indicate that hyaluronic acid methacrylate hydrogels can be used as controlled-release carriers for exosomes. The 3D-printed polycaprolactone scaffold modified by hyaluronic acid methacrylate hydrogel loaded with exosomes has good biocompatibility and has the potential to promote the formation of neovascularization. 
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    Finite element simulation and experimental test of normal coracoclavicular ligament and flexible reconstruction
    Ji Guizhu, Zheng Qiu, Wang Wuxiang, Wang Guan, Li Wen, Lu Xiaobo, Duan Ke, Li Zhong, Yang Hongbin, Liang Cheng
    2024, 28 (5):  706-711.  doi: 10.12307/2024.262
    Abstract ( 175 )   PDF (1873KB) ( 13 )   Save
    BACKGROUND: For dislocation of acromioclavicular joint induced by coracoclavicular ligament fracture, single EndoButton Plate reconstruction and double EndoButton Plates reconstruction are common repair methods. Further study on the stress distribution and fracture risk of the two repair methods is of great significance.
    OBJECTIVE: To study the biomechanical properties of the coracoclavicular ligament, and compare the fixation effect, stress distribution and failure mode of single and double EndoButton Plates reconstruction.
    METHODS: (1) Finite element simulation analysis: Mimics, Wrap and SolidWorks were used to establish normal coracoclavicular ligament, single EndoButton Plate reconstruction and double EndoButton Plates reconstruction. Ansys software was used to analyze the stress and deformation of the scapula and clavicle of each model under vertical load. (2) Sample experiment: Fifteen intact scapular-clavicle specimens were randomly grouped into five groups, with three specimens in each group. In group A, the acromioclavicular ligament was severed and the coracoclavicular ligament remained intact. In group B, acromioclavicular ligaments and trapeoid ligaments were severed, leaving intact conical ligaments. In group C, acromioclavicular ligaments and conical ligaments were cut off, and the intact traprex ligaments were retained. In group D, acromioclavicular and coracoclavicular ligaments were severed, and coracoclavicular ligaments were repaired by single EndoButton Plate reconstruction. In group E, acromioclavicular and coracoclavicular ligaments were severed, and the coracoclavicular ligaments were repaired by double EndoButton Plates reconstruction. The mechanical experiment was carried out by a mechanical testing machine to analyze the biomechanical status, stress distribution and failure patterns of the scapular-clavicle and clavicle. 
    RESULTS AND CONCLUSION: (1) Finite element simulation analysis: The average stress of coracoclavicular ligament attached specimens was the lowest, and the risk of coracoclavicular fracture was less than that of single and double EndoButton Plates reconstruction. The mean stress of the coracoid process was similar in single and double EndoButton Plates reconstruction, and the fracture risk was similar. (2) Sample experiment: In groups A, B, C, D and E, the stiffness of specimens was (26.4±3.5), (19.8±2.8), (21.3±3.2), (57.7±4.1), and (46.2±2.8) N/mm, respectively; the ultimate loads were (545.5±53.7), (360.1±42.1), (250.9±44.4), (643.5±39.1), and (511.9±31.7) N, respectively; global stiffness in groups D and E was higher than that in group A (P=0.000 06, 0.000 3); ultimate load in group D was higher than that in group A (P < 0.05); the ultimate load was not significantly different between the group E and group A (P > 0.05). Ligament fracture was observed in groups A, B and C and coracoid process fracture was found in groups D and E. (3) These results suggest that from the biomechanical analysis, Single EndoButton Plate reconstruction and double EndoButton Plates reconstruction are effective treatment techniques for coracoclavicular ligament fracture in acromioclavicular joint dislocation, but increase the risk of fracture. The double EndoButton Plates reconstruction dispersed the stress of the steel plate and reduced the contact force between the steel plate and bone, but slightly reduced the ultimate bearing capacity. Single and double EndoButton Plates reconstruction should be selected according to the actual clinical situation.
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    Different contents of B2O3 affect mechanical properties and bioactivity of bioactive glass scaffolds
    Wang Jianchun, Yang Shuqing, Su Xin, Wang Hongyuan
    2024, 28 (5):  712-716.  doi: 10.12307/2024.264
    Abstract ( 192 )   PDF (1496KB) ( 65 )   Save
    BACKGROUND: Bioactive glass bone repair material has bone-bonding ability, bone induction ability and bone conduction characteristics. However, the performance of bioactive glass does not meet the requirements of clinical application, and the addition of boron is expected to improve the performance of bioactive glass.
    OBJECTIVE: To study the effect of different contents of B2O3 replacing SiO2 on the mechanical properties and bioactivity of bioactive glass.
    METHODS: Based on bioactive glass containing phosphorus nitrogen and oxygen (composition: SiO2-CaO-ZnO-Na2O-Si3N4-P2O5), B2O3 was used to partially replace the SiO2. The basic glass containing B2O3 with a mass fraction of 0% (group A), 5% (group B), 10% (group C), and 15% (group D) was fired using the high-temperature melting method (the total mass fraction of SiO2 and B2O3 in the basic broken glass was 41%). Porous bioactive glass scaffolds were fabricated by the organic foam impregnation method. Uniaxial compression and three-point bending method of universal mechanical testing machine were used to test mechanical properties. Four groups of scaffolds were immersed in simulated body fluids to detect the degradation performance of scaffolds. Scanning electron microscopy was used to observe the morphological changes of scaffolds before and after soaking. X-ray diffraction was used to analyze the phase composition of scaffolds before and after soaking.
    RESULTS AND CONCLUSION: (1) With the increase of the mass fraction of B2O3, the compressive strength and bending strength of the porous bioactive glass scaffold increased, and there was a significant difference between the compressive strength and bending strength of the four groups (P ≤ 0.05). (2) After soaking in simulated body fluids, the porous bioactive glass scaffolds degraded gradually with the extension of time. At the same soaking time point, the degradation rate of the scaffolds was accelerated with the increase of the mass fraction of B2O3, and the compressive strength and bending strength of the scaffolds in the four groups were significantly different (P ≤ 0.05). (3) Scanning electron microscopy after soaking in simulated body fluids showed that a large number of granular materials were deposited on the surface of group A and group B after soaking for 1 day. After 3 days, the granular materials on the surface fused with each other to form film-like deposits. After 7 days, the films on the surface fused with each other to form pieces, basically covering the entire surface of the specimen. After soaking for 1 day, film-like material deposition was formed on the surface of group C, and after 3 days, the films on the surface were fused into pieces, basically covering the whole surface of the specimen. After soaking for 1 day in group D, flake material covering the whole surface of the specimen could be seen. (4) X-ray diffraction analysis after 1 day of immersion in simulated body fluids showed that the deposits on the surface of the four groups of scaffolds were crystallized hydroxyapatite. (5) B2O3 replacement of SiO2 can enhance the mechanical properties, degradation properties and in vitro mineralization activity of porous bioactive glass scaffolds.
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    In vitro degradation behavior of Mg-Zn-Ca alloys
    Lan Weiwei, Yu Yaodong, Huang Di, Chen Weiyi
    2024, 28 (5):  717-723.  doi: 10.12307/2024.263
    Abstract ( 184 )   PDF (2399KB) ( 49 )   Save
    BACKGROUND: Due to the complex physiological environment of the human body, a wide variety of simulated physiological fluids have been chosen for the current degradation experiments. Therefore, it is of great interest to analyze the degradation behavior of Mg-Zn-Ca alloys in different simulated body fluid environments.
    OBJECTIVE: To investigate the degradation process and property changes of Mg-Zn-Ca alloy in different simulated body fluids, and to clarify the influence of Ca content and simulated body fluid type on the alloy.
    METHODS: Mg-Zn-Ca alloys with calcium content of 0.2%, 0.5% and 1% were prepared by melting extrusion molding process and were named Mg-Zn-0.2Ca, Mg-Zn-0.5Ca and Mg-Zn-1Ca alloys in turn, with Mg-Zn alloy as the control. The prepared alloys were placed into three simulated body liquids (physiological saline, PBS and Hank’s solution), and the morphology, compositional changes, mass loss, pH value and mechanical properties were characterized and analyzed during the degradation.
    RESULTS AND CONCLUSION: (1) With the extension of degradation time, a large number of nanoscale lamellae and columnar structures were generated on the surface of the degraded alloy, and the main components were MgO and Mg(OH)2. The degradation rate of the four kinds of alloys in physiological saline was the fastest, and that in Hank’s solution was the slowest. The degradation rate in physiological saline was as follows: Mg-Zn < Mg-Zn-0.2Ca < Mg-Zn-0.5Ca < Mg-Zn-1Ca. The degradation rate in PBS and Hank’s solution was as follows: Mg-Zn < Mg-Zn-0.2Ca ≈ Mg-Zn-0.5Ca < Mg-Zn-1Ca. (2) With the extension of degradation time, all four kinds of alloys had a certain mass loss. The degradation in physiological saline was the fastest; the degradation in Hank’s solution and PBS was slow, and in the same simulated body fluid, with the increase of calcium content in the alloy, the corrosion rate of the alloy was obviously accelerated. (3) The pH rise was mainly concentrated in 1 day and slowed down after that, and the pH change was the largest in PBS. In the same simulated body fluid, with the increase of calcium content in the alloy, the pH value in the degradation environment increased significantly. (4) In the initial state, the elastic modulus of all Mg-Zn-Ca alloys was higher than that of Mg-Zn alloys. After being placed in simulated body fluids, the elastic modulus of the four alloys decreased with the extension of degradation time, and the decrease was most obvious in physiological saline. (5) In conclusion, a small amount of Ca addition improved the mechanical properties of Mg-Zn-Ca alloy. A small amount of Ca does not accelerate the degradation rate of the alloy, but excessive Ca accelerates the degradation rate of the alloy. During the degradation, the effect of physiological saline simulated body fluid on the mechanical strength of the alloy was the most significant.
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    In vitro evaluation of sustained release Kartogenin by gelatin methacryloyl microspheres for repairing nucleus pulposus degeneration
    Tian Xin, Liu Tao, Yang Huilin, He Fan
    2024, 28 (5):  724-730.  doi: 10.12307/2024.247
    Abstract ( 203 )   PDF (1285KB) ( 73 )   Save
    BACKGROUND: The imbalance of matrix synthesis and degradation is the main cause of nucleus pulposus degeneration. Small molecule drug Kartogenin (KGN) can restore the balance of matrix synthesis and degradation. Sustained release of KGN using an appropriate drug delivery system is essential for the long-term and effective treatment of KGN.
    OBJECTIVE: To prepare the injectable hydrogel microspheres by encapsulating KGN with gelatin methacryloyl (GelMA) by microfluidic technology and to investigate the biocompatibility and biological function of nucleus pulposus cells.
    METHODS: β-Cyclodextrins (β-CD) and KGN were mixed firstly and then mixed with 10% GelMA at a volume of 1:9. Injectable hydrogel microspheres GelMA@β-CD@KGN were prepared by microfluidic technology. The micromorphology of the microspheres was characterized using a scanning electron microscope. The drug release of hydrogel microspheres immersed in PBS within one month was measured. Nucleus pulposus cells were isolated from SD rats and passage 1 cells were cultured in three groups. In the control group, nucleus pulposus cells were cultured separately. In the other two groups, GelMA@β-CD microspheres and GelMA@β-CD@KGN microspheres were co-cultured with nucleus pulposus cells. Cell proliferation was detected by CCK-8 assay and cell survival was detected by live/dead cell staining. Cells were cultured by two complete media with and without interleukin-1β with two kinds of microspheres. mRNA expressions of matrix synthesis and decomposing proteins in nucleus pulposus cells were detected by RT-PCR.
    RESULTS AND CONCLUSION: (1) Under the scanning electron microscope, the GelMA@β-CD@KGN microspheres after lyophilization were regularly spherical, highly dispersed, uniform in size and full in shape. GelMA@β-CD@KGN microspheres sustained drug release in vitro, reaching 62% of the total drug release at 30 days. (2) Live/dead cell staining showed that GelMA@β-CD@KGN could maintain the activity of nucleus pulposus cells. CCK-8 assay showed that GelMA@β-CD@KGN could promote the proliferation of nucleus pulposus cells. (3) In the complete media with and without interleukin-1β, mRNA expression of aggrecan and type II collagen was higher in the GelMA@β-CD@KGN microsphere group than that in the GelMA@β-CD microsphere group (P < 0.05, P < 0.01); mRNA expression of matrix metalloproteinase 13 and platelet reactive protein disintegrin metallopeptidase 5 was lower than that in the GelMA@β-CD microsphere group (P < 0.01). (4) These findings indicate that GelMA@β-CD@KGN microspheres have good biocompatibility and sustained drug release ability. As a drug delivery system, it is a kind of biomaterial with broad application prospects.
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    Design, synthesis and properties of oral composite resin monomers with different photoinitiators
    Wei Yuxue, Wang Di, Liu Xiaoqiu
    2024, 28 (5):  731-735.  doi: 10.12307/2023.834
    Abstract ( 188 )   PDF (835KB) ( 88 )   Save
    BACKGROUND: At present, the dental composite resin filling material composed of resin matrix monomer is the first choice material for the filling treatment of dental defects, but with the increase of its use time in the oral environment, the dental tissue will develop secondary caries and the filling material will wear and break. The main cause of these problems is the polymerization shrinkage of the filling material and its mismatch with the mechanical properties of the dental tissue. 
    OBJECTIVE: To synthesize a new type of dental composite resin monomer by adding initiators with different components, to improve the traditional double bond conversion rate of the system and further improve the mechanical properties of the material. 
    METHODS: A new composite resin matrix system was prepared by adding different initiators to the monomer of 3,3′,5,5′-tetramethoxybiphenyl-4,4′-diol epoxy acrylate resin. In group A, camphorquinone with a mass fraction of 1.1% was added. In group B, 1-phenyl-1,2-propanedione with a mass fraction of 2.1% was added. In group C, a mixture of camphorquinone and 1-phenyl-1,2-propanedione (a mass ratio of the two was 1:1) with a mass fraction of 3.1% was added. The double bond conversion, polymerization shrinkage and mechanical properties of the samples were determined. 
    RESULTS AND CONCLUSION: (1) The double bond conversion rate of groups B and C was higher than that of group A (P < 0.05). The polymerization shrinkage of group B was higher than that of group A (P < 0.05), while that of group C was lower than that of group A (P < 0.05). (2) The flexural strength, elastic modulus and compressive strength of groups B and C were higher than those of group A (P < 0.05, P < 0.01). Vickers hardness of group B was higher than that of group A 
    (P < 0.05), and the Vickers hardness of group C was lower than that of group A (P < 0.01). (3) These findings suggest that 1-phenyl-1,2-propanedione is an initiator with ideal performance. The combined application of 1-phenyl-1,2-propanedione and camphorquinone can effectively improve the double bond conversion rate of the resin matrix system and further improve the mechanical property of the resin. 
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    Bone defect blocked by bone cement segmental filling in single-plane tibial bone transport
    Zhou Xiaowen, Fu Zuchang, Huang Fei, Ai Jianguo, Zhao Feng
    2024, 28 (5):  736-740.  doi: 10.12307/2024.254
    Abstract ( 186 )   PDF (964KB) ( 18 )   Save
    BACKGROUND: Bone transport has been used for a variety of reasons in bone defects with good clinical results. However, various complications have also attracted the attention of practitioners and the avoidance of non-healing of the docking point has become a common concern for doctors and patients. 
    OBJECTIVE: To explore effective methods of avoiding non-healing of the docking point in the treatment of tibial bone defects by bone transport so as to shorten the treatment period and reduce the pain of patients. 
    METHODS: The clinical data of 21 patients with unilateral tibial bone defect admitted to the No. 910 Hospital of Joint Logistics Support Force of Chinese PLA from January 2018 to January 2021 were retrospectively analyzed, including 16 males and 5 females, aged (32.8±10.3) years, with an average bone defect length of 10.2 cm. All 21 patients received bone transport surgery, during which the bone defect area was filled with bone cement to reduce the adverse factors affecting the healing of the docking point. The Association for the Study and Application of the Methods of Ilizarov, healing index and incidence of adverse reactions were evaluated during postoperative follow-up. 
    RESULTS AND CONCLUSION: The 21 patients were followed up for 15 to 24 months after surgery, and the extended area was all well mineralized and had no malformations, and no refractures occurred during treatment. Among them, one patient had foot drop, which could not be completely corrected after surgical release of the Achilles tendon and wearing foot and ankle orthotics. 19 patients had different degrees of needle tract infection, and no deep infection occurred after timely needle tract nursing. The healing rate of the docking point was 100%; the healing index was 36-45 d/cm and the average was 38 d/cm. The Association for the Study and Application of the Methods of Ilizarov showed that bone healing was excellent in 17 cases (81%) and poor in 4 cases (19%). The results of limb function were excellent in 18 cases (86%) and good in 3 cases (14%). These findings show that bone cement segmental filling during bone transport is an effective method to solve the non-healing of the docking point, shorten the patient’s treatment period and reduce the patient’s pain.
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    Structural design and mechanical property analysis of trabecular scaffold of triply periodic minimal surface with a radial gradient
    Zhang Yihai, Shang Peng, Ma Benyuan, Hou Guanghui, Cui Lunxu, Song Wanzhen, Qi Dexuan, Liu Yancheng
    2024, 28 (5):  741-746.  doi: 10.12307/2024.253
    Abstract ( 229 )   PDF (2260KB) ( 32 )   Save
    BACKGROUND: The elastic modulus of traditional bone implants is large and does not match the elastic modulus of human bone, which will cause a stress shielding effect and lead to bone resorption. The trabecular scaffold of the triply periodic minimal surface with radial gradient has elastic modulus matching with human cancellous bone, and its yield strength is greater than that of human cortical bone, which provides a new choice for the design of bone scaffold. 
    OBJECTIVE: Triply periodic minimal surface structure with radial gradient was constructed by the implicit surface method. The sample was manufactured by laser selective melting technology, and the quasi-static compression test was carried out to obtain trabecular scaffolds with mechanical properties matching human bones.
    METHODS: Four types of the trabecular scaffolds of the triply periodic minimal surface with a radial gradient of G, I, P and D were established by the implicit surface method. Samples were manufactured by laser selective melting technology. We observed the surface morphology of the molded sample, evaluated the molding quality, conducted a quasi-static compression test, and evaluated the mechanical properties of the samples.
    RESULTS AND CONCLUSION: The quasi-static compression test results showed that compared with the four triply periodic minimal surface scaffolds, the platform stress of the G scaffold had less fluctuation and no failure or fracture, indicating that the G scaffold had the best plasticity. The mechanical properties of the G scaffolds with 45%, 55% and 65% porosities were analyzed. It was found that the elastic modulus of G scaffolds with 55% porosity was within the range of elastic modulus of human cancellous bone (0.022-3.7 GPa), and the yield strength was close to the maximum yield strength of human cortical bone (187.7-222.3 MPa). In conclusion, G triply periodic minimal surface scaffold with 55% porosity can reduce the stress shielding effect, bear a higher body load, improve the stability of the implant, and prolong the service life of the implant.
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    Mechanism and influencing factors in molecular weight degradation of non-cross-linked hyaluronic acid
    Li Jiaqi, Huang Yuanli, Li Yan, Wang Chunren, Han Qianqian
    2024, 28 (5):  747-752.  doi: 10.12307/2024.312
    Abstract ( 248 )   PDF (1048KB) ( 85 )   Save
    BACKGROUND: The structure, physical and chemical properties (such as rheological properties) and biological activity of hyaluronic acid with different molecular weights are quite different. When the degradation degree of non-cross-linked hyaluronic acid is too large and the high-molecular-weight hyaluronic acid is degraded to low-molecular-weight hyaluronic acid, the properties and biological functions of the product will also change, which will affect the use of the product.
    OBJECTIVE: To review the mechanism of molecular weight degradation of non-cross-linked hyaluronic acid and the impacts of molecular weight degradation on the structure, rheological properties, biological activity and applications of non-cross-linked hyaluronic acid.
    METHODS: The first author searched the articles related to the molecular weight of hyaluronic acid collected in PubMed, CNKI database and other databases. The high-quality articles with high correlation were screened according to the inclusion and exclusion criteria. The search time was from January 2017 to December 2022. The Chinese and English search terms were “hyaluronic acid, non-cross-linked hyaluronic acid, molecular weight, degradation, structure, rheological properties, biologic activity”. Finally, 47 articles were included for review and analysis.
    RESULTS AND CONCLUSION: (1) The molecular weight of non-cross-linked hyaluronic acid is mainly degraded by specific enzymatic hydrolysis and non-specific free radical degradation. (2) The molecular weight degradation of non-cross-linked hyaluronic acid will change its structure and rheological properties, resulting in the untie of polymer network structure, the decrease of rheological properties such as viscosity and viscoelasticity, and the decrease of mechanical properties, which will eventually affect the practical application effect of the product. (3) The biological activity of non-cross-linked hyaluronic acid is molecular weight dependent, and the biological activity of different molecular weight hyaluronic acid is different. Even the same receptor combined with high-molecular-weight hyaluronic acid and low-molecular-weight hyaluronic acid will express completely opposite biological effects. (4) The degradation of molecular weights of non-cross-linked hyaluronic acid will reduce the safety and efficacy of the products, affect their service life and application performance, and ultimately influence the clinical application results. (5) Non-cross-linked hyaluronic acid has great potential as a biodegradable biomaterial in wound healing, tissue engineering, aesthetic medicine and other fields, and further research and understanding of the correlation between molecular weight degradation of non-cross-linked hyaluronic acid and bioactivity is a prerequisite for better development of wound dressings, drug delivery systems and tissue-engineered scaffolds. (6) However, there are currently few studies on the molecular weight degradation of non-cross-linked hyaluronic acid, and it is unclear how to effectively avoid the potential risks associated with the molecular weight degradation of non-cross-linked hyaluronic acid in clinical applications. (7) Therefore, a series of potential risks associated with the molecular weight degradation of non-cross-linked hyaluronic acid during its application, including the effects on its structure, properties and biological activity, and the resulting changes on the body, is one of the future directions that need to be closely investigated. 
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    Application value of nanocomposite gelatin methacryloyl hydrogels in different bone defect environments
    Zhu Liwei, Wang Jiangyue, Bai Ding
    2024, 28 (5):  753-758.  doi: 10.12307/2024.315
    Abstract ( 267 )   PDF (1280KB) ( 41 )   Save
    BACKGROUND: At present, nanocomposite gelatin methacryloyl hydrogels have been extensively studied in bone tissue engineering.  
    OBJECTIVE: To review the latest research progress of nanocomposite gelatin methacryloyl hydrogels, and introduce the application of nanocomposite gelatin methacryloyl hydrogels in different bone defect environments. 
    METHODS: The computer retrieval was conducted for relevant literature published in CNKI, WanFang, PubMed, and Web of Science databases from 2016 to 2023. The Chinese and English search terms were “gelatin, methacryl*, nano*, bone, bone tissue engineering, bone regeneration, osteogenesis”.  
    RESULTS AND CONCLUSION: (1) Up to now, inorganic nanomaterials, organic nanomaterials and organic-inorganic hybrid nanomaterials are the main nanomaterials used as fillers for gelatin methacryloyl. (2) Inorganic nanomaterials enhance the mechanical strength of gelatin methacryloyl, improve its thixotropic properties and degradation rate, and realize the antibacterial, osteogenic, immunoregulatory, angiogenic and other functions of gelatin methacryloyl hydrogel through its surface charge regulation, drug/factor loading, metal ion self-degradation release, etc. (3) Organic nanomaterial and organic-inorganic hybrid nanomaterial composite gelatin methacryloyl hydrogel are two emerging materials. At present, there are relatively few studies, but from the published research, compared with inorganic nanomaterial gelatin methacryloyl hydrogel, organic nanomaterial gelatin methacryloyl hydrogel has better biocompatibility and drug-loading performance. The interaction between nano phase and organic polymer phase is stronger, and the dispersion of nano particles is better. (4) Organic-inorganic hybrid nanomaterial composite gelatin methacryloyl combines the advantages of the previous two, and has better controllability of metal ion release, which proves great research potential. (5) Nanomaterials can enhance the antibacterial, immune regulation, osteogenesis and other biological properties of gelatin methacryloyl, so as to promote bone regeneration in the complex bone defect microenvironment, such as infected bone defect, diabetes, osteosarcoma resection and so on. However, the relevant research of nanocomposite gelatin methacryloyl hydrogel in bone repair is still limited to animal experiments. Further safety testing and clinical studies are still needed. 
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    Research advance in preparation and functional modification of porous polytetrafluoroethylene artificial blood vessels
    Xu Rong, Wang Haojie, Geng Mengxiang, Meng Kai, Wang Hui, Zhang Keqin, Zhao Huijing
    2024, 28 (5):  759-765.  doi: 10.12307/2024.256
    Abstract ( 251 )   PDF (1383KB) ( 89 )   Save
    BACKGROUND: Medium- and large-diameter polytetrafluoroethylene artificial blood vessels have been widely used in clinical practice. However, most of the products were imported from other countries. Small-diameter porous polytetrafluoroethylene vessels are easy to form thrombosis and intimal hyperplasia, resulting in an extremely low long-term patency rate, which is difficult to fulfill clinical requirements.  
    OBJECTIVE: To review and summarize the research progress of polytetrafluoroethylene in the field of artificial blood vessels, which can provide a reference for the functional modification of small-diameter polytetrafluoroethylene artificial blood vessels and the improvement of their long-term patency rate.
    METHODS: The relevant articles published  from October 2022 to March 2023 in CNKI, Web of Science, Wiley Online Library, SpringerLink, Science Direct and IOP Science databases were searched by the first author. The search terms in Chinese were “porous polytetrafluoroethylene, vascular graft, electrospinning, medical application, functional modification”. The search terms in English were “ePTFE, porous polytetrafluoroethylene, vascular graft, electrospinning, medical application, functional modification”. All the articles about the preparation and modification of polytetrafluoroethylene artificial blood vessels were retrieved.
    RESULTS AND CONCLUSION: The preparation and functional modification of porous polytetrafluoroethylene artificial blood vessels were still research hotspots and difficult problems. From the research progress in and outside China in recent years, the preparation of porous polytetrafluoroethylene artificial blood vessels mainly adopted the rapid thermal stretching method, but the preparation of polytetrafluoroethylene artificial blood vessels by electrospinning was a promising new method. By analyzing and summarizing different functional modification methods, it was found that the long-term patency rate of porous polytetrafluoroethylene artificial blood vessels had been improved. However, the functional modification of small-diameter polytetrafluoroethylene artificial blood vessels still needed further exploration and optimization. 
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    Application of core-shell structured nanofibers in oral tissue regeneration
    Yin Tong, Yang Jilei, Li Yourui, Liu Zhuoran, Jiang Ming
    2024, 28 (5):  766-770.  doi: 10.12307/2024.257
    Abstract ( 215 )   PDF (979KB) ( 57 )   Save
    BACKGROUND: The combination of good biomechanical properties, controlled drug release and multi-functionality of core-shell structured nanofibers is receiving more and more attention, which also makes them promising for a wide range of applications in the field of oral tissue regeneration.
    OBJECTIVE: To summarize the preparation, drug loading and release mechanisms of core-shell structured nanofibers and their application in the regenerative repair of oral tissues.
    METHODS: A computer search of the literature collected in CNKI and PubMed from January 2000 to November 2022 was applied, and the search terms in English and Chinese were “electrospinning, core-shell structures, drug delivery systems, jaw bone regeneration, cartilage regeneration, periodontal tissue regeneration”. 
    RESULTS AND CONCLUSION: (1) There are various methods for the preparation of core-shell structured nanofibers, but the coaxial and emulsion methods of electrostatic spinning have unique advantages such as simple operation, diverse material selection and good biocompatibility. (2) Core-shell structured nanofibers can be used as bacteriostatic agents, carriers of different types of drugs, and scaffolds for cell adhesion, providing new therapeutic options for oral tissue regeneration. (3) Controlled degradation and drug release rate of core-shell structured nanofibers can better adapt to the healing process of oral tissue defect repair and achieve ideal tissue regeneration. 
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    Effect of micro-arc oxidation treatment on biological activity of medical metals
    Wang Yeyuan, Du Yilang, Yu Dehao, Ning Fengting, Bai Bing
    2024, 28 (5):  771-776.  doi: 10.12307/2024.265
    Abstract ( 200 )   PDF (818KB) ( 137 )   Save
    BACKGROUND: Among the surface modification technologies of metal implants, micro-arc oxidation has been widely concerned for its convenience, low cost and ability to effectively adjust the microstructure and elements of surface coatings. 
    OBJECTIVE: To summarize research advances in physical and chemical properties and biological activities of oxidation coatings prepared by micro-arc oxidation on different materials. 
    METHODS: The articles about the effects of micro-arc oxidation on the biological activity of medical metals were searched in PubMed and Web of Science based on the English search terms “MAO, micro-arc oxidation, osseointegration, mechanical property, biological activity, angiogenesis, fibrogenesis”. The search time was from January 2016 to December 2022. According to the inclusion and exclusion criteria, 82 articles were finally retained for review.
    RESULTS AND CONCLUSION: Micro-arc oxidation is a potential surface modification technology, which can greatly improve the success rate of implantation, and can be widely used in other fields. The specific reasons are as follows: (1) Micro-arc oxidation technology forms special porous morphology on the surface of materials, which can optimize the mechanical properties such as wear resistance and corrosion resistance, contributing to the reduction of the degradation rate of magnesium alloys. (2) Micro-arc oxidation technology can significantly enhance the bioactivity and improve the bioinertness of titanium and titanium alloys through the addition of strontium, hydroxyapatite and other metallic or nonmetallic substances to its porous morphology for helping elevate its osteogenic differentiation, angiogenesis, fibrogenesis and other biological activities.
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    Research status on element selection of medical magnesium alloy
    Liu Anhong, Cai Mengmeng, Han Xiao, Wang Zhanhui
    2024, 28 (5):  777-782.  doi: 10.12307/2024.269
    Abstract ( 220 )   PDF (946KB) ( 50 )   Save
    BACKGROUND: Due to natural degradation, excellent biocompatibility and good mechanical properties, magnesium alloy has become a very valuable implant material in the biomedical field. However, the rapid degradation rate of magnesium alloy limits its further development and application. 
    OBJECTIVE: To review the principle of the degradation of magnesium and its alloys in a physiological environment. The current research status of alloying elements selection is mainly introduced from the aspects of the safety of elements and their influence on the properties of magnesium and its alloys.  
    METHODS: The articles were searched by using the databases of CNKI, PubMed, Web of Science and Elsevier. The key words were “magnesium (alloy), metal name (such as: bismuth (Bi), aluminum (Al)), corrosion, biocompatibility, metal toxicity, scaffold (stent)/screw” in Chinese and English. The search period was from 2013 to 2023. As a result, 70 articles were applied for analysis after reading the contents of the articles.
    RESULTS AND CONCLUSION: Magnesium alloy has been widely studied in the medical field. Although some products have been applied in clinical practice, the high degradation rate of magnesium alloy in the human environment is still the main limitation of large-scale clinical application. The focus of future development is to control its corrosion rate. Alloying is a kind of method to improve the corrosion resistance of magnesium alloys, and various properties can also be improved by adding different alloy components. However, simple alloying cannot satisfy the pursuit of diversified properties of magnesium alloys. To develop multifunctional magnesium alloy products with excellent performance, it is necessary to combine various optimization methods, such as alloying and surface modification, to make up for the shortcomings of their respective methods in the future. In addition, the alloy structure updating with preparation process improvement is combined to enhance the properties of magnesium alloy.
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    Application of metal-organic frameworks in implant surface modification
    Yin Kaiwen, Li Yunfeng
    2024, 28 (5):  783-788.  doi: 10.12307/2024.260
    Abstract ( 201 )   PDF (982KB) ( 32 )   Save
    BACKGROUND: In recent years, metal-organic frameworks have been widely used in the biomedical field because of their unique properties, and metal-organic frameworks can be applied to implant surface modification for improving their biological properties and the surgery’s success rate. 
    OBJECTIVE: To introduce metal-organic frameworks commonly used in implant surface modification and the preparation and action mechanism of surgical implants modified by metal-organic frameworks. 
    METHODS: The articles concerning metal-organic frameworks used in implant surface modification published from 2010 to 2023 were searched on PubMed, Web of Science and CNKI. Finally, 64 articles were included for review.
    RESULTS AND CONCLUSION: (1) Metal-organic frameworks have the properties of high porosity, large specific surface area, and diverse spatial structure. As bioactive material, metal-organic frameworks have attracted much attention in tissue engineering and regenerative medicine. (2) The metal-organic frameworks commonly used in the field of implant surface modification include three types. Zeolitic imidazolate frameworks are commonly used as carriers, carrying various drugs and biomolecules. The MIL series are suitable for drug carriers and nanoenzymes. Bio-metal-organic frameworks have many applications because of their diverse structure and are characterized by excellent biosafety. (3) The preparation of implant materials modified by metal-organic frameworks can be mainly divided into two types: one is to incorporate metal-organic frameworks into pretreated implants; the other is to synthesize metal-organic frameworks in situ on pretreated implants. (4) Metal-organic frameworks on the implant surface could release their components, load drugs, catalyze active reactions, or combine with other materials, giving implants antibacterial and anti-inflammatory characteristics and promoting osseointegration. The preparation method of metal-organic framework coatings needs further improvement, and the metabolism and distribution of metal-organic framework coatings should be deeply explored, and its clinical application should be actively promoted. 
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    Preparation and application of injectable sodium alginate hydrogels
    Chen Xiaofang, Zheng Guoshuang, Li Maoyuan, Yu Weiting
    2024, 28 (5):  789-794.  doi: 10.12307/2024.245
    Abstract ( 351 )   PDF (988KB) ( 151 )   Save
    BACKGROUND: Sodium alginate, a natural polysaccharide, has become one of the ideal materials for preparing injectable hydrogels because it is an abundant and cheap resource, and has good biocompatibility and biodegradability. It has been widely used in the production of injectable hydrogels.
    OBJECTIVE: To review the properties of sodium alginate, the preparation of injectable sodium alginate hydrogel, and its application progress in tissue engineering.
    METHODS: Web of Science, PubMed, and CNKI were searched by computer. Chinese search terms were “sodium alginate; hydrogel; injectable”, and English search terms were “alginate; hydrogel; inject”. The time range of searching literature was mainly from June 2017 to June 2022.
    RESULTS AND CONCLUSION: Alginic acid comes from a wide range of sources, and there are many modifiable groups in its molecular structure, so many injectable hydrogels with excellent properties can be produced by various chemical crosslinking or physical crosslinking methods. Introducing other bioactive molecules or drugs into sodium alginate gel can adjust its properties and broaden its application fields. In addition, injectable sodium alginate hydrogels have great application prospects in biomedicine because of their good biocompatibility, biodegradability and other physical and chemical properties. Sodium alginate hydrogels are evenly mixed with various drugs, cells, factors or other biological molecules in vitro, and can form gels in the human body, which plays a pivotal role in gene carrier, cell scaffold and wound repair.
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    Advantages, discomfort and challenges of clinical application of orthopedic hemostatic materials
    Liu Chuang, Shan Shuo, Yu Tengbo, Zhou Huan, Yang Lei
    2024, 28 (5):  795-803.  doi: 10.12307/2023.979
    Abstract ( 262 )   PDF (1475KB) ( 221 )   Save
    BACKGROUND: Bone wax is a filler that can be used for bone hemostasis. Although modification of bone wax formulations is attempted worldwide, its inertness is still the main challenge today. There is an urgent clinical need to develop novel orthopedic hemostatic materials with hemostasis, osteogenesis and antibacterial properties.
    OBJECTIVE: To review the development of orthopedic hemostatic materials including bone wax and its substitutes. 
    METHODS: PubMed, Web of Science, WanFang, CNKI and VIP databases were searched for literature related to bone wax, hemostatic materials, and research progress of orthopedic hemostatic materials, and 136 articles were selected for inclusion in the review by reading the abstracts of the articles in the initial screening. 
    RESULTS AND CONCLUSION: To replace traditional bone wax, researchers have developed various orthopedic hemostatic materials based on the needs of practical scenarios such as hemostasis and osteogenesis. However, relevant studies mostly focus on basic physical and chemical and performance tests, lack a systematic evaluation system, and lack sufficient reports of large animal experiments and clinical trials. Therefore, bone wax is still a recognized orthopedic hemostatic material at present. The fundamental reason is that the design of existing materials cannot timely meet the new needs of intraoperative hemostasis, postoperative osteogenesis and clinical practice. In the future, the structure, composition and function of existing hemostatic and osteogenic materials need to be integrated and redesigned to meet the increasing demand for hemostatic and osteogenic materials.
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    Angiogenesis mechanism of metal ions and their application in bone tissue engineering
    Wang Jiani, Chen Junyu
    2024, 28 (5):  804-812.  doi: 10.12307/2024.243
    Abstract ( 246 )   PDF (1312KB) ( 64 )   Save
    BACKGROUND: Owing to excellent angiogenesis activity and their participation in the physiological processes such as angiogenesis in osteogenesis, the researches and applications of a variety of metal ions are getting deeper in the field of bone tissue engineering.
    OBJECTIVE: To systematically explain the mechanism of angiogenesis of different metal ions such as copper ion (Cu2+), magnesium ion (Mg2+), strontium ion (Sr2+), zinc ion (Zn2+), cobalt ion (Co2+) and their current research situation as well as application in the treatment of diseases in the field of bone tissue engineering. 
    METHODS: The two authors used PubMed and CNKI to search the literature published between 2017 and 2022 with the search terms “copper ion, magnesium ion, strontium ion, zinc ion, cobalt ion, bone, angiogenesis” in Chinese and “copper, cuprum, Cu, magnesium, Mg, strontium, Sr, zinc, Zn, cobalt, Co, metal ion, angiogenesis, bone” in English. After reading titles and abstracts, the articles were initially screened, and irrelevant articles were excluded. Finally, 114 articles were included for review.
    RESULTS AND CONCLUSION: (1) Metal ions can regulate angiogenesis by acting on vascular endothelial growth factors, hypoxia-inducible factors, angiogenesis-related genes, endothelial cells and conducting immune regulation of macrophages. (2) Metal ions such as copper, magnesium, strontium, zinc and cobalt are often used to improve the performance of tissue engineering scaffolds due to their significant angiogenic effect. Among them, hydrogels, bioceramics and synthetic polymer materials are widely used at present, and magnesium and its alloys also have advantages due to their excellent bearing capacity. However, these materials all have some defects. Currently, there is no ideal bone replacement material. (3) Various metal ions show different application potentials in bone replacement materials: Copper has antibacterial, angiogenic and osteogenic properties, and is mainly used for bone defects caused by infection and tumors. Magnesium and zinc have strong biodegradability, so the degradation rate should be controlled. Magnesium is corrosive and is mainly used as an alloy. The angiogenesis mechanism of zinc is less involved. Magnesium and strontium are effective in treating osteoporotic bone defects. (4) The above five metal ions (copper, magnesium, strontium, zinc and cobalt) have a significant role in promoting angiogenesis and then promote osteogenesis through angiogenesis. Some ions, such as copper ions, have a bactericidal effect. These ions can be used as a new strategy for the treatment of bone defects caused by tumors, osteoporosis, infection and trauma, but the current clinical trials and application studies of products are relatively insufficient.
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    Meta-analysis of cement-augmented pedicle screw for thoracolumbar degenerative diseases with osteoporosis
    Yu Zhaoyu, Tan Lixin, Sun Kai, Lu Yao, Li Yong
    2024, 28 (5):  813-820.  doi: 10.12307/2023.980
    Abstract ( 182 )   PDF (1158KB) ( 85 )   Save
    OBJECTIVE: Cement-augmentation pedicle screws have been widely used in spinal internal fixation surgery combined with osteoporosis in recent years, which can significantly improve the fixation strength, but compared with conventional methods, whether it has more advantages is still inconclusive of evidence-based medicine. To systematically evaluate the efficacy and safety of cement-augmented pedicle screw in the treatment of thoracolumbar degenerative diseases with osteoporosis.
    METHODS: Clinical controlled trials concerning the cement-augmented pedicle screw and the traditional pedicle screw placement for thoracolumbar degenerative diseases with osteoporosis were retrieved from the electronic databases such as CNKI, CBM, WanFang, VIP, PubMed, Cochrane Library, Web of Science and Embase. According to the unified criteria, we performed literature screening and quality evaluation. The meta-analysis was performed using RevMan 5.4 software.
    RESULTS: (1) Totally 20 articles were selected eventually, involving 2 randomized controlled studies and 18 retrospective cohort studies, totally 1 566 patients. Among them, 789 cases were in the cement-augmented screw group and 777 cases in the conventional screw group. (2) Meta-analysis results showed that Japanese Orthopaedic Association score, intervertebral space height and fusion rate were higher in the cement-augmented screw group than those in the conventional screw group (MD=1.60, 95%CI: 1.14, 2.07, P < 0.000 01; MD=1.26, 95%CI: 0.62, 1.90, P=0.000 1; OR=11.24, 95%CI: 2.86, 44.14, P=0.000 5). Operation time was longer in the cement-augmented screw group than that in the conventional screw group (SMD=0.82, 95%CI: 0.42, 1.23, P < 0.000 1). Postoperative visual analog scale score, Oswestry dysfunction index score and incidence of screw loosening were lower in the cement-augmented screw group than those in the conventional screw group (MD=-0.50, 95%CI: -0.78, -0.21, P=0.000 7; SMD=-0.49, 95%CI: -0.88, -0.10, P=0.01; OR=0.08, 95%CI: 0.05, 0.12, P < 0.000 01). Hospitalization time, intraoperative blood loss, and postoperative drainage volume were not significantly different between the two groups (P > 0.05). 
    CONCLUSION: Compared with conventional pedicle screw placement, cement-augmented pedicle screw is more effective in the treatment of osteoporotic thoracolumbar degenerative disease by improving fusion rate and interbody height, reducing the incidence of screw loosening, and elevating long-term efficacy.
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