BACKGROUND:Platelet-rich fibrin(PRF)has many advantages,such as simple preparation,low production cost,and high safety,and has been widely used in the study of bone defect repair in oral and maxillofacial surgery,but there are problems such as too fast degradation rate and short release time of growth factors. OBJECTIVE:PRF was loaded into gelatin methacryloyl(GelMA)hydrogel and its osteogenic properties were analyzed by in vivo and in vitro experiments. METHODS:(1)New Zealand white rabbit venous blood was extracted to prepare PRF.GelMA hydrogels containing 0,0.05,0.075,and 0.1 g PRF were prepared,respectively,and were recorded as GelMA,GelMA/PRF-0.05,GelMA/PRF-0.075,and GelMA/PRF-0.1,respectively,to characterize the micromorphology and in vitro slow-release properties of the hydrogels.(2)Four kinds of hydrogels were co-cultured with MC3T3-E1 cells,respectively,and the cell proliferation activity was detected with the single cultured cells as the control.After osteogenic induction,alkaline phosphatase activity,mineralization ability,mRNA and protein expression levels of osteogenic genes(osteocalcin,osteopontin,RUNX2),ERK1/2-p38 MAPK pathway protein mRNA and protein expression levels were detected.(3)Fifteen New Zealand white rabbits were taken.Four full-layer bone defects of 8 mm diameter were prepared in the skull of each rabbit,one of which was implanted without any material(blank control group),and the other three were implanted with GelMA hydrogel,PRF,and GelMA/PRF-0.1 hydrogel,respectively.The bone defect was detected by Micro-CT and bone morphology was observed at 4,8,and 12 weeks after operation. RESULTS AND CONCLUSION:(1)Scanning electron microscopy observed that all the hydrogels of the four groups had honeycomb pore structure,and the pore size of the hydrogels decreased slightly with the increase of PRF content,but there was no significant difference between the groups.The three groups of GelMA/PRF hydrogel could release transforming growth factor β1 and insulin-like growth factor 1 at a certain rate,and the cumulative release of transforming growth factor β1 and insulin-like growth factor 1 increased significantly with the extension of time.(2)CCK-8 assay and live/dead staining showed that GelMA/PRF hydrogel could promote the proliferation of MC3T3-E1 cells.The results of alkaline phosphatase staining,alizarin red staining,and osteogenic gene detection showed that GelMA/PRF hydrogel could promote the osteogenic differentiation of MC3T3-E1 cells,and inhibit the expression of ERK1/2-p38 MAPK pathway protein,and showed a PRF content dependence.(3)Micro-CT scan showed that the bone mineral density and bone volume fraction in the bone defect of GelMA/PRF-0.1 hydrogel group were higher than those in the other three groups(P<0.05).Hematoxylin-eosin staining showed that compared with the other three groups,GelMA/PRF-0.1 hydrogel group had faster and more mature new bone formation at the bone defect.(4)These findings indicate that GelMA/PRF hydrogel has good osteogenic activity both in vivo and in vitro,which may be related to inhibiting the expression of ERK1/2-p38 MAPK pathway protein.

BACKGROUND:The healing of mandibular fractures after rigid internal fixation is influenced by many factors,including the material of the bone plate,fracture site,and bone density of the patient.However,there are relatively few studies on the relationship between the stability of mandibular fracture fixation in different bone qualities and they lack a scientific basis. OBJECTIVE:To analyze the stability of fixation of mandibular fractures with different bone qualities with bioabsorbable plates and miniature titanium plates by finite element analysis. METHODS:Three-dimensional finite element models of class Ⅰ-Ⅳ mandibular fractures were developed according to the bone quality classification method proposed by ZARB and LEKHOLM.The fractures at the median mandibular symphysis,mandibular body,and mandibular angle were simulated under different bone qualities.Bioabsorbable bone grafting plates(or miniature titanium plates)were placed at each fracture site for fixation and to simulate the state of healthy side occlusion.Finite element analysis on the model was used to analyze the relative displacement of the fracture segments and the stress distribution of fixators. RESULTS AND CONCLUSION:(1)The maximum stress value during fixation with titanium plates increased gradually with the increase of bone class,in which the maximum stress value of titanium plates was the highest in the mandibular body class Ⅳ bone group,which was 382.74 MPa and 96.11 MPa in the miniature titanium plate and bioabsorbable plate groups.The results for mandibles of the same bone type showed that the maximum stress value of titanium plates was much higher than that of bioabsorbable plates.(2)For fractures of the median middle of the mandible in types Ⅲ and Ⅳ,the displacement of the fracture breaks at the fixation site was large and exceeded the limiting value of bone healing(>150 μm),regardless of whether the fixation was performed with a miniature titanium plate or a bioabsorbable plate.For type Ⅳ mandibular fractures,the fracture end displacement in the bioabsorbable plate group exceeded the healing limit value,and the fracture end displacement in the miniature titanium plate group was close to the healing limit value.Under the same bone quality and fracture site,the fracture displacement of the miniature titanium plate group was smaller than that of the bioabsorbable plate group.(3)The results showed that the strength and stiffness of the two internal fixations were sufficient to support bone healing of fractures at three sites of the types Ⅰ-Ⅳ mandible,and the fixation stability of the bioabsorbable plate was almost the same as that of the miniature titanium plate,which could provide early healing conditions for fractures.Mandibular bone type should be taken into consideration in the treatment of mandibular fracture.The higher the mandibular bone grade,the worse the stability of fracture fixation,and the more likely the complications such as poor bone healing will occur after surgery.

BACKGROUND:Magnetic nanomaterials have biological activities such as promoting osteogenic differentiation of stem cells and inhibiting osteoclast formation,and can effectively promote the healing of injured bone tissue under the synergistic effect of magnetic fields.They have a very broad application prospect in bone injury repair. OBJECTIVE:To review the mechanism of magnetic nanomaterials and magnetic fields promoting bone repair,as well as their research progress in the field of bone injury repair. METHODS:Relevant literature search was conducted in PubMed and Web of Science databases with the search terms"magnetic nanomaterials,magnetic field,bone repair,bone tissue engineering,stem cell,osteoblast,osteoclast."The time limit of literature search was from 2003 to 2023,which was screened and analyzed.Some classic articles were manually retrieved,and 98 articles were finally included for analysis. RESULTS AND CONCLUSION:(1)Magnetic nanomaterials have biological effects such as promoting osteoblast differentiation,inhibiting osteoclast formation and regulating the immune microenvironment.In addition,magnetic nanomaterials can regulate the physicochemical properties of tissue engineering scaffolds,such as mechanical properties and surface morphology,and endowed with magnetic properties,which is conducive to the regulation of the adhesion,proliferation and osteogenic differentiation of stem cells.(2)The magnetic field has the ability to regulate multiple cell signaling pathways to promote osteoblast differentiation,inhibit osteoclast formation,stimulate angiogenesis and other biological effects,thus accelerating the healing of damaged bone tissue.(3)The joint application of magnetic nanomaterials and magnetic field accelerates the repair of bone damage by activating mechanotransduction,increasing the content of intracellular magnetic nanoparticles,and enhancing the effect of micro-magnetic field,which provides a new idea for the research of bone tissue engineering.(4)Magnetic field has demonstrated definite efficacy in the treatment of clinical fractures,osteoporosis,and osteoarthritis diseases,which is beneficial for bone tissue growth,reducing bone loss,alleviating pain,and improving the quality of life of patients.(5)Magnetic nanomaterials and magnetic fields have great potential for application in bone damage repair and regeneration,but the interaction mechanism between magnetic nanomaterials,magnetic fields,and cells has not been fully elucidated.Moreover,the key parameters of magnetic fields that regulate intracellular molecular events,including the type,intensity,frequency,duration,and mode of the magnetic field,as well as the precise biological effects of a specific magnetic field on osteoblasts and the underlying mechanisms,have yet to be defined.(6)Further attention needs to be paid to the effects on osteoclasts,nerves,blood vessels,and immune cells in the microenvironment of damaged tissues.Finally,the safety of magnetic materials for human use is yet to be systematically studied in terms of their distribution,metabolism,and acute and chronic toxicities.

BACKGROUND:Zinc-based alloy medical implant materials have excellent mechanical properties,complete degradability and good biocompatibility,and are mainly used in orthopedic implants,cardiovascular stents,bile duct stents,tracheal stents,nerve catheters,etc. OBJECTIVE:To review the research progress of biodegradable zinc-based alloys in bone defect repair and prospect the promising research direction and achievements of zinc-based materials. METHODS:After searching PubMed,Web of Science,WanFang Data,and CNKI databases from the establishment of the database to June 2023,various relevant articles on biodegradable zinc-based alloys for bone implant material research were collected.The basic characteristics of biodegradable zinc based alloys were summarized,and the role of zinc-based alloys in promoting bone tissue repair was sorted and summarized.The current research hotspots and shortcomings were discussed. RESULTS AND CONCLUSION:(1)Zinc-based alloys have good biocompatibility.Using zinc-based alloys as the matrix material,with the help of scaffold structure construction technology and coating optimization process,the bone conductivity of zinc-based alloys will be effectively improved,and their degradation products will have efficient bone induction to regulate the gene expression of osteoblasts and osteoclasts,thereby promoting the repair and reconstruction of bone defects.(2)However,in the research on optimizing zinc-based alloys,the coating process is relatively insufficient,and additive loading technology is still lacking.(3)Zinc-based alloys have excellent mechanical and biological properties.Through special processes,their bone conductivity and osteoinductivity can be increased to effectively improve their ability to promote bone repair and reconstruction,and it is expected to further achieve the development of personalized transplant materials.Further research and development are needed to optimize the integration of coating and additive loading technologies into zinc-based alloys.

BACKGROUND:Gradient artificial bone repair scaffolds can mimic unique anatomical features in musculoskeletal tissues,showing great potential for repairing injured musculoskeletal tissues. OBJECTIVE:To review the latest research advances in gradient artificial bone repair scaffolds for tissue engineering in the musculoskeletal system and describe their advantages and fabrication strategies. METHODS:The first author of the article searched the Web of Science and PubMed databases for articles published from 2000 to 2023 with search terms"gradient,bone regeneration,scaffold".Finally,76 papers were analyzed and summarized after the screening. RESULTS AND CONCLUSION:(1)As an important means of efficient and high-quality repair of skeletal system tissues,gradient artificial bone repair scaffolds are currently designed bionically for the natural gradient characteristics of bone tissue,bone-cartilage,and tendon-bone tissue.These scaffolds can mimic the extracellular matrix of native tissues to a certain extent in terms of structure and composition,thus promoting cell adhesion,migration,proliferation,differentiation,and regenerative recovery of damaged tissues to their native state.(2)Advanced manufacturing technology provides more possibilities for gradient artificial bone repair scaffold preparation:Gradient electrospun fiber scaffolds constructed by spatially differentiated fiber arrangement and loading of biologically active substances have been developed;gradient 3D printed scaffolds fabricated by layered stacking,graded porosity,and bio-3D printing technology;gradient hydrogel scaffolds fabricated by in-situ layered injections,simple layer-by-layer stacking,and freeze-drying method;and in addition,there are also scaffolds made by other modalities or multi-method coupling.These scaffolds have demonstrated good biocompatibility in vitro experiments,were able to accelerate tissue regeneration in small animal tests,and were observed to have significantly improved histological structure.(3)The currently developed gradient artificial bone repair scaffolds have problems such as mismatch of gradient scales,unclear material-tissue interactions,and side effects caused by degradation products,which need to be further optimized by combining the strengths of related disciplines and clinical needs in the future.

BACKGROUND:With the improvement of diet and living standards,acidic diet and orthodontic treatment have become the main causes of enamel surface demineralization.As the first step of dental caries,enamel demineralization should be actively intervened.Mechanical grinding has great damage and does not conform to the concept of minimally invasive medicine.Biomimetic remineralization is the best way to deal with enamel demineralization at present. OBJECTIVE:To summarize the mechanism,application and research progress of biomimetic remineralization of early enamel demineralization,and provide ideas for further overcoming the hot issues of biomimetic remineralization. METHODS:English keywords"enamel demineralization,biomimetic remineralization,amelogenin,amorphous calcium phosphate"were used to search PubMed.Chinese keywords"enamel demineralization,biomimetic remineralization,amelogenin"were used to search CNKI.Through screening,72 articles were finally obtained for review. RESULTS AND CONCLUSION:(1)At present,there are drug treatments for enamel demineralization,such as fluoride preparations,laser treatment,resin penetration,remineralization treatment and other treatment methods.Biomimetic remineralization is the most ideal repair method for early enamel demineralization.(2)In the narrow sense,enamel remineralization refers to the mineral re-deposition inside the enamel after early enamel demineralization.In the broad sense,enamel remineralization includes the mineralization deposition on the surface and inside of enamel.(3)Clinical biomimetic remineralization reagents are mainly composed of amelogenin,non amelogenin,amelogenin peptide,casein phosphopeptide-amorphous calcium phosphate complex,etc.The advantages of protein and peptide materials are that they conform to the physiological mechanism and can generate high-strength remineralized materials by inducing orientation.The disadvantages are that the manufacturing process is relatively complex and the cost is high.The remineralization effect of amorphous calcium phosphate complex is good,but it needs to be combined with other materials to play a role.Other calcium phosphate materials are easy to carry and beautiful,but they are easy to cause the formation of dental calculus.(4)Future research should focus on the following aspects:increasing experimental data and clinical results,and clarifying the indications of various methods;explore more biomimetic remineralization methods and find suitable alternative materials;find a reasonable way to combine materials,so that their advantages and disadvantages complement each other.The portability of clinical application can be strengthened to increase the frequency of daily use,so that short-term experimental conclusions can be supported by long-term clinical data.

BACKGROUND:The use of fiber post to repair the endodontically treated non-carious cervical lesions teeth can change the stress distribution of the tooth and significantly reduce the risk of fracture of the affected tooth.However,the mechanical mechanism of fiber posts improving tooth fracture resistance and the optimal crown restoration for endodontically treated non-carious cervical lesions teeth are still debated. OBJECTIVE:To review the stress distribution pattern after restoration of endodontically treated non-carious cervical lesions teeth with fiber posts,the fracture resistance and fracture pattern under various stress states,and the latest research progress on fiber posts combined with different crown restorations. METHODS:The computerized search was applied in PubMed and CNKI to retrieve articles published from September 2008 to September 2023 with Chinese and English search terms"non-carious cervical lesions,endodontically treated teeth restoration,endodontically treated teeth stress distribution."Finally,56 articles were included for analysis. RESULTS AND CONCLUSION:The application of fiber post restoration for endodontically treated non-carious cervical lesion teeth can partially improve the cervical stress of the tooth without increasing the risk of vertical root fracture,can lead to a more consistent distribution of stress and enhance the tooth's ability to withstand fractures.Non-carious cervical lesion teeth with fiber posts that fracture would show favorable,restorable,or repairable fracture patterns.Fiber posts in combination with porcelain veneers or veneer-type inlays may become a more desirable minimally invasive restoration for repairing endodontically treated non-carious cervical lesion teeth.

BACKGROUND:The optimal surgical technique for treating posterior cruciate ligament tibial attachment point avulsion injuries is debatable.With the application and maturity of arthroscopic surgery,it has great prospects in the diagnosis and treatment of posterior cruciate ligament tibial attachment point avulsion fractures. OBJECTIVE:To summarize the application and progress of arthroscopic technology in the treatment of posterior cruciate ligament tibial attachment point avulsion fractures,including different arthroscopic treatment methods,surgical approach,tibial tunnel design,suture material selection,and internal fixation implant selection. METHODS:Relevant literature was retrieved from PubMed,Web of Science,and ScienceDirect databases through computers.The search period was from January 2003 to November 2023.Chinese search terms were"posterior cruciate ligament,posterior cruciate ligament,avulsion fracture,arthroscopy".English search terms were"posterior cruciate ligament,injury,fracture,tibia,arthroscopic,operation,fixation,treatment".Totally 97 articles were included for review. RESULTS AND CONCLUSION:Arthroscopic technology provides a reliable treatment for posterior cruciate ligament tibial attachment point avulsion fractures.Arthroscopic treatment for avulsion fractures of the tibial attachment point of the cruciate ligament can be divided into several categories based on the type of approach,suture material,and the number of approaches used for suture and fixation of the tibial tunnel:arthroscopic suture fixation combined with autologous graftenhancement and reconstruction,arthroscopic multicross band suture bridge fixation,arthroscopic strong thread fixation,and arthroscopic direct anterior posterior suture suspension fixation.In various studies,commonly used outcome measures include knee range of motion,Lysholm scale,International Knee Documentation Committee,and KT-2000 arthrometer.Studies have shown that at the last follow-up,the score results showed significant improvement compared to surgery.In the radiological follow-up results of various arthroscopic techniques,all studies have shown satisfactory results.During the follow-up process,all types of patients who received arthroscopic treatment for cruciate ligament tibial attachment point avulsion fractures did not experience serious complications,such as traumatic arthritis,neurovascular injury,perioperative wound infection,thrombosis,and nonunion of fractures.

BACKGROUND:The Twin-block orthodontic appliance is commonly used for the correction of Class Ⅱ malocclusion.Its mechanism of action in stimulating mandibular growth has been confirmed in many studies,but its impact on maxillary growth is not very clear. OBJECTIVE:By establishing a finite element model to analyze the stress distribution of the maxillary complex,surrounding bone sutures,and maxillary dentition in patients with Class Ⅱ malocclusion wearing Twin-block orthodontic appliances. METHODS:One patient with Class Ⅱ malocclusion who underwent orthodontic treatment at Qingdao Hospital/Qingdao Municipal Hospital of Shandong Rehabilitation University was selected.The bite force data of the patient when wearing the Twin-block orthodontic appliance was measured,and CBCT data were collected.A finite element model was established,including the maxillary complex,peripheral sutures,Twin-block orthodontic appliance,and maxillary dentition.ABAQUS software was used to simulate the stress distribution in the maxilla and maxillary dentition when the patient was wearing the Twin-block appliance. RESULTS AND CONCLUSION:The equivalent stress on the maxillary anterior teeth was significantly smaller than that on the posterior teeth,and the maximum equivalent stress on both sides of the teeth were 4.797 5 Mpa and 8.716 1 Mpa,respectively,which were located at the first premolar.The maximum displacements were presented at the maxillary incisors on both sides of the teeth,which were 0.080 5 mm and 0.081 0 mm,respectively.The maximum equivalent stress on the bone suture was 1.284 Mpa,which was mainly concentrated in the pterygopalatine suture and the frontal-maxillary suture on both sides,and there was almost no difference in the force of the rest of bone sutures;the maximum displacement of the bone suture was 0.07 mm,with the pterygopalatine suture having the largest displacement,followed by the frontal-maxillary suture.The maximal equivalent stress on the maxillary complex was 27.18 Mpa,which was mainly concentrated on both sides of the anterior pyriform foramen of the maxilla,around the nasofrontal suture and around the pterygopalatine suture at the posterior part of the jaws.The maximal displacement of the maxilla was 0.07 mm,which was mainly concentrated on the maxillary alveolar bone.All these findings show that the occlusal force acts on the maxillary complex through the Twin-block appliance,resulting in clockwise rotation of the maxilla and steepening of the dentition plane.Measures should be taken to compensate for this tendency,for example,by considering maxillary molar elongation and intrusion in the process of occlusion,which are not only able to flatten the occlusal plane,but facilitate the mandibular protraction,thereby further improving Class Ⅱ malocclusion orthodontic treatment.

BACKGROUND:It has been found that abnormal apoptosis of bone tissue cells induced by abnormal iron metabolism plays an important role in the progression of osteoporosis. OBJECTIVE:To investigate the effect of naringin on iron metabolism and cell apoptosis in bone tissue of rats with osteoporosis. METHODS:Fifty 2-month-old female Sprague-Dawley rats were randomly divided into five groups with 10 rats in each group:sham group,osteoporosis group,naringin low-dose group,naringin high-dose group,and naringin high-dose+DKK-1 group.Except for the sham group,rat models of osteoporosis were established by removing bilateral ovarian tissues in the other groups.At 8 weeks after modeling,rats in the naringin low-and high-dose groups were given 100 and 400 mg/kg/d naringenin by gavage,respectively,and rats in the naringenin high dose+DKK-1 group were given 400 mg/kg/d naringin by gavage and subcutaneous injection of 25 mg/kg/d DKK-1,an inhibitor of the Wnt1 signaling pathway,for 7 consecutive days.Relevant indexes were detected after administration. RESULTS AND CONCLUSION:Compared with the osteoporosis group,naringin could enhance the bone mineral density and serum calcium and superoxide dismutase levels in rats(P<0.05),and reduce the serum levels of osteocalcin,malondialdehyde,and phosphorus(P<0.05),while DKK-1 could partially inhibit the interventional effect of naringin(P<0.05).Results from Micro-CT scanning,hematoxylin-eosin and TUNEL staining showed that compared with the osteoporosis group,naringin significantly improved bone microstructure and reduced the rate of cell apoptosis,while DKK-1 partially inhibited the interventional effect of naringin.Immunofluorescence staining results showed that compared with the osteoporosis group,naringin could reduce the oxygen content,anti-tartaric acid phosphatase expression,and elevate the expression of alkaline phosphatase in active tibia tissues(P<0.05),while DKK-1 could partially inhibit the interventional effect of naringin(P<0.05).Results from Prussian blue staining and immunohistochemical staining showed that compared with the osteoporosis group,naringin reduced iron deposition in bone and liver tissues as well as the expression of transferrin receptor 1(P<0.05),and elevated the protein expression of ferroportin 1(P<0.05)in bone tissue,and DKK-1 partially inhibited the intervention of naringin(P<0.05).PCR and western blot assay of tibia specimens showed that compared with the osteoporosis group,naringin decreased the expression of anti-tartrate acid phosphatase,transferrin receptor 1 and Bax(P<0.05),and elevated the expression of alkaline phosphatase,ferroportin 1,Bcl-2,Wnt1 and β-catenin(P<0.05),while DKK-1 partially inhibited the interfering effect of naringin(P<0.05).To conclude,naringin inhibits the progression of osteoporosis by reducing iron deposition and apoptosis rate in bone tissue,which may be related to the activation of the Wnt1 signaling pathway.