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The finite element method(FEM)is a widely employed mathematical technique in mechanical research that divides an object into discrete and interacting finite elements. Medically, finite element analysis(FEA)enables the simulation of biomechanical experiments that are challenging to conduct. Orbital surgery poses significant challenges to ophthalmologists due to its inherent difficulty and steep learning curve. FEM enables the simulation and analysis of the mechanical properties of orbital tissue, offering a novel approach for diagnosing and treating orbital-related diseases. With technological advancements, FEM has significantly matured in the diagnosis and treatment of orbital diseases, becoming a popular area of research in orbital biomechanics. This paper reviewed the latest advancements in orbital FEM, encompassing the development of orbital FEA models, simulation of orbital structure, and its application in orbital-related diseases. Additionally, the limitations of FEM and future research directions are also discussed. As a digital tool for auxiliary diagnosis and treatment, orbital FEA will progressively unlock its potential for diagnosing and treating orbital diseases alongside technological advancements.
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Objective@#To explore the effect of different miniscrew placement heights on the distribution of biological forces produced by clear aligner combined with intramaxillary traction for mandibular molar distalization, to identify the miniscrew location that is conducive to the protection of lower anterior tooth anchorage and to provide a reference that can be used when designing clinical treatments.@*Methods@#Mimics, GeomagicStudio 2017, SolidWorks 2016, and Ansys workbench were used to establish finite element analysis models and perform mechanical analysis under the following six working conditions: working condition 1 was the control group without miniscrews; working conditions 2 to 5 had miniscrew in the buccal bone cortex between the first and second molars of the lower jaw 10 mm, 7 mm, 4 mm, and 1 mm from the top of the alveolar crest, respectively; working condition 6 had the miniscrew in the center of the buccal tongue at the anterior edge of the ascending branch of the lower jaw 5 mm above the occlusal plane.@*Results@#On the sagittal axis, miniscrew anchorage caused distal displacement of all teeth. Compared to the control group, in the miniscrew group, the displacement of the anterior molars exceeded that of the second molars. On the vertical axis, the result in the control group was similar to backward bending; the results in the miniscrew groups resembled the effect of a lever, lowering the lateral incisors and canines and raising the central incisors and first premolars. On the coronal axis, the second premolars and the first molars showed lingual displacement in the control group, and only the premolars and first molars showed lingual displacementin the miniscrew groups. The canines were the teeth that were most strongly affected by the change in miniscrew placement height.@*Conclusion@#The higher the miniscrew position is, the stronger the protective effect on the anterior anchorage. According to the miniscrew placement height, the mandibular arch should be properly narrowed, the central incisors and first premolars should be lowered, and the lateral incisors and canines should be raised when designing clinical treatments.
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ObjectiveTo observe the effect of gastrodin on the steroid regulatory element-binding protein 1c （SREBP1c） signaling pathway in high-fat high-cholesterol diet （HFHC）-induced mice and explore the mechanism of gastrodin in the treatment of non-alcoholic fatty liver disease （NAFLD）. MethodEight-week-old male C57BL/6J mice were used in vivo and divided into the following four groups， with six mice in each group： normal group， gastrodin group （50 mg·kg-1）， model group， and model + gastrodin group （50 mg·kg-1）. NAFLD model was established by feeding mice with HFHC for four weeks， and the mice were euthanized and the liver tissues were collected after four weeks. In vitro experiments were performed using Huh7 cells which were divided into five groups， and induced with free fatty acids （FFA， 200 μmol·L-1， oleic acid-palmitic acid 2∶1） to establish an NAFLD cell model. After 24 h， different concentrations of gastrodin （0， 5， 10， 20， and 40 μmol·L-1） were added to each group and cultured for another 24 h. Oil red O staining was used to detect lipid accumulation in mouse liver and Huh7 cells. Hematoxylin-eosin （HE） staining was used to observe pathological changes in liver tissue. Levels of serum total cholesterol （TC）， low-density lipoprotein cholesterol （LDL-C）， and triglycerides （TG） were measured using an automatic biochemical analyzer. Relevant assay kits were used to detect liver TC， TG， and FFA levels. Real-time quantitative polymerase chain reaction （Real-time PCR） and Western blot were used to detect the expression of lipid synthesis-related proteins fatty acid synthase （FASN）， acetyl-CoA carboxylase 1 （ACC1）， and stearoyl-CoA desaturase 1 （SCD1）. ResultCompared with the normal group， the model group showed significantly increased serum TC， LDL-C， and TG levels （P<0.01）， liver TC， TG， and FFA levels （P<0.01）， increased lipid accumulation in Huh7 cells （P<0.01）， and significantly increased expression levels of lipid synthesis-related genes SREBP1c， FASN， ACC1， and SCD1 in mice and Huh7 cells （P<0.01）. Compared with the model group， after gastrodin treatment， the serum TC， LDL-C， and TG levels in mice significantly decreased （P<0.05， P<0.01）， the severity of fatty liver disease improved significantly， liver TC， TG， and FFA levels decreased significantly （P<0.05， P<0.01）， lipid accumulation in Huh7 cells decreased significantly （P<0.05， P<0.01）， the expression levels of lipid synthesis-related genes SREBP1c， FASN， ACC1， and SCD1 in mice and Huh7 cells decreased significantly （P<0.05， P<0.01）. ConclusionGastrodin can reduce hepatic lipid accumulation and blood lipid levels， improve HFHC-induced NAFLD， and its mechanism of action may be related to the regulation of the SREBP1c lipid synthesis-related signaling pathway.
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ObjectiveTo investigate whether paeonol exerts a protective effect on mice with alcoholic liver injury by regulating the takeda G-protein-coupled receptor 5 （TGR5）/protein kinase A （PKA）/cAMP response binding element （CREB） signaling pathway mediated by Eubacterium. MethodC57BL/6 mice were randomly divided into five groups： normal group， model group， paeonol group （480 mg·kg-1）， antibiotic group （Abs group）， and antibiotic + paeonol group. Lieber-DeCarli liquid was used to feed C57BL/6 mice on the second day of modeling for 10 days. The blood lipids， liver function， inflammatory factors， and oxidative stress levels in mice were measured. Hematoxylin-eosin staining （HE） and oil red O staining were used to observe the morphological changes and fat accumulation in liver tissue. 16S rDNA sequencing was used to detect the diversity of intestinal microbiota in the blank， model， and paeanol groups. Western blot was used to detect the effect of paeonol on the expression levels of protein related to the signaling pathway of atresia band protein 1 （ZO-1）， Claudin-1， and TGR5/PKA/CREB in mouse ileal tissue. ResultCompared with those in the blank group， the blood lipids， liver function， oxidative stress levels， and the expression of inflammatory factors in the model group increased （P<0.01）， and the liver fat vacuoles were obvious. The ileal mucosa was seriously damaged， and the protein contents of ZO-1， Claudin-1， and TGR5/PKA/CREB in the ileal tissue decreased significantly （P<0.01）. The intestinal microbiota changed， and the proteobacteria phylum increased significantly. The ratio of Bacteroidetes to Firmicutes decreased. The relative abundance of Dubosiella newyorkensis， Lactobacillus， Bifidobacterium， and other genera decreased， while the relative abundance of Escherichia-Shigella， Morganella， Providencia， and Proteus increased significantly. Compared with the model group， paeonol significantly reduced the blood lipids， liver function， oxidative stress levels， and expression of inflammatory factors in mice with alcohol diet-induced liver injury （P<0.05）， decreased liver fat vacuoles， improved and restored the ileal intestinal barrier， and restored the normal structure of hepatocytes and ileal cells. The intestinal microbiota disorder caused by alcohol was improved， and the relative abundance of beneficial bacteria such as Eubacterium spp. was increased. The protein expression levels of ZO-1， Claudin-1， and TGR5/PKA/CREB in ileal tissue were increased （P<0.05）. ConclusionPaeonol has a protective effect on alcoholic liver injury in mice， and the mechanism of action is achieved by regulating the Eubacterium-mediated TGR5/PKA/CREB signaling pathway to ensure anti-inflammatory effect and improve the intestinal barrier.
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Metal elements are the most common and widely distributed chemical elements in nature,which are closely related to human health,and their excess or lack will have a profound impact on the physio-logical and pathological processes of the body.This paper defines the concept of"metal element stress re-sponse",that is,the stress response that can occur in various cells,tissues and organs throughout the body when the content of metal elements in the body exceeds or falls below a certain level.According to the degree of stress,it can be divided into four dimensions:physiological stress,burden stress,pathological stress and disease stress.This paper comprehensively describes the degree,mode and biological effect of the interaction between metal elements and organism,and"four-dimensional theory"of metal element stress response is pro-posed,aiming to provide new ideas and new methods for seeking the potential intervention strategies of metal element stress response in the future
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Objective To investigate the analgesic effect and mechanism of Buyang Huanwu Decoction on diabetic peripheral neuropathy(DPN)rats.Methods Sixty rats were divided into normal group,model group,low-,medium-and high-dose groups of Chinese medicine,and high-dose + H-89[protein kinase A(PKA)inhibitor]group,with 10 rats in each group.Except for the normal group,rats in all other groups were fed with high-fat and high-sugar chow combined with intraperitoneal injection of streptozotocin(STZ)method to construct DPN model.At the end of drug administration,the foot thermal pain threshold of rats was detected,the motor nerve conduction velocity(MNCV)and sensory nerve conduction velocity(SNCV)of rats was measured,the intraepidermal nerve fiber(IENF)in the epidermis was observed by immunohistochemistry,and serum fasting insulin(FINS),total cholesterol(TC),triglyceride(TG),low-density lipoprotein cholesterol(LDL-C),high-density lipoprotein cholesterol(HDL-C),insulin resistance index(HOMA-IR),and the interleukin(IL)-1β,IL-6,tumor necrosis factor α(TNF-α),vascular endothelial growth factor(VEGF),angiopoietin 1(Ang-1),CD34 levels,cyclic adenosine monophosphate(cAMP)concentration in the sciatic nerve tissues were detected by enzyme-linked immunosorbent assay(ELISA),and Western Blot assay to detect the PKA and the carbohydrate responsive element binding(CREB)in the sciatic nerve tissues.Results Compared with the normal group,foot thermal pain threshold,TC,TG,LDL-C,HOMA-IR,IL-1β,IL-6 and TNF-α levels were significantly increased in the model group(P＜0.05),HDL-C,FINS,VEGF,Ang-1,CD34,IENF,MNCV and SNCV values,cAMP concentration levels,PKA and CREB phosphorylation levels were significantly reduced(P＜0.05).Compared with the model group,the above indexes were significantly improved in the low-,medium-and high-dose groups of Chinese medicine(P＜0.05)in a dose-dependent manner.Compared with the Chinese medicine high-dose + H-89 group,all the indexes were reversed in the Chinese medicine high-dose group.Conclusion Buyang Huanwu Decoction can improve insulin resistance and lipid metabolism,reduce limb pain,improve local microcirculation disorder,and protect nerve function in DPN rats,which reflects the therapeutic characteristics of"activating blood circulation and relieving pain".The pain-relieving effect of Buyang Huanwu Decoction may be related to the improvement of local microcirculation,inhibition of inflammatory factor release and regulation of cAMP/PKA/CREB signaling pathway protein expression.
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Objective To design a search and rescue UAV that is portable and user-friendly in order to meet the needs of rescue personnel on the battlefield.Methods Three-dimensional design software CATIA was used to complete the structural design of the UAV body.In order to make full use of the internal space of the UAV body,folding wings were adopted to reduce the volume of the UAV.By using ABAQUS,the finite elements of the key parts of the UAV were analyzed before the modal analysis of the whole vehicle was conducted to verify the reliability of the structure.The robot simulation software Webots was used for motion simulation of the UAV.Results Simulation analysis and test verification suggested that the structural design of the UAV was well-grounded.It could be quickly and properly deployed by means of hand launch or barrels,which made it easier for rescuers to use the UAV.Conclusion The design and simulation research of UAVs with portable folding wings for search and rescue is of great significance for the research and development of physical prototypes.This study is expected to stimulate new ideas for the development of rescue equipment in the PLA,and contribute to miniaturization of UAVs.
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Objective To explore the association between serum trace element levels in early pregnancy and gestational dia-betes mellitus(GDM),and the mediating effect of bile acid metabolism changes in this association.Methods A nested case-con-trol study was designed based on the Guangxi Zhuang Birth Cohort.A total of 248 pregnant women(case group=124,control group=124)were included from June 2015 to July 2019 in Nanning city.The concentrations of 8 trace elements and 31 bile acids in serum were measured in early pregnancy.Conditional logistic regression and BKMR models were used to analyze the associa-tion and combined effect between trace elements and GDM risk,respectively.Orthogonal partial least squares-discriminant anal-ysis(OPLS-DA)was used to screen potential bile acid biomarkers associated with GDM,and then conditional logistic regression was used to determine the association between specific bile acid levels and GDM risk.Multiple linear regression was used to e-valuate the association of serum trace element concentrations with differential bile acid metabolites.Mediation analysis was used to evaluate the mediating role of bile acids in the relationship between trace element exposure and GDM.Results After adjus-ting for confounding factors,serum vanadium(V)was found to be positively associated with the risk of GDM,while chromium(Cr),manganese(Mn),zinc(Zn),selenium(Se)and molybdenum(Mo)were negatively correlated with the risk of GDM(all P＜0.05).The OPLS-DA model and conditional Logistic regression analysis showed that taurocholic acid(TCA),glycochenodeoxy-cholic acid 3-sulfate(GCDCA-3S),glycochenodeoxycholic acid-3-O-β-glucuronide(GCDCA-3Gln),glycoursodeoxycholic acid-3-sulfate(GUDCA-3S),taurodeoxycholic acid-3-sulfate(TDCA-3S),and chenodeoxycholic acid(CDCA)might be potential bile acid metabolic markers of GDM(all P＜0.05).The concentrations of multiple trace elements were also significantly correlated with the levels of specific bile acids(all P＜0.05).Mediation analysis showed that GCDCA-3Gln and TCA mediated the associa-tion between serum Zn and Se and GDM risk,respectively(all P＜0.05).Conclusion Serum trace elements such as V and Cr are significantly associated with the risk of GDM in early pregnancy,and changes in bile acid metabolism may precede the occur-rence of GDM.It is suggested that the effect of trace elements on the metabolism of bile acids,especially conjugated bile acids,may be one of the mechanisms affecting the risk of GDM.
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Objective To investigate the ameliorating effect of salidroside(SAL)on cisplatin(CIS)-induced damages of cochlear hair cells(CHC)and spiral ganglion neurons(SGNs)and its relationship with cyclic adenosine monophosphate(cAMP)/protein kinase A(PKA)/cAMP response element binding protein(CREB)pathway.Methods The cochlear basilar membranes of newborn C 57BL/6 mice were isolated and separated into control(C)group,CIS group,SAL group,SAL+SQ22536(cAMP inhibitor)group and SAL+H-89(PKA inhibitor)group,20 per group.Immunofluorescence staining was applied to observe the damages of CHC and SGNs.The kits were applied to detect the contents of ROS and cAMP in the basement membrane of the cochlea.Western blot was applied to detect the protein levels of PKA,p-CREB,CREB,Bcl-2,BDNF,and NF-M.Results CHC in CIS group were disorderly arranged and enlarged in size,SGNs had fragmented nuclei and lost neurites.SAL alleviated the damages of CHC and SGNs.Compared with the C group,the numbers of CHC and SGNs in the CIS group were less(P＜0.05),the contents of ROS and cAMP,and the levels of PKA,BDNF,NF-M,Bcl-2 proteins and p-CREB/CREB were higher(P＜0.05).Compared with the CIS group,the numbers of CHC and SGNs in the SAL group were higher(P＜0.05),the content of ROS was lower(P＜0.05),the content of cAMP,and the levels of PKA,BD-NF,NF-M,Bcl-2 proteins and p-CREB/CREB were higher(P＜0.05).Both SQ22536 and H-89 reversed the pro-tective effects of SAL on CHC and SGNs.Conclusion SAL may promote the expression of anti-apoptotic proteins and neuroprotective factors by activating the cAMP/PKA/CREB pathway to alleviate the damages of CHC and SGNs caused by CIS.
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BACKGROUND:Lingual movable wing is a new type of lingual orthodontic technique and the different stretching lengths of the wring affect the torque control effect of anterior teeth.However,there is yet no related biomechanical research. OBJECTIVE:To investigate the displacement trend of dentition during adduction of mandibular anterior teeth and the effect of different wing stretching lengths on the biomechanical effect of mandibular anterior teeth. METHODS:The data of the mandible and lower dentition were collected by cone-beam CT and reconstructed using Mimics software to establish a three-dimensional finite element model of mandibular anterior teeth adducted by the lingual movable wing.The ANSYS software was used to analyze the initial displacement of the mandibular anterior teeth under the following conditions:A,2 mm stretching length;B,2.5 mm stretching length;C,3 mm stretching length;and D,3.5 mm stretching length. RESULTS AND CONCLUSION:The trend of initial displacement of lower dentition:The central incisors moved lingually with depression,the lateral incisors and canines moved mildly lingually with mesial lingual torsion,the second premolar was tilted distally with a marked lingual inclination and the first molar showed an overall mesial inclination with mesial crown eversion.Therefore,in the adduction cases of mandibular tooth extraction,attention should be paid to the lingual movement of the second premolar,which could be offset by corresponding techniques in clinic.The trend of anterior tooth displacement in all directions:from condition A to condition D,in the sagittal direction,the difference value in crown-root displacement of central incisors changed from-11.891 μm to-5.757 4 μm,indicating that the central incisor changes from oblique movement to overall movement.The difference value in crown-root displacement of lateral incisors changed from-11.828 1 μm to-6.711 45 μm,and that of canines changed from-7.572 3 μm to-4.695 5 μm,indicating that the oblique movement of the lateral incisors and canines is also changing to an overall movement.In the vertical direction,from condition A to condition D,the reduction of incisors was gradually increased,while that of canines was gradually decreased.These findings indicate that the stretching length of the wing can affect the oblique movement trend of the anterior teeth.As the wing continues to stretch,the torque control of the lower anterior teeth will become better.
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BACKGROUND:The proximal femoral nail antirotation is the preferred treatment for reverse osteoporotic intertrochanteric fractures.Bone cement enhancement can reduce the probability of proximal femoral nail antirotation cut-out and cut-through,but there are no relevant biomechanical studies demonstrating the effect of bone cement content and location on the stress and displacement of the fracture end. OBJECTIVE:To investigate the effects of different contents and locations of bone cement in cement-reinforced proximal femoral nail antirotation on stress,strain,and displacement of reverse osteoporotic femoral intertrochanteric fractures in the elderly by finite element analysis. METHODS:A healthy adult female right femur model was extracted by Mimics software and smoothed in Geometric software.Five types of internal fixation methods of proximal femoral nail antirotation(cementless,cephalic spherical 1 mL,cephalic spherical 2 mL,cephalic spherical 3.4 mL,and cylindrical 5 mL around spiral blade)and femoral intertrochanteric fracture(AO subtype 31-A3.1 type)model were established in Solidworks software.After assembly,the total stress distribution,peak stress and displacement of the five models of implants with the femur were compared in Ansys software. RESULTS AND CONCLUSION:(1)The peak stresses of proximal femoral nail antirotation with head-end spherical 1 mL,head-end spherical 2 mL,head-end spherical 3.4 mL,and cylindrical 5 mL enhanced proximal femoral nail antirotation around the spiral blade respectively were 571.07 MPa(located at the junction of the spiral blade and the main nail),495.45 MPa(located at the junction of the spiral blade and the main nail),467.20 MPa(located at the junction of the main nail and the distal screw connection),642.70 MPa(located at the junction of the main nail and distal screw connection),and 458.58 MPa(located at the junction of the spiral blade and the main nail).(2)The maximum displacements of proximal femoral nail antirotation with head end sphere 1 mL,head end sphere 2 mL,head end sphere 3.4 mL,and with cylindrical 5 mL enhancement around the spiral blade were 9.260 5,7.589 1,7.316 8,6.790 7,and 6.615 7 mm,respectively,all of which were located at the proximal end of the femoral head.(3)These findings revealed that for reverse femoral intertrochanteric fractures treated with proximal femoral nail antirotation,the bone cement enhancement had significant mechanical stability compared with no enhancement,and the enhancement of the spiral blade 5 mL around the perimeter was the best,which is more preferable for aged unstable intertrochanteric fractures.
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BACKGROUND:In the treatment of edentulous maxillary implants supported fixed repair,the selection of upper scaffold structure materials and the design of different distal implant implantation methods have a close influence on the long-term stability of the whole mouth implant repair. OBJECTIVE:To comprehensively explore the influence of three different materials of upper scaffold and two implant fixation designs on the biomechanics of the fixed maxillary implant repair based on the three-dimensional finite element method. METHODS:Based on the conical beam CT data of a healthy adult with normal jaws,the Mimics software was used to separate the maxillary and maxillary dentin three-dimensional solid models,and the Geomagic Studio software was used to construct the three-dimensional finite element model of denture with denture implant and fixed maxillary arch combined with specific model parameters.According to the different designs of distal implants in the maxillary posterior region,two scheme models were established.Scheme 1(Design 1)was designed in accordance with the"All-on-4"design used in clinical practice.Two implants were vertically implanted in the bilateral incisor region of the maxilla,and the other two implants were implanted in the bilateral second premolar region at a 30° angle.In scheme 2(Design 2),two implants were vertically implanted in the lateral incisor region of the maxilla,and two short implants were vertically implanted in the posterior region of the maxilla in the bilateral second premolar region.Three materials(titanium,zirconia and polyether ether ketone)were used to assign values to the upper scaffold structure in the two designs,and six different models were obtained.The biomechanical effects of the implant,surrounding bone tissue and the upper scaffold structure were compared and analyzed in the oblique loading direction. RESULTS AND CONCLUSION:(1)The maximum stress peaks of all models were distributed in the neck region around the posterior implant and the cortical bone under the two edentulous implant fixed restoration schemes,regardless of the material of the upper scaffold.(2)Compared with the alternative design of Design 2,which adopted vertical implantation of short implants,Design 1 showed a more ideal stress distribution on the maxilla.(3)The scaffold model constructed by polyether ether ketone material transferred higher stress to the implant and surrounding bone tissue close to the loading zone of the upper jaw bone,followed by titanium and zirconia.As for the support itself,the peak stress of the upper scaffold of polyether ether ketone was significantly lower than that of the zirconia and titanium scaffolds.Zirconia scaffolds were used among the three upper scaffolds to disperse the stress distribution of implant and bone tissue.(4)The results suggest that both designs can be applied to clinical practice.However,from the perspective of biomechanics,the stress distribution of the implant,surrounding bone tissue and upper scaffold in Design 1 is more rational,which is more conducive to the long-term prognosis of fixed implant repair in patients with edentulous jaws.The upper scaffold material has a certain influence on the stress distribution of the implant-bone interface.
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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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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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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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BACKGROUND:Due to the treatment of cervical spondylosis,the Zero-P system of the anterior cervical interbody fusion system will have problems such as screw loosening and fracture after operation,so a novel Low-P system has been developed. OBJECTIVE:To compare the effects of the novel Low-P and Zero-P anterior cervical intervertebral fusion systems on the biomechanical properties of adjacent segments of the cervical spine and to perform stress analysis on the internal fixation system,so as to provide a theoretical reference for clinical treatment. METHODS:A complete model of the C1-C7 segment of the cervical spine was established.Based on the effectiveness of the model,a finite element model of Low-P(type Z Low-P and type H Low-P)and Zero-P system implanted in C4-C5 segments was established.The stress distribution of implanted devices and adjacent vertebral nucleus pulposus,fibrous rings and end plates was analyzed under the conditions of forward flexion,posterior extension,lateral bending and rotation. RESULTS AND CONCLUSION:(1)After implantation of Low-P and Zero-P internal fixation devices,the range of motion of the type H Low-P system was large;the maximum stress value of type Z Low-P system was small;the maximum stress of Zero-P on the nucleus pulposus of adjacent segments was large;the maximum stress of end plate was small.(2)The influence of three internal fixation systems on adjacent segment fiber rings was close.(3)The screw stress of the Zero-P internal fixation system was much greater than that of the Low-P system.(4)It is indicated that compared with Zero-P type internal fixation system,the novel Low-P system reduces the stress value of steel plate and screw,which can reduce screw loosening and internal fixation system failure.The Low-P system has less stress on the nucleus pulposus of adjacent discs and reduces disc degeneration in adjacent segments.This paper provides a theoretical basis for the clinical study of a Low-P type internal fixation system.
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BACKGROUND:Among the pathogenic factors of cervical spondylosis,herniation of the intervertebral disc,dislocation of the facet joint and the stenosis of the intervertebral foramen are important factors leading to symptoms in patients.Moreover,inappropriate manipulation may aggravate the possibility of cervical disc rupture,leading to exacerbation of symptoms in patients. OBJECTIVE:To compare the effect between sagittal cervical manipulation and traditional cervical rotation manipulation on the area of the intervertebral disc,facet joint and intervertebral foramen at the operative segment by the finite element analysis. METHODS:The neck CT data of a male volunteer with a normal neck were selected and imported into Mimics 17.0 three-dimensional reconstruction software.Geo-magic Studio 12.0,Solidworks 2017 and Ansys Workbench 17.0 software were used for the construction of the finite element model of cervical vertebrae(C3-6)including intervertebral disc and articular cartilage.The lower end plate of the C5 vertebral body was fixed.A uniformly distributed vertical downward 50 N load was applied on the upper surface of the upper vertebral body(C3).The stress,deformation and deformation direction of the C4-5 intervertebral disc,joint capsule stress,the displacement of facet joints and the area of bilateral intervertebral foramen were compared between sagittal cervical manipulation and traditional rotation reduction. RESULTS AND CONCLUSION:(1)When using the rotation technique,the maximum normal equivalent stress(von Mises stress)of the C4-5 disc was 8.06 MPa;the total deformation was 1.05 mm,and the fiber ring expanded to the left and outside.When using the sagittal tip lifting technique,the maximum normal equivalent stress(von Mises stress)of the C4-5 disc was 2.60 MPa;the total deformation was 0.90 mm,and the fiber ring expanded to the left and back.Compared with the rotation technique,the pressure of the cervical manipulation technique on the disc was less(about 32.3%of the rotation technique),and the deformation degree of the disc was also light(about 85.7%of the rotation technique).(2)When the rotation technique was used,the maximum stresses of the left and right articular capsule ligaments were 0.37 MPa and 1.69 MPa,respectively.The overall displacement of the facet joint was 2.21 mm.The area of the right intervertebral foramen decreased by about 3.8%and the area of the left intervertebral foramen increased by about 0.9%.When the sagittal end lifting manipulation was performed,the maximum stresses of the left and right articular capsule ligaments were 0.27 MPa and 1.70 MPa,respectively;the overall displacement of the facet joint was 1.63 mm;the area of the right intervertebral foramen increased by about 2.6%,and the area of the left intervertebral foramen decreased by about 0.9%.Compared with rotation manipulation,sagittal end lifting manipulation had fewer changes in the displacement of facet joint,joint capsule stress and intervertebral foramen area,so it was safer to operate.(3)In conclusion,compared with cervical rotation manipulation,sagittal end lifting manipulation has fewer changes in facet joint displacement,intervertebral disc stress/deformation degree,joint capsule stress,and foraminal area.In clinical practice,more appropriate manipulation should be selected based on biomechanical results after an accurate assessment of patients'conditions.
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BACKGROUND:Endoscopic treatment of lumbar disc herniation has obvious advantages over traditional open surgery.Endoscopic surgery involves the implantation of a working cannula,which requires only partial bone removal,and there are no studies on the effects of two types of intraoperative foraminoplasty and laminoplasty on the mechanical properties of the local structure of the lumbar spine. OBJECTIVE:To compare the effect of foraminoplasty and laminoplasty on the biomechanical properties of disc and isthmus of the responsible segment. METHODS:The lumbosacral CT images of a healthy male volunteer were taken,and a finite element model M0 of the L3 to sacral vertebrae was established,on which the primary and secondary foraminoplasty models M1 and M2 of the L5/S1 and the laminoplasty model M3 were built.The same load was applied to compare the intervertebral motion range,disc Von Mises stress and equivalent stress characteristics of L5 vertebral isthmus with each model. RESULTS AND CONCLUSION:(1)Compared with M0,M1 and M2 motion range in L5/S1 segment did not change significantly in all directions;M2 overall motion range increased by 8.60%in flexion;M3 increased by 8.23%and 8.26%in L5/S1 right bending and right torsion,and 5.39%and 5.67%in overall motion range in flexion and right bending,with no significant changes in motion range in the rest of working conditions.(2)Compared with M0,M1 showed no significant change in the extremes of Von Mises stress at L5/S1 disc;M2 increased 11.06%,12.50%,18.32%,and 15.48%in flexion,extension,left torsion,and right torsion;M3 increased 12.22%,19.54%,10.05%,and 9.97%in flexion,extension,left torsion,and right torsion,and the rest working conditions and L4/5 disc maximum Von Mises stress did not change significantly.(3)Compared to M0,the maximum Von Mises stress in the left isthmus of L5 of M1 increased by 12.43%in left bending,18.38%,13.29%,13.62%,and 40.00%in the right isthmus in extension,right bending,left torsion,and right torsion.The maximum Von Mises stress in the left isthmus of L5 of M2 increased by 38.87%,42.63%,16.95%,and 19.35%,and that in the right isthmus increased by 12.58%,33.70%,12.92%,and 17.42%in flexion,extension,left bending,and left torsion.The maximum Von Mises stress in the left isthmus of L5 of M3 increased 67.07%,78.14%,32.33%,62.94%,and 89.99%in flexion,extension,left and right bending,and right torsion.(4)The results suggest that foraminoplasty and laminoplasty have a small effect on spinal motion range;there is a mild increase in the extreme values of disc Von Mises stress in the segments operated by interbody laminoplasty and secondary foraminoplasty;there is no significant change in the extreme values of disc Von Mises stress in adjacent segments,and there is a significant increase in the Von Mises stress in the ipsilateral isthmus operated by the interbody laminoplasty model.
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BACKGROUND:Ankylosing spondylitis is a chronic inflammatory disease with chronic rheumatic immunity.Soft tissue ossification and fusion and spinal stiffness can cause biomechanical changes. OBJECTIVE:To reconstruct the lumbar-sacral intervertebral disc in ankylosing spondylitis patients with lumbar kyphosis by finite element analysis,and to study the range of motion of each segment of T11-S1 and the biomechanical characteristics of annulus fibrosus and nucleus pulposus. METHODS:The imaging data were obtained from an ankylosing spondylitis patient with lumbar kyphosis.The original CT image data of continuously scanned spine were imported into Mimics 21.0 in DICOM format,and T11-S1 was reconstructed respectively.The established model was imported into 3-Matic software in the format of"Stl"to reconstruct the intervertebral disc,and the fibrous intervertebral disc model was obtained.The improved model was further imported into Hypermesh software,and the vertebra,nucleus pulposus,annulus fibrosus and ligament were mesh-divided.After the material properties were given,the model was imported into ABAQUS software to observe the range of motion of each vertebral body in seven different working conditions of T11-S1,and analyze the biomechanical characteristics of each segment of annulus fibrosus and nucleus pulposus. RESULTS AND CONCLUSION:(1)The range of motion of L1 vertebrae was higher than that of other vertebrae under six different working conditions:extension,forward flexion,rotation(left and right),and lateral flexion(left and right).The maximum range of motion was 2.18° during L1 vertebral flexion,and the minimum range of motion was 0.12° during L5 vertebral extension.(2)The annular fiber flexion at L2-L3 segments was greater than the extension(P<0.05),and the annular fiber flexion at L3-L4 and L4-L5 segments was less than the extension(P<0.05).The left rotation of L1-L2 annular fibers was greater than the right rotation(P<0.05).The left flexion of the annulus was greater than the right flexion in L1-L2,L2-L3,L3-L4,L4-L5 and L5-S1 segments(P<0.05).(3)The nucleus pulposus stresses of T11-L12,L1-L2,L2-L3,L3-L4 and L4-L5 segments in forward flexion were greater than in extension(P<0.05).The left rotation of T12-L1 and L3-L4 segments was smaller than the right rotation(P<0.05),and that of T11-T12,L1-L2,and L2-L3 segments was larger than the right rotation(P<0.05).The left flexion was larger than the right flexion in the T11-S1 segment.(4)It is concluded that in ankylosing spondylitis patients with lumbar kyphosis,the minimum range of motion of the vertebral body is located at the L5 vertebral body in extension.To prevent fractures,it is recommended to avoid exercise in the extension position.During the onset of lumbar kyphosis in patients with ankylosing spondylitis,the maximum stress of the annulus fibrosus and nucleus pulposus is located in the L1-L2 segment,which is fixed and will not alter with the change of body position.The late surgical treatment and correction of deformity should focus on releasing the pressure of the annulus fibrosus and nucleus pulposus in this segment to avoid the rupture of the annulus fibrosus and the injury of the nucleus pulposus.
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BACKGROUND:The incidence of high lumbar disc herniation in elderly patients with osteoporosis is increasing.The changes in lumbar overall mechanical strength and biomechanical properties of adjacent vertebrae after conventional posterior approach decompression and interbody fusion have not been clarified.Finite element analysis has great value in the field of biomechanics because of its advantages of non-invasiveness,high repeatability and accuracy. OBJECTIVE:To explore the establishment of a finite element model of senile osteoporotic L3/4 lamina decompression using finite element analysis and intervertebral fusion spine,and to evaluate the biomechanical status of the internal fixation complex of bones under bending motion in elderly patients with osteoporosis. METHODS:Mimics 21.0 was used to extract the DICOM data of the spine CT to establish the 3D bony structure of the lumbar spine(T12-L5),which was imported into Geomagic wrap 2017.The L3/4 full lamina decompression model was established after redrawing the mesh,deleting the nails,cutting the model,filling the cavity,detecting and editing the contour line,constructing curved surfaces and grids,fitting curved surfaces and other operations.Solidworks 2017 was used to construct pedicle screws,connecting rods,and intervertebral fusion cages,which were assembled into the L3/4 full lamina decompression model.Intervertebral discs and articular process cartilage and other structures were established through operations such as stretching,isometric surfaces,moving and copying entities.ANSYS Workbench 17.0 was utilized for material assignment,simulating spinal ligaments,meshing,applying force and limiting boundary conditions.A complete osteoporotic L3/4 laminar decompression and intervertebral fusion spine finite element model was established.The stress,strain and displacement cloud diagram of the L3/4 lamina decompression and intervertebral fusion full lumbar spine finite element model were observed under simulated bending conditions. RESULTS AND CONCLUSION:(1)In terms of the stress cloud diagram:The T12-L1 vertebra had the highest average stress value;L2 dropped by 24%;L3 dropped by 55%,and L4-5 dropped by about 80%.The stress concentration in the L4/5 articular process area was the highest,followed by L2/3,and lighter in L1/2 and T12/L1.The stress concentration at the junction of the screw and the connecting rod was obvious,followed by the screw at the entrance and exit of the pedicle.(2)In terms of strain and displacement cloud map:The strain degree of L4/5 and L2/3 articular process was the highest;the strain degree of T12/L1 and L1/2 was the second,and the L3/4 segmental fusion cage,pedicle screw and connecting rod had no any visible deformation.The intervertebral discs of all segments showed great deformation.(3)It is concluded that the cooperative operation of multiple software can successfully construct a finite element model of the spine with L3/4 lamina decompression and intervertebral fusion in elderly patients with osteoporosis.Elderly patients after lumbar spine surgery can tolerate forward flexion,confirming that L3/4 laminar decompression and intervertebral fusion can maintain the shape of the spine and ensure the stability of the spine,but it is necessary to be alert to the occurrence of thoracolumbar stress fractures and adjacent spondylopathy.