Objective:To construct the finite element models of maxillary central incisor and the simu-lations with crown lengthening surgery and post-core restoration in management of different crown-root fracture types, to investigate the stress intensity and distributions of these models mentioned above, and to analyze the indications of crown lengthening from the point of view of mechanics. Methods:An extrac-ted maxillary central incisor and alveolar bone plaster model were scanned by Micro-CT and dental impression scanner ( 3shape D700 ) respectively. Then the 3D finite element models of the maxillary central incisor and 9 simulations with crown lengthening surgery and post-core restoration were construc-ted by Mimics 10. 0, Geomagic studio 9. 0 and ANSYS 14. 0 software. The oblique static force (100 N) was applied to the palatal surface ( the junctional area of the incisal 1/3 and middle 1/3 ) , at 45 degrees to the longitudinal axis, then the von Mises stress of dentin, periodontal ligament, alveolar bone, post and core, as well as the periodontal ligament area, were calculated. Results:A total of 10 high-precision three-dimensional finite element models of maxillary central incisor were established. The von Mises stress of models: post >dentin >alveolar bone >core >periodontal ligament, and the von Mises stress increased linearly with the augmentation of fracture degree ( besides the core) . The periodontal ligament area of the crown lengthening was reduced by 12% to 33%. The von Mises stress of periodontal ligament of the B2L2c, B2L3c, B3L1c, B3L2c, B3L3c models exceeded their threshold limit value, respective-ly. Conclusion: The maxillary central incisors with the labial fracture greater than three-quarter crown length and the palatal fracture deeper than 1 mm below the alveolar crest are not the ideal indications of the crown lengthening surgery.

Objective: To compare influences of different retention attachments on stress among supporting structures .Methods: By 3-dimensional laser scanner and reverse engineering computer aided design ( CAD) software , a basic partially edentulous digital model with mandibular premolar and molar missing was established .Implant attachment and removable partial dentures ( RPD) were added into the basic model to build three kinds of models: RPD only, RPD +implant +Locator attachment , and RPD +implant +Magfit attachment .Vertical and inclined loads were put on artificial teeth unilaterally . By means of 3-dimensional finite element analysis , the stress distribution and displacement of the main supportive structures were compared . Results: A complete 3-dimensional finite element model was established , which contained tooth structure , and periodontal structures .The displacement of the denture was smaller in Locator (9.38μm vertically, 45.48μm obliquely) and Magfit models (9.54μm vertically, 39.45 μm obliquely) compared with non-implant RPD model (95.27 μm vertically, 155.70 μm oblique-ly) .Compared with the two different attachments , cortical bone stress value was higher in Locator model ( Locator model 10.850 MPa vertically , 43.760 MPa obliquely;Magfit model 7.100 MPa vertically , 19.260 MPa obliquely).The stress value of abutment periodontal ligamentin Magfit model (0.420 MPa vertically) was lower than that in Locator model (0.520 MPa vertically).Conclusion:The existence of implant could reduce maximum von Mises value of each supportive structure when Kennedy Ⅰpartially edentulous mandible was restored .Comparing the structure of Magfit and Locator attachment , the contact of Magfit attachment was rigid , while Locator was resilient .Locator attachment could improve stability of the denture dramatical -ly.Locator had stronger effect on defending horizontal movement of the denture .

Purpose: To analyze the effect of the intraarticufar contact of the temporomandibular joint ( TMJ ) on three dimensional nonlinear simulation of human TMJ forces in order to simulate the distribution and transfer of TMJ forces more realistically and logically. Materials and Methods: Combining helical CT scanning technology with three dimensional finite element method, together with Auto CAD software, three dimensional nonlinear finite element models were developed in vivo for comparison with the changes in the stress within the TMJ in different contact conditions. Results: The stresses on the surfaces of articular disc and condyle in the finite element models with contact elements between the disc and condyle were mainly distributed on their anterior and medial regions, and the stresses on other regions were relatively smaller. But, the stresses of those models without contact element were mainly distributed on their midposterior and medial aspacts. Moreover, the stress values were higher. When the friction coefficient was in the range of 0 0.15, the distribution extent and magnitude of the contact stress between the disc and the condyle in the TMJ were completely same. Meanwhile, the surface stresses on the disc and the condyle were nearly coincident in three ways of disc condyle contact, which were no friction contact, rigid contact and elastic contact. Conclusion: In the issue of disc condyle contact of simulating TMJ forces with three dimensional nonlinear method, the stress distribution in the joint with complete contact relationship between the disc and the condyle conforms more to the physiological condition. The lower friction coefficient ( 0 0.15 ) in the TMJ and various contact patterns between the disc and condyle had no evident influence on the stress distribution in the TMJ. Three dimensional nonlinear analysis for the forces in the TMJ might be more realistic and reasonable because of contact simulation among various structures within the TMJ.

Objective:To investigate the clinical efficacy of mechanical solitaire AB stents thrombectomy combined with intra-arterial thrombolysis in the treatment of patient with acute ischemic stroke.Methods:Fifteen patients with acute ischemic stroke admitted into our hospital from August 2014 to August 2016 were treated with mechanical thrombectomy with solitaire AB stents plus intra-arterial thrombolysis.The National Institutes of Health Stroke Scale score (NIHSS) of all patients were evaluated before and after treatment to compare the clinical efficacy.The prognosis ofpatients between two groups were compared via evaluating modified Rankin score (mRS)and gelasijia coma score (GCS).Results:After mechanical thrombectomy with solitaire AB stents plus intra-arterial thrombolysis treatment,14 patients achieved complete or part recanalization,and 1 patient was terminated treatment due to vital signs instability,and the rate ofrecanalization was 93.3％.The NIHSS score of patients before treatment was 12.93± 4.25,which was much higher than that after treatment (4.33± 1.45,P＜0.05).After follow-up by 3 months,the good mRS scores were obtained in all 18 patients,including 2 patients with mRS score of 2,5 patients with 1,and 8 patients with 0.Additionally,there was no patient with re-obstruction during follow-up period.Conclusion:Mechanical thrombectomy with solitaire AB stents combined with intra-arterial thrombolysis had a good capability and safety in the treatment of patients with acute ischemic stroke.

BACKGROUND: Biomechanical mechanisms are complex, and previous studiers focus on the stress conduction in the carpus. However, the stress distribution and characteristics of trabecula in the carpus are rarely reported.OBJECTIVE: To investigate the stress distribution and deformation characteristics of the normal lunate through a two-dimensional sagittal finite element model.METHODS: A normal cadaveric lunate sample was scanned with Micro-CT and the central sagittal image was chosen for further finite element analysis (FEA). The chosen image was processed and imported into the finite element analysis software (Ansys 14.0). A two-dimensional sagittal finite element model of the lunate bone was established. Axial pressure was applied to the model with the wrist held in different positions, and nine regions of interests (ROIs) were identified, for which stress and displacement nephograms were created. These included the first principal stress (S1, the maximum stress in a principal plane), the third principal stress (S3, the minimal stress in a principal plane), shear stress (SXY, the component of stress coplanar with a material cross section), von Mises stress (SEQV, yielding begins when the elastic energy of distortion reaches a critical value)and displacement of each ROI (UY, displacement on the vertical plane of the lunate) which were calculated and compared.RESULTS AND CONCLUSION: (1) The stresses on ROIs located in the proximal and volar cortices of the lunate bone were much higher than those in the distal and dorsal cortices. At the proximal lunate, S1 was less than S3; however at the distal lunate, S1 was greater than S3. The ROIs of the distal and proximal ends of the lunate bone received much higher stress than the ROIs of the middle part. As for axial trabecular displacement,both distal and proximal ROIs were compressed by axial pressure. However, the dorsal and the volar parts of the proximal lunate moved in different directions at different wrist postures. Besides, the stress values and magnitudes of displacement were elevated in wrist flexion and extension compared to neutral position.Furthermore, the stress concentration zones (the proximal volar ROI, the proximal dorsal ROI, the distal volar ROI, and the distal dorsal ROI) had different directions of shear stress and displacement in different wrist postures. (2) These results suggest that when stress is loaded on a normal lunate model, four stress concentration zones, the proximal volar ROI, the proximal dorsal ROI, the distal volar ROI, and the distal dorsal ROI are found. The wrist postures can significantly affect the value and distribution of axial stress on the sagittal lunate.

Objective To make a mechanical analysis on three-dimensional finite element models of the mandibular first molar defect restored with post core and all-ceramic crown,and to provide a guideline for planning restoration for such kind of tooth structure defect.Methods Cone-beam CT based threedimensional finite element models of post and core restored first mandibular molars were established,with 6 different ferrule designs(the ferrule with only 180 axial wall on different locations).The yon Mises criterion was applied for comparing the maximum von Mises stress value of dentin and stress concentration areas in six models which restored with fiber post or cast NiGr alloy post core or Au alloy post core under the maximum,vertical,inclined and horizontal direct loads.Results The restoration effects in six models were compared,and the maximum yon Mises stress concentration areas were not obviously different.The maximum yon Mises stress value of NiCr alloy post core and crown was 62.81 MPa.Under horizontal load,the maximum von Mises stress value of dentin increased remarkably.Conclusions The location of residual dentin has little influence on the stress distribution,when restored by post core and crown.Au alloy post core and crown or fiber post core and crown are superior to NiCr alloy post core and crown.

Objective: To observe the dynamics of antibody response in great gerbils infected with Yersinia pestis in experiment. Method: A total of 211 great gerbils were captured in the southern margin of plague natural focus of Junggar Basin of the Xinjiang Uygur Autonomous Region in 2011. Among them, there were 167 great gerbils without infection of Y. pestis and 44 great gerbils infected by Y.pestis. Y.pestis No. 2504 was employed for this experimental strain, which was strong toxic strain with negativity in the reduction experiment of nitrate. 35 great gerbils without the infection of Y. pestis were divided randomly and averagely into 7 groups including 6 experimental groups and 1 control group. Great gerbils in the 1st to 6th experimental groups were exposed first with 1 × 10⁶-1 × 10¹¹ CFU/ml of bacterial fluid with 10 times of gradient dilution; groin areas of great gerbils in the control group were injected subcutaneously with physiological saline; and the amount of infection was all 1 ml. 17 great gerbils infected with Y. pestis and the first detection of F1-antibody titer in 1∶256-1∶4 096 were grouped according to F1-antibody titer: group 1∶4 096 (n=4), group 1∶2 048 (n=4), group 1∶1 024 (n=3), group 1∶512 (n=3) and group 1∶256 (n=3); and blood in caudal regions was collected in asepsis for the detection of F1-antibody, with a total of 5 times. 9 great gerbils which were selected from the remaining great gerbils infected with Y. pestis and detected F1-antibody negative 2 times were exposed 1×10⁶ CFU/ml of bacterial fluid for the second infection, with the amount of infection being 1 ml. Blood in caudal regions of great gerbils after the first and second infection were collected for the detection of plague F1-antibody on the 3rd, 5th, 7th, 15th, 30th, 60th, 90th and 120th day after infection. Declined regression models for great gerbils' antibodies were established with unary linear regression equation; declined change diagrams for the antibodies were drawn to observe the declined F1-antibody after great gerbils were exposed to Y. pestis. Results: In great gerbils with the first infection of Y. pestis, antibodies were detected in the 1 × 10⁶-1 × 10⁸ CFU/ml of group on the 30th, 15th and 15th day, respectively; the positive rates of antibody were 1/4, 3/4 and 4/5, respectively; the group 1×10⁷ and 1× 10⁸ CFU/ml reached to the highest antibody titer with 1∶256 on the 120th day; antibodies were revealed in the group 1×10⁹, 1×10¹⁰ and 1×10¹¹ CFU/ml from the 5th to 7th day when the seroconversion of all antibodies was observed; group 1×10¹¹ CFU/ml reached to the highest antibody titer on the 120th day with 1∶4 096. In the great gerbils with the second exposure to Y.pestis, positive antibodies were detected on the 3rd day with the positive rate being 2/9; and the highest antibody titer with 1∶2 048 was noted on the 90th day. Unary linear regression equation of declined F1 antibody of great gerbils was y=0.045x- 0.321 (F=115.40, P< 0.001), and the shortest duration for F1-antibody titer declining from 1∶4 096 to 0 was 140 d and the longest duration 200 d. Conclusion Great gerbils infected with the high concentration of Y. pestis fluid show shorter duration in producing F1-antibody, the antibody positive rate is also higher, and the highest antibody titer can reach 1∶4 096. The great gerbils could hold the plague F1 antibodies for a long time which was about 140 to 200 days from the highest titer.

Objective To construct three-dimensional finite element models with modified crown lengthening surgery and post-core restoration in management of various crown-root fracture types,to investigate the intensity and distribution of stressin models mentioned above,and to compare and analyze the indications of traditional and modified crown lengthening surgeries from the mechanic point of view.Methods Nine three-dimensional finite element models with modified crown lengthening surgery and post-core restoration were established and analyzed by micro-CT scanning technique,dental impression scanner,Mimics 10.0,Geomagic studio 9.0 and ANSYS 14.0 software.The von Mises stress of dentin,periodontal ligament,alveolar bone,post and core,as well as the periodontal ligament area and threshold limit value were calculated and compared with the findings of traditional crown lengthening models which had been published earlierby our research group.Results The yon Mises stress intensity of modified crown lengthening models were:dentin＞post＞core＞alveolar bone＞periodontal ligament.The maximum von Mises stress of dentin(44.37-80.58 MPa) distributed in lingual central shoulder.The periodontal ligament area of the modified crown lengthening surgery was reduced by 6％ to 28％,under the same crown-root fracture conditions,the periodontal ligament area of modified crown lengthening models was larger than that of the traditional crown lengthening models.In modified crown lengthening surgery models,the yon Mises stress of periodontal ligament of B3L1m,B3L2m,B3L3m models exceeded their limit values,however,the yon Mises stress of periodontal ligament of the B2L2c,B2L3c,B3L1c,B3L2c,B3L3c models exceeded their limit values in traditional crown lengthening surgery models.Conclusions The modified crown lengthening surgery conserves more periodontal supporting tissues,which facilitates the long-term survival of teeth.The indication of modified crown lengthening surgery is wider than traditional method.The maxillary central incisors with labial fracture at gingival margin level and with palatal fracture at or below the alveolar crest level are not the indication of the crown lengthening surgery.

Objective:To establish a finite element model of the mandibular first molar with three wall defects, simulate the repair effect of fiber post porcelain crown and modified inlay, and analyze the effect of crown defect location on abutment stress.Methods:One intact mandibular first molar was extracted due to periodontal disease. Conical beam computed tomography (CBCT) was used to obtain the data, Mimics, Geomagic, and Ansys software were used to construct the mandibular first molar model, and 8 groups of models (groups A, B, C, D of fiber post all-porcelain crown and groups E, F, G, and H of modified onlays) were established according to different locations and repair methods of the three wall defects. Four forces (F1, F2, F3 and F4) were selected to compare the maximum Von Mises stress and its distribution.Results:The extreme values of dentin Von Mises stress were 19.334 9-19.907 1 MPa(F1), 8.295 47-8.466 08 MPa(F2), 19.433 5-19.441 4 MPa(F3) for fiber post all-porcelain crown restoration (group A, B, C and D models), respectively. 36.109 3-36.199 8 MPa(F4); The maximum values of Von Mises stress were 19.493-19.864 8 MPa(F1) in modified high inputate restoration (E, F, G, H). 9.077 35-9.317 12 MPa(F2), 22.770 6-23.541 2 MPa(F3), 35.724 2-35.989 7 MPa(F4). There was little change among the models. The extreme value of dentin stress increased with the increase of loading Angle. Under the same defect mode, the extreme value of dentin stress in groups A, B, C and D was less than that in groups E, F, G and H at F2 and F3. At F1 and F4, the extreme values of dentin stress in the eight groups were similar, but the dentin stress concentration area in groups A, B, C and D was located on the tooth surface, and the stress concentration area appeared in the pulp chamber in groups E, F, G and H.Conclusions:The position of the defect has no significant effect on the repairing effect of the modified inlay and the fiber post porcelain crown. The fiber post porcelain crown is more beneficial to disperse the dentin stress.

Hereditary hemochromatosis is a rare autosomal genetic disorder that can cause multi-organ dysfunction in the liver,pancreas,spleen,heart and pituitary gland,with diverse clinical manifestations,make the diagnosis difficult.In recent years,with the deepening of clinical understanding and the development of genetic diagnosis tools,the diagnostic rate of this disease has increased significantly.In this paper,we report a case of hereditary hemochromatosis type 3 involving multiple organs and complicated by severe heart failure,aiming to improve the clinicians'understanding of this disease and reduce the leakage and misdiagnosis.