Objective: To obtain a prokaryotic expression vector containing saliva binding region (SBR) gene of Streptococcus mutans. Methods: By directional cloning method, SBR gene fragment was cloned into the expression vector pcMVT7, the recombinant plasmid pcMVT7-SBR was transformed to E.coli JM109 (DE3). The gene expression was induced with IPTG. Restriction endonuclease and DNA sequencing techniques were used to identify the recombinant plasmid DNA, and finally target protein was purified by affinity chromatography. Results:The DNA sequence of SBR in the reconstructed vector pcMVT7-SBR was in corresponding with the initial design. The C-terminal 6?His tagged SBR fusion protein was expressed in JM109(DE3) and was purified by affinity chromatography. The expression rate of target protein was 29.73%. Conclusion:The recombinant expression plasmid pcMVT7-SBR was constructed.

Objective To propose an optimal therapeutic scheme, finite element analysis was used to evaluate the biome?chanical status of femoral head under daily activities. Methods Non?necrotic femoral head volunteers (11 people) and necrotic femoral head patients (7 cases) were included in this study. All these participants were divided into two groups:control group and abnormal group. The DICOM imaging files of each participant were imported into ScanIP software to form a mask showing the prox?imal femurs. Then the finite element models of proximal femurs were progressively reconstructed. The generated models were im?ported into Abaqus, and the forces were added on these models to simulate daily activities, including standing, sitting, upstairs, and squatting etc. The loads and boundary conditions of digital daily activities simulation were collected from Orthoload database. All of the femoral finite element models were progressed in Abaqus under above activity conditions. After the models were pro?cessed, stress concentrating region was defined in each models respectively, which expressed the main bearing structure in each model based on the result of finite element analysis. At last, the elastic modulus (E?modulus) and strain of the stress concentrating region in each femoral model were extracted and calculated. Results There was no significant difference in age, weight, and height between these two groups. In control group, no significant differences of E?modulus (7 125±745 MPa on left, and 7 112±751 MPa on right) and strain (micro?strain:952 on left, and 954 on right)were found between their bilateral proximal femurs;however in abnormal group, the patients' E?modulus (5 798±1036 MPa on normal side, and 6 667±888 MPa on necrotic side) and strain (mi?cro?strain:1 261 on normal side, and 987 on necrotic side) of necrotic side were significantly lower than normal side. As to all the daily activities which were considered in this study, in abnormal group, the E?modulus among each postures of abnormal side were significantly lower than the E?modules of healthy side;the micro?strain in downstairs was also significantly lower than other pos?tures. Conclusion Daily activities with different intensity could generate different mechanical effects on femoral head, espe?cially on necrotic femoral head. The higher intensity of posture, the greater damage would be found in necrotic femoral head.

OBJECTIVETo establish three-dimension finite element model of mandible with two kinds of Replace implant, and to study stress of implant and abutment.

METHODSThe data of components of the dental implant was measured, cross section of the mandible was scanned by spiral CT and image reconstruction technique was conducted. Three-dimension finite element analysis software UG and MSC. Marc/Mentat were used to built the conjunction model and bone model of two implant systems. Axial loading (200N) and 30 degrees oblique loading (100N) were applied on the models respectively, the stress distribution patterns of the implant and abutment of two implant systems were analyzed.

RESULTSThe peak stress district was concentrated on the structure of the implant cervix, which was more obviously displayed on the Replace Select implant. The peak stress of oblique loading was higher than that of axial loading. The peak stress on the implant cervix of Replace Select implant was higher than that of Replace External Hex implant in all loadings.

CONCLUSIONTo Replace Select especially, oblique force should be avoided on clinical practice in case of the implant fracture.

Alveolar Process ; Dental Implants ; Dental Stress Analysis ; Finite Element Analysis ; Humans ; Mandible ; Stress, Mechanical