Type a3.3 femoral intertrochanteric fracture with augmented proximal femoral nail anti-rotation in the elderly: Finite element analysis of the optimal amount of bone cement / 中国组织工程研究

BACKGROUND: Osteoporosis and fracture type are two important reasons for the postoperative failure of proximal femoral nail anti-rotation. The treatment of elderly patients with type AO31-A3.3 femoral intertrochanteric fractures by bone cement augmented proximal femoral nail anti-rotation can effectively reduce the failure rate, but the specific amount of bone cement injected remains to be discussed. OBJECTIVE: To investigate the optimal amount of bone cement in the treatment of type A3.3 intertrochanteric femur fracture with augmented proximal femoral nail anti-rotation in elderly. METHODS: CT data of one volunteer were imported into Mimics 19.0 and Geomagic studio 2017 to extract and optimize the three-dimensional model of the right femur. Internal fixation model was drawn and assembled with femur model according to the standard operation technology, then imported into Hypermesh 14.0 software to simulate type AO31-3.3 intertrochanteric femur fracture. The spongy bone around the proximal helical blade was redefined as bone cement, obtaining A, B and C models with 2.2 mL, 4.2 mL, and 6.4 mL of bone cement, respectively. The material property parameters, boundary conditions, and applied loads were set and imported into LS-DYNA software for solution. RESULTS AND CONCLUSION: (1) There was no significant difference in the inversion and rotation angles of the head and neck fragment and the overall stress in three models, but the blade cutting in model B and model C was severe and the helical blade was broken, while the blade cutting in model A was slight and did not break. (2) The strong anchoring force of bone cement could stabilize the helical blade, but easily led to local stress concentration. (3) The amount of bone cement injected into the proximal femoral nail anti-rotation for the treatment of type A3.3 intertrochanteric femur fracture in elderly should not be too much, and less than 3 mL may have the best biomechanical effect.

Bone cement augmented proximal femoral nail antirotation for type a3.3 intertrochanteric femoral fractures in elderly: A finite element analysis / 中国组织工程研究

BACKGROUND: Osteoporosis and fracture type are two important reasons for the failure of internal fixation of proximal femoral nail antirotation. Type AO31-A3.3 intertrochanteric fracture, because of its involvement in the lateral wall, greatly increased the instability of the fracture. In addition, the elderly are mostly osteoporosis patients, so failure and postoperative complications of internal fixation of proximal femoral nail antirotation in the elderly with type AO31-A3.3 intertrochanteric fracture are higher. OBJECTIVE: To explore the difference of biomechanics between bone cement augmented and common proximal femoral nail antirotation in the treatment of type AO31-A3.3 intertrochanteric fracture. METHODS: CT data of one 75-year-old volunteer with intertrochanteric fracture were selected to import into Mimics 19.0 and Geomagic studio 2017 software to extract and optimize the three-dimensional model of the right femur. SolidWorks 2017 software was used to draw the internal fixation model and assemble it with the femur model according to the standard operation technology. The model was imported into Hypermesh 14.0 software to cut the bone to obtain the type AO31-A3.3 model with common proximal femoral nail antirotation. The cancellous bone around the proximal end of the screw blade was redefined as bone cement, which is the model of bone cement augmented proximal femoral nail antirotation. The material property parameters, boundary conditions and applied loads were set up and stored as K files respectively and imported into LS-DYNA software for solution. RESULTS AND CONCLUSION: (1) Compared with the common proximal femoral nail antirotation, the treatment of the elderly type AO31-A3.3 intertrochanteric fracture with the bone cement augmented proximal femoral nail antirotation has the advantages of lighter cutting degree of the screw blade, smaller varus, rotation angle and displacement of the femoral head and neck bone block, and better biomechanical effect. (2) The complete lateral wall can effectively support the femoral head and neck bone block and resist the skull and neck bone block as the lateral action point of three-point support. The pronation and rotation tendency can effectively prevent the head and neck screws from withdrawing. (3) The strong anchoring force of bone cement can stabilize the screw blade, enhance the internal action point of three-point support, and conduct and disperse the pressure.

Incidence and mortality of colorectal cancer in Zhejiang Province / 预防医学

Objective@#To understand the incidence and mortality of colorectal cancer in tumor registration areas of Zhejiang Province,and to provide reference for prevention and control strategies for colorectal cancer.@*Methods@#The colorectal cancer data was retrieved from fourteen tumor registries in Zhejiang Province were collected,the incidence rate and mortality rate were calculated and standardized according to the Chinese standard population in 2010 and Segi's world population in 2000. The incidence and mortality of colorectal cancer in different sex,age group and region were analyzed.@*Results@#The crude incidence rate of colorectal cancer from 2010 to 2014 was 35.82/100 000（20 983 cases）. The standardized incidence rate by Chinese and world standard population were 20.80/100 000 and 23.01/100 000. The crude mortality rate of colorectal cancer was 15.25/100 000 （8 934 cases）. The standardized mortality rate by Chinese and world standard population were 8.01/100 000 and 9.39/100 000. The ratio of mortality to incidence was 0.43:1. From 2010 to 2014,the incidence and mortality rates of colorectal cancer were stable（P>0.05）. The incidence rates of colorectal cancer in urban and rural residents were 37.69/100 000 and 31.14/100 000,and the mortality rates were 15.73/100 000 and 14.05/100 000. The incidence rates of colorectal cancer in males and females were 41.53/100 000 and 30.11/100 000,and the mortality rates were 17.74/100 000 and 12.76/100 000. The incidence and mortality rates of colorectal cancer both increased with age. The incidence rate increased significantly in people after 40 years old,and peaked with 187.35/100 000 in people aged 80-84 years. The morbidity rate peaked with 171.27/100 000 in people aged 85 years or over. @*Conclusion@#The incidence and mortality of colorectal cancer in Zhejiang Province were stable,but the incidence was higher than the national average level. The incidence of colorectal cancer in people aged over 40 years increased significantly.

Study on the digital laser speckle technique of three-dimensional displacement of cantilever fixed partial denture under oblique loading / 生物医学工程学杂志

The purpose of this study was to investigate the three-dimensional displacement of the cantilever fixed partial denture (CFPD) under an oblique loading. One Beagle dog was used in this experiment. The CFPD, which used the second premolar and the first molar as abutments and the second molar as pontic, was made in vitro fresh mandible of the Beagle dog, and the digital laser speckle (DLS) technique was employed to measure the three-dimensional displacement of the CFPD under the oblique loading for the first time. We found that when an oblique loading was exerted on the pontic, the displacement of CFPD was the greatest, and the displacement of the abutment near the pontic was smaller than that of the pontic but greater than that of the abutment far from the pontic. We also found that when an oblique loading was exerted on the abutment, the displacement of the directly loaded abutment was greater than that of the other abutment and the pontic. Under the oblique loading, the displacement increased with increasing of load. The experiment demonstrated that it would be advisable for the clinicians to avoid oblique loading, especially the oblique loading of the pontic when using the CPDF. The DLS technique may be one kind of methods for measuring the three-dimensional displacements of the small and irregular objects.

Effectiveness assessment of 3-D cone beam CT used in human bite marks identification / 生物医学工程学杂志

The present study was aimed to use the 3-D cone beam CT (CBCT) as a new method in human bite marks identification which was carried out in experimental pigskin to assess its effectiveness in our laboratory. Bite marks were digital photographed according to American Board of Forensic Odontology (ABFO) guidelines. In this study, the data of the suspect's dental casts were collected by scanning in two ways: one was after plate scanning, in which the comparison overlays were generated by Adobe Photoshop 8.0 software; the other was by CBCT, which generated comparison overlays automatically. The bite marks were blind identified with the two kinds of data of the suspect's dental casts respectively. ROC curve was used to analyze the sensitivity, specificity, and 95% confidence interval. The results showed that CBCT method got a larger area under the ROC curve: 0.784 (SE = 0.074, 95% CI = 0.639-0.929), and got a very high specificity (specificity 98.7%, 95% CI = 94.5%-99.8%). Thus, this study illustrates that the CBCT used in bite mark identification is an effective and accurate tool and has stronger ability to exclude suspects compared with the conventional method, but the comparison process needs further study to enhance its effectiveness in bite mark identification.

Three-dimensional displacement of implant-supported cantilever fixed partial denture under oblique loading / 生物医学工程学杂志

The purpose of this study was to research the three-dimensional displacements of implant-supported cantilever fixed partial denture (CFPD) under oblique loading. One Beagle dog was used in this experiment. Two immediate implants of ITI were inserted in the mandible of the dog, and the implant-supported CFPD which used the implants as abutments was made in vitro fresh mandible. Then the digital laser speckle technique was employed to measure the three-dimensional displacements of CFPD under different oblique loading. We found that when an oblique loading was exerted on the pontic, the displacement increased with increasing of load. Under equal loading, the displacement of the abutment near to the pontic was smaller than that of the pontic but greater than that of the abut-ment far from the pontic. When oblique loading was exerted on the abutment, the displacement of the direct loaded abutment was greater than that of the other abutment and the pontic. Under the.eeual loading, the displacement of implant-supported CFPD of loading on pontic was greater than that of loading on abutments. The experiments demonstrated that implant-supported cantilever fixed partial denture (CFPD) is an effective and advisable therapy for totally? or partially edentulous patients. However, it is also suggested that the clinicians should avoid exerting oblique loading, especially the obliqe loading of the pontic when th e CPDF is used.

Analysis of the effect of contact strength on three-dimensional displacement of an implant-supported fixed bridge under axial-concentrated load using digital laser speckle photography / 生物医学工程学杂志

The purpose of this study was to investigate the effect of four kinds of different contact strength on the three-dimensional displacement of an implant-supported fixed bridge using digital laser speckle photography method. An in vitro model of beagle mandible with an implant-supported fixed bridge in its right premolar region was developed. The bridge was Au-Pt metal-ceramic. The contact was recovered to four different tightnesses, named 0, 1, 2, and 3. Different axial concentrated static load was applied to abutments and bridge respectively. The three-dimensional displacement of the implant-supported fixed bridge was measured using digital laser speckle photographic method. The results demonstrated that the influence of contact tightness was mainly on the mesio-distal and buccal lingual parts. When the contact tightness reached number 3, the regularity of displacement distribution was changed. The present study proved that digital laser speckle photography was an effective method of measuring the micro-displacement. One of the criterions of contact recovering decreased the implant displacement effectively without changing the regularity of displacement distribution.

The effect of notch's angle and depth on crack propagation of zirconia ceramics / 生物医学工程学杂志

This paper is aimed to study the effect of notch's angle and depth on crack propagation of zirconia ceramics. We fabricated cuboid-shaped zirconia ceramics samples with the standard sizes of 4. 4 mm x 2. 2 mm x 18 mm for the experiments, divided the samples into 6 groups, and prepared notches on these samples with different angles and depth. We placed the samples with loads until they were broke, and observe the fracture curve of each sample. We then drew coordinates and described the points of the fracture curve under a microscope, and made curve fitting by the software-Origin. When the notch angle beta = 90 degrees, the crack propagation is pure type I; when beta = 60 degrees, the crack propagation is mainly type I; and when beta = 30 degrees, the crack propagation is a compound of type I and type III. With the increasing of the notch depth, the effect of notch angles on crack propagation increases. In addition, Notch angle is a very important fracture mechanics parameter for crack propagation of zirconia ceramics. With the increasing of notch depth, the impact of notch angle increases.

Contributions of edentulous mandibular alveolar ridge height and denture adhesive to complete denture retention / 生物医学工程学杂志

The present paper is to investigate the relationship between height and stress-bearing area of mandibular alveolar ridge, their influence on retention of complete denture, and the effectiveness of denture adhesive (DA). Five mandibular edentulous models of different heights and a rabbit palate model were prepared in Die-Stone. Measurements were made on the heights and stress-bearing areas of mandibular alveolar ridge, the retention force of mandibular models 15 min after DA administration, and the retention force on the rabbit palate before and after adhering. All available data were analyzed statistically. Linear regression relationship was demonstrated between ridge height and bearing area, ridge height and retention force, and bearing area and retention force (P<0.01), separately. Retention force per unit area was positively related to the height and area. Retention force increased to 2.87 times postadhesive-treating. Height and stress-bearing area of mandibular alveolar ridge directly correlate with the retention of complete denture, and DA significantly improves the retention ability of complete denture.

Research on the aging of all-ceramics restoration materials / 生物医学工程学杂志

All-ceramic crowns and bridges have been widely used for dental restorations owing to their excellent functionality, aesthetics and biocompatibility. However, the premature clinical failure of all-ceramic crowns and bridges may easily occur when they are subjected to the complex environment of oral cavity. In the oral environment, all-ceramic materials are prone to aging. Aging can lead all-ceramic materials to change color, to lower bending strength, and to reduce anti-fracture toughness. There are many factors affecting the aging of the all-ceramic materials, for example, the grain size, the type of stabilizer, the residual stress and the water environment. In order to analyze the aging behavior, to optimize the design of all-ceramic crowns and bridges, and to evaluate the reliability and durability, we review in this paper recent research progress of aging behavior for all-ceramics restoration materials.

Study on the relationships of the width of periodontal ligaments and the capacity ratio of collagen fibers with the elastic modulus of fresh bovine periodontal ligaments / 生物医学工程学杂志

This experiment was aimed to shed light on the correlation and quantitative relationships between the width of bovine periodontal ligament (PDL) and the elastic modulus and, more over, between the width of bovine PDL and the capacity ratio of collagen fibers. The width and length of periodontal ligament of PDL were determined by stereomicroscope, and the elastic modulus by the materials testing systems. The collagen fibers in cross section of the specimen were stained with 1% Sirius Red F3B in saturated carbazotic acid, and the photo of stained PDL was collected by stereomicroscope. Image pro plus6.0 image analysis software was used to measure and calculate the capacity ratio of collagen fibers. It was found that there is a negative correlation between the width of bovine periodontal ligament and elastic modulus. The correlation coefficient is -0.21 and the simple linear regression model is Y = 71. 681-0.021x (Width of PDL); there is a positive correlation between capacity ratio of collagen fibers and elastic modulus. The coefficient correlation is 1.583 and the simple linear regression model is Y = -34.944 + 1.583x (The percentage of collagen fibers). Thus, the elastic modulus of bovine PDL increases while the width of bovine PDL decreases, and it increases while the capacity ratio of collagen fibers increases.

Intestinal absorption of the effective components of Schisandra chinensis Baill by rats single-pass perfusion in situ / 药学学报

The aim of the study is to investigate rat intestinal absorption behavior of three main active components, schisandrol A, schisandrin A and schisandrin B in Schisandra chinensis Baill extracts in intestine of rats. With phenol red as the indicator, in situ single pass intestinal perfusion (SPIP) model was used and the concentrations of three main active components in perfusion solution of different intestinal segments (duodenum, jejunum, ileum, and colon) were determined by HPLC in combination with diode array detection. The results showed that the absorption rate constant (Ka) and effective permeability values (Peff) of three main active components in Schisandra chinensis Baill extracts had significant difference (P 0.05). The absorption of the three active components displayed significant difference (P schisandrin B > schisandrol A in other intestinal segments, and there is significant difference (P < 0.05) between them.

A research in biomechanics of bite marks on porker limb / 生物医学工程学杂志

This research was designed to illuminate the change in biomechanical parameters of soft tissue for bite marks on porker limb. The authors used a prefabricate nob to press perpendicularly on porket limb and so to establish bite mark under three forces: 100 N, 200 N and 300 N. After the procedure of biting, the stress-strain relationship and changes in extension of soft tissue were recorded. Meanwhile, the elasticity was measured with a press meter at nine time-points. When bite mark was formed, with the development of stress, the strain of soft tissue increased. But the speed of increment slowed down when stress exceeded some extent. After bite mark was formed, the extension and elasticity of soft tissue decreased with the increase of pressure.

Targeted Monitoring and Analysis of Surgical Site Infection / 中华医院感染学杂志

OBJECTIVE To study on control measures of surgical site infection.METHODS By forward-looking survey methodology,surgical patients(including obstetrics) with surgical incision infection were investigated.RESULTS The highest infection rate(2.67%) were found in patients with surgical trauma to the largest,longest operation time,coronary artery bypass grafting.In 11 cases surgical site infections,only 1 case were given antibiotics before anesthesia,10 cases were administrated antibiotics post operation more than 4 days.The correct rate of preoperative and postoperative usage of antibiotics was only 9.09%.The size of surgical trauma,operative time,perioperative usage of antibiotics were related to the infection rate.CONCLUSIONS Target monitoing of the surgical site infection can decrease the infection rate.

Mutational analysis of WT1 and PLCE1 in three Chinese families with steroid-resistant nephrotic syndrome / 中华肾脏病杂志

Objective To examine mutations in the WT1 and PLCE1 gene in three Chinese families with autosomal recessive steroid-resistant nephrotic syndrome (SRNS) once mutations in NPHS2 had been excluded. Methods Peripheral blood samples were collected for genetic analysis from three probands of three Chinese families and their parents, and two probands' siblings, and 50 adult volunteers with normal urinalysis. Genomic DNA was isolated from peripheral blood leucocytes. Ten exons and exon-intron boundaries of WT1, and 31 exons and exon-intron boundaries of PLCE1 were amplified by polymerase chain reaction (PCR). Mutational analysis was performed by DNA sequencing directly and RFLP (restriction fragment length polymorphism) and/or PCR. Results No mutation in both WT1 and PLCE1 was identified in three probands from three Chinese families with autosomal recessive SRNS. However, three variants of WT1, 126C>T, ⅣS5-64A>G and 903A>G, and 13 variants of PLCE1, -134A>G, 810T>C, 960G>A, ⅣS11-28C>G, ⅣS15+26A>C, 4724G>C, ⅣS20+40C>T, ⅣS21+64G>A, ⅣS22-26T> A, 5320C>T, 5780A>G, ⅣS27+24A>G and ⅣS31 +48_49insT, were detected in three probands and some controls, indicating that all these variants were gene polymorphisms. WT1 polymorphism ⅣS5-64A>G, and PLCE1 polymorphism ⅣS22-26T>A were novel. Conclusion All the encoding exons and exon-intron boundaries of both WT1 and PLCE1 in three probands are examined, and no causative mutations in WT1 and PLCE1 axe found, suggesting that mutation in WT1 and PLCE1 genes is not a major cause of the Chinese families with autosomal recessive SRNS.

The influence of the tyrosine Kinase inhibitor imatinib mesylate on the cell repair function after DNA damage in K562 cells / 中华检验医学杂志

Objeetive To construct the cell DNA damage models for the human CML K562 cell line before or after imarlnib mesylate treatment and observe the repairing process dynamically for investigating the iniluence of imatinib mesylate on the repair function of K562 cells after cell DNA danlage.Methods The MTT assay was used to estimate the optimal pretreatment concentration of imatinib mesylate in K562 cells and Western blot was employed to evaluate the phosphorylation status in K562 cells after imatinib mesylate treatment to estimate BCR/ABL tyrosine kinase inhibition by imatinib mesylate.The comet assay was used to detect the DNA damage induced by hydrogen peroxide at various concentrations in K562 cells with or without the pretreatment of imatinib mesylate.A dynamic observation on the repairing process after cell DNA damage was made by the comet assay.Results The pretreatment by imatinib mesylate for K562 cells was optimized to be at a final concentration of 1 μmol/L for 24 h as revealed by the MTT assay additionly imatinib mesylate treatment at this concentration could effectively inhibit the phosphorylation of the BCR-ABL fusion protein at Tyr177(Deusityrate 0.100±0.018).When compared with the control group(Deusityrate 0.425±0.039),the BCR/ABL phosphorylation at Tyr177 was significantly decreased by (77. 11±5.59) % (t=4. 57,P＜0. 05). The cell DNA damage models for both imatinib mesylate-nontreated and imatinib mesylate-pretreated K562 cell groups were constructed with hydrogen peroxide treatment at a final concentration of 10 μmol/L for 10 min at 4℃ as confirmed by the comet assay. When compared with the control imatinib mesylatenontreatod K562 cell group,the time duration required for the DNA repair in imatinib mesylate-pretreated K562 cell group was significantly prolonged (F= 97.79,P＜0. 05 ). Conclusions The cell DNA damage models for the leukemic K562 cell groups before or after imatinib mesylate treatment were successfully constructed and the tyrosine kinase inhibitor imatinib mesylate for BCR/ABL fusion protein was revealed to attenuate the DNA repair capacity of the K562 cells after DNA damage.

The comparison of retention of diferent post and core systems / 生物医学工程学杂志

To study the effects of different post design on retention. 27 simulated tooth roots made of PMMA were divided into three groups, then manufactured the cement-expanded composite screw post-core system (CECSP), cement screw post-core system (CSP) and cast metal post-core system (CMP). The root and post-core system was tensiled by the speed of 10 mm/min on the Instron 4302 and recorded the retention force. It appeared significantly different between retention force of CECSP and CSP and CAM (P < 0.05). As a result, the retention mechanical properties of CECSP was much better than those of cement screw post-core system and cast metal post-core system. Therefore, it is possible to find a new way for restoration of endodontically treated teeth.

Influence of convergence angle on the retention of cast metal post and core restorations / 中国组织工程研究

BACKGROUND: The residual root of anterior teeth are usually repaired by means of post and cores plus porcelain fused metal crown in clinic, and the retention force is mainly provided by the post because of the deletion of crown, so the retention force provided by the post is directly correlated with the long-term effect of repair.OBJECTIVE: To analyze the changes of retention of cast metal post and core restorations with different convergence angles, and investigate the influence of convergence angles on retention.DESIGN: A repeated observational measurement.SETTING: Department of Prosthodontics, West China School of Stomatology, Sichuan University.MATERIALS: The experiments were carried out in the building of high polymer material of Sichuan University in May 2005. Fifty-four simulated tooth roots were manufactured by the numerical control machine tools.They were divided into six groups according to the convergence angles of post being 0°, 3.93°, 5.71°, 7.48°, 11.31° and 14.71°, with nine specimens in each group.METHODS: ① Manufacture of the standard specimens: The tooth roots with the convergence angles of 0°,3.93°, 5.71°, 7.48°, 11.31° and 14.71° were prepared with the digital control precision machine. ② Manufacture of the cast post and cores: The post and core wax patterns of the specimens were made in the condition similar to the clinical practice. The post and cores were cast and tried in, necessary grinding was made to ensure the adoption of the posts and the specimens. Then the posts were luted to the specimens with ZPC after the posts and the simulated root canals having een cleaned by alcohol. The posts and the specimens were pressed until the ZPC solidified. ③ Retention Force test: After having been dipped in physiological saline for 24 hours, the bonded castings and specimens were subjected to a tensile testing at the drawing speed of 10 mm per minute.The retention force of post was the load recorded when the post was pulled out from the specimen. ④ Planar bonding strength test: We cut a PMMA stick into the same little cylinders and made angular milling on the flank of the cylinders. The angle between the milled bevel and the central axis of the cylinder was controlled to 0°, 1.9°, 3°, 6°, 9°, 12° and 15°. Afterwards we cut the brass into pieces. Eight wafers were cast with the same diameter of 8 mm and thickness of 1 mm. With the same procedure of bonding the posts to specimens, the brass pieces were bonded to the cylinder bevels and the wafers were adhered to the upside of some unmachinized cylinders.Immerged in physiological saline for 24 hours, their bonding force were tested at the speed of 10 mm per minute, and the load was recorded when the pieces and wafers were separated from the cylinders. ⑤ Calculation of the frictional and interlocking forces: As the post can be regarded as a frustum, the bonding surface area can be calculated with the formula calculating the flank area of frustum, and the area of the occlusal bonding surface is the sum of the annulus part of the root surface and the circular part of the post tip. Some regressions were made to the retention force, frictional strength, bonding strength per unit area, retention force per unit area and frictional force per unit area to convergence angles.MAIN OUTCOME MEASURES: ① Bonding strength of different convergence angles; ② Influence of different convergence angles on the area and bonding strength of the post; ③ Retention force and frictional force of posts with different convergence angles; ④ The results of the one-way analysis of variance (ANOVA) of bonding strength, retention force and frictional force per unit area.RESULTS: ① The bonding strength of different convergence angles: It was 0.309 0 N/mm2 for the occlusal plane, 0.128 3 N/mm2 for the axial plane with a convergence angle of 0°, 0.108 7 N/mm2 for the 1.9°axial plane, 0.107 2 N/mm2 for the 3°axial plane, 0.084 9 N/mm2 for the 6°axial plane, 0.056 7 N/mm2 for the 9°axial plane, 0.046 3 N/mm2 for the 12°axial plane, 0.027 4 N/mm2 for the 15°axial plane. ② Bonding strength and bonding area of posts with different convergence angles: The post with a 0°convergence angle had a total post area of 108.047 mm2 and bonding strength of 19.041 N; The most tapered post with 14.71°had a total post area of 90.245 mm2 and bonding strength of 5.131 N. ③ The retention force of cast post and the bonding strength of ZPC declined with the increasing of convergence angles of the post. For the parallel post (convergence angle=0°), the retention force was 321.60 N, the frictional force was 302.559 N, retention force per unit area was 2.976 N/mm2,frictional strength was 3.885 N/mm2; for the most tapered post (convergence angle=14.71°), the retention force was 9.93 N, frictional force was 54.799 N, retention force per unit area was 0.664 N/mm2, frictional force was 0.681 N/mm2. ④ A one-way ANOVA showed that there were significant differences in the bonding strength, retention force and frictional force per unit area among the groups (P ＜ 0.05).CONCLUSION: The retention force, frictional force and the bonding strength of ZPC decrease with the increasing of convergence angles of posts, so the convergence angles of posts should be reduced as much as possible to obtain greater retention.

Comparison of experimental and computing mechanics for repair materials of porcelain fused to metal / 中国组织工程研究

BACKGROUND: The physical property of porcelain fused to metal (PFM) differs from those of its constituents, which nake impacts on PFM,and the mechanical property of most composites can be estimated with mixture rule. However, there are various factors influencing the mechanical property of PFM and great differences found in the estimations, thus it is necessary to combine the theoretical analysis of mechanical property and mechanics of materials by matbematical models, and provide guidances for PFM' s application.OBJECTIVE: To explore the experiment and computing methods of mechanical analysis on PFM repair materials, and analyze its correlativity and internal relation.DESIGN: Three-point bending experiment and mixture rule of the composites were applied to measure and calculate the intensity and modulus of materials, and then the experimental results and computations were compared.SETTING: Repair Department of Stomatology, West China Stomatological College.MATERIALS: According to the different metal-porcelain ratios, 15 PFM test pieces of 26 mm×4 mm×1.5 mm were divided into 5 groups, with 3 in each.METHODS: Three-point bending experiment was used to detect the bending level and elastic modulus of PFM, whose changing rule was observed,and then was compared with theoretical computed value as well as study the correlation.MAIN OUTCOME MEASURES: PFM experimental result, theoretical computation and the comparison of the two,RESULTS: There were obvious correlations between the experimental measurement and theoretical results, which indicated that the mechanical property of PFM could be predicted by the revised formula.CONCLUSION: The mechanical property of PFM has regular relations with the geometrical morphous parameter and mechanical parameter of PFM constituents, and can be predicted and improved by revised theoretical formula.

Norovirus-induced Nosocomial Diarrhea:Surveillance and Control / 中华医院感染学杂志

OBJECTIVE To provide a practical action plan which can prevent and control the similar occurrence through studying the epidemiological characteristics of a norovirus-induced diarrhea outbreak in the wards of our hospital. METHODS To obtain the information about the epidemic situation of norovirus involving 15 patients in the two wards of our hospital, during the period from Nov 12 to 15, 2006. RESULTS It was a norovirus gastroenteritis outbreak in the 8 cases among 15 patients and there were other 7 sporadic cases. The consummate monitoring system on nosocomial infection could gain the information of disease, and be very helpful to control its transmission. Beijing Municipal Center for Quality Control and Improvement of the Management of Nosocomial Infection was known the information and shared it among different kinds of hospitals. Thus an unnecessary panic was avoided in Beijing at that time. CONCLUSIONS The social factor, senile situation and immunocompromise are the causes of this norovirus outbreak. The effective control measures and the information exchange in time could prevent the spread of infection. It is shown that the nosocomial infection monitoring network could catch the epidemic tendency of nosocomial infection sensitively, so to strengthen the monitoring network is the key.