Laparoscopic rectopexy for recurrent volvulus of J pouch after total proctocolectomy and ileal pouch anal anastomosis

Ileal‐pouch anal anastomosis (IPAA) is most commonly performed after total proctocolectomy for ulcerative colitis and familial adenomatous polyposis. Small‐bowel obstruction is one of the complications that can occur years after the operation, but intestinal obstruction due to volvulus of the J pouch is a rare condition. We report a case of recurrent volvulus in a patient who had undergone IPAA after total proctocolectomy for cancer of the rectum and multiple colonic polyps. The patient underwent laparoscopic rectopexy and had no recurrence of volvulus.     

A mathematical analysis of shrinkage stress development in dental composite restorations during resin polymerization.

OBJECTIVE: To derive an analytical solution of shrinkage stresses in a simplified Class-I composite restoration using a visco-elastic material model. METHODS: Simplified, multi-layer, circular plane models were used to represent different sections of a tooth with a Class-I restoration: one section is close to the top occlusal surface and the other is at a deeper location of the restoration. The sections are therefore subjected to different stress states, i.e., plane-stress and plane-strain, respectively. The analytical solution obtained was compared with the numerical results from finite element analysis. A sensitivity study was then carried out to examine the relative influence of geometric and material parameters on the shrinkage stress development. RESULTS: The analytical solution for the shrinkage stress agrees reasonably well with the numerical results given by finite element analysis of more realistic geometries. The result shows that the residual stresses deep inside the restoration are much higher than those at the occlusal surface. This is because material at the former location is subjected to a stress state similar to that of equi-triaxial tension, which limits stress relaxation through viscous flow. However, a stress concentration exists at the restoration margin on the occlusal surface. Sensitivity analysis indicates that the most important factor in shrinkage stress development is material shrinkage, and the second most important factor is Young's modulus. Viscosity and polymerization rate only affect the residual stresses at the surface. The size of the restoration had relatively little influence on the residual stress development. On the other hand, increasing the enamel thickness increases the stresses inside the restoration but not those at the occlusal surface. SIGNIFICANCE: A visco-elastic solution for the shrinkage stresses developed in a simplified Class-I restoration during polymerization has been derived. The solution allows the influence of several geometric and material parameters on shrinkage stress development to be examined readily. It also provides a benchmark test for more elaborate numerical schemes before they are used to analyse more complicated cases.     

Biomechanics of Cantilever Fixed Partial Dentures in Shortened Dental Arch Therapy

PURPOSE: The purpose of the present study was to investigate, by means of 3-dimensional finite element analysis, aspects of the biomechanics of cantilever fixed partial dentures replacing the maxillary canine in shortened dental arch therapy. The null hypothesis was that no differences would be identified by finite element analysis in the mechanical behavior of the 2 designs of cantilever fixed partial denture under different scenarios of occlusal loading. MATERIALS AND METHODS: Single- and double-abutted cantilever fixed partial dentures were modeled and analyzed using the finite element packages PATRAN and ABAQUS. Displacement and maximum principal stresses (magnitude and location) within the fixed partial dentures, supporting structures, and the periodontal ligament/bone and abutment/retainer interfaces were examined under 20 different scenarios of axial and lateral occlusal loading. RESULTS: The results indicate that more displacement occurred in the 2 rather than the 3-unit cantilever fixed partial denture, with the greatest displacement having occurred under lateral loading. The maximum principal stresses observed in the periodontal ligament/bone interfaces were greatest buccocervically, with the highest value being observed in the 2-unit fixed partial denture under lateral loading. The highest maximum principal stresses observed in the retainer/abutment interfaces were located cervically in relation to the distal margin of the retainer of the 2-unit fixed partial denture under axial loading. CONCLUSIONS: It was concluded that in adopting a cantilever fixed partial denture approach for the replacement of a missing maxillary canine in shortened dental arch therapy, there may be merits, in terms of mechanical behavior, in selecting a double-rather than a single-abutment design. Furthermore, prostheses' displacement and functional stresses may be minimized by reducing lateral loading and avoiding pontic only loading.     

An acoustic emission study on interfacial debonding in composite restorations

Objective

This paper studied in vitro the effect of the C-factor on interfacial debonding during curing of composite restorations using the acoustic emission (AE) technique. Finite element (FE) analyzes were also carried out to evaluate the interfacial stresses caused by shrinkage of the composite resin in restorations with different C-factors.

Materials and methods

Twenty extracted third molars were divided into 4 groups of 5. They were cut to form Class-I (Groups 1 and 2) and Class-II (Groups 3 and 4) cavities with different C-factors. The average C-factors of the four groups were 3.37, 2.88, 2.00, and 1.79, respectively. The cavities were then applied with an adhesive and restored with a composite, which was cured by a halogen light for 40 s. A 2-channel AE system was used to monitor the interfacial debonding, caused by shrinkage stress, between the tooth and restoration through an AE sensor attached to the surface of the specimen. Recording of the AE started at the same time as curing of the composite and lasted 10 min. Simplified FE models were used to evaluate the interfacial stresses in restorations with different C-factors, with a thermal load (temperature decrease) being applied to the composite resin to simulate its shrinkage.

Results

The mean and standard deviation of the total number of AE events for the four groups were 29.6 ± 15.7, 10.0 ± 5.8, 2.6 ± 1.5, and 2.2 ± 1.3, i.e. the number of AE events increased with an increase in the C-factor. The FE results also showed that, the higher the C-factor of the restoration, the higher the interfacial tensile stress between the tooth and restoration.

Significance

From the results of the AE tests and FE simulations, it can be concluded that, the higher the C-factor, the higher the shrinkage stress and the more likely is interfacial debonding.     

A comparison of bond strengths measured using cantilever bending and micro-tensile methods

Objectives

The purpose of this study was to evaluate the cantilever-bending test as a bond-strength measurement method for enamel/composite adhesion.

Materials and methods

The buccal surface of bovine incisors were flattened and subsequently placed with composite Z250 (3M ESPE) incrementally after either self-etching adhesive (SE) or etch-and-rinse adhesive (SB) was applied. Then, they were cut with a low-speed cutter to obtain stick-shape samples. The samples were divided into four groups (n = 30 each) according to the adhesive and test method: SET, SE-B, SB-T and SB-B, where T denotes the microtensile test and B denotes the cantilever-bending test. The failure mode of each sample was examined under the microscope. Those samples with the fracture surface lying entirely or partially in the adhesive layer were considered to have provided successful measurements. The results from the two test methods were compared.

Results and discussion

The cantilever-bending method produced a comparable success rate of bond strength measurement to that of the microtensile method. The bond strengths of SE and SB from the cantilever-bending test were 58% and 40% higher, respectively, than those measured with the microtensile method. The adhesive SE exhibited almost the same bond strength as SB, irrespective of the test method.

Conclusions

Cantilever bending can be used as an alternative method for bond strength measurement. The ratio of bending to tensile strength is around 1.5.     

Single suture craniosynostosis: Identification of rare variants in genes associated with syndromic forms

We report RNA‐Sequencing results on a cohort of patients with single suture craniosynostosis and demonstrate significant enrichment of heterozygous, rare, and damaging variants among key craniosynostosis‐related genes. Genetic burden analysis identified a significant increase in damaging variants in ATR, EFNA4, ERF, MEGF8, SCARF2, and TGFBR2. Of 391 participants, 15% were found to have damaging and potentially causal variants in 29 genes. We observed transmission in 96% of the affected individuals, and thus penetrance, epigenetics, and oligogenic factors need to be considered when recommending genetic testing in patients with nonsyndromic craniosynostosis.

     

转化生长因子β1在白细胞介素1β诱导大鼠肾小管上皮细胞转分化及大黄素干预中的作用

目的:大黄素对白细胞介素1β诱导NRK52E细胞转分化有显著抑制作用。实验拟进一步观察转化生长因子β1在白细胞介素1β诱导大鼠肾小管上皮细胞-肌成纤维细胞转分化及大黄素抑制作用中的意义。方法:实验于2006-10/2007-05在泸州医学院附属医院免疫实验室完成。⑴实验材料及分组:以培养的大鼠肾小管上皮细胞株(NRK52E)为观察对象,按如下分组分别添加不同处理因素:①对照组:仅加入体积分数为0.05小牛血清的高糖DMEM培养基。②白细胞介素1β诱导组:加含白细胞介素1β终浓度为10μg/L的高糖DMEM培养基。③SB431542阻断组:加含白细胞介素1β终浓度为10μg/L及SB431542终浓度为10μmol/L的高糖DMEM培养基。④白细胞介素1β 大黄素组:同时加分别含白细胞介素1β终浓度为10μg/L及大黄素终浓度为25mg/L的高糖DMEM培养基。⑵实验评估:培养48h后用倒置相差显微镜观察细胞形态,细胞免疫化学染色法检测肌酸激酶、α-平滑肌肌动蛋白及转化生长因子β1的表达。结果:①白细胞介素1β可诱导部分细胞由卵圆形转变为梭形,且肌酸激酶表达减弱(P<0.01),α-平滑肌肌动蛋白及转化生长因子β1表达显著增强(P<0.01)。②SB431542特异性抑制转化生长因子β1作用后,白细胞介素1β诱导的细胞形态改变受抑,同时肌酸激酶表达增强(P<0.01),α-平滑肌肌动蛋白表达减弱(P<0.01),但转化生长因子β1的表达却无明显变化。③大黄素对白细胞介素1β诱导的细胞形态改变及肌酸激酶、α-平滑肌肌动蛋白的表达有明显抑制作用,其抑制作用与SB431542的作用相比无显著差异;同时,大黄素对白细胞介素1β诱导的转化生长因子β1的表达也有明显抑制作用(P<0.01)。结论:转化生长因子β1可能介导了白细胞介素1β诱导大鼠肾小管上皮细胞-肌成纤维细胞转分化,并参与了大黄素抑制白细胞介素1β诱导大鼠肾小管上皮细胞转分化的作用。     

Demographic characteristics and prevalence of serologic markers among donors who use the confidential unit exclusion process: the Retrovirus Epidemiology Donor Study

BACKGROUND: Most blood centers utilize a confidential unit exclusion (CUE) process, intended to reduce the risk of transfusion-associated infectious diseases by allowing high-risk donors confidentially to exclude their blood from use for transfusion. The effectiveness of this method remains controversial. STUDY DESIGN AND METHODS: Confirmatory or supplemental test results for antibodies to human immunodeficiency virus, human T-lymphotropic virus type I, and hepatitis C virus, as well as hepatitis B surface antigen and syphilis and screening test results for antibodies to hepatitis B core (antigen) and alanine aminotransferase levels were obtained for approximately 1.8 million units donated during 1991 and 1992 at five blood centers within the United States. The prevalences of these infectious disease markers in units that the donors confidentially excluded (CUE+) and units that the donors did not exclude (CUE-) were calculated and examined within demographic subgroups. RESULTS: Units that were CUE+ were 8 to 41 times more likely to be seropositive for antibodies to human immunodeficiency virus and hepatitis C virus, hepatitis B surface antigen, and syphilis and three to four times more likely to react for antibody to hepatitis B core (antigen) or to have elevated alanine aminotransferase levels than units that were CUE- (p < 0.001). The positive predictive value of CUE (the percentage of CUE+ units that were confirmed seropositive for any marker) was 3.5 percent, and the sensitivity of CUE (the percentage of confirmed-seropositive units that were CUE+) was 2.3 percent. CONCLUSION: The current CUE process has low sensitivity and apparently low positive predictive value, and in many cases, it appeared that donors misunderstood it. Yet, CUE was not a “random process,” as CUE+ units were more likely to be seropositive for any infectious disease marker than CUE- units. This suggests that efforts to improve the CUE system may be warranted. As risk factors for transfusion-transmitted infection become more difficult to identify by history-based screening, however, such efforts may have limited effect.