Monolithic crowns fracture analysis: The effect of material properties,cusp angle and crown thickness

ObjectivesThis study aimed to investigate the collective influence of material properties and design parameters on the fracture behavior of monolithic dental crowns.MethodsThree-dimensional (3D) models (N = 90) with different combinations of design parameters (thickness, cusp angle and occlusal notch geometry) and material type (lithium disilicate, feldspar ceramic, zirconia, hybrid resin ceramic and hybrid polymer-infiltrated ceramic) were developed for the failure analysis using extended finite element method (XFEM) to identify the stress distribution, crack initiation load, fracture surface area and fracture pattern. Analytical formulation, in vitro fracture tests and fractographic analysis of dedicated models were also performed to validate the findings of the XFEM simulation.ResultsFor all material types considered, crowns with a sharp occlusal notch design had a significantly lower fracture resistance against occlusal loading. In most of the models, greater crown thickness and cusp angle resulted in a higher crack initiation load. However, the effect of cusp angle was dominant when the angle was in the low range of 50° for which increasing thickness did not enhance the crack initiation load.SignificanceComparing the critical load of crack initiation for different models with the maximum biting force revealed that for the studied monolithic materials excluding zirconia, a design with a rounded occlusal notch, 70° cusp angle and medium thickness (1.5 mm occlusal) is an optimum combination of design parameters in terms of tooth conservation and fracture resistance. Zirconia crowns exhibited sufficient strength for a more conservative design with less thickness (1.05 mm occlusal) and sharper cusp angle (60°).     

医院物业持续改进工作平台建设

医院物业与医院的日常运行关系密切相关,医院物业管理的水平和效率直接影响到医院工作的方方面面。为提升医院整体管理的水平,从医院物业的特点出发,认真分析物业工作现状,根据持续改进医疗服务工作的需要,引入闭环管理思维,打造医院物业持续改进工作平台,使得医院物业管理工作在物业质量、生产安全、人性化服务上取得了长足的进步,医院物业管理水平得到了全面的提升。     

基于物料性质表征技术的蒲地蓝消炎口服液 儿童用药顺应性改善研究

蒲地蓝消炎口服液安全有效,显效迅速,临床应用广泛,但在儿科用药领域,由于用药剂量不明确与口服顺应性差成为制约其发展的主要原因。基于此,本研究通过分析其问题产生的根源并深入探究其解决方案,通过物料性质表征技术、复合矫味技术、剂型优化技术以提升蒲地蓝消炎口服液的口服顺应性,同时探讨蒲地蓝消炎口服液的儿童精准用药策略,为儿童精准用药的临床前研究提供技术指导。     

Fractal dimension in CT low attenuation areas is predictive of long-term oxygen therapy initiation in COPD patients: Results from two observational cohort studies

BackgroundSome chronic obstructive pulmonary disease (COPD) patients develop hypoxemia with disease progression, with some even requiring long-term oxygen therapy (LTOT). Lung function, especially diffusing capacity, and the annual decline in PaO₂, are reported to be predictive factors of chronic respiratory failure. However, the association between lung morphometry evaluated using computed tomography (CT) images and LTOT initiation is unknown.MethodsWe retrospectively evaluated the relationship between clinical indices, including pulmonary function, body mass index (BMI), and CT parameters, at baseline and LTOT initiation in two prospective COPD cohorts. In the Nara Medical University cohort (n = 76), the low attenuation area (LAA) and its fractal dimension (fractal D) were adapted as the indices for parenchymal destruction in CT images. The association between these CT measurements and LTOT initiation was replicated in the Kyoto University cohort (n = 130).ResultsIn the Nara Medical University cohort, lower BMI (hazard ratio [HR]:0.70, p = 0.006), lower % diffusing capacity (%DLCO) (HR: 0.92, p = 0.006), lower %DLCO/VA (HR, 0.90, p = 0.008), higher RV/TLC (HR, 1.26, p = 0.012), higher LAA% (HR: 1.18, p = 0.001), and lower fractal D (HR: 3.27 × 10^?8, p < 0.001) were associated with LTOT initiation. Multivariate analysis in the Kyoto University cohort confirmed that lower %DLCO and lower fractal D were independently associated with LTOT initiation, whereas LAA% was not.ConclusionFractal D, which is the index for morphometric complexity of LAA in CT analysis, is predictive of LTOT initiation in COPD patients.     

系统中药学指导下的益母草多维评价研究

系统中药学是基于现代中药学学科的开创者凌一揆教授"大中药"的思想,是研究中药复杂系统品种、品质、制药、药性、功效、应用等关键要素发生、发展、变化的科学。本文论述了系统中药学的科学内涵,报告了在系统中药学指导下益母草"品质制性效应"的研究实践。     

基于超分子“印迹模板”理论探讨中药升降浮沉

在前期提出超分子化学对中药四性理论特殊影响的基础上,进一步分析中药升降浮沉的历史沿革、研究概况,并运用超分子"印迹模板"理论对中药"升降浮沉"理论进行解析,提出对中药"升降浮沉"的评价方法。人体与中药均是印迹模板印迹作用的聚集体,在印迹模板作用规律下,不同类型的中药成分与人体的靶点通过"锁-钥"关系以非共价键结合,中药客体超分子通过键的作用可纠正人体主体超分子在自识别、自组织、自组装、自复制过程时发生的寒热、气机失调。人体具备抵抗外界病邪侵袭的能力,有赖于其气机"升降出入"的正常;中药具有"升降浮沉"的性能并能祛除病疾,有赖于其能调整人体气机紊乱,或顺应气机、祛邪外出以增强机体免疫的能力。基于此,在分析中药"升降浮沉"药理作用的基础上,探究其物质基础,并建立中药"升降浮沉"的评价方法,通过超分子印迹模板理论对中药升降浮沉进行剖析,揭示其科学内涵,推动中药药性理论不断创新。     

Structural Response Prediction of Thin-Walled Additively Manufactured Parts Considering Orthotropy,Thickness Dependency and Scatter

Besides the design freedom offered by additive manufacturing, another asset lies within its potential to accelerate product development processes by rapid fabrication of functional prototypes. The premise to fully exploit this benefit for lightweight design is the accurate structural response prediction prior to part production. However, the peculiar material behavior, characterized by anisotropy, thickness dependency and scatter, still constitutes a major challenge. Hence, a modeling approach for finite element analysis that accounts for this inhomogeneous behavior is developed by example of laser-sintered short-fiber-reinforced polyamide 12. Orthotropic and thickness-dependent Young’s moduli and Poisson’s ratios were determined via quasi-static tensile tests. Thereof, material models were generated and implemented in a property mapping routine for finite element models. Additionally, a framework for stochastic finite element analysis was set up for the consideration of scatter in material properties. For validation, thin-walled parts on sub-component level were fabricated and tested in quasi-static three-point bending experiments. Elastic parameters showed considerable anisotropy, thickness dependency and scatter. A comparison of the predicted forces with experimentally evaluated reaction forces disclosed substantially improved accuracy when utilizing the novel inhomogeneous approach instead of conventional homogeneous approaches. Furthermore, the variability observed in the structural response of loaded parts could be reproduced by the stochastic simulations.     

Influence of phase transformation on the torsional and bending properties of nickel-titanium rotary endodontic instruments

AIM: To investigate the relationship between the functional properties and the phase transformation of nickel-titanium endodontic instruments. METHODOLOGY: Five types of rotary nickel-titanium endodontic instruments with a 0.30 mm diameter tip (EndoWave, HERO 642, K3, ProFile.06, and ProTaper) were selected to investigate torsional and bending properties, and phase transformation behaviour. A torsional test was performed according to ISO publication 3630-1, and maximum torque and angular deflection at fracture were measured. Bending load of the instruments was measured in a cantilever-bending test at 37 degrees C with the maximum deflection of 4.0 mm. A stainless steel K-file was used for reference. Phase transformation behaviour was measured by differential scanning calorimetry (DSC). From the DSC curve, transformation temperatures were calculated. Data were analysed by anova and the Tukey-Kramer's test. RESULTS: The maximum torsional torque values of HERO, K3 and ProTaper were significantly higher (P < 0.05) than those of EndoWave, ProFile and K-file. The K-files had the lowest torque value. Angular deflection at fracture was significantly higher (P < 0.05) for K-files than that for any nickel-titanium instrument. The bending load values of HERO and K3 were significantly higher (P < 0.05) than those of EndoWave, ProFile, ProTaper and K-file. The K-files had the lowest load value, although residual deflection remained. The transformation temperatures of HERO and K3 were significantly lower (P < 0.05) than those of EndoWave, ProFile and ProTaper. CONCLUSIONS: The functional properties of nickel-titanium endodontic instruments, especially their flexible bending load level, were closely related to the transformation behaviour of the alloys.