背景:随着无牙颌修复需求增加,“All-on-4”技术被广泛应用。种植体与天然牙的载荷传递方式不同,三维有限元分析可研究功能载荷作用下种植体及周围骨组织的应力分布,并在此基础上为寻找适合的种植体材料、优化种植体的几何结构、设计临...背景:随着无牙颌修复需求增加,“All-on-4”技术被广泛应用。种植体与天然牙的载荷传递方式不同,三维有限元分析可研究功能载荷作用下种植体及周围骨组织的应力分布,并在此基础上为寻找适合的种植体材料、优化种植体的几何结构、设计临床手术方案提供了研究方法。目的:对三维有限元分析法在“All-on-4”技术方面的相关研究作一综述。方法:检索中国知网和PubMed数据库2003-2023年相关文献,英文检索词为“Finite Element Method,All-on-4,edentulous,Biomechanics”,中文检索词为“有限元,All-on-4,无牙颌,生物力学”,根据纳入排除标准筛选符合标准的文献,最终纳入65篇文献进行综述。结果与结论:①对水平骨量不足的情况,研究者们可以选择应用窄直径种植体,但需要注意悬臂的存在对应力分布的影响,降低失败的风险。②“All-on-4”概念通过倾斜远中种植体的方法,减少骨的应力分布,但在不同的颌骨类型中,远中种植体倾斜的理想角度还需要进一步的研究。③悬臂的存在会增加种植失败的风险,将悬臂长度/AP距(CL/AP)的比值控制在0.9时,有助于减少机械并发症的发生。④用弹性模量较低的材料制作支架时,支架自身的应力较小,但会增加种植体、中央螺丝、基台及种植体周围骨组织的应力,相反使用弹性模量较大的材料,会降低修复体组件和种植体周围骨组织的应力,但支架本身的应力较高。⑤“All-on-4”概念可以实现较好的力学平衡,但需结合患者自身的具体情况制定一个长期有效的治疗方案。⑥合理的咬合设计是影响种植治疗成功的关键,尖牙引导牙合和组牙功能牙合在修复体的寿命方面无差异。然而,影响咬合设计的原因有很多,未来还需要进一步的体外实验以及大量临床研究来探索“All-on-4”理想的咬合设计。展开更多
The stability of buildings on the surface will be influenced by underground mining. For the purposes of safe mining and buildings protecting around mining area, the rock and sod distortion should be forecasted. By usi...The stability of buildings on the surface will be influenced by underground mining. For the purposes of safe mining and buildings protecting around mining area, the rock and sod distortion should be forecasted. By using the results of the elastic-finite-element method simulation, we can calculate the tilting, horizontal deformation and curvature of the surface and the strata. Wushan Copper Mine was taken as an example to analyze the reasons of accident and beyond standard limit, and the influence on the safety of the packed volumn.展开更多
In this article, research was conducted to improve Linter machines that remove short fibers remaining in ginned cotton seeds at cotton ginneries. The study examined the effect of changing the dimensions of the brush d...In this article, research was conducted to improve Linter machines that remove short fibers remaining in ginned cotton seeds at cotton ginneries. The study examined the effect of changing the dimensions of the brush drum, guide and mesh surface in the cleaning device proposed for the linting machine on the movement of the peg and the cleaning efficiency, and the highest level of efficiency in separating impurities from the peg was determined. During the study, the main factors influencing the effective operation of the improved linting machine were identified, the limits of their values were determined, and studies were carried out using the mathematical modeling method. As a result, at the values of the given coefficients, efficient operation of the improved linting machine was observed, that is, the lint cleaning efficiency reached 55.1%.展开更多
文摘背景:随着无牙颌修复需求增加,“All-on-4”技术被广泛应用。种植体与天然牙的载荷传递方式不同,三维有限元分析可研究功能载荷作用下种植体及周围骨组织的应力分布,并在此基础上为寻找适合的种植体材料、优化种植体的几何结构、设计临床手术方案提供了研究方法。目的:对三维有限元分析法在“All-on-4”技术方面的相关研究作一综述。方法:检索中国知网和PubMed数据库2003-2023年相关文献,英文检索词为“Finite Element Method,All-on-4,edentulous,Biomechanics”,中文检索词为“有限元,All-on-4,无牙颌,生物力学”,根据纳入排除标准筛选符合标准的文献,最终纳入65篇文献进行综述。结果与结论:①对水平骨量不足的情况,研究者们可以选择应用窄直径种植体,但需要注意悬臂的存在对应力分布的影响,降低失败的风险。②“All-on-4”概念通过倾斜远中种植体的方法,减少骨的应力分布,但在不同的颌骨类型中,远中种植体倾斜的理想角度还需要进一步的研究。③悬臂的存在会增加种植失败的风险,将悬臂长度/AP距(CL/AP)的比值控制在0.9时,有助于减少机械并发症的发生。④用弹性模量较低的材料制作支架时,支架自身的应力较小,但会增加种植体、中央螺丝、基台及种植体周围骨组织的应力,相反使用弹性模量较大的材料,会降低修复体组件和种植体周围骨组织的应力,但支架本身的应力较高。⑤“All-on-4”概念可以实现较好的力学平衡,但需结合患者自身的具体情况制定一个长期有效的治疗方案。⑥合理的咬合设计是影响种植治疗成功的关键,尖牙引导牙合和组牙功能牙合在修复体的寿命方面无差异。然而,影响咬合设计的原因有很多,未来还需要进一步的体外实验以及大量临床研究来探索“All-on-4”理想的咬合设计。
文摘The stability of buildings on the surface will be influenced by underground mining. For the purposes of safe mining and buildings protecting around mining area, the rock and sod distortion should be forecasted. By using the results of the elastic-finite-element method simulation, we can calculate the tilting, horizontal deformation and curvature of the surface and the strata. Wushan Copper Mine was taken as an example to analyze the reasons of accident and beyond standard limit, and the influence on the safety of the packed volumn.
文摘In this article, research was conducted to improve Linter machines that remove short fibers remaining in ginned cotton seeds at cotton ginneries. The study examined the effect of changing the dimensions of the brush drum, guide and mesh surface in the cleaning device proposed for the linting machine on the movement of the peg and the cleaning efficiency, and the highest level of efficiency in separating impurities from the peg was determined. During the study, the main factors influencing the effective operation of the improved linting machine were identified, the limits of their values were determined, and studies were carried out using the mathematical modeling method. As a result, at the values of the given coefficients, efficient operation of the improved linting machine was observed, that is, the lint cleaning efficiency reached 55.1%.
