三维有限元方法分析“All-on-4”技术的生物力学特征

Biomechanical characteristics of“All-on-4”concept analyzed by three-dimensional finite element method

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。

BACKGROUND:With the increasing demand for edentulous jaw restoration,“All-on-4”concept is widely used.The load transfer mode of implant is different from that of natural tooth.The three-dimensional finite element analysis can study the stress distribution of implants and surrounding bone tissues under functional loading.On this basis,it provides research methods for finding suitable implant materials,optimizing implant geometry,and designing clinical surgical protocols.OBJECTIVE:To review researches related to three-dimensional finite element analysis in“All-on-4”concept.METHODS:Relevant literature published from 2003 to 2023 was searched in CNKI and PubMed databases with the search terms of“finite element method;All-on-4;edentulous;biomechanics”in Chinese and English.Finally,65 articles were included for review.RESULTS AND CONCLUSION:(1)In the case of insufficient horizontal bone mass,we can choose to apply narrow diameter implants,but we need to pay attention to the effect of the presence of the cantilever on the stress distribution and reduce the risk of failure.(2)The“All-on-4”concept reduces the stress distribution of bone by tilting the distal middle implant,but the ideal angle of the distal implant tilt in different jaw types requires further study.(3)The presence of cantilevers increases the risk of implant failure,and keeping the cantilever length/AP distance ratio at 0.9 helps to minimize mechanical complications.(4)When a framework is made of a material with a lower elastic modulus,the stress on the framework itself will be smaller,but it will increase the stress on the implant,prosthetic screw,abutment and peri-implant bone.On the contrary,when a material with a higher elastic modulus is used,it can reduce the stress on the prosthetic components,implants and peri-implant bone in the restoration,but the stress on the framework itself is higher.(5)The“All-on-4”concept allows for a better mechanistic balance,but requires the development of a long-term,effective treatment program that is tailored to the patient’s specific situation.(6)Proper occlusal scheme is the key to the success of implant treatment,and there is no difference between canine-guide occlusion and group function occlusion in terms of the longevity of the restoration.However,there are many factors that influence occlusal design,and further in vitro experiments as well as a number of clinical studies are needed to explore the ideal occlusal design of the“All-on-4”.