不同下颌骨密度对4颗种植体支持Locator式覆盖义齿的有限元生物力学分析

Finite element biomechanical analysis of various bone mineral densities on edentulous mandibular four-implant-supported overdentures fixed using Locator attachments

背景:四颗种植体支持的覆盖义齿是下颌牙列缺失的常用治疗方法,而下颌骨的骨密度会影响生物力学结果、种植体支持修复体的稳定和周围组织的健康,进而影响长期治疗效果。目的:通过三维有限元分析评价骨密度对使用Locator附着体固定的四颗种植体支持的无牙下颌覆盖义齿应力分布的影响。方法:选择4例无全身系统性疾病的男性下颌牙列缺失患者,建立三维有限元模型,4例患者均已安装四颗种植体支持的Locator式下颌种植覆盖义齿,基于其锥形束计算机断层扫描数据建立基于4种不同骨类型(类型1、2、3和4,对应骨松质的弹性模量依次为9.5,5.5,1.6,0.69GPa)的4个无牙下颌骨模型(M1、M2、M3和M4),均通过4颗种植体支持的Locator附着体种植覆盖义齿修复。在右下第一磨牙上施加3个方向120 N的力后,测量骨密质、骨松质和种植体上的von Mises应力。结果与结论:(1)对于骨密质(或骨松质),在模型M1、M2、M3和M4的种植体周围区域出现了最高的应力集中,主要在远端种植体的右侧(加载区域),在3种载荷条件下,骨密质最大vonMises应力从模型M1逐渐增加到模型M4,骨松质的最大vonMises应力从模型M4逐渐增加到模型M1。(2)在种植体颈部、种植体和Locator附着体之间的接触区域观察到最高的应力集中,尤其是在远端种植体的加载侧,最高应力值出现在模型M4,最低值出现在模型M1。(3)结果表明,骨密度高的1型和2型骨最适合下颌种植覆盖义齿,骨密度低的4型骨可能会增加生物和机械并发症的风险。

BACKGROUND:The four-implant-supported overdenture is a commonly used treatment for the edentulous mandibular patient,while the bone mineral density affects the biomechanical outcome,the stability of the implant-supported prostheses,and the health of surrounding tissue,thus influences the long-term therapeutic effect.OBJECTIVE:To evaluate the influence of bone mineral density on stress distribution of edentulous mandibular four-implant-supported overdentures via Locator attachments through a three-dimensional finite element analysis.METHODS:Four edentulous mandibular male patients without systemic disease,who had worn four-implant-supported overdentures via Locator attachments,were selected to establish three-dimensional finite element models.Four edentulous mandible models(M1,M2,M3,and M4)made of four different bone types(type 1,2,3,and 4,corresponding to the order of cancellous bone whose modulus of elasticity is 9.5,5.5,1.6,0.69 GPa)and embedded with four implants in the interforaminal region were established based on cone beam computerized tomography data.The mandibles were restored using four-implantsupported overdentures via Locator attachments.After 3 forces(F1,F2,and F3)of 120 N magnitudes from various directions applied on the right lower first molar,the von Mises stresses on the cortical and cancellous bones and the implants were determined.RESULTS AND CONCLUSION:(1)For the cortical bone or the cancellous bone,stress concentrations were found on the peri-implant area of models(M1,M2,M3,and M4),particularly on the loading side in all the models.The maximum von Mises stress increased progressively for the cortical bone and implants,but decreased progressively for the cancellous bone from type 1(M1)to type 4(M4)bones under three loading conditions.(2)For the implant,stress concentrations were found at the necks of implants and at the contact zones between implants and the Locator abutments,especially on the loading side.The highest maximum von Mises stress was found on M4,while the lowest maximum von Mises stress was found on M1.(3)Results indicate that compact bones(types 1 and 2)are the most suitable bones for edentulous mandibular implant-supported overdentures.Poor bone mineral density(type 4 bone)may increase the risk of biological and mechanical failures.