穿下颌种植体周围骨界面应力分析

目的：探讨穿下颌种植体数目，钛金基板对穿通下颌骨种植体周围骨界面应力分布的影响。方法：本研究采用ANsys5．7三维有限元分析软件对经CT扫描后的无牙下颌骨进行建模分析，得出不同条件下穿下颌种植体（二单位、四单位，加与未加基板）周围骨界面颈部骨皮质，松质骨上1／3，松质骨中1／3，松质骨下1／3，下颌骨下缘骨皮质及种植体尖部的最大拉应力，最大压应力，位移值。结果以统计直方图，应力分布图等表示。结果：二单位加连接杆加基板穿下颌种植受唇舌向加载时，最大拉应力及压应力均表现在颈部骨皮质的唇侧及舌侧，受近远中向加载时，最大拉应力表现在左侧种植体左侧的骨皮质颈部，最大压应力表现在右侧种植体的右侧骨皮质颈部，受垂直向加载时，最大拉应力表现在种植体的尖部，最大压应力表现在颈部骨皮质及种植体尖部。位移分布规律与应力分布相对应。四单位加连接杆加基板穿下颌种植在受各向加载时，应力分布及位移分布规律基本同二单位式，但相对的应力值较小。未加基板穿下颌种植在受各向加载时，其应力分布规律与加基板者基本相似，但加基板种植的根部应力小于未加基板者，而种植体尖部应力较大。结论：增加穿通式种植体的数目，可以减小种植体周颈部密质骨的最大应力值，加基板多个穿通式种植可以分散下颌骨下缘应力集中。提示：在进行穿通式种植覆盖义齿修复的临床应用中，应考虑增加种植体的数目并在下颌骨下缘使用基板连接。

The Stress Analysis of the Bone Interface Around Transmandibular Dental Implants

Objective: To explore the influence of the number of transimandibular implants and base-plate of titanium on the stress distribution patterns at the bone interface around the transmandibular implants.Methods: An edentulous mandible was scanned by CT to establish the model with the ANsys 5.7 software of three-dimention finite element analysis.The implants were loaded vertically along the long axis by 160N force and horizontally with 20N force directed buccal- lingual and distal-medial.The maximum compressive and tensil stress and of displacement at the area of neck of corticle bone,the area of upper1/3,middle1/3 and lower1/3 of marrow bone of the bone interface around the transmandibular implants ,and apex of implants were countted by the ANsys 5.7 software with three-dimention finite element analysis. The results were shown by histogram and stress distribution chart .Results: The maximum compressive and tensil stress at the bone interface around the transmandibular implants of tow unit with connected bar and base-plate loaded equably were located mostly on the cervical labial and lingual part of cortical bone.When loaded equably by medial-distal(left to right) stress, the maximum tensil stress appeared at the left cortical neck of the left implant,the maximum compressive stress appeared at the rigth cortical neck of the right implant. The maximum tensil stress appeared at the apex of the implants,the maximum compressive stress appeared at the neck of cortical and apex of implants when implants were loaded equably by vertical force.The maximum stress appeared at the cortical neck of both the loading implant and the unloading implant when loaded intensively, however, the stress in the unloading implant is less than which in the loading implant significantly.The characteristic of displacement distribution is corespond with that of stress distribution.Compared with the two-unit transmandibular, The characteristic of the stress and motion distribution of the four-unit transmandibular with connected bar and base-plate is correspond with but less than that of the two-unit one whenever loaded from different direction.The characteristic of the stress distribution of theimplant without base-plate is correspond with that of implant with base-plate,but the stress at the sharp point of apex of the four-unit implant with base-plate is larger and the stress at the neck or apex is less than that of implant without base-plate.Conclusions: The maximum stress at the area of cortical bone around the neck of the implant decrease with the increasing the number of the transmandibular implants or application of connecting base-plate, However the stress around the apex of the implant will be increased and the stress on the lower margin of the mandible will be decrease with the use of connecting base-plate. The results imply that increasing the mumber of implant and the application of connecting base-plate may be good clinic method for a successful shows that in the clinic use of the transmandibular implant, the number of the implants should be increased and the implants should be connected with baseplate at the margin of mandible.