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目的基于三维有限元的方法,分析下颌第一磨牙即刻种植即刻负重时,不同牙根形态对种植体及其周围骨界面生物力学分布的影响。方法用两组牙根解剖形态不同的下颌第一磨牙建立下颌第一磨牙即刻种植即刻负重的三维有限元模型。两组牙齿分别为牙根分叉角度(interradicular angle,IA)不同组、根柱高度(root trunk height,RT)不同组。每个模型以100N的力分别轴向(冠根向)、斜向舌侧45°、舌颊向、近远中向加载,应用ANSYS软件分析种植体的位移及种植体骨界面的应力值。结果成功建立了下颌第一磨牙即刻种植即刻负重的三维有限元模型;有限元分析结果显示:随根分叉角度增大,根柱高度变短,各加载方向上种植体的最大位移、种植体骨界面的最大应力都呈下降趋势。种植体的最大位移中最大值在近远中向加载RT=5.3 mm时出现达0.461 mm,最小值出现在轴向加载IA=42°时,为0.008 mm。骨界面的应力集中于颈部皮质骨及螺纹接触部位较薄弱的松质骨上。骨界面的应力最大值在近远中向加载IA=10°时出现,最小值在轴向加载IA=18°时出现。结论不同牙根解剖形态对下颌第一磨牙即刻种植即刻负重种植体骨结合的形成有一定影响,使牙根间隔骨量减少的解剖因素增加了第一磨牙即刻种植即刻负重失败的风险。
OBJECTIVE: To analyze the effect of different root morphology on the biomechanical distribution of the implant and the surrounding bone interface of the mandibular first molar immediately after immediate implantation based on the three-dimensional finite element method. Methods Three-dimensional finite element model of immediate load-bearing immediate implants of mandibular first molar was established by using two groups of mandibular first molar with different root anatomy. The two groups of teeth were different groups of interradicular angle (IA) and different groups of root trunk height (RT). Each model was loaded with force of 100 N in the axial direction (crown root), oblique lingual side 45 °, buccal direction, mesial and proximal directions. The stress of implant displacement and implant bone interface were analyzed by ANSYS software. Results The immediate three-dimensional finite element model of immediate mandibular first molar was established immediately. The results of finite element analysis showed that with the increase of root bifurcation, the height of root column became shorter, the maximum displacement of implant in each loading direction, The maximum stress of the bone interface showed a downward trend. The largest maximum displacement of the implant appeared up to 0.461 mm in the near-mid-range to RT = 5.3 mm at RT and 0.008 mm in the minimum at IA = 42 ° in the axial direction. The stress of the bone interface is concentrated on the cortical bone of the neck and the weaker cancellous bone at the contact area of the thread. The maximal stress of the bone interface appears in the near-mid-range at IA = 10 ° and the minimum at IA = 18 ° in the axial direction. Conclusion Different anatomical forms of root have some effect on the formation of osseointegration of immediate load-bearing implants with immediate mandibular first molars. The anatomical factors that reduce the amount of osseous septum increases the risk of failure of first molars immediate implants.