| 摘要: | 摘要
本論文之研究主要為找尋骨整合產生顯著共振頻率之方向以協助骨整合優劣之評估。顯著共振頻率的方向可以提供共振頻率分析的相關資訊。研究中探討植體周圍的自然牙齒與介面組織對於植體的最大共振頻率值的影響。研究中使用ANSYS Workbench Inc. 軟體進行模態分析及諧波響應分析。其中，模態分析可獲得自然頻率與模態結構，而諧波響應分析給定共振頻率之頻譜，用以判斷出最高之共振頻率值。在頻譜上得到最高共振頻率值後，可繪出雷達圖顯示下顎骨模型的共振方向趨勢線。整體研究過程是基於動態結構理論及有限元素法進行分析。
本實驗利用懸臂樑原理來分析植體結構並解釋在主要案例(下顎骨模型)中發生的現象。在懸臂量圓形與方型剖面分析中，圓形橫切面的結果顯示在不同激振方向有相同的共振頻率，反之方型橫切面也是。使用的人造骨塊分別為結表皮層厚度1mm的兩塊及2mm的一塊，其中1mm的人造骨塊又可分為有含介面組織及不含介面組織，而2mm的人工骨塊則不含介面組織。1mm的人造骨塊量測結果得知，不含介面組織的人工骨塊與植牙體結合硬度大於含介面介質的人工骨塊；2mm的人工骨塊將量測方向分為短軸 (頰舌buccal-lingual, BL) 方向與長軸 (近遠心mesial-distal, MD) 方向，且發現短軸方向之頻率高於長軸。
在本研究中，依據植體兩側有無牙齒將下顎骨模型分成三種型式。模型一為兩側皆有牙齒；模型二為兩側皆無牙齒；模型三為僅一側有牙齒。介面組織依骨整合程度採用三種楊氏係數 (即2, 25，137 MPa) ，並分別應用到上述三類下顎骨模型中作分析。結果顯示，剛性2 MPa的介面組織在不同模態與各種激振方向，都產生幾乎相同的共振頻率，而剛性25 MPa與137 MPa的介面組織在不同的激振方向，共振頻率則有明顯差異。
關鍵字: 顯著共振方向,共振頻率,模型結構,共振頻率分析,有限元素分析。
;Abstract
The work within this thesis investigates the significant direction of resonance frequency for osseointegration assessment. The significant directions of resonance frequencies give information to support the resonance frequency analysis. This study discusses about the influence of natural teeth and interface tissue as the structures around dental implantation to the resonance frequencies. The analysis performed in numerical by using modal analysis and harmonic response analysis from ANSYS Workbench Software Inc. Modal analysis determine the natural frequencies and mode shapes of a structure, whereas harmonic response analysis determine the resonance frequencies spectrum. After the highest resonance frequency obtained on the spectrum, it plotted into the radar graph and see the direction trend line in certain mandible models. The analysis based on the theories of dynamic structure by using finite element method.
The analysis of cantilever beam and artificial bone block were performed as an initial analysis to explain phenomena that occur in the main case (mandible models). Cantilever beam used two different types of cross-sections, circular and rectangular. The resonance frequency results of circular cross-section were all the same in different excitation directions, vice versa for rectangular cross-section. Artificial bone block was modeled with cortical thickness without-interface tissue, 2mm. The resonance frequency value in buccal-lingual (BL) direction is higher than mesial-distal (MD) direction. The other artificial bone blocks were modeled in two different conditions of interface tissue with cortical thickness, 1mm. The result showed that the behavior of a physical structure without-interface tissue is stiffer than with-interface tissue but the mode shapes remain the same.
In this thesis, the mandible was varied into three different models, based on position of teeth beside implant structure with different interface tissue stiffness. Model-1 was mandible with teeth beside implant structure; Model-2 was mandible without teeth beside implant structure; Model-3 was the mandible with teeth only on one side of implant structure. Interface tissue was varied into three different values of Young’s modulus (2, 25, 137 MPa) and it applied on each mandible models. The result showed the lower stiffness (2MPa) had almost the same resonance frequency in every direction, vice versa for higher stiffness (25, 137MPa) which had a significant direction in different excitation load directions.
Keywords: significant direction, resonance frequencies (RFs), mode shape, resonance frequency analysis (RFA), finite element analysis (FEA). |
