| 摘要: | 近年來，矯正釘植入為齒顎矯正最常搭配的治療方式之一。矯正釘植入的失敗率約為20%。手術失敗的原因很多，最主要是穩定度。除了患者本身的問題外，矯正釘的設計、材質、植入角度及受力方向都與穩定度有關。本研究將針對影響矯正釘植體穩定度的一些重要因素作探討。在臨床上，矯正釘的植入角度及受力方式非常多元，本研究模擬分析時分成三種植入角度(90°、60°、30°)，搭配8種不同的受力方向。骨頭的材料性質分別設定為等向性或正交性，以進行比較。矯正釘植入後便會立即開始使用，矯正釘與骨頭之結合可分成兩個階段。第一階段為剛植入時是屬於未骨整合狀態，隨後由於骨頭隨時間逐漸生長到植體上，會進入第二階段骨整合狀態。在判別植體穩定度的指標方面則採用矯正釘及骨頭的位移、等效應力及等效應變。此外，本研究進行矯正釘植體的側向彎曲模擬分析及實驗，瞭解植體的勁度，並提出人造骨白化現象的分析模型修正方式。
研究結果顯示，矯正釘的位移在植入角度為90°時最大，在30°時最小。矯正釘受力方向要避免與植入角度垂直，否則容易造成矯正釘位移及骨頭最大主應力過大，導致穩定度下降。骨頭採用正交性材料性質的結果在趨勢上是比較接近實際狀況，採用等向性材料性質的結果會被低估。在骨整合狀態下，骨頭的最大主應力比較大，但並沒有超過抗拉強度，不會造成骨頭破壞。在未骨整合狀態下，矯正釘的位移比較大，骨頭的等效應變超過了3000 με，會降低骨整合的程度，說明此狀態穩定度較差。矯正釘與骨頭受力反應之對稱性，此現象可用以簡化後續的模擬分析，只需要分析受力方向0°~180°，即可推測受力方向180°~360°的結果。若不考慮人造骨在植入矯正釘時產生的白化現象，則矯正釘植體勁度的模擬值明顯大於實驗值。本研究提出修正模型，調整模型的白化層區域大小及降低此區的楊氏模數，可使模擬分析的勁度值與實驗值相近。
;In recent years, orthodontic miniscrew implantation is one of the most commonly used methods of orthodontic treatment. The failure rate of miniscrew implantation is about 20%. There are many reasons for failure, the most important being stability. In addition to the patient′s own problems, the design, material, implant angle and loading direction of the miniscrew are related to the stability. In this study, some important factors affecting the stability of miniscrew implants were discussed. Clinically, the implantation angle and loading mode of the miniscrew are very diverse. The simulation analysis in this study was divided into three implant angles (90°, 60° and 30°), with eight different loading directions. The material properties of the bones were set as isotropic or orthogonality, respectively, for comparison. Immediately after the insertion of the miniscrew, the fixation of the miniscrew to the bone can be divided into two stages. The first stage is the state of non-osseointegration at the time of implantation, and then the bone gradually grows into the implant over time and enters the second stage of osseointegration. The index of stability of implant was the deformation, equivalent stress and equivalent strain of miniscrew and bone. In addition, the lateral bending simulation analysis and experiment of the miniscrew implant were carried out to understand the stiffness of the implant, and the method of modifying the analytical model of artificial bone albinism was proposed.
The results showed that the deformation of the miniscrew was maximum at the implantation angle of 90° and minimum at 30°. The loading direction of the miniscrew should not be perpendicular to the implantation angle, otherwise it is easy to cause larger deformation of the miniscrew and larger maximum principal stress of the bone, resulting in the decrease of stability. The results of orthogonality in bone properties tend to be close to reality, while those of isotropy are underestimated. The displacement of the miniscrew is relatively large in the non-osseointegration state. In the state of osseointegration, the maximum principal stress of bone is relatively large. It shows that the stability of the miniscrew is poor without osseointegration. The simulated values of implant stiffness were significantly higher than the experimental values without considering the influence of bone autogenous layer. In this study, a modified model was proposed to adjust the size of the whitening area of the model and reduce the Young′s modulus of this area, so as to make the simulated stiffness value close to the experimental value. |
