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Abstracts


在外傷力學的研究當中,由於動態撞擊力量作用的時間,通常只有l-20毫秒(ms),這樣的瞬時動態力量除了會造成撞擊物的整體運動(rigid body motion),也會使得撞擊物的共振頻率受激發,並同時伴隨著振動發生。由於動態特性分析是分析外傷機轉的方法之一,因此本研究使用模態測試法搭配有限元素分析,以瞭解下顎骨在受外力撞擊時可能產生的動態反應,藉以瞭解下顎骨的振動與下顎骨骨折之間的關係。實驗方法上,在十個已乾燥的下顎骨上參考骨折好發的位置規劃7個測試點進行體外共振頻率與振動模態的量測,量測得乾燥的下顎骨的振動頻率平均值為578.6±11.67Hz,與所建構的三維下顎骨有限元素模型計算的頻率567.3Hz相差僅1.9%, 利用驗證後之模型模擬正常下顎骨的共振頻率為501.4Hz,同時發現當振動發生時,下顎髁與下顎聯合附近將產生較大的振幅與較高的變形,在下顎骨體中點則產生較小的振幅與較低的變形。從此研究結果可以發現,當下顎骨受外力撞擊而產生振動時,其共振頻率與振動模態不會因撞擊位置與撞擊力大小而改變,而因撞擊引發振動所產生的高變形位置,與臨床觀察骨折位置相吻合,此結果表示除了下顎骨本身的形狀,結構,及骨骼的材料性質差異會對下顎骨折造成影響外,受撞擊時下顎骨的振動特性也扮演了重要的角色。

Parallel abstracts


Since dynamic response analysis is an important basis for examining the mechanism of trauma, in order to evaluate the possibility of vibrational assessment of the mandible, in this study, resonance frequency (RF) was carried out as a parameter for assessing the relationship between the dynamic behavior of the mandible and mandibular fractures. Ten mandibles positioned on a soft cushion to provide free-free boundary conditions were tested using a model testing method. Each mandible was triggered to vibrate by an impact hammer at 7 points which were designated by clinical fracture sites. Then the RE values and vibrational mode were recorded. Our results showed that the RE values fell between 560 and 598 Hz with a mean cit 578.6±11.67Hz. Then, the RF value of the finite element (FE) model was calculated as 567.3 Hz which was only 1.9% smaller than the results of the in vitro test. That is, the EE model was validated as a credible model for dynamic response analysis. The RE value of a fresh mandible was then calculated as 501.4 Hz using the FE model. The result also indicated that the middle area of the mandibular body is probably a nodal position where bone fracture is less likely to occur. On the contrary, the greatest amplitudes were found in the parasymphysis of the mandible and in the subcondyle region where bone fractures are prone to occur The results obtained from this study provide insights into the basic dynamic properties of the human mandible.

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