不同截面設計之鎳鈦旋轉器械之力學分析

Mechanical analysis of different cross-section designs for Ni-Ti rotary instruments

童翌萱(Yi-Shiuan Tung)

指導教授 ： ARRAY(0xc644f38)

中原大學/工學院/醫學工程研究所/碩士(2009年)

https://doi.org/10.6840/CYCU.2009.00781

摘要

雖然鎳鈦旋轉器械至今已被廣泛使用，但器械之斷裂機制仍然是製備根管最大的問題所在。過去本研究團隊已驗證實驗與有限元素分析有一致性，也已提出較佳的螺紋設計來達到分段切削之功效，故本研究以有限元素分析為基礎來提出較佳之截面設計，並評估不同截面設計之鎳鈦旋轉器械其力學行為。主要探討三種不同截面參數之設計，其中包括(a)與外接圓接點、(b)導平面寬度以及(c)三螺旋角度。分別給予器械之相同彎曲程度與扭轉度數之負載邊界條件，以評估於彎曲分析與扭轉分析中，各項參數變異對器械本身力學行為之影響。由彎曲分析結果發現，當減少與外接圓接點數，器械與根管壁之接觸面積有降低的趨勢；當導平面寬度及三螺旋角度增加，皆會導致器械之凹槽深度增加，進而減少器械表面之最大盟麥斯應力；多變化螺距之器械其彎曲應力較固定螺距低。由扭轉分析結果發現，三螺旋角度之截面設計以及螺距越小之器械，具有較大之彈性變形區域且勁度較低。透過本研究之電腦輔助工程分析，建議較佳之鎳鈦旋轉器械截面設計應為(1)具有三螺旋角度之設計；(2)與外接圓接點數為兩點，以降低器械與根管壁之接觸面積；(3)具有導平面與較小的核直徑，來增加器械彎曲彈性。透過上述器械改良之參數，可以減少器械彎曲斷裂及靜態扭轉斷裂之風險。

關鍵字

截面形狀 ； 螺距 ； 鎳鈦旋轉器械 ； 有限元素法

並列摘要

Recently, Nickel-Titanium (NiTi) rotary instruments have been widely used. However, instrument fracture is still a critical issue during canal preparation. From our previous studies, there is a high correlation between our experiments and finite element analysis. It is confirmed that the finite element analysis is a useful tool for the evaluation of rotary instruments. The design concept of the thread for the files is the cutting by stage and the alteration major cutting region. Thus, the goal of this study was to investigate the influence of three different cross-sectional design parameters on the mechanics of NiTi rotary instrument. The selected parameters are: (a) the number of points in contact with the circumferential circle of the file, (b) the width of radial land, (c) the angle of triple helix. The loading and boundary conditions were applied for bending and torsional simulations. In the bending simulation, when the number of points in contact with the circumferential circle was decreased, the contact area was reduced. When the width of the radial land and the angle of triple helix were increased, it would lead to a deeper flute and the maximum von Mises stress of the file is decreased. The stress of the file with various pitches is lower than that of files with uniform pitch. In the torsional simulation, the file with triple helix has longer region of elastic deformation and more flexible. When the pitch length of the file was reduced, the maximum von Mises stress was decreased and the region of elastic deformation for the rotary instrument was increased. According to the results, a better design of cross-sectional area for NiTi rotary instrument may be suggested: (1) the angle of the triple-helix would increase the flexibility; (2) two contact points with the circumferential circle may cause less contact area between the instrument and root canal; (3) larger radial land and smaller core diameter may increase the flexibility of the file. The risks of bending fracture and static torsional fractures may be reduced when the above design suggestions were adopted.

並列關鍵字

finite element analysis ； NiTi rotary instrument ； pitch ； cross-sectional design

參考文獻

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