鎳鈦旋轉器械機械性質探討及大尺寸雙光子聚合製程之研究

The quantitative analysis of mechanical properties in endodontic Ni-Ti drilling needles, study of large fabrication using two-photon induced polymerization

劉昭沅(Chao-Yuan Liu)

指導教授 ： 單秋成

共同指導教授 ： Patrice. Baldeck(Patrice. Baldeck)

國立臺灣大學/工學院/機械工程學研究所/博士(2014年)

https://doi.org/10.6342/NTU.2014.10092

摘要

牙科的急診約三分之一的病例為牙髓及根尖相關疾病，而百分之九十的牙科疼痛急症是因根管問題所引起，顯見根管治療在牙科領域上的重要性。治療所使用的旋轉銼針，在開擴髓腔取出壞死神經時，偶有發生疲勞斷裂的事件，殘餘的斷件，往往不易取出而成為病人的困擾，因此如何避免與預警銼針斷裂已成為近年來的研究方向。
研究分為兩部分，第一部份建立一標準測試方法，模擬根管彎道參數，提出改善疲勞壽命和材料強度一系列措施並且利用光纖感測器精確、靈敏且易於安裝的優點，置於牙科手持器上，監測銼針於髓腔內運轉產生的振動訊號，經傅立葉轉換得到銼針運轉的特徵頻率在斷裂前的強度變化開發根管銼針運轉監測系統。此外，數據顯示，不同種類的熱處理和往復運轉的方式皆會使根管銼針疲勞壽命有所提升，此結果與材料內部之晶相組成和器械所承受的最大張應力降低有關。然而，鎳鈦合金材料內部麻田散鐵含量的增加在利於疲勞壽命改善的同時卻降低了切削效率。為此，研究上也利用超深冷技術改善切削性質，最終提出疲勞壽命和切削效率的最佳化方案。
第二部份為利用雙光子聚合製程製作高解析度的大型構件。於法國傅立葉大學LiPhy實驗室，有別於傳統雙光子聚合製程使用壓電控制器在產品尺寸上的侷限，使用線速度為5mm/sec的X-Y控制平台和高生物相容性的Ormocer樹酯製作達800微米細胞腳手架和1.2釐米長的高分子銼針。為提升雙光子立體顯影的產品品質，本研究亦運用PSF軟體提出雷射聚焦的功率校正方法，在雙光子立體顯影的製作過程中，由於物鏡的不同，聚焦的形狀也有所區別，這使得當聚焦平面上升時，需要更多的雷射功率來維持相同的紡梭狀結構尺寸，為校正該缺陷，本文提出校正功率的數學式，該推導來自於修正顯影平面上的曝光條件使其等同初始平面之值。

關鍵字

鎳鈦旋轉器械 ； 根管彎道參數 ； 光纖感測器 ； 特徵頻率 ； 往復運轉 ； 麻田散鐵 ； 超深冷技術 ； 大尺寸雙光子聚合結構 ； 細胞腳手架 ； 雷射功率校正

並列摘要

One third of dental emergencies and a high percentage of toothaches are endodontics related. Rotary instruments employed in endodontic treatment may break inside the root canal due to material fatigue. Once broken, extracting the fractured part from the canal is a difficult job and is annoying to both the patient and the dentist. Therefore, warning of an imminent fracture during clinical use or developing good strategies to increase its mechanical properties will be a great help to avoid medical/ legal complications.
The research is studied from two parts. The first part established a standard testing platform, simulating several root canal parameters, proposing a series of strategies to improve the fatigue life and material’s mechanical properties. Also, a monitoring system employing Fiber Bragg Grating (FBG) sensors has been attempted. The reason of using FBG is its small size which is very promising in integrating with the handpiece of the endodontic equipment. In the current work, by picking up and analyzing the stress wave through Fast Fourier Transform (FFT), we can reveal the energy variation and the frequency shifting phenomenon under some characteristic frequencies. It is hoped that with these information, we can avoid/alleviate the occurrence of unexpected fracture. As for the fatigue test, data showed that the fatigue life can be improved when certain heat treatment or reciprocating rotation method applied. Such phenomenon may be closely related to the phase composition in Ni-Ti Alloy and the maximum tension stress is decreased when reciprocating movement applied. Studies showed that the more content of martensite phase in the needle, the more fatigue life can be achieved. However, it may need to take compromise with needle’s cutting efficiency. For this issue, we can combine cryogenic treatment and heat treatment to get better fatigue life without compromising with its cutting efficiency.
The second part is to fabricate high resolution, large size of new type endodontic needles by employing two-photon polymerization (TTP) technique. The work is done in the university of Joseph-Fourier LiPhy lab, France. Unlike traditional TPP manufacturing, which had a limitation of its products size due to small lase power, repetition rate and piezo driven stage, we use Ormocer resin, 130 kHz, 1W powerful 532 nm laser with step motor driven X-Y stage to fabricate high bio-compatible 800 μm cell scaffold and 1.2 cm height needle. Also, to improve the product quality of TPP, the laser power correction approach had been attempted. During TPP fabrication, the laser focusing shape changed when the fabrication surface was moved up in z direction. This results in that we need more power to ensure the voxel size is the same at different z. To correct such defect, a method of the laser power correction and formula for the correcting power are proposed. The formula is derived from the concept of keeping exposure condition the same.

並列關鍵字

Ni-Ti rotary instrument ； root canal parameter ； FBG ； characteristic frequency ； reciprocating movement ； martensite phase ； cryogenic treatment ； two-photon polymerization ； Large size of TPP ； scaffold ； laser correction method

參考文獻

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