臺灣博碩士論文加值系統

齒列矯正治療(orthodontic treatment)在治療完成後，必須將黏附於牙齒上的矯正托架(bracket)拆除，並清除殘餘的黏著材料(residual adhesive)，恢復原來光滑潔淨的牙釉質(enamel)表面，這整個過程，一般稱之為去鍵結(debonding)。去鍵結成功與否，在於是否能保持完整的牙釉質，不當的去鍵結過程，會危害牙釉質，造成表面龜裂，牙釉稜柱(enamel prism)斷裂，影響美觀，導致牙齒敏感酸痛，且易致蛀牙及牙髓壞死，故深入了解去鍵結機制實屬重要。
過去的研究，只有寥寥可數的報告提及不同拆除托架技術(debracketing technique)在拆除金屬托架過程對牙釉質的影響，而其研究方法有共同的缺陷，皆以手工操作拆除托架，其施力大小與方向未能標準化，個人變異(individual variation)極大，勢必影響統計檢定結果的正確性，故各種拆除法的優劣，在臨床上仍莫衷一是，造成醫師操作的困擾。
本研究目的在於評估三種程序標準化的拆除托架技術對牙釉質的破壞，在這個研究中，三種不同的拆除托架技術對牙釉質的影響被研究，這三組個別夾擠，剪力及拉力法，其樣本數分別是30，33和30。拆除托架技術模擬臨床狀況以標準化工具配合Instron機器施以夾擠（squeezing），剪力（shearing force）及拉力（tensile force），每一組的小臼齒以Enlight（Ormco）粘著劑粘上標準型雙翼托架（Dentaurum）並以特殊方向架上Instron機器以便拆除托架。How Plier（Task），Direct Bond Bracket Remover（Task）或Debracketing Instrument（3M-Unitek）以專門訂製的固位座架在Instron機器上，以力量位移圖記錄下拆除托架的力量；以影像處理系統用來計算留在牙釉質表面的殘餘粘著劑面積；並用掃描式電子顯微鏡觀察這三組牙釉稜柱的斷裂面。其結論如下：
1． 以Instron萬用測試機所得的拆除托架力量 (debracketing force)，經力臂、力矩的討論後，得到三種拆除托架技術實際所施力量70N到80N之間，對應所採用的托架面積，合於一般研究所建議的剪力鍵結強度6.0MPa到8.0MPa。而其變異係數分別為12.58% , 25.53% , 17.04% ,低於一般鍵結測試的變異係數值，表示本實驗條件控制的一致性高，資料數據效度良好。
2． 以光學顯微鏡，CCD攝影機及電腦影像分析系統可測得黏著劑殘留面積比率(Adhesive Remnant Area Ratio)，經統計檢定，分析得夾擠法與拉力法這兩組無顯著差異，為臨床可接受之拆除托架技術，剪力法的破壞性較大，臨床操作傷害到牙釉質的風險較高。
3． 以掃瞄式電子顯微鏡觀察顯微斷裂結構，在夾擠法樣本試片沒發現斷裂的牙釉稜柱，拉力法只有1/30顆發現些微的牙釉稜柱斷裂，極不明顯，剪力法則有3/33顆發現斷裂的牙釉稜柱，其中一顆有較大面積，明顯呈現垂直於牙釉質稜柱走向的斷裂模式，這也顯示剪力法較易傷害牙釉質。
基於本研究，剪力法拆除托架技術會引起較嚴重的牙釉質破壞，臨床上不推薦使用。

After orthodontic treatment finished, debonding is required for removing brackets and residual adhesive from tooth surface. The success of debonding relies on keeping intact enamel structure while brackets are removed. Improper debonding will injure the enamel and result in cracking of its surface, enamel prism fracture and potentially further cause esthetic problems, tooth sensitivity, increasing risk of caries and pulp necrosis. Therefore, it is important to understand the mechanism of debonding.
From the literature, few reports on comparing the enamel structure with different debracketing procedures were found. Those studies were performed with manual debonding which cannot be standardized for consistency of force magnitude and its direction. The individual variation was unavoidable and decreased the validity of these studies. As the results, there were no conclusions drawn from these studies on different debracketing procedures and no rules to follow for debonding on patients for clinicians.
The goal of this research is to evaluate the damages on enamel among three debracketing techniques with standardized procedures. In this study, the effect on enamel with three different techniques of debracketing was studied. The sample numbers for the three groups, squeezing, shearing force and tensile force, were 30, 33 and 30. The debracketing techniques were simulated as for clinical situations with standardized instruments for application of squeezing, shearing or tensile force with Instron machine. The premolars in each group were bonded with standard twin brackets（Dentaurum）and Enlight（Ormco）and mounted on Instron machine with specific orientation for debracketing. How Plier（Task）, Direct Bond Bracket Remover（Task）or Debracketing Instrument（3M-Unitek）were mounted on Instron machine with custom made holders. Force-displacement diagram was recorded for debracketing force. Image processing system was used to calculate the area of residual adhesives left on enamel surface. Scanning electron microscope was also used to observe the fracture surface on enamel prism among these three groups. Ther conclusion is as the followings:
1. The debracketing force of these debonding technique is 70N to 80N with the consideration of fulcrum. The resulting debond-strength for brackets of 3mm x 4mm is equivalent to 6 to 8 Mpa which falls into the suggested range from manufactures. The coefficients of variation of these methods are 12.58%, 25.53%, and 17.04% respectively, which is far lower than other commonly used methods in literature. This indicates the consistency of our experimental procedures and the validity of our data.
2. From light microscope, CCD and image analysis system, adhesive remnant area ratios were calculated. Both squeezing and tensile force for debracketing were cliniccally acceptable procedures and there was no significant difference between these two groups. However, shearing force for debracketing was found to have greater risk for damaging enamel.
3. Using SEM, there was no enamel prism fracture found in squeezing group. One tooth with minor enamel prism fracture in tensile force group. However, three teeth with fractured enamel prism were noticed in shearing force group. One of these three teeth was found to have keyhole and cone-shaped rod fractures. This also indicates that shearing force caused more damage on enamel.
Based on this study, shearing force debracketing technique,which caused more damages on enamel, is not recommended for clinical use.

目錄
題目
中文摘要……………………………………………….1
英文摘要……………………………………………….4
前言…………………………………………………….7
文獻回顧……………………………………………….9
研究目的………………………………………………13
材料與方法……………………………………………15
結果…………………………………………………….28
討論…………………………………………………….36
結論…………………………………………………….43
參考文獻……………………………………………….45
圖表…………………………………………………….47
統計附錄………………………………………………63

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