| 摘要: | 在齒顎矯正的拔牙症例中，尤其會面臨空間關閉的問題。然而存在於矯正器及矯正線之間的摩擦力，常會影響牙齒初期的移動，造成初期移動效果緩慢，因此必須了解矯正器及矯正線之間的摩擦阻力表現，以做為臨床選擇矯正裝置的參考。本研究主要針對目前常用之矯正器/矯正線的組合，來進行摩擦阻力的研究及探討。具體目標有二：第一，探究不同材質的矯正器及矯正線在相對滑動時的最大靜摩擦阻力的差異，並同時了解改良式超彈性鎳鈦合金線(improved super-elastic nickel-titanium alloy wire，亦稱為low-stress hysteresis wire, LH wire)的摩擦力表現。第二，觀測不同矯正線的表面性質，以了解矯正線表面性質與摩擦阻力的關係。
本研究選用三種矯正器及四種矯正線之組合。選用之三種矯正器，包括：不鏽鋼金屬矯正器、透明塑膠矯正器合併金屬溝槽及自鎖式矯正器；四種矯正線，包括：不鏽鋼矯正線、LH矯正線、Sentalloy鎳鈦合金線及鈦鉬合金線(Beta-titanium wire)。樣本數一共有12組，每組10個樣本，總計120個樣本數。實驗分為兩部分：一是摩擦阻力測試：使用材料測試機搭配荷重元為測試平台，量測滑動模式下之最大靜摩擦阻力。二是矯正線表面性質觀測：包括定量分析矯正線的表面硬度及表面粗度與定性分析(以金相顯微鏡及掃描式電子顯微鏡)觀測摩擦阻力測試前後矯正線表面型態的變化。
實驗結果顯示：第一部分摩擦阻力測試結果，在矯正線的比較為鈦鉬合金線所測得的最大靜摩擦阻力最高；不鏽鋼矯正線最小；Sentalloy鎳鈦合金線及LH矯正線介於兩者之間。矯正器的比較為自鎖式矯正器mini Clippy所測得的最大靜摩擦阻力最小；不鏽鋼金屬矯正器及透明塑膠矯正器合併金屬溝槽在與LH矯正線、Sentalloy鎳鈦合金線及鈦鉬合金線三者組合時，最大靜摩擦阻力沒有顯著差異。第二部分矯正線表面性質觀測結果：在表面硬度測量結果為不鏽鋼矯正線表面硬度最大，鈦鉬合金線居中，LH矯正線及Sentalloy鎳鈦合金線表面硬度最小且兩者無顯著差異；表面型態的觀測由金相顯微鏡觀測到四種矯正線表面型態皆不相同，其中不鏽鋼矯正線呈現亮度最高、表面最為平滑的影像，其他三者則亮度明顯較暗，而掃描式電子顯微鏡在1000倍下觀測到實驗後之LH矯正線及Sentalloy鎳鈦合金線表面有明顯abrasion現象，鈦鉬合金線除了abrasion現象還伴隨adhesion現象產生；表面粗度測量結果為LH矯正線表面粗度最大，Sentalloy鎳鈦合金線次之且與LH無顯著差異，鈦鉬合金線居中，不鏽鋼矯正線最小。
Sliding a tooth along an archwire is a very common orthodontic procedure, especially during closure of spaces in the extraction case. A frictional force generated at bracket/archwire interface tends to resist the desired movement, thus reduce the efficiency of orthodontic treatment. Therefore, understanding the frictional force between brackets and archwires is one of the important issues. The objectives of this in vitro study were to evaluate the frictional mechanism between different sets of the orthodontic brackets and archwires during sliding, and surface characteristics of the archwires including hardness, surface topography and surface roughness.
Three types of preadjusted maxillary canine brackets were selected in this study: metal brackets, plastic brackets with metal slot, and self-ligating brackets. Four types of archwires were also used: stainless steel wires, Sentalloy nickel-titanium (Ni-Ti) alloy wires, low-stress hysteresis (LH) wires, and Beta-titanium wires (TMA). The experiment were divided into two parts: (1) frictional force testing: each bracket-archwire combination was subjected to 10 independent evaluations, giving a total of 120 trials in this study. Testing was performed on a material testing machine with a 10-N load cell. The static frictional friction, peak point of friction, was used as the evaluation index. (2) measurement of the surface characteristics of archwires: surface hardness, surface roughness, and surface topography obtained from metallographic microscope and scanning electron microscope (SEM).
The results of the study showed that the significant differences were observed in the frictional forces among the different combinations of brackets and archwires. Basically, Self-ligating brackets showed the lowest frictional forces in all type of archwires. Furthermore, except to the stainless steel wires group, no significant difference between metal brackets and plastic brackets. For the three types of brackets, TMA wires showed the highest frictional force and stainless steel wires showed the lowest. In addition, no significant difference between LH wires and Sentally Ni-Ti alloy wires were observed. Compared to the new archwire, from the SEM image at 1000 magnitude, the surface topography of the tested wires were quite different: LH wires and Sentally Ni-Ti alloy wires appeared full continuous lines due to the obvious difference of surface hardness of both wires and stainless steel wires. TMA wires showed irregular rough surface that are attributed to the phenomenon of adhesion and abrasion. Comparing the results from four types of archwires in this study, no correlation was found between the increase surface roughness and frictional force. |
