有效的清潔與修形根管系統是根管治療成功的關鍵之一。對於根管型態複雜（如：C型根管）或彎曲的根管，現今臨床上多使用鎳鈦旋轉器械來進行根管的修形。C型根管型態在亞洲族群的下顎第二大臼齒發生率高達31%-45%，因其型態上又具有數種變異類型以及具有難以清潔到之峽部構造，讓C型根管之下顎第二大臼齒在根管治療上具有一定難度，一直以來也有許多文獻在探討如何更完整清潔修形及充填這類型的根管。 本實驗選擇具有C型根管之被拔除的下顎第二大臼齒，將其透過牙科斷層掃瞄組成立體影像，經由三維列印輸出成具有一致性之模擬牙根樣本，再使用兩種運動模式不同之鎳鈦旋轉器械（Waveone Gold、Protaper Next），分別對三維列印根管做修形，欲了解不同器械在C型根管中修形之情形。 實驗結果觀察到所使用之兩種鎳鈦旋轉器械皆未發生根管穿孔、器械破折之嚴重修形錯誤。兩種器械修形後之根管寬度呈連續錐度自根尖往冠部逐漸擴大，在根管各位置都可觀察到根管偏移的情況，且兩種器械在根尖部分及距離根尖6-7mm處造成的根管偏移具有統計上顯著差異。推測為受到根尖彎曲型態及C型根管的峽部結構影響所致。本實驗使用的兩種鎳鈦旋轉器械都能夠完成3D列印模型中C型根管系統的主根管修形，使用鎳鈦旋轉器械可簡化根管治療的操作步驟。但對於如何再減少根尖處的根管偏移，仍需要更多的研究探討。
Effective cleaning and shaping of canal systems is one of the key points led to success of endodontic treatment. For some complicated canals such as C-shaped or curved canals, we can use NiTi rotary instuments to help shaping the canals. 31%-45% C-shaped canals occur in the mandibular second molar in Asians. Because the variations of canal system and the structure of isthmus, it is difficult to cleaning and shaping the C-shaped canal. There were many literatures that discuss how to cleaning, shaping and filling the entire canal system completely. In this experiment, we used CBCT to scan the extracted lower mandibular second molar with C-shaped canal. Then we got the reconstructed 3D image of the tooth, and duplicated the tooth’s models by 3D printing technique. Two kinds of NiTi rotary instruments, Waveone Gold and Protaper Next, with different motions were used to shaping the canals in the models. No perforation or fracture of the instrument were observed. After shaping, the canal width was increased in continuous taper from apical to coronal portion, and canal transportation was observed in all levels of the canal. The amounts of transportation were significantly different between two kinds of instruments at apex and 6-7mm from apex. It was considered that the transportation was influenced by apical curvature and isthmus of the canals. Though Waveone Gold and Protaper Next could finish shaping the main canals of 3D printed C-shaped canal system, it still need more improvement to reduce canal transportation at apical third.
