Nd:YAP雷射移除根管壁塗抹層之效果

Effect of Nd:YAP Laser in Removing the Smear Layer of the Root Canal

大部分學者認為在根管治療過程中將塗抹層移除是必要的，並且在雷射之應用上較少使用200μm直徑光纖進行根管壁照射的研究，因此本研究的目的是利用立體顯微鏡及電子顯微鏡觀察使用Nd：YAP雷射照射根管壁後其形態變化及移除根管壁塗抹層的效果。將35顆單根管牙齒先使用傳統根管治療方式修形，牙根部分縱部成兩半。除了對照組外，其餘各組標本使用Nd：YAP雷射照射根管壁，所使用光纖直徑為200μm，而照射方式為光纖和牙根表面呈10度，從根尖往牙冠方向做清掃的動作，每次移動的時間為1秒，照射5秒便使用1毫升蒸餾水沖洗，再使用紙針吸乾。固定照射頻率5 Hz，依照不同照射能量（180 mJ/pulse、280 mJ/pulse及360 mJ/pulse）及不同照射時間（30 s及60 s）並包含對照組共分成7組，每組5個標本。將處理過三標本分別在立體及電子顯微鏡下觀察，並依評量表進行數直評分以評估移除塗抹層程度。結果發現使用Nd：YAP雷射在5Hz照射頻率下，以280 mJ/pulse能量照射60秒時，其表面塗抹層可被移除，部分牙本質小管開口打開，並有熔融現象；數值評分結果280 mJ/pulse ×5 Hz×60s及360 mJ/pulse ×5 Hz×60s 兩組數值最低，塗抹層移除較明顯。然而以能量360 mJ/pulse照射30 s或60 s時，均造成根管壁產生裂痕。由本研究所得結論建議以Nd：YAP雷射能量組合280 mJ/pulse ×5 Hz×60s照射根管，可移除塗抹層，並形成熔融表面，且不造成根管壁傷害。

Most investigators found that removing the smear layer was essential to root canal therapy. Besides, there were few studies of lasers using the optic fiber with a diameter of 200μm to irradiate laser beam on the root canal wall. Therefore, the purpose of this study was to investigate the suitable laser parameter by the image observation of the root canal dentin after laser irradiation using the fiber with a diameter of 200μm. Thirty-five of teeth with one root and one canal was treated with traditional root canal treatment and the roots of the teeth were longitudinally sectioned. The speciments were randomly devided into one control group and 6 experimental groups which were different form pulse energy (180 mJ/pulse, 280 mJ/pulse and 360 mJ/pulse) and irradiation time (30s and 60s). The speed of a sweeping motion form he apical site to the coronal site of the root canal was once for 1 s. Distilled water of 1 ml was irrigated and then was absorbed with paper point between every 5 sweeping motions. The prepared samples were observed under the stereoscope and scanning electorn microscope. The scores were also recorded to evaluate the result of removing the smear layer. The results showed that the smear layer was removed and the dentinal tubules were partially opened after laser irradiation with the pulse energy 280 mJ/pulse ×5 Hz×60s and 360 mJ/pulse ×5 Hz×60s had the lowest score which meant the effect of removing the smear layer was better. However, crack lines were found after laser irradiation with the pulse energy of 360 mJ/pulse ×5 Hz×60s . In conclusion, we recommend using Nd:YAP laser to irradiate the root canal dentin with the parameter of 280 mJ/pulse ×5 Hz×60s for removing the smear layer and it is no harm to the dentin surface.