Er,Cr:YSGG雷射作用下牙根表面形態觀察及根管內溫度變化

Abstract

Er,Cr:YSGG 雷射已被證實可以用來移除牙齒硬組織，然而應用於移除牙根表面的沈積物卻沒有很明確的研究。本實驗的目的即利用掃瞄式電子顯微鏡觀察並研究不同的參數設定情況下，Er,Cr:YSGG 雷射照射對牙根表面的影響；並利用溫度測量儀監控根管內的溫度改變，以觀察其在根管系統的溫度變化所扮演的角色。 實驗方法：切取三個月內拔除的牙齒之牙根製成試片，第一部份：利用不同的雷射參數設定（雷射功率：0.5W，0.75W，1.0W；出水量：20%，40%，60%；噴氣量：10%，30%，50%）於1.5mm的距離，以Er,Cr:YSGG雷射對試片進行照射2秒鐘。完成後，接著進行固定及序列性脫水，並於真空電鍍儀中以雙重電鍍法將試片鍍上金箔，再以掃瞄式電子顯微鏡（Scanning Electric Microscope）進行形態變化之觀察；第二部分：利用固定的雷射參數設定，在距離試片表面1.5mm處，以不同的照射角度（90°，60°，30°，10°）對試片進行照射2秒鐘，再以掃瞄式電子顯微鏡進行形態變化之觀察；第三部分：利用溫度監控儀在不同的參數設定（雷射功率：0.5W，0.75W，1.0W，1.5W；出水量：10%，40%，90%；噴氣量：10%，30%，90%）下，於1.5mm的距離，對牙根進行照射2秒鐘，監控根管內的溫度變化並予以記錄、分析。 根據實驗的觀察結果可以發現：當雷射功率及噴氣量設定在最低，而噴水量設定在最高時，對牙根表面造成的痕跡最不明顯；隨著能量及噴氣量的增加，雷射在牙根表面造成的痕跡就越深範圍也越大；而在照射角度方面的結果可以發現：當照射角度越小的時候，照射範圍就越大，表面的痕跡就越不明顯；根管內溫度變化的結果顯示，Er,Cr:YSGG雷射照射牙根表面並不會造成根管內對牙髓組織有傷害性的升溫效應。

Removal of hard tissue with Er,Cr:YSGG laser has been extensively researched, however, removal of root substances such as microbial deposits and calculus by Er,Cr:YSGG laser has not clearly been demonstrated. The purpose of this in vitro study was to investigate the effects of Er,Cr:YSGG laser on root surfaces at different parameter settings using scanning electron microscopy (SEM), and to analyze the thermal changes of the root canals during the laser irradiation at different settings with thermometer.

Caries-free, no obvious damage of root surfaces, extracted in three months human teeth were sectioned. This study was divided in to three parts. Part I: Specimens were categorized into groups related to laser power (0.5W, 0.75W, and 1.0W), water output (20%, 40%, and 60%),and air output (10%, 30%, and 50%). Part II: Specimens were irradiated with different irradiation angle(90°, 60°, 30°,and 10°) at the parameter of 0.75W, 40% water, and 30% air. The Er,Cr:YSGG laser irradiation was set for 2 seconds in noncontact mode while the tip was held perpendicularly to the root surface side of the specimens. The distance between the laser tip and surfaces of the specimens was set to be 1.5mm. After laser irradiation, all specimens were evaluated using a SEM. Part III: Five specimens were selected and performed root canals preparation. K-type thermal couple was inserted into the root canals of the specimens to detect the changes of temperatures inside the root canals. The root canal walls were 1.5~2mm in thickness at the eight irradiation sites of each specimens. Laser irradiation was performed perpendicularly on the surfaces of the root specimens in different setting of power levels (0.5W, 0.75W, 1.0W, 1.5W), water volumes(10%, 40%, 90%), and air output(10%, 30% ,90%) for 120 seconds while the laser tip was 1.5mm away from the specimens. Thermal changes were monitored by thermometer. The results revealed: Part I: As the output power and air volumes increased, the irradiated areas were affected with increased crater area and depth, while the higher values of the water spray could have opposite results. Part II: The smaller irradiation angles could be resulted in wider irradiation area and no clear ablation. Part III: The thermal changes were elevated within the physiologically tolerable levels of pulp tissue irradiated with the utilized laser parameters. Conclusion: The Er,Cr:YSGG laser treatment may be a safe way without disturbing the structure of root surface under proper settings of parameter. The pulp tissue will not be damaged from heat generated by laser application in utilized setting of energy, water, and air output in this study.