不同參數對Er,Cr:YSGG雷射切削人類牙本質效率之比較

Comparison of Various Parameter Settings of Er,Cr:YSGG Laser on the Ablation Rate of Human Dentin

當雷射與牙齒硬組織作用時，其結果會受到雷射的能量、噴水量、噴氣量等等參數的影響。本實驗目的即在於比較不同參數條件設定之下，各個參數條件設定對牙本質切削效率的影響。收集拔除之無蛀牙無復形物人類大臼齒30顆，以鑽石切片慢速骨鋸將大臼齒切成厚度約2 mm之牙本質切片，保存於4C蒸餾水中備用。將30片牙齒切片隨機分為三組，每組10片。三組分別比較不同能量、噴水量、噴氣量對牙齒牙本質切削效率的影響。將各組的牙本質切片依照所設定的條件照射Er,Cr:YSGG雷射30秒後，分別在光學與電子顯微鏡下觀察。之後，使用牙科印模材對牙本質坑洞取模以評估牙本質坑洞之形態並在光學顯微鏡下測量坑洞之深度與面積。實驗結果顯示，除了噴水量小於20%，會造成牙本質表面熔融、焦黑碳化等現象外，不同能量、噴水量與噴氣量所造成之牙本質坑洞皆得到類似之表面形態變化。能量與噴氣量設定值和牙本質切削效率有正相關之關係，而噴水量則有負面的效果，雖然較小的噴水量顯示出較佳之切削效果，然而當噴水量過低時，將對牙本質造成熔融與碳化之現象。根據本實驗可得到以下結論: 1.不同能量、噴水量、噴氣量等參數值的大小皆造成類似之牙本質坑洞表面形態變化。2.當噴水量小於20%時，會造成牙本質熔融、焦黑等現象。3.能量與噴氣量愈大，切削效率愈高，噴水量愈大，切削效率愈低。

When laser beam interacts with dental hard tissues, the results can be affected by the parameters of laser, such as power, water spray, air spray etc. The purpose of this study was to compare the influences of various parameters on the efficiency of dentin ablation. Thirty extracted human molars without caries or restorations were cut into dentin slices of 2 mm in thickness using Isomet. The dentin slices were stored in 4oC distilled water. The specimens were randomly divided into 3 groups to evaluate the influences of different power settings, water spray, and air spray on the ablation rate of human dentin. Each group contained 10 dentin slices. The specimens were observed under light microscope (LM) and scanning electron microscope (SEM) after 30 s of Er;Cr:YSGG laser irradiation. In order to evaluate the topography of laser-induced crater on each specimen, we used dental impression material to take negative impression of crater and measured the depth and area of the impression under LM. The results showed that the morphological changes of craters created by different power settings, water spray, and air spray were similar except for the melted and charred dentin surfaces when the water spray was less than 20%. The power settings and air spray were positively correlated with the cutting efficiency of human dentin while the water spray had an opposite effect. Although lower water spray could cut dentin more efficiently, the dentin appeared melted and charred if the amount of water spray was too low. From this study the following conclusions could be addressed: 1. Different power settings, air spray, and water spray cause similar morphological changes of dentin. 2. If the amount of water spray is below 20%, melted and charred dentin are produced. 3. The cutting efficiency of dentin is elevated as the power settings and air spray is increased. However, the more water spray, the lower the cutting efficiency of dentin.