Malmström H S, McCormack S M, Fried D, Featherstone J D
Eastman Dental Center, University of Rochester, Rochester, NY 14620-2989, USA.
J Dent. 2001 Nov;29(8):521-9. doi: 10.1016/s0300-5712(01)00028-8.
The objective of this study was to evaluate the potential effects on underlying dental hard tissues of a high pulse rate carbon dioxide (CO2) laser that was designed for soft tissue surgery.
Eighteen extracted human teeth were sectioned longitudinally, cleaned, and varnished, leaving nine exposed windows on each: six on the coronal surface (enamel) and three on the root surface (cementum, dentin). The CO2 irradiation conditions used were: wave length 10.6 microm; 1.2-2.6J/cm(2) fluence per pulse; repetition rate 120-1000Hz; 100-200ms pulse duration; and cumulative fluences ranging from 14 to 2200J/cm(2). Each window was irradiated with a 0.3mm beam diameter at one of nine power settings for 0.1, 0.5, or 1.0s. The pulp chamber temperature was measured with a microthermocouple. The irradiated teeth were evaluated by Polarized Light Microscopy (PLM) and Scanning Electron Microscopy (SEM).
The pulp chamber temperature rise ranged from 0.5 to 19 degrees C depending on the location of the window and distance to pulp chamber. SEM revealed crystal fusion in both enamel and dentin at all cumulative fluences. At cumulative fluences of 40J/cm(2), 200 pulses/second and higher, measurable tissue loss was observed with PLM both in dentin and enamel.
These results indicate there are threshold conditions above which pulsed CO2 laser light used for soft tissue surgery may cause detrimental changes to underlying oral hard tissue and to the pulp.
本研究的目的是评估一种专为软组织手术设计的高脉冲率二氧化碳（CO₂）激光对牙齿硬组织的潜在影响。
将18颗拔除的人类牙齿纵向剖开，清洁并涂清漆，每颗牙齿上留下9个暴露窗口：6个在冠部表面（牙釉质），3个在根部表面（牙骨质、牙本质）。使用的CO₂激光照射条件为：波长10.6微米；每脉冲能量密度1.2 - 2.6J/cm²；重复频率120 - 1000Hz；脉冲持续时间100 - 200毫秒；累积能量密度范围为14至2200J/cm²。每个窗口用直径0.3mm的光束在9种功率设置之一照射0.1、0.5或1.0秒。用微型热电偶测量牙髓腔温度。通过偏光显微镜（PLM）和扫描电子显微镜（SEM）对照射后的牙齿进行评估。
牙髓腔温度升高范围为0.5至19摄氏度，具体取决于窗口位置和与牙髓腔的距离。扫描电子显微镜显示，在所有累积能量密度下，牙釉质和牙本质中均出现晶体融合。在累积能量密度为40J/cm²、每秒200脉冲及更高时，偏光显微镜观察到牙本质和牙釉质中均有可测量的组织损失。
这些结果表明，存在阈值条件，超过该条件，用于软组织手术的脉冲CO₂激光可能会对下方的口腔硬组织和牙髓造成有害变化。
