Coffelt D W, Cobb C M, MacNeill S, Rapley J W, Killoy W J
Department of Periodontics, University of Missouri-Kansas City 64108-2716, USA.
J Clin Periodontol. 1997 Jan;24(1):1-7. doi: 10.1111/j.1600-051x.1997.tb01177.x.
The Nd:YAG and CO2 lasers have been shown to be bactericidal at relative low energy densities. However, at energy densities exceeding 120 J/cm2 (CO2) and 200 J/cm2 (Nd:YAG), laser irradiation also causes irreparable root surface damage. The purpose of this study was to determine, in vitro, the energy density threshold at which microbial ablation could be achieved while inflicting the least amount of damage to the root surfaces of human teeth. Pairs of Escherichia coli colonies cultured on broth agar were treated with a CO2 laser using a pulsed waveform at approximate energy densities ranging from 3 to 110 J/cm2. One of each colony-pair was then examined by scanning electron microscopy (SEM) and the other subcultured for viable microbes. Roots of extracted teeth were lightly scaled and treated by CO2 laser, again with pulsed beam using approximate energy densities of 3 to 110 J/cm2: and examined by SEM. Regardless of the level of energy density, residual bacteria could be subcultured from all laser treated microbial colonies. The inability of the laser to completely obliterate microbial colonies was likely due to: depth of energy penetration, difficulty in precisely overlapping beam focal spots, irregular beam profile, and presence of microbes at the periphery of the beam focal spot. The threshold energy density for bacterial obliteration was determined to be 11 J/cm2 and that for root damage was 41 J/cm2. Root damage was evident by charring, crater formation, melt-down and resolidification surface mineral, and increasing surface porosity. The results of this in vitro study indicate that when used at an energy density between 11 and 41 J/cm2 the CO2 laser may destroy microbial colonies without inflicting undue damage to the tooth root surface.
已证明钕钇铝石榴石（Nd:YAG）激光和二氧化碳（CO2）激光在相对较低的能量密度下具有杀菌作用。然而，当能量密度超过120 J/cm²（CO2激光）和200 J/cm²（Nd:YAG激光）时，激光照射也会对牙根表面造成不可修复的损伤。本研究的目的是在体外确定能够实现微生物消融同时对人牙根表面造成最小损伤的能量密度阈值。在肉汤琼脂上培养的成对大肠杆菌菌落，使用脉冲波形的CO2激光以大约3至110 J/cm²的能量密度进行处理。然后，每组菌落中的一个通过扫描电子显微镜（SEM）检查，另一个进行传代培养以检测存活微生物。拔除牙齿的牙根进行轻度刮治后，再次使用脉冲光束的CO2激光以大约3至110 J/cm²的能量密度进行处理，并通过SEM检查。无论能量密度水平如何，所有经激光处理的微生物菌落都能传代培养出残留细菌。激光无法完全消除微生物菌落可能是由于：能量穿透深度、精确重叠光束焦点困难、光束轮廓不规则以及光束焦点周边存在微生物。确定细菌消除的阈值能量密度为11 J/cm²，牙根损伤的阈值能量密度为41 J/cm²。牙根损伤表现为炭化、坑洼形成、熔化和再凝固的表面矿物质以及表面孔隙率增加。这项体外研究的结果表明，当以11至41 J/cm²的能量密度使用时，CO2激光可能在不严重损伤牙根表面的情况下破坏微生物菌落。
