Palamara J, Phakey P P, Orams H J, Rachinger W A
Department of Physics, Monash University, Clayton, Victoria, Australia.
Scanning Microsc. 1992 Dec;6(4):1061-70; discussion 1070-1.
This study aimed to investigate the ultrastructural changes that occur in dental enamel irradiated with pulsed excimer-dye, continuous-wave (CW) argon-ion and CW CO2 lasers. The pulsed excimer-dye laser produced deep craters, rough damaged surfaces with underlying porosity and amorphous vitrified material. The vitrification of the enamel indicated that the temperature in these areas must have been at least in the range 1280 to 1600 degrees C. The CW argon-ion laser irradiation produced a changed non-cratered surface with inter-crystalline porosity and a mixture of small and some large irregularly packed recrystallized enamel crystals. The CW CO2 laser produced shallow craters, surface crazing and lifting off the removal of the surface layer to expose the underlying roughened enamel. The ultrastructure revealed inter- and intra-crystalline porosity, a mixture of small but variable size irregularly packed recrystallized enamel crystals and also well packed large crystals which indicated further grain growth. The porosity in lased enamel was overall very similar to that seen in enamel heated in an electric furnace to a temperature of 600 degrees C. The presence of recrystallized enamel crystals indicated a temperature rise of approximately 1000 degrees C and the grain growth indicated that a temperature > or = 1000 degrees C existed for some time after the laser irradiation. In general the excimer-dye laser produced most surface destruction because of its higher power density and shorter interaction time and the argon-ion laser produced least damage. These results indicated that the lasers used in this study require much more refinement before they can find therapeutic application to dental enamel, and this may well be the case for other lasers being investigated for clinical dental practise.
本研究旨在调查用脉冲准分子染料激光、连续波（CW）氩离子激光和CW二氧化碳激光照射牙釉质后发生的超微结构变化。脉冲准分子染料激光产生了深凹坑、表面粗糙且有潜在孔隙以及无定形玻璃化物质的损伤表面。牙釉质的玻璃化表明这些区域的温度必定至少在1280至1600摄氏度范围内。连续波氩离子激光照射产生了一个有晶间孔隙的非凹坑状变化表面，以及大小不一、不规则堆积的再结晶牙釉质晶体混合物。连续波二氧化碳激光产生了浅凹坑、表面裂纹以及表层脱落，从而暴露出下面粗糙的牙釉质。超微结构显示晶间和晶内孔隙、大小不一但不规则堆积的再结晶牙釉质晶体混合物以及排列紧密的大晶体，这表明有进一步的晶粒生长。激光照射后的牙釉质中的孔隙总体上与在电炉中加热到600摄氏度的牙釉质中的孔隙非常相似。再结晶牙釉质晶体的存在表明温度升高了约1000摄氏度，而晶粒生长表明在激光照射后一段时间内温度≥1000摄氏度。一般来说，准分子染料激光由于其较高的功率密度和较短的相互作用时间而产生了最大程度的表面破坏，而氩离子激光造成的损伤最小。这些结果表明，本研究中使用的激光在能够用于牙釉质的治疗应用之前还需要进一步改进，对于正在研究用于临床牙科实践的其他激光来说可能也是如此。
