Spencer P, Payne J M, Cobb C M, Reinisch L, Peavy G M, Drummer D D, Suchman D L, Swafford J R
Department of Oral Biology, School of Dentistry, University of Missouri-Kansas City, 64108, USA.
J Periodontol. 1999 Jan;70(1):68-74. doi: 10.1902/jop.1999.70.1.68.
Collateral thermal damage and residual char formation have severely limited the use of conventional lasers in the surgical preparation of bony tissue. Thermal damage from lasers can be minimized by selecting a wavelength that is strongly absorbed and by reducing the laser pulse duration. In contrast to the fixed wavelengths and microsecond pulse intervals of conventional lasers, the Vanderbilt free electron laser (FEL) can be set at wavelengths ranging from 2.1 to 9.8 microm, and the pulse duration can be reduced to a series of 1 to 2 picosecond (ps) micropulses delivered in succession over intervals of 4 microsecond macropulses. The purpose of this study was to compare the morphologic and chemical changes induced in the near-surface region of bone following exposure to the FEL at 3.0, 6.1, and 6.45 microm wavelengths. The selected wavelengths coincide with the vibrational modes of proteins and water within bone.
Under general anesthesia, laser incisions were made in the tibias of 14 skeletally mature rabbits. Laser parameters included 22.5+/-2.5 mJ/pulse delivered in individual 4 microsecond macropulses at a repetition rate of 30 Hz, focused to 200 microm and 500 microm spot sizes. Laser incisions were made using a computer-assisted surgical program, and control incisions were created with a bone saw. Rabbits were euthanized after the final incision, tibias recovered, and non-decalcified specimens processed for light microscopy. Separate samples were prepared for FTIR (Fourier transform infrared) photoacoustic spectroscopic analysis.
The light microscopy sections of the ablation defects created at the differing wavelengths showed similar features, i.e., 2 zones of collateral damage, a zone generally < 10 mm of extensive thermal damage, and a wider zone of empty lacunae. In comparing treated and untreated surfaces, the spectral differences were limited to a relative decrease in intensity of the amide II and III absorption peaks in all laser-treated surfaces.
Spectroscopic and histologic results indicated minimal thermal damage to bone ablated at 3.0, 6.1, and 6.45 microm wavelengths using the FEL (Fourier transform infrared) at the specified parameters. The FTIR photoacoustic spectroscopic results suggest that the char layer is limited to an area less than approximately 6 microm from the surface.
附带热损伤和残余焦炭形成严重限制了传统激光在骨组织手术制备中的应用。通过选择强吸收波长和缩短激光脉冲持续时间，可以将激光产生的热损伤降至最低。与传统激光固定的波长和微秒级脉冲间隔不同，范德比尔特自由电子激光（FEL）的波长可设置在2.1至9.8微米范围内，脉冲持续时间可缩短为一系列在4微秒宏脉冲间隔内连续发射的1至2皮秒（ps）微脉冲。本研究的目的是比较在3.0、6.1和6.45微米波长下暴露于FEL后，骨近表面区域诱导的形态学和化学变化。所选波长与骨内蛋白质和水的振动模式一致。
在全身麻醉下，对14只骨骼成熟的兔子的胫骨进行激光切开。激光参数包括以30Hz的重复频率在单个4微秒宏脉冲中传递22.5±2.5mJ/脉冲，聚焦到200微米和500微米光斑尺寸。使用计算机辅助手术程序进行激光切开，并用骨锯制作对照切口。最后一次切开后对兔子实施安乐死，取出胫骨，对未脱钙的标本进行光镜检查。制备单独的样本用于傅里叶变换红外（FTIR）光声光谱分析。
在不同波长下产生的消融缺损的光镜切片显示出相似的特征，即2个附带损伤区域、一个通常<10mm的广泛热损伤区域和一个较宽的空骨陷窝区域。在比较处理过和未处理过的表面时，光谱差异仅限于所有激光处理过的表面中酰胺II和III吸收峰强度的相对降低。
光谱和组织学结果表明，使用特定参数的FEL（傅里叶变换红外）在3.0、6.1和6.45微米波长下对骨进行消融时，热损伤最小。FTIR光声光谱结果表明，焦炭层仅限于距表面小于约6微米的区域。
