摘　要：为探讨利用光学相干成像技术（OCT）定量评估Er:YAG激光消融后牙本质表面特征的可行性，以人无龋第三磨牙为试验样品，制备牙本质圆盘，用50 μs超短脉宽Er:YAG激光在水喷雾下垂直切削牙本质表面，对照组为金刚砂球钻切削和砂纸抛光组，OCT观察表层性状及测量表层光强改变，组织病理切片分析表层结构；表面切削后使用37%磷酸蚀刻30 s，扫描电镜（SEM）观察表面形貌，能量色散X射线光谱仪（EDX）测量表面元素组成。OCT显示，所有试验组牙本质表层光散射特性均发生改变，可见高亮层形成，激光组高亮层厚度高于砂纸组和球钻组（P<0.05）。组织切片显示，激光组表层可见连续的嗜碱性深染改性层，球钻组及砂纸组改性层少且不连续，改性层厚度与OCT高亮层结果相关。SEM显示，酸蚀后激光组牙本质小管开口扩大，但未见胶原纤维网暴露。酸处理后激光组的钙、磷含量均高于砂纸及球钻组（P<0.05），这意味着受激光影响的牙本质变得更耐酸。研究结果表明，OCT可能成为一种可精确评估牙本质表层特性的无创性工具，这将有助于牙医确定粘接修复策略。
关键词：Er:YAG激光；牙本质；光学相干成像技术；元素组成；酸蚀
中图分类号：R781　　　　　　文献标志码：ADOI：10.3969/j.issn.1007-7146.2021.02.006

Abstract: The feasibility of quantitatively evaluating the surface character of dentin after Er:YAG laser irradiation by using optical coherence tomography (OCT) is examined. Dentin specimens were prepared from human extracted third molars free of decay. Er:YAG laser non-contact irradiation was performed at pulse duration of 50 μs under water spray. The control groups were sandpaper polishing group and traditional bur treated group. OCT techniques were used to observe the surface properties and measure the changes of surface light intensity of dentin specimens. Histopathological sections were used to analyze the surface structure. Then 37% phosphoric acid was etched for 30 seconds after surface treatment, and the surface morphology was then observed by scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) spectroscopy was used to measure the composition of surface elements. OCT results demonstrated that a layer with high image intensity generated on all experimental dentin surface. Quantitative results obtained that the thickness of these affected layers produced by Er:YAG laser was markedly higher than those of bur- and sandpaper-treated groups (P<0.05). Histology demonstrated that thin denatured layers were created in laser-treated dentin. Little denatured layer on bur- and sandpaper-treated area. The modified layer of histological examination was consistent with the light intensity changes of OCT images. After acid treatment, the dentinal tubules’ entrance enlarged, whereas collagen fibrils network was not exposed in the SEM images of Er:YAG laser groups. After acid treatment for the same time period, EDX spectroscopy showed that the content of Ca and P ion in laser-treated group were higher than bur- and sandpaper-treated groups (P<0.05), which means the laser-treated dentin becomes being more acid resistant. This study demonstrated OCT may become a noninvasive tool to precisely evaluate the character of dentin that would be useful to dentists in helping determine adhesive restoration strategies.
Key words: Er:YAG laser; dentin; optical coherence tomography; element composition; acid etching
（Acta Laser Biology Sinica, 2021, 30(2): 131-137）