AIM:To evaluate the nanohardness and Young’s modulus of dentin after Er:YAG laser irradia-tion using a nano-indentation tester.METHODS:1 5 dentin disks obtained from extracted human third molars were prepared and exposed to a single pulse laser irradiation at 80 mJ/pulse.5 specimens were observed for the morphology of laser-ablated dentin surface using a SEM.The remaining 1 0 specimens were crosscut through the expose center of the lased point.Among the 1 0,5 were observed under SEMfor the subsurface-lased dentin,5 lased and 5 sound den-tin specimens were measured for nanohardness and Young’s modulus.RESULTS:The irradiated dentin surface was irregular,scaly or flaky.Laser irradiation denatured subsurface layer about 1 5 μm deep was present.The nanohardness and Young’s modulus of the Er:YAG laser denatured dentin were significantly lower than those of sound dentin (P<0.05).CONCLUSION:Er:YAG laser irradiation can affect the nanohardness and Young’s modulus of dentin subsurface.%目的：运用纳米压痕测量仪检测评估Er：YAG激光辐射对牙本质的纳米硬度和杨氏模量的影响。方法：选择新鲜拔除的健康人离体第三磨牙，制备成冠中部牙本质切片15个。将样本置于单脉冲（80 mJ／脉冲）、水冷却模式的Er：YAG激光下辐射后，5个样本用于扫描电镜（SEM）观察激光辐射牙本质表面形态；其余10个样本沿辐射点的中心纵向切开，5个样本用于SEM观察激光辐射影响层内牙本质形态，另外5个样本用纳米压痕技术检测激光辐射影响层牙本质的纳米硬度及杨氏模量。结果：经Er：YAG激光辐射后，牙本质表面粗糙、呈鱼鳞状改变。辐射影响深度约10～15μm，激光辐射影响变质层牙本质的纳米硬度和杨氏模量均明显低于正常牙本质。结论：Er：YAG激光辐射可引起变质层牙本质的形态学及纳米硬度与杨氏模量的改变。
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