Er∶YAG激光对牙体硬组织切割效率及表面形态的影响

Efficiency of Er∶YAG laser for dental hard tissue ablation and its effect on dental surface morphology

目的观察Er∶YAG激光不同频率和照射时间对牙体硬组织切割效率和表面形态的影响。方法 80个牙釉质样本和80个牙本质样本分别按照射时间10 s和20 s,使用随机数字表法分为两组(n=40),每组再分为5个亚组(n=8),分别用频率为10、15、20、25、30 Hz Er∶YAG激光对每个样本进行照射,体视显微镜测量牙釉质和牙本质凹坑直径、深度,扫描电镜观察牙釉质和牙本质表面形态。结果 Er∶YAG激光频率10~20 Hz、照射时间10 s及20 s时,牙釉质和牙本质凹坑的直径、深度随频率增加和照射时间延长而增加(P<0.05);Er∶YAG激光频率25~30 Hz、照射时间10 s及20 s时,牙釉质和牙本质凹坑的直径、深度随频率增加和照射时间延长出现缓慢增加的趋势(P>0.05)。扫描电镜下观察,牙釉质和牙本质表面形态发生了一定的变化,Er∶YAG激光频率为25~30 Hz时,牙釉质和牙本质表面出现裂纹、熔融等热损伤现象。结论 Er∶YAG激光适宜的频率和照射时间不仅可以获得牙体硬组织良好的切割效率,而且不会引起牙体硬组织表面形态热损伤。

Objective To assess the efficiency of Er ：YAG laser with different frequencies and irradiation time for ablation of dental hard tissues and its effect on dental surface morphology. Methods Eighty enamel samples and 80 dentin samples were randomly divided into 2 groups （n=40） with Er ：YAG laser ablation for 10 s or 20 s, and each group was further divided into 5 subgroups （n=8） for ablation with Er ：YAG laser at frequencies of 10, 15, 20, 25, or 30 Hz. After irradiation, the diameter and depth of enamel and dentin pits were observed under stereoscopic microscope, and the surface morphology of the enamel and dentin was observed by scanning electron microscopy （SEM）. Results The diameter and depth of enamel and dentin pits following Er ：YAG laser ablation were increased significantly as the laser frequency increased within the range of 10-20 Hz and the ablation time extended （P 〈 0.05）. The diameter and depth of the pits were increased only slightly as the laser frequency increased to 25 and 30 Hz and the ablation time increased to 20 s （P〉0.05）. SEM showed alterations on the surface morphology of enamel and dentin after the ablation, and damages such as crack and melting occurred on the enamel and dentin surface after laser ablation at frequencies of 25 and 30 Hz. Conclusion Er ：YAG laser with an appropriate frequency and ablation time is efficient for dental hard tissue ablation without causing thermal damage to the dental surface.