Er, Cr: YSGG激光照射后牙体硬组织抗酸性变化的研究

目的 对Er，Cr：YSGG激光照射后牙体硬组织人工龋蚀的抗酸性变化进行体外研究，为其临床应用提供有价值的理论依据。方法 牙釉质标本采用6W，牙本质标本采用4W Er，Cr：YSGG激光照射6s，0．1mol／L乳酸脱矿，原子吸收分光光度计检测脱矿液中溶解的钙离子浓度，能谱分析仪进行原子含量分析，扫描电镜观察牙体硬组织表面结构变化。结果 Er，Cr：YSGG激光照射后牙釉质和牙本质的钙离子溶出浓度均显著低于对照组，钙含量在牙釉质和牙本质均显著高于对照组，磷含量在牙釉质和牙本质标本中都增高，但仅在牙釉质组差异有统计学意义，钙／磷重量比差异均无统计学意义。激光照射后釉质表面不平呈鳞片状，无玷污层，釉质结构清晰可见；牙本质小管开放，无熔融及碳化。结论 Er，Cr：YSGG激光照射后牙体硬组织抗酸性增强，而且激光照射不对牙体硬组织造成热损伤。

A study on acquired acid resistance of enamel and dentine irradiated by Er, Cr: YSGG laser in vitro

OBJECTIVE: To evaluate the acid resistance of enamel and dentin irradiated by Er, Cr: YSGG laser to artificial caries formation in vitro. METHODS: Enamel and dentin samples were irradiated with Er, Cr: YSGG laser at 6 W or 4 W for 6 second, respectively. Every sample was immersed in 3 ml of lactic demineralization solution at pH 4.8 and incubated at 37 degrees C for 24 hours. The parts per million of calcium ion of each solution was measured by atomic absorption spectrophotometry, the quantities of calcium and phosphate on the surface of enamel and dentin sample were examined by SED-X and the ultrastructure was investigated by SEM. RESULTS: In the enamel and dentin samples, the dissolved Ca(2+) concentration in laser group were significantly decreased compared with that of the control group (P < 0.05). The quantities of Ca (weight%) in enamel and dentin were significantly higher in the laser group than in the control group (P < 0.05). The content of P was increased in dentin and enamel samples, but only the increase in enamel sample was significant (P < 0.05). In both samples, no significant changes on Ca/P weight ratio were found between the groups. The irradiated enamel and dentin surface lacked a smear layer and showed various patterns of microirregulation with a scaly appearance, the openings of dentinal tubules were clearly visible, but no melting or carbonization was observed. CONCLUSION: Er, Cr: YSGG laser irradiation is effective for increasing acid resistance of dental hard tissue and does not cause thermal side effect.