Abstract: Objective    To evaluate the influence of dentin age and Er，Cr∶YSGG laser on the microtensile bond strength of a rensin cement to dentin. Methods    Twenty extracted molars from subjects over 65 years old（Group A） and 20～44 years old（Group B） were selected and randomly divided into subgroups（Group A1，A2，B1，B2）. Then teeth in Group A1 and B1 were processed with Er，Cr∶YSGG laser while teeth in Group A2 and B2 were processed with high-speed dental turbine handpiece，combined with self-etching adhesive and filled with composite resin （Z350）. All subjuects were saved in distilled water for 24 hours at 37℃ .Then they were cut into hourglass-shaped specimens and the microtensile bond strength was evaluated. All specimens were examined under stero-microscope. Results    There was significant difference between aged dentin group and young dentin group （P < 0.05） but no difference between  Er，Cr∶YSGG laser group and turbine handpiece group （P > 0.05）.There was no significant difference of breakage modes among four groups（P > 0.05）.Conclusion    This in vitro study showed that aging of dentin negatively affects the microtensile bond strength，while  Er，Cr∶YSGG laser irradiation does not negatively affect the bond strength of aged and young dentin.

Key words: Er, Cr∶YSGG laser, aged dentin, microtensile bond strength, breakage mode

摘要： 目的    比较老年牙本质和青年牙本质与复合树脂间粘接强度的差异，评价Er，Cr∶YSGG激光对牙本质与复合树脂间粘接强度的影响。方法    于2012 年2—3月在中国医科大学口腔医学院收集老年人（A组）和青年人（B组）离体牙标本各10颗，每组随机分为2个亚组，即A1、A2组和B1、B2组。A1、B1组采用Er，Cr∶YSGG激光预备，A2、B2组采用传统涡轮手机预备，自酸蚀粘接剂结合Z350复合树脂充填，37 ℃水浴24 h后，制备成沙漏状试件并进行微拉伸粘接强度测试。体式显微镜下观察并记录断裂模式。结果    微拉伸粘接强度测试结果，青年牙本质组明显高于老年牙本质组，差异有统计学意义（P < 0.05）；激光预备组略高于手机预备组，差异无统计学意义（P > 0.05）。各组断裂模式多为界面断裂，组间差异无统计学意义（P > 0.05）。结论    老年牙本质由于增龄性变化导致粘接强度降低；Er，Cr∶YSGG激光预备对牙本质与复合树脂间粘接强度无不利影响，可作为传统涡轮手机的替代方法。

关键词: Er, Cr∶YSGG激光, 老年牙本质, 微拉伸粘接强度, 断裂模式