工作时间对双固化树脂水门汀性能的影响

目的 对比两种类型的双固化树脂水门汀不同的工作时间对其粘结性能的影响。方法 选用正畸拔除或牙周病拔除的新鲜无龋坏单根管前磨牙60颗,随机分成两组。分别使用Embr aceTM及ParaCore充填桩道。在控制室温为25 ℃的条件下，每种材料的操作时间（混合材料至完全固化）分别为1 min，3 min，7 min。1 d后，自凝树脂包埋，分别截取冠部、根颈部、根尖部组织切片。微推出实验测量粘结强度。最后进行电镜观察，观察电镜下粘结界面的形态。结果 ParaCore在3种工作时间条件下，粘结强度均高于EmbraceTM,且差异有统计学意义( P< 0.01)。在操作时间为1 min时，ParaCore根颈部粘结失败的数量明显多于EmbraceTM组。每种材料的粘结强度依次随操作时间的增大而减少，同时发生粘结失败的几率也减小。结论 ParaCore具有较高的粘结性能，但临床可控工作时间较短，且易受操作环境的影响，容易发生粘结失败。EmbraceTM虽然粘结性能弱于ParaCore，但临床可控工作时间较长，且受操作环境影响的程度要低于ParaCore。无论何种粘结系统均应推迟光照激活，在确保充分的工作时间的同时获得材料更好的粘结强度及机械性能。

The influence of working time on the property of dual-cured resin cement

Objective To investigate the effect of various working time on the adhesive property of two commercial dual-cured resin cements. Methods 60 extracted human premolars were randomly assigned to two groups. Two commercial resin cements（EmbraceTM and ParaCore） were used to cement at three kinds of working time（1 min，3 min and 7 min).The whole process was conducted at 25 ℃. After 24 h, each tooth was embedded by PMMA. Then each tooth was sectioned into three blocks that were approximately 1mm thick from the coronal, cervical and apical parts of the tooth. All bond strength of specimens was tested by a universal testing machine. Contrast adhesive interface between original and tested specimens was observed by scanning electron microscope（SEM）. Results There was statistically significant difference in bond strength between ParaCore and EmbraceTM. The bond strength of ParaCore was higher than EmbraceTM at all kinds of working time. But as working time was 1 min, the cervical specimens of ParaCore showed higher failure rate than the same parts of EmbraceTM. Bond strength and failure rate decreased with the increase of the working time .Conclusion Although ParaCore can produce a higher adhesive property, clinical controlled time (CCT) is shorter, and it is more easily affected by the operational environment and it fails more easily. Although EmbraceTM bonding performance is weaker, its CCT is longer, and it is less susceptible to external environment influence. Whatever the bonding system is, the light curing time should be extended, to ensure sufficient time to work on and at the same time get better bonding strength and mechanical properties of the materials.