Methods 60 extracted premolars were randomly devided into 3 groups,and respectively bonded with shedding brackets after sandblasting,shedding brackets after heat treatment and new brackets.

• 方法将60颗离体双尖牙随机平分成三组,分别粘结经喷砂处理后的脱落托槽、热处理后的脱落托槽和未经使用的新托槽,对各组作剪切粘接破坏力和拉伸粘接破坏力的测试并进行比较。