Methods: The retentive force of 10 samples of modified RPI clasps was measured on a human mandible with intact teeth of 7+7 with a multi functional tester(Instron Co.USA).

• 方法 :采用人离体下颌骨作为模型 ,在垂直脱位力作用下 ,测试改良RPI卡环的固位力 ,并分别与RPA卡环及RPI卡环比较。