Weiss E I, Kozak D, Gross M D
The Maurice and Gabriela Goldschleger School of Dental Medicine, Tel-Aviv University, Tel Aviv, Israel.
J Prosthet Dent. 2000 Aug;84(2):194-9. doi: 10.1067/mpr.2000.108069.
Implant abutment screw joints tend to loosen under clinical conditions. During impression and prosthesis fabrication, repeated clinical closing and opening of abutment screws may cause component wear and decrease frictional fit of the mating parts, resulting in altered resistance to opening and potential for loss of preload in function.
This study recorded changes in opening torque values due to multiple consecutive closures at a constant torque within and between different abutment/implant (A/I) systems.
Repeated opening-closing cycles were used to simulate in vitro embedment relaxation and component wear of 7 A/I systems from 5 manufacturers. Screw opening torque values were recorded up to 200 consecutive closures at 20 N/cm.
A progressive decrease in opening torque values was measured in all implant systems. Significant differences were found between A/I systems. Systems with morse tapered and spline connections consistently maintained a higher resistance to opening force. Percentage torque loss ranged from 3% to 20% on immediate opening, and from 4.5% to 36% for average of first 30 opening/closing cycles.
Repeated opening and closing of implant abutment screws caused progressive loss of torque retention with variations between systems. This was probably due to a decrease in the coefficient of friction between the mating components.
种植体基台螺钉连接在临床情况下容易松动。在取印模和制作修复体过程中，基台螺钉反复的临床旋紧和旋松可能会导致部件磨损，并降低配对部件的摩擦配合，从而改变抗旋松能力，并在功能上导致预紧力丧失。
本研究记录了在不同基台/种植体（A/I）系统内部以及不同系统之间，在恒定扭矩下连续多次旋紧后，开启扭矩值的变化情况。
采用反复的旋开-旋紧循环来模拟5家制造商生产的7种A/I系统的体外嵌入松弛和部件磨损情况。在20N/cm的扭矩下，记录螺钉开启扭矩值，直至连续旋紧200次。
在所有种植体系统中均测得开启扭矩值逐渐降低。在A/I系统之间发现了显著差异。具有莫氏锥度和花键连接的系统始终保持对开启力的更高抵抗力。首次旋开时扭矩损失百分比在3%至20%之间，前30次旋开/旋紧循环的平均扭矩损失百分比在4.5%至36%之间。
种植体基台螺钉的反复旋开和旋紧导致扭矩保持力逐渐丧失，且不同系统之间存在差异。这可能是由于配对部件之间的摩擦系数降低所致。
