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The Purpose of this study was to observe force required to remove some kinds of pin from dentin. The teeth were embedded within a resin cylinder and the occlusal surface was sectioned at a right angle to the axis of the cylinder to expose dentin surface. Thread mate system pin (minim and regular), friction Iocked pin and cemented pin were tested Pin holes were drilled by handpiece and depths of pin holes were tested 1,2 and 3mm. After insertion of the pins into pinhole, tensile loading was performed on the Instron testing machine at the speed of 0.5 inch/min. Results were follewed: 1. In retention, the cemented pins are the least, the friction locked pins intermediate and the self threading pins the greatest in all pins. In self threading pins, regalar pin has greater retention than minim pin 2. The deeper the depth of the pin hole is, the more the retention of the pin increases.
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