铸造金属全冠的基本固位条件是牙冠高度、聚合度和表面面积。铸件和洞壁的表面粗糙程度也有助于固位,但影响较小。粘结剂的粘结强度也能帮助固位。牙冠短小,错位或形态异常的牙难以获得足够的固位形。为了改进不正常冠的固位,本文研究了针道对于加强全冠固位的效果。材料和方法选择10个拔除的无龋磨牙彻底清洁,在牙根部制作固位沟,目的是使之在实验中不会产生移动,将已制备基牙的根部平齐颈部,埋藏在自凝塑料内,然后将一半基牙制 Casting metal crown of the basic retention conditions are crown height, degree of polymerization and surface area. The surface roughness of the castings and cave walls also contribute to retention, but with less impact. The bond strength of the adhesive can also help retain the position. Tooth short crown, malposition or abnormal shape of the teeth is difficult to get enough retention shape. In order to improve the retention of abnormal crowns, this paper studies the effect of needle track on enhancing crown retention. MATERIALS AND METHODS Ten clean unpolluted molars were selected and thoroughly cleaned. A retention groove was made at the root of the tooth. The purpose was to make it free from movement during the experiment. The neck of the prepared abutment was aligned with the neck and buried in self- Plastic inside, then half the abutment system