Zhou Tuan-feng, Wang Xin-zhi
Department of Prosthodontics, Peking University School and Hospital of Stomatology, Beijing 100081,China.
Beijing Da Xue Xue Bao Yi Xue Ban. 2012 Feb 18;44(1):93-7.
To compare the stress distribution of teeth restored with one-piece of computer aided design and computer aided manufacturing (CAD/CAM) zirconia post-cores in three different radiuses.
Constructing the 2D finite element models of the standard maxillary central incisal restored by one-piece of CAD/CAM zirconia post-cores and all ceramic crowns, the radius of post was 1.5 mm, 2.0 mm and 2.5 mm respectively. Two tooth root types with or without the ferrule were constructed and there were 6 models in general. Group 1:100 N force loading to the restored teeth through the long axle of teeth and veritical the incisal edge. Group 2: 100 N inclined force loading beneath the incisal edge 2.0 mm by 45° cross the long axle of teeth in the palate side. The stress distribution characteristic of post-cores and teeth roots were analysed.
In veritical loading, the stress distribution of one-piece of CAD/CAM zirconia post-core with 2.0 mm radius was better distributed than the two others, The stress concentration of teeth roots locate at the root canal wall where the end of the post exists, which increased with the wider radius of the post-core. In 45° inclined loading, the maximum stress of the zirconia post-core and the teeth root was more than three times of which in vertical loading. In post-cores, the stress concentration was in the labia middle 1/3 of the post. In teeth roots, the stress concentration located at the lateral wall in the post end and the area of the apical foramen. The stress of the post-cores and teeth roots was decreasing in the teeth root with a 2.0 mm ferrule.
2.0 mm radicus of the one-piece of CAD/CAM zirconia post-core is a better choice in clinic. There should be a conical degree in the teeth roots preparing for one-piece of CAD/CAM zirconia post-core restoration. The force of protrusive movement has a greater influence on the post-core and teeth roots. The area of apical may be apt to break in overloading.
比较三种不同半径的一体化计算机辅助设计与计算机辅助制造（CAD/CAM）氧化锆桩核修复牙齿的应力分布。
构建由一体化CAD/CAM氧化锆桩核和全瓷冠修复的标准上颌中切牙的二维有限元模型，桩的半径分别为1.5mm、2.0mm和2.5mm。构建两种有或无箍的牙根类型，共6个模型。第1组：通过牙齿长轴并垂直于切缘向修复后的牙齿施加100N力。第2组：在腭侧切缘下方2.0mm处，以45°角与牙齿长轴交叉施加100N斜向力。分析桩核和牙根的应力分布特征。
垂直加载时，半径为2.0mm的一体化CAD/CAM氧化锆桩核应力分布优于其他两种，牙根应力集中位于桩末端所在的根管壁处，且随桩核半径增大而增加。45°斜向加载时，氧化锆桩核和牙根的最大应力是垂直加载时的三倍以上。在桩核中，应力集中在桩的唇侧中1/3处。在牙根中，应力集中位于桩末端的侧壁和根尖孔区域。有2.0mm箍的牙根中桩核和牙根的应力降低。
一体化CAD/CAM氧化锆桩核2.0mm半径在临床上是较好的选择。在制备一体化CAD/CAM氧化锆桩核修复的牙根时应有一定锥度。前伸运动力对桩核和牙根影响较大。过载时根尖区域可能易折断。
