Isidor F, Brøndum K, Ravnholt G
Department of Prosthetic Dentistry and Stomatognathic Physiology, Royal Dental College, Aarhus University, Denmark.
Int J Prosthodont. 1999 Jan-Feb;12(1):78-82.
The purpose of this in vitro study was to evaluate the influence of post and ferrule length on the resistance to cyclic (fatigue) loading of teeth with prefabricated titanium posts (ParaPost) and crowns.
Ninety bovine teeth with similar dimensions were mounted in acrylic blocks with artificial silicone periodontal ligaments. Combinations of post lengths of 5 mm, 7.5 mm, and 10 mm, and ferrule lengths (i.e., the vertical dentinal overlap of the crown) of 0 mm, 1.25 mm, and 2.5 mm made up 9 different groups consisting of 10 teeth each. The posts were cemented with zinc phosphate cement. Composite-resin cores were made and crowns were cemented. Each test specimen underwent cyclic loading of 400 N with a frequency of 1 load per second at an angulation of 45 degrees to the long axis of the tooth.
All but 2 specimens failed with a root fracture; in the remaining 2 specimens the core lost retention. A large variation in the results between the various groups was observed. A nonparametric 2-way analysis for groups with a natural order revealed that the fracture resistance to cyclic loading increased statistically significantly with increasing ferrule length (P < 0.01), whereas increasing post length did not increase fracture resistance (P = 0.44).
Ferrule length was more important than post length in increasing fracture resistance to cyclic loading of crowned teeth.
本体外研究的目的是评估桩和箍套长度对采用预制钛桩（帕拉桩）和全冠修复的牙齿抗循环（疲劳）加载能力的影响。
将90颗尺寸相似的牛牙安装在带有人工硅胶牙周韧带的丙烯酸树脂块中。桩长度分别为5毫米、7.5毫米和10毫米，箍套长度（即全冠的垂直牙本质重叠部分）分别为0毫米、1.25毫米和2.5毫米，共组成99个9个不同组，每组10颗牙。用磷酸锌粘固剂粘固桩。制作复合树脂核并粘固全冠。每个测试标本以每秒1次的加载频率、400牛的载荷、与牙长轴呈45度角进行循环加载。
除2个标本外，所有标本均因牙根折断而失败；其余2个标本中核失去固位。观察到不同组之间的结果差异很大。对具有自然顺序的组进行的非参数双向分析显示，随着箍套长度增加，抗循环加载的断裂阻力在统计学上显著增加（P < 0.01），而桩长度增加并未增加断裂阻力（P = 0.44）。
在增加戴冠牙齿抗循环加载的断裂阻力方面，箍套长度比桩长度更重要。
