Mörmann W H, Bindl A, Lüthy H, Rathke A
Department of Preventive Dentistry, University of Zurich, Switzerland.
Int J Prosthodont. 1998 Jul-Aug;11(4):333-9.
Computer-aided design/computer-integrated machining (CAD/CIM) allows defect-oriented custom-shaping of the inside surfaces of all-ceramic crowns. The purpose of this study was to examine the effect of inside crown form on fracture strength of cemented and bonded crowns.
Four preparation types were used: (1) "classic" with a butt shoulder of 1.2 mm, abutment height of 4 mm, and 6-degree convergence, (2) like type 1 with mesio-occlusodistal cavity, (3) like type 1 with height reduced by 50%, and (4) like type 1 with abutment reduced by 100% plus a pulp chamber cavity. Crowns were CAD designed on preparations 1 to 4 using identical outside morphology. Machined crowns were placed on abutments (a) without any media as controls (n = 15), (b) cemented (n = 15), and (c) bonded (n = 15), and were loaded until fracture.
Zinc phosphate-cemented crowns (1b, 2b, 3b, and 4b) showed significant (P < 0.001) increase of fracture load values compared to uncemented control crowns (1a, 2a, 3a, 4a). Fracture load values of bonded crowns (1c, 2c, 3c) were significantly (P < 0.001) higher than those for cemented crowns. Bonded crowns with thick occlusal dimensions (3c and 4c) showed the highest fracture load values.
Bonded all-ceramic CAD/CIM crowns with defect-oriented inside morphology and increased occlusal dimensions showed high fracture load values.
计算机辅助设计/计算机集成制造（CAD/CIM）技术可实现全瓷冠内表面的缺陷导向定制塑形。本研究旨在探讨冠内形态对粘结和非粘结全瓷冠断裂强度的影响。
采用四种预备类型：（1）“经典型”，对接肩台为1.2mm，基牙高度为4mm，聚合度为6°；（2）类似于类型1，但有近中-咬合-远中洞；（3）类似于类型1，但高度降低50%；（4）类似于类型1，但基牙减少100%并加上髓腔洞。使用相同的外部形态在预备体1至4上进行CAD设计制作全瓷冠。将加工好的全瓷冠放置在基牙上：（a）不使用任何介质作为对照（n = 15）；（b）粘结（n = 15）；（c）粘结（n = 15），然后加载直至断裂。
与未粘结的对照冠（1a、2a、3a、4a）相比，磷酸锌粘结冠（1b、2b、3b和4b）的断裂载荷值显著增加（P < 0.001）。粘结冠（1c、2c、3c）的断裂载荷值显著高于粘结冠（P < 0.001）。具有较厚咬合面尺寸的粘结冠（3c和4c）显示出最高的断裂载荷值。
具有缺陷导向内部形态且咬合面尺寸增加的粘结式全瓷CAD/CIM冠显示出较高的断裂载荷值。
