Department of Stomatology, University of Valencia, Valencia, Spain.
Int J Prosthodont. 2012 May-Jun;25(3):294-300.
Clinical studies have revealed a high rate of fracture for porcelain-veneered zirconia-based restorations that varies between 6% and 15% over a 3- to 5-year period. These are high values compared to the 4% fracture rate shown by conventional metal-ceramic restorations over 10 years. To date, little in vitro research has been carried out on the fracture resistance of the new generation of ceramic crowns. The aims of this study were to develop preliminary research on the mechanical failure behavior of three types of porcelain-veneered crowns with zirconia cores when subjected to static compressive loading and to analyze fracture characteristics using scanning electron microscopy (SEM).
Eighty individual full-coverage crowns were studied: 60 crowns with a zirconia core and 20 with a metal core (control).
Values obtained in compressive testing were as follows: ZirPress: 1,818.01 N, ZirCAD: 1,773.92 N, Lava: 2,210.95 N, and metal-ceramic (control): 2,310.49 N. SEM analysis revealed that 71.66% of zirconia-based restoration mechanical failures were cohesive, while 100% of mechanical failures for metal-ceramic restorations were adhesive.
The mechanical behavior of the porcelain veneering on a zirconia core is more fragile than that on metal-ceramic crowns, and when load forces exerted on these restorations lead to mechanical failure, this will occur in the interior of the porcelain veneering.
临床研究显示，在 3 至 5 年的时间内，烤瓷熔附氧化锆修复体的骨折率很高，为 6%至 15%不等。与传统金属陶瓷修复体在 10 年内显示的 4%骨折率相比，这些数值都很高。迄今为止，针对新一代陶瓷冠的抗断裂性能，体外研究甚少。本研究旨在初步研究三种氧化锆核烤瓷熔附全冠在静态压缩载荷下的机械失效行为，并使用扫描电子显微镜（SEM）分析断裂特征。
对 80 个全冠个体进行了研究：60 个具有氧化锆核的冠和 20 个具有金属核的冠（对照组）。
压缩试验中获得的值如下：ZirPress：1818.01N，ZirCAD：1773.92N，Lava：2210.95N，金属陶瓷（对照组）：2310.49N。SEM 分析显示，71.66%的氧化锆基修复体机械失效为内聚性，而 100%的金属陶瓷修复体机械失效为黏附性。
氧化锆核烤瓷的瓷层的机械行为比金属陶瓷冠更脆弱，当这些修复体上的负荷力导致机械失效时，这种失效将发生在瓷层的内部。
