Bonfante Estevam A, da Silva Nelson R F A, Coelho Paulo G, Bayardo-González Daniel E, Thompson Van P, Bonfante Gerson
Department of Prosthodontics, Integrated Center for Research, Bauru School of Dentistry, University of São Paulo, Bauru, SP, Brazil.
Eur J Oral Sci. 2009 Apr;117(2):194-9. doi: 10.1111/j.1600-0722.2008.00608.x.
This study evaluated the effect of core-design modification on the characteristic strength and failure modes of glass-infiltrated alumina (In-Ceram) (ICA) compared with porcelain fused to metal (PFM). Premolar crowns of a standard design (PFMs and ICAs) or with a modified framework design (PFMm and ICAm) were fabricated, cemented on dies, and loaded until failure. The crowns were loaded at 0.5 mm min(-1) using a 6.25 mm tungsten-carbide ball at the central fossa. Fracture load values were recorded and fracture analysis of representative samples were evaluated using scanning electron microscopy. Probability Weibull curves with two-sided 90% confidence limits were calculated for each group and a contour plot of the characteristic strength was obtained. Design modification showed an increase in the characteristic strength of the PFMm and ICAm groups, with PFM groups showing higher characteristic strength than ICA groups. The PFMm group showed the highest characteristic strength among all groups. Fracture modes of PFMs and of PFMm frequently reached the core interface at the lingual cusp, whereas ICA exhibited bulk fracture through the alumina core. Core-design modification significantly improved the characteristic strength for PFM and for ICA. The PFM groups demonstrated higher characteristic strength than both ICA groups combined.
本研究评估了与金属烤瓷冠（PFM）相比，核设计改良对玻璃渗透氧化铝（In-Ceram）（ICA）的特征强度和失效模式的影响。制作了标准设计（PFM和ICA）或改良框架设计（PFMm和ICAm）的前磨牙冠，粘固在代型上，并加载直至破坏。使用直径6.25 mm的碳化钨球在中央窝处以0.5 mm/min的速度对冠进行加载。记录断裂载荷值，并使用扫描电子显微镜对代表性样本进行断裂分析。计算每组的双侧90%置信限的概率威布尔曲线，并获得特征强度的等高线图。设计改良使PFMm组和ICAm组的特征强度增加，PFM组的特征强度高于ICA组。PFMm组在所有组中显示出最高的特征强度。PFM和PFMm的断裂模式经常在舌尖处到达核界面，而ICA则通过氧化铝核出现整体断裂。核设计改良显著提高了PFM和ICA的特征强度。PFM组的特征强度高于两个ICA组的总和。
