UCLA School of Dentistry, Los Angeles, CA 90095-1668, USA.
J Prosthet Dent. 2012 Mar;107(3):163-9. doi: 10.1016/S0022-3913(12)60050-X.
Porcelain fused to zirconia prostheses are widely used. However, porcelain chipping, spalling, fracture, and delamination are common clinical problems. Residual stresses of thermal origin have received attention, but clear data and firing guidelines remain absent.
The purpose of this study was to measure the influence of heating and cooling protocols on the strength of porcelain fused to zirconia.
A modified 4-point flexural testing technique was used to measure strength, and porcelain buttons were bonded to the beam between the 2 central loading points. Beams (n=54) were made of a tetragonal polycrystalline zirconium dioxide that was partially stabilized with an yttria core and a feldspathic dental porcelain. Three different heating rates and 3 different cooling regimens were used during firing. Two-way analysis of variance (ANOVA) was used to evaluate the 2 main effects of the heating and cooling regimens and their interaction with the delamination force (α=.05). The Tukey multiple comparisons test was used to identify differences among heating or cooling regimens.
During loading, the porcelain buttons separated from the zirconia beams because of delamination within the porcelain, which was close to the porcelain to zirconia interface. ANOVA revealed that the effects of the cooling regimen and heating rate had statistically significant effects on failure load (P<.05). The effect of the cooling regimen was greater than that of the heating regimen.
Slow cooling and slow heating regimens should be used when firing porcelain to zirconia. Cooling regimens were found to be more influential than heating rates. Failure was localized to the porcelain adjacent to the porcelain-zirconia interface, not to the interface itself, indicating that the residual stresses of thermal origin within the porcelain dominated. The preparation of zirconia with 50 μm aluminum oxide at a pressure of 0.34 MPa was sufficient to prevent interfacial failure.
烤瓷熔附氧化锆修复体被广泛应用。然而，瓷裂、剥落、断裂和分层是常见的临床问题。热残余应力受到了关注，但仍缺乏明确的数据和烧制指南。
本研究旨在测量加热和冷却方案对烤瓷熔附氧化锆强度的影响。
采用改良的四点弯曲测试技术测量强度，将瓷按钮粘接到位于两个中心加载点之间的梁上。梁（n=54）由部分稳定的四方多晶氧化锆制成，核心为氧化钇，基底为长石质牙科瓷。烧制过程中使用了 3 种不同的加热速率和 3 种不同的冷却方案。采用双向方差分析（ANOVA）评估加热和冷却方案的 2 个主要效应及其与分层力的相互作用（α=0.05）。采用 Tukey 多重比较检验来确定加热或冷却方案之间的差异。
在加载过程中，由于瓷层内的分层，瓷按钮从氧化锆梁上分离，这与瓷层与氧化锆层之间的界面接近。ANOVA 显示，冷却方案和加热速率对失效载荷有统计学显著影响（P<.05）。冷却方案的影响大于加热方案。
烧制烤瓷熔附氧化锆时应采用缓慢冷却和缓慢加热方案。冷却方案比加热方案的影响更大。失效发生在靠近瓷-氧化锆界面的瓷层中，而不是界面本身，这表明瓷层内的热残余应力起主导作用。用 0.34 MPa 的压力对氧化锆进行 50 μm 氧化铝预处理足以防止界面失效。
