Faculty of Dental Medicine, Al-Azhar University, Cairo, Egypt.
J Prosthet Dent. 2010 Jan;103(1):45-52. doi: 10.1016/S0022-3913(09)60216-X. Epub 2009 Dec 22.
Titanium is the most biocompatible metal used for dental casting; however, there is concern about its marginal accuracy after porcelain application since this aspect has direct influence on marginal fit.
The purpose of this study was to determine the effect that metal selection and the porcelain firing procedure have on the marginal accuracy of metal ceramic prostheses.
Cast CP Ti, milled CP Ti, cast Ti-6Al-7Nb, and cast Ni-Cr copings (n=5) were fired with compatible porcelains (Triceram for titanium-based metals and VITA VMK 95 for Ni-Cr alloy). The Ni-Cr alloy fired with its porcelain served as the control. Photographs of metal copings placed on a master die were made. Marginal discrepancy was determined on the photographs using an image processing program at 8 predetermined locations before airborne-particle abrasion for porcelain application, after firing of the opaque layer, and after firing of the dentin layer. Repeated-measures 2-way ANOVA was used to investigate the effect of metal selection and firing stage, and paired t tests were used to determine the effect of each firing stage within each material group (alpha=.05).
ANOVA showed that both metal selection and firing stage significantly influenced the measured marginal discrepancy (P<.001), and there was interaction between the 2 variables (P<.001). Student-Newman-Keuls multiple comparison tests showed that there were significant differences between any 2 metals compared, at each stage of measurement. Paired t tests showed that significant changes in marginal discrepancy occurred with opaque firing on milled CP Ti (P=.017) and cast Ti-6Al-7Nb alloy (P=.003).
Titanium copings fabricated by CAD/CAM demonstrated the least marginal discrepancy among all groups, while the base metal (Ni-Cr) groups exhibited the most discrepancy of all groups tested.
钛是用于牙科学铸造的最生物相容的金属；然而，人们担心在施加瓷层后其边缘精度会受到影响，因为这方面直接影响边缘适合性。
本研究的目的是确定金属选择和瓷烧制程序对金属陶瓷修复体边缘精度的影响。
铸造 CP Ti、铣削 CP Ti、铸造 Ti-6Al-7Nb 和铸造 Ni-Cr 冠（n=5）与配套瓷粉（钛基金属的 Triceram 和 Ni-Cr 合金的 VITA VMK 95）一起烧制。用其瓷烧制的 Ni-Cr 合金作为对照。将金属冠放置在主模具上的照片制成。在进行瓷层喷涂前的空气颗粒磨损前、不透明层烧制后和牙本质层烧制后，使用图像处理程序在 8 个预定位置确定边缘差异。使用重复测量 2 方式 ANOVA 研究金属选择和烧制阶段的影响，使用配对 t 检验确定每个材料组内每个烧制阶段的影响（α=.05）。
ANOVA 表明，金属选择和烧制阶段都显著影响所测量的边缘差异（P<.001），并且这两个变量之间存在相互作用（P<.001）。Student-Newman-Keuls 多重比较检验表明，在每个测量阶段，任何两种金属之间都存在显著差异。配对 t 检验表明，在铣削 CP Ti（P=.017）和铸造 Ti-6Al-7Nb 合金（P=.003）的不透明烧制阶段，边缘差异发生了显著变化。
CAD/CAM 制造的钛冠在所有组中表现出最小的边缘差异，而基底金属（Ni-Cr）组表现出所有测试组中最大的差异。
