Chai John, Chu Frederick C S, Chow Tak W, Liang Bernard M H
Northwestern University, Evanston, Illinois, USA.
Int J Prosthodont. 2007 Nov-Dec;20(6):587-95.
This study was undertaken to investigate the chemical solubility and flexural strengths of 3 zirconia-based dental ceramics: In-Ceram Zirconia (IZ), In-Ceram 2000 YZ CUBES (YZ Zirconia) (Vita Zahnfabrik), and Cercon (Dentsply). A pressable lithium disilicate-reinforced glass ceramic (IPS Empress 2, Ivoclar Vivadent) was used as a control.
Ten block specimens (12 x 6 x 4 mm) of each ceramic material were prepared for chemical solubility testing. Each specimen was refluxed in 4% acetic acid solution for 16 hours. The percentage loss of mass and the loss of mass per unit of surface area for each specimen were calculated. Ten bar-shaped (21 x 5 x 2 mm) and 10 disk-shaped (16 mm diameter, 1.2 mm thickness) specimens of each ceramic material were prepared and tested for uniaxial flexural strength (UFS) and biaxial flexural strength (BFS). X-ray diffraction analyses were conducted to determine the relative amount of the monoclinic phase of the as-sintered and fractured surfaces of the zirconia ceramics.
There were no significant differences among the ceramics in chemical solubility by percentage mass or mass/surface area. For UFS, YZ Zirconia (899 +/- 109 MPa) > Cercon (458 +/- 95 MPa) IZ (409 +/- 60 MPa) > Empress 2 (252 +/- 36 MPa). For BFS, YZ Zirconia (1,107 +/- 116 MPa) > Cercon (927 +/- 146 MPa) > IZ (523 +/- 51 MPa) > Empress 2 (359 +/- 43 MPa). The fractured YZ Zirconia surface contained approximately 5 times as much monoclinic phase compared to that of its intact surface. The fractured IZ and Cercon surfaces contained approximately twice as much monoclinic phase compared to those of intact surfaces.
The ceramics tested all satisfied the chemical solubility allowance required of core ceramic material (type I, Class 1 or type II, Class 1) according to the International Organization for Standardization 6872:1995(E) specifications on dental ceramic. The zirconia-based ceramics possessed significantly higher flexural strengths than the control lithium disilicate ceramic. Their clinical application appears sufficiently promising for long-term clinical studies to be undertaken.
本研究旨在调查3种氧化锆基牙科陶瓷的化学溶解度和抗弯强度：In-Ceram氧化锆（IZ）、In-Ceram 2000 YZ CUBES（YZ氧化锆）（维他齿科有限公司）和Cercon（登士柏公司）。使用一种可压制的硅酸锂增强玻璃陶瓷（IPS Empress 2，义获嘉伟瓦登特公司）作为对照。
制备每种陶瓷材料的10个块状试样（12×6×4mm）用于化学溶解度测试。每个试样在4%乙酸溶液中回流16小时。计算每个试样的质量损失百分比和单位表面积的质量损失。制备每种陶瓷材料的10个条形试样（21×5×2mm）和10个盘形试样（直径16mm，厚度1.2mm），并测试其单轴抗弯强度（UFS）和双轴抗弯强度（BFS）。进行X射线衍射分析，以确定氧化锆陶瓷烧结表面和断裂表面的单斜相相对含量。
按质量百分比或质量/表面积计算，各陶瓷材料的化学溶解度无显著差异。对于UFS，YZ氧化锆（899±109MPa）＞Cercon（458±95MPa）＞IZ（409±60MPa）＞Empress 2（252±36MPa）。对于BFS，YZ氧化锆（1107±116MPa）＞Cercon（927±146MPa）＞IZ（523±51MPa）＞Empress 2（359±43MPa）。YZ氧化锆断裂表面的单斜相含量约为其完整表面的5倍。IZ和Cercon断裂表面的单斜相含量约为完整表面的2倍。
根据国际标准化组织6872:1995（E）牙科陶瓷规范，所测试的陶瓷均满足核心陶瓷材料（I类1级或II类1级）所需的化学溶解度允许范围。氧化锆基陶瓷的抗弯强度明显高于对照硅酸锂陶瓷。它们的临床应用前景似乎很广阔，值得进行长期临床研究。
