1 Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY, USA.
2 Key Laboratory of Transparent Opto-functional Inorganic Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, China.
J Dent Res. 2018 Mar;97(3):289-295. doi: 10.1177/0022034517733742. Epub 2017 Oct 4.
An ideal ceramic restorative material should possess excellent aesthetic and mechanical properties. We hypothesize that the high translucency and strength of polycrystalline ceramics can be achieved through microstructural tailoring. The aim of this study is to demonstrate the superior optical and mechanical properties of a new class of submicron grain-sized alumina ceramics relative to the current state-of-the-art dental ceramic materials. The translucency, the in-line transmission ( T) in particular, of these submicron alumina ceramics has been examined with the Rayleigh-Gans-Debye light-scattering model. The theoretical predictions related very well with the measured T values. The translucency parameter ( TP) and contrast ratio ( CR) of the newly developed aluminas were measured with a reflectance spectrophotometer on a black-and-white background. For comparison, the T, TP, and CR values for a variety of dental ceramics, mostly measured in-house but also cited from the literature, were included. The flexural strength of the aluminas was determined with the 4-point bending test. Our findings have shown that for polycrystalline alumina ceramics, an average grain size <1 µm coupled with a porosity level <0.7% could yield translucency values ( T, TP, CR) similar to those of the commercial high-translucency porcelains. These values are far superior to the high-translucency lithium disilicate glass-ceramic and zirconias, including the most translucent cubic-containing zirconias. The strength of these submicron grain-sized aluminas was significantly higher than that of the cubic-containing zirconia (e.g., Zpex Smile) and lithia-based glass-ceramics (e.g., IPS e.max CAD HT). A coarse-grained alumina could also reach a translucency level comparable to that of dental porcelain. However, the relatively low strength of this material has limited its clinical indications to structurally less demanding applications, such as orthodontic brackets. With a combined high strength and translucency, the newly developed submicron grain-sized alumina may be considered a suitable material for dental restorations.
一种理想的陶瓷修复材料应具备优异的美观和机械性能。我们假设，通过微观结构设计，可以实现多晶陶瓷的高透光率和高强度。本研究旨在展示一类新型亚微米晶粒尺寸氧化铝陶瓷相对于当前最先进的牙科陶瓷材料的卓越光学和机械性能。这些亚微米氧化铝陶瓷的透光率，特别是在线传输 (T)，已通过瑞利-甘斯-德拜光散射模型进行了研究。理论预测与实测 T 值非常吻合。用黑白背景反射分光光度计测量了新开发氧化铝的透光率参数 (TP) 和对比度比 (CR)。为了进行比较，还包括了各种牙科陶瓷的 T、TP 和 CR 值，其中大部分是在内部测量的，但也有一些是从文献中引用的。用四点弯曲试验测定了氧化铝的抗弯强度。我们的研究结果表明，对于多晶氧化铝陶瓷，平均晶粒尺寸<1 µm 且孔隙率<0.7%，可以产生类似于商业高透光率陶瓷的透光率值 (T、TP、CR)。这些值远优于高透光率的锂二硅玻璃陶瓷和氧化锆，包括最透光的含立方氧化锆。这些亚微米晶粒尺寸的氧化铝的强度明显高于含立方氧化锆的氧化锆（例如 Zpex Smile）和含锂的玻璃陶瓷（例如 IPS e.max CAD HT）。粗晶粒氧化铝也可以达到与牙科瓷相当的透光率水平。然而，这种材料相对较低的强度限制了其在临床上的应用，仅限于结构要求较低的应用，如正畸托槽。新开发的亚微米晶粒尺寸氧化铝具有高强度和透光率，可被视为牙科修复的合适材料。
