Dental Materials Science, Discipline of Applied Oral Sciences and Community Dental Care, Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR.
Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hong Kong SAR.
J Prosthodont Res. 2021 Aug 21;65(3):311-320. doi: 10.2186/jpr.JPR_D_20_00002. Epub 2020 Oct 6.
Purpose To seek a simple solution that can recycle and regenerate dental CAD/CAM zirconia green blanks from its waste residuals.Methods Waste residuals (3M® Lava™ Plus HT) were pulverized after dry milling and cutting, and subsequently sieved before pickling in a 0.5 M nitric acid. These powders were then dry-pressed and pre-sintered into blocks at seven different temperatures in the range 800-1100 °C. New zirconia blocks flagged with the same batch numbers were used as control. These blocks were cut into bars before subjected them to manufacturer-recommended sintering at 1450 °C. Crystalline phases (by XRD), elemental compositions (by EDX), surface morphologies (by SEM), machinability, linear shrinkage rate, relative density, and Knoop microhardness were evaluated before and after sintering, and four-point flexural strengths were also evaluated for the sintered zirconia bars.Results Only tetragonal phases were found in both pre- and fully-sintered recycled zirconia blocks. SEM results showed that pre-sintered samples at 950 °C had smooth and flat surfaces with evenly distributed particles. Recycled and control zirconia blocks had similar elemental compositions. Results from machined surface, linear shrinkage rate, relative density, and Knoop microhardness established that 950 °C and 1000 °C were suitable pre-sintering temperatures for recycling zirconia. Pre-sintered recycled zirconia had no significant differences in flexural strengths, however, samples pre-sintered at 1000 °C exhibited the closest value (897 MPa) compared to that of the control (904 MPa).Conclusions Dental CAD/CAM zirconia can be recycled and reused from its waste residuals by adopting a simple method that requires a pre-sintering at 950 or 1000 °C.
目的 寻求一种简单的解决方案，以从废弃的牙科 CAD/CAM 氧化锆坯料中回收和再生氧化锆。
方法 将废弃的氧化锆废料（3M® Lava™ Plus HT）经过干法研磨和切割后进行粉碎，然后在 0.5 M 硝酸中酸洗前进行筛分。然后将这些粉末进行干压并在 800-1100°C 的七个不同温度下预烧结成块。使用相同批次编号标记的新氧化锆块作为对照。这些块被切割成棒材，然后按照制造商建议在 1450°C 下烧结。评估烧结前后的晶体相（XRD）、元素组成（EDX）、表面形貌（SEM）、可加工性、线性收缩率、相对密度和努普硬度，并评估烧结氧化锆棒材的四点弯曲强度。
结果 仅在预烧结和完全烧结的回收氧化锆块中发现四方相。SEM 结果表明，950°C 下的预烧结样品表面光滑平整，颗粒分布均匀。回收和对照氧化锆块具有相似的元素组成。加工表面、线性收缩率、相对密度和努普硬度的结果表明，950°C 和 1000°C 是适合回收氧化锆的预烧结温度。预烧结回收氧化锆的弯曲强度没有显著差异，但在 1000°C 下预烧结的样品表现出与对照值（904 MPa）最接近的值（897 MPa）。
结论 通过采用需要在 950 或 1000°C 下预烧结的简单方法，可以从废弃的牙科 CAD/CAM 氧化锆中回收和再利用氧化锆。
