Department of Prosthodontics, University Hospital Heidelberg, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany.
Department of Prosthodontics, University Hospital Heidelberg, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany.
Dent Mater. 2022 Oct;38(10):1565-1574. doi: 10.1016/j.dental.2022.07.004. Epub 2022 Aug 4.
To test strength and reliability of 3D printed compared to milled zirconia.
Cylindrical specimens were fabricated from milled (group G1; e.max ZirCAD LT) and from 3D printed (group G2; LithaCon 3Y 230) 3-mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP). While G1 and G2 were sintered in one step, a further series (G3) of 3D printed 3Y-TZP was sintered in two steps including intermediate color infiltration. In each group, two different conditioning strategies were applied (n ≥ 20 samples/subgroup): (1) final polishing with #1200 diamond discs according to ISO 6872, and (2) final polishing with #220 diamond discs resulting in imperfectly polished surfaces. All samples were tested to fracture with a universal testing device (cross-head speed: 1 mm/min). Characteristic strengths and Weibull moduli were calculated. Effects were analyzed by means of either ANOVA (homocedastic data) or Welch ANOVA (heterocedastic data).
For samples conditioned according to ISO 6872, mean flexural strengths were 1462 ± 105 MPa (G1), 1369 ± 280 MPa (G2), and 1197 ± 317 MPa (G3). For the imperfectly polished subgroups, strength values were 1461 ± 121 MPa (G1), 1349 ± 332 MPa (G2), and 1271 ± 272 MPa (G3). Although all groups showed high mean strength values, the reliability of milled zirconia (Weibull moduli 14 < m <16) outperformed that of the 3D-printed material (3 < m <6).
Even after color infiltration in a partially sintered state, the tested 3D printed zirconia exceeded the ISO flexural strength criteria for all types of fixed ceramic restorations by far (800 MPa for class 6, ISO 6872), indicating its high potential for clinical use. Further optimization of the internal material structure after sintering might improve the reliability of 3D printed zirconia which is currently inferior to that of milled zirconia.
测试 3D 打印与铣削氧化锆的强度和可靠性。
从铣削（组 G1；e.max ZirCAD LT）和 3D 打印（组 G2；LithaCon 3Y 230）3mol%氧化钇稳定四方氧化锆多晶体制备圆柱形试件。虽然 G1 和 G2 一次性烧结，但进一步的 3D 打印 3Y-TZP 系列（G3）进行了两次烧结，包括中间颜色渗透。在每组中，应用了两种不同的预处理策略（n≥20 个样品/亚组）：（1）根据 ISO 6872 用#1200 金刚石盘进行最终抛光，（2）用#220 金刚石盘进行最终抛光，导致表面抛光不完全。所有样品均在万能试验机（十字头速度：1mm/min）上进行断裂测试。计算特征强度和威布尔模量。通过方差分析（同方差数据）或 Welch ANOVA（异方差数据）分析效果。
根据 ISO 6872 进行预处理的样品，抗弯强度平均值为 1462±105MPa（G1）、1369±280MPa（G2）和 1197±317MPa（G3）。对于抛光不完全的亚组，强度值为 1461±121MPa（G1）、1349±332MPa（G2）和 1271±272MPa（G3）。尽管所有组都显示出较高的平均强度值，但铣削氧化锆（威布尔模数 14<m<16）的可靠性优于 3D 打印材料（3<m<6）。
即使在部分烧结状态下进行颜色渗透后，测试的 3D 打印氧化锆仍远远超过所有类型固定陶瓷修复体的 ISO 弯曲强度标准（6 类为 800MPa，ISO 6872），表明其在临床应用中有很大的潜力。烧结后进一步优化内部材料结构可能会提高 3D 打印氧化锆的可靠性，目前其可靠性逊于铣削氧化锆。
