Rues Stefan, Herpel Christopher, Ilani Ali, Schmitt Clemens, Rammelsberg Peter, Schwindling Franz Sebastian
Department of Prosthodontics, Heidelberg University Hospital, Heidelberg, Germany.
Department of Prosthodontics, Heidelberg University Hospital, Heidelberg, Germany.
Dent Mater. 2024 Mar;40(3):484-492. doi: 10.1016/j.dental.2023.12.018. Epub 2023 Dec 27.
To evaluate the effect of accelerated firing on 3D-printed zirconia.
To check if formulae provided by ISO 6872 can be extended to thin samples, finite element analyses were carried out in advance of fabricating 3-mol% yttria-stabilized tetragonal zirconia polycrystal discs by milling and by 3D-printing. Four groups (n = 38 each) of 3D-printed specimens were produced with two nominal thicknesses (0.6 mm and 1.2 mm) and two firing strategies (long: 51 h, accelerated: 14.5 h). In the milled group (thickness 1.2 mm, n = 30), a standard firing program (9.8 h) was selected. Biaxial flexural strength tests were applied and mean strength, characteristic strength, and Weibull modulus were calculated for each group. Differences were analyzed using Welch ANOVA and Dunnett-T3 post-hoc tests.
Maximum tensile stresses occurring during biaxial strength testing can be calculated according to ISO 6872 for thin samples with b > 0.3 mm. Variability of measured strengths values was smaller for milled zirconia compared with 3D-printed zirconia. The 1.2-mm-thick 3D-printed samples had significantly decreased strength after accelerated firing than after long firing. However, for the 0.6-mm-thick samples, comparable mean biaxial strength values of about 1000 MPa were measured for both firing protocols.
At the moment, long fabrication time for zirconia restorations is a major drawback of 3D-printing when compared with milling technology. This investigation showed that the strength of 0.6-mm-thick zirconia discs fabricated by 3D-printing was not impaired by accelerated firing. Thus, overnight firing of thin-walled 3D-printed zirconia restorations could be possible.
评估加速焙烧对3D打印氧化锆的影响。
为检验ISO 6872提供的公式是否可扩展至薄样品，在通过铣削和3D打印制造3摩尔％氧化钇稳定的四方氧化锆多晶体圆盘之前，先进行了有限元分析。制作了四组（每组n = 38）3D打印试样，有两种标称厚度（0.6毫米和1.2毫米）和两种焙烧策略（长时间：51小时，加速：14.5小时）。在铣削组（厚度1.2毫米，n = 30）中，选择了标准焙烧程序（9.8小时）。进行双轴弯曲强度测试，并计算每组的平均强度、特征强度和韦布尔模量。使用Welch方差分析和Dunnett-T3事后检验分析差异。
对于b> 0.3毫米的薄样品，可根据ISO 6872计算双轴强度测试期间出现的最大拉应力。与3D打印的氧化锆相比，铣削氧化锆的测量强度值的变异性较小。1.2毫米厚的3D打印样品在加速焙烧后的强度明显低于长时间焙烧后的强度。然而，对于0.6毫米厚的样品，两种焙烧方案测得的双轴平均强度值相当，约为1000兆帕。
目前，与铣削技术相比，氧化锆修复体的制造时间长是3D打印的一个主要缺点。这项研究表明，通过3D打印制造的0.6毫米厚氧化锆圆盘的强度不会因加速焙烧而受损。因此，薄壁3D打印氧化锆修复体可能可以进行过夜焙烧。
