Statement of problem

Direct-metal laser-sintering (DMLS) technologies are being used to manufacture removable partial denture frameworks; however, the build parameters are not well documented.

Purpose

The purpose of this in vitro study was to investigate the impact of 3 different build angulations on a dental cobalt-chromium (Sint-Tech ST2724G) alloy by comparing the tensile properties and nanoindentation hardness. The null hypothesis was that no change would be found in the tensile properties of the different build angulation groups.

Material and methods

Dumbbell-shaped tensile specimens were produced by using stereolithographic models in accordance with American Society for Testing and Materials testing standard E8/E8M-16ae1. Specimens (n=10) were fabricated by using DMLS additive manufacturing with 3 different angulations (0, 45, and 90 degrees). Tensile testing was carried out to assess yield strength (0.2% permanent offset), elongation (%) at failure, and ultimate tensile strength (GPa). Scanning electron microscope (SEM) images were used to analyze the fracture surfaces. One 10×10×10 mm cube specimen at each orientation was prepared, and nanoindentation was used to determine hardness and elastic modulus. One-way ANOVA was used to evaluate the overall effects with interaction between groups and post hoc testing applied where the interaction was statistically significant (α=.05).

Results

The 45-degree build angulation resulted in the lowest mean elastic modulus of 213.3 GPa and the highest tensile strength of 1180.9 MPa. The 90-degree build angulation resulted in the highest mean elongation of 10.6% and the highest elastic modulus of 234.0 MPa. Within comparison of the different angulations indicated that various groups had statistically significant differences (P<.05). The SEM analysis indicated different fracture topography among the different build angles.

Conclusions

The cobalt-chromium dental alloy manufactured by DMLS produced favorable mechanical properties. The SEM analysis combined with the tensile test results suggest that the direction of the build angle in relation to the laser melt pattern does impact the mechanical properties of the alloy.

中文翻译：

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构建角度对用于可摘局部义齿框架的直接金属激光烧结钴铬合金机械性能的影响

问题陈述

直接金属激光烧结 (DMLS) 技术正用于制造可摘局部义齿支架；但是，构建参数没有很好的文档记录。

目的

这项体外研究的目的是通过比较拉伸性能和纳米压痕硬度来研究 3 种不同的构建角度对牙科钴铬 (Sint-Tech ST2724G) 合金的影响。无效假设是在不同构建角度组的拉伸特性中不会发现任何变化。

材料与方法

根据美国材料与试验协会测试标准 E8/E8M-16ae1，使用立体光刻模型制作哑铃形拉伸试样。样本 (n=10) 是通过使用具有 3 种不同角度（0、45 和 90 度）的 DMLS 增材制造制造的。进行拉伸测试以评估屈服强度（0.2% 永久偏移）、断裂伸长率 (%) 和极限拉伸强度 (GPa)。使用扫描电子显微镜 (SEM) 图像分析断裂表面。制备每个取向的 10×10×10 mm 立方体试样 1 个，采用纳米压痕法测定硬度和弹性模量。单向方差分析用于评估组间交互作用的总体效果，并在交互作用具有统计显着性 (α=.05) 的情况下应用事后检验。

结果

45 度构建角度导致 213.3 GPa 的最低平均弹性模量和 1180.9 MPa 的最高拉伸强度。90 度构建角度导致 10.6% 的最高平均伸长率和 234.0 MPa 的最高弹性模量。不同角度的比较表明，各组有统计学显着差异（P <.05）。SEM 分析表明不同构建角度之间的断裂形貌不同。

结论

DMLS 制造的钴铬牙科合金具有良好的机械性能。SEM 分析结合拉伸试验结果表明，与激光熔化模式相关的构建角度方向确实会影响合金的机械性能。