Statement of problem

Electron beam melting (EBM) is a promising additive manufacturing technique for fabricating denture baseplates; however, studies evaluating its accuracy are sparse.

Purpose

The purpose of this in vitro study was to compare the fit accuracy of titanium maxillary complete denture baseplates fabricated by using the EBM technique with those fabricated by using the conventional casting technique and to evaluate the dimensional accuracy of the EBM baseplate by using a 3-dimensional inspection software program.

Material and methods

Definitive casts of an edentulous maxilla were prepared. After the casts were optically scanned, computer-aided designs for the EBM baseplate were created by using a software program for standard tessellation language file editing. The EBM baseplates were fabricated with an EBM machine by using a Grade II titanium powder as the raw material. The cast baseplates were fabricated with a lost-wax casting technique by using refractory casts duplicated from the definitive casts. After fitting the EBM and cast baseplates to their corresponding definitive cast, they were embedded in a Type IV stone. The embedded baseplates on the casts were sectioned at 3 regions: posterior palatal seal, molar, and premolar. The maximum gaps between the baseplate and definitive cast were measured in these 3 regions. The virtual casts obtained by scanning the EBM baseplate were superimposed on the computer-aided design to evaluate the dimensional accuracy. Distribution color maps were then generated, and the mean absolute deviations and root mean square deviations were calculated. One-way analysis of variance and t tests were used for statistical analysis (α=.05).

Results

No significant differences in the maximum gaps among the 3 regions were found in the cast or EBM baseplate groups (P>.05). The EBM baseplate group showed significantly lower values than the cast baseplate group in all regions (premolar: P=.008; molar: P=.003; posterior palatal seal: P=.004). The mean maximum gap for the 3 regions in the cast baseplates was 168.0 μm and that in the EBM baseplates was 60.7 μm. The distribution color map of the EBM baseplate showed a favorable dimensional accuracy. The mean absolute deviation value was 19.7 μm, and the root mean square deviation value was 25.1 μm.

Conclusions

The EBM baseplates had a significantly higher fit accuracy than the cast baseplates. Thus, the fit accuracy of the EBM technique is suitable for fabricating metal baseplates.

中文翻译：

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电子束熔化技术制作的钛合金上颌全口义齿基板的准确性：体外研究

问题陈述

电子束熔化 (EBM) 是一种很有前途的增材制造技术，用于制造义齿底板；然而，评估其准确性的研究很少。

目的

本体外研究的目的是比较使用 EBM 技术制造的钛上颌全口义齿基板与使用传统铸造技术制造的钛上颌全口义齿基板的配合精度，并使用 3 维评估 EBM 基板的尺寸精度。检查软件程序。

材料与方法

准备了无牙颌骨的最终模型。在对铸件进行光学扫描后，使用用于标准曲面细分语言文件编辑的软件程序创建 EBM 底板的计算机辅助设计。EBM 基板是用 EBM 机制造的，使用 II 级钛粉作为原材料。通过使用从最终铸件复制的耐火铸件，通过失蜡铸造技术制造铸造基板。在将 EBM 和铸造底板安装到相应的最终铸件上后，将它们嵌入 IV 型宝石中。铸件上嵌入的底板被分成 3 个区域：后腭密封、磨牙和前磨牙。在这 3 个区域中测量了底板和最终铸件之间的最大间隙。通过扫描 EBM 基板获得的虚拟铸件叠加在计算机辅助设计上，以评估尺寸精度。然后生成分布颜色图，并计算平均绝对偏差和均方根偏差。方差的单向分析和t检验用于统计分析 (α=.05)。

结果

在铸件或 EBM 基板组中，3 个区域之间的最大间隙没有显着差异（P > .05）。EBM 底板组在所有区域均显示出显着低于铸造底板组的值（前磨牙：P =.008；磨牙：P =.003；后腭密封：P =.004）。铸造基板中 3 个区域的平均最大间隙为 168.0 μm，EBM 基板中的平均最大间隙为 60.7 μm。EBM 底板的分布颜色图显示出良好的尺寸精度。平均绝对偏差值为19.7 μm，均方根偏差值为25.1 μm。

结论

EBM 底板的配合精度明显高于铸造底板。因此，EBM 技术的配合精度适用于制造金属基板。