Doctoral student, Department of Dental Laboratory Science and Engineering, College of Health Science, Korea University, Seoul, Republic of Korea.
Researcher, Medical Device Research Division, National Institute of Food and Drug Safety Evaluation, Osong, Republic of Korea.
J Prosthet Dent. 2021 Jan;125(1):139-145. doi: 10.1016/j.prosdent.2019.12.014. Epub 2020 Feb 20.
Layer thickness in additive manufacturing has stair-step effects that greatly affect the accuracy of the definitive prosthesis. Although the layer thickness can be set, insufficient data comparing and analyzing the accuracy of the fabricated prosthesis after adjusting the layer thickness are available.
The purpose of this in vitro study was to evaluate and compare the accuracy of trial dentures fabricated with different layer thicknesses by using stereolithography (SLA) apparatus.
A maxillary complete edentulous cast was duplicated with silicone material to make a master gypsum cast which was scanned by using a laboratory scanner and saved as a standard tessellation language (STL) file. This was exported into a computer-aided design software program to produce and store the trial denture. Twenty dentures were fabricated according to the set layer thicknesses (50 μm and 100 μm) by using the SLA. The trueness was measured by scanning the intaglio and cameo surfaces to find the best overlap with the reference model to obtain the root mean square value. The precision was evaluated based on the RMS value gained by superimposing the identical scan data from each group and using the combination formula. The Mann-Whitney U-test was used to confirm significant differences among the groups (α=.05).
The trueness of the 50-μm-SLA trial denture and the 100-μm-SLA trial denture was significantly different for the intaglio and cameo surfaces (P<.05). However, the intaglio surface did not show a statistically significant difference (P=.987) for precision, but the cameo surface did (P<.05).
It is clinically more appropriate to set the layer thickness to 100 μm rather than 50 μm for the fabrication of accurate trial dentures by using SLA.
增材制造中的层厚具有阶梯效应，极大地影响了最终修复体的精度。尽管可以设置层厚，但对于调整层厚后制造的修复体的精度比较和分析，数据还不够充分。
本体外研究的目的是评估和比较使用立体光固化（SLA）设备制造不同层厚的试戴义齿的准确性。
用硅橡胶材料复制上颌全口无牙颌模型，制作石膏母模，用实验室扫描仪扫描，保存为标准 tessellation language（STL）文件。将其导入计算机辅助设计软件程序中，制作和存储试戴义齿。根据设定的层厚（50μm 和 100μm），使用 SLA 制作了 20 个义齿。通过扫描凹面和凸面，找到与参考模型最佳重叠的位置来测量准确性，以获得均方根值。根据从每组中叠加相同扫描数据并使用组合公式获得的 RMS 值来评估精度。使用 Mann-Whitney U 检验来确认组间的显著差异（α=.05）。
50-μm-SLA 试戴义齿和 100-μm-SLA 试戴义齿的凹面和凸面的准确性有显著差异（P<.05）。然而，对于精度，凹面没有统计学上的显著差异（P=.987），但凸面有（P<.05）。
在使用 SLA 制造准确的试戴义齿时，临床更适合将层厚设置为 100μm 而不是 50μm。
