Master's Candidate and Resident, Department of Prosthodontics , Peking University School and Hospital of Stomatology, Beijing, PR China.
Technician, Dental Laboratory, Peking University School and Hospital of Stomatology, National Clinical Research Center for Oral Diseases, National Engineering Laboratory for Digital and Material Technology of Stomatology, Beijing Key Laboratory of Digital Stomatology, Beijing, PR China, Peking University School and Hospital of Stomatology, Beijing, PR China; and Department of Dental Materials, Peking University School and Hospital of Stomatology, Beijing, PR China.
J Prosthet Dent. 2024 Feb;131(2):331.e1-331.e7. doi: 10.1016/j.prosdent.2023.10.027. Epub 2023 Nov 17.
Despite studies focusing on the accuracy and dimensional stability of additive manufacturing, research on the impact of storage conditions on these properties of 3-dimensional (3D) printed objects is lacking.
The purpose of this in vitro study was to investigate the influence of storage temperature on the dimensional stability of digital light processing (DLP) printed casts and to determine how different locations in printed casts react differently.
A completely dentate maxillary typodont model was digitized with a desktop laser scanner. The typodont was subsequently modified with a software program by adding cuboids with a side length of 3 mm on both maxillary central incisors, first molars, and second molars. The file was saved in the standard tessellation language (STL) format. The modified digitized typodont was then processed through the DLP technology printing process with a desktop DLP printer and photopolymerizing resin. The casts were printed 32 times and stored in sealed plastic bags, shielded from light, and subjected to 4 different temperature conditions (-20 °C, 4 °C, 20 °C, and 37 °C, n=8 each). The cuboids on the central incisors were labeled as the P1 group, first molars as the P2 group, and second molars as the P3 group. The distance between the cuboids was measured 5 times, with results recorded immediately after cast production and at 1, 2, 3, 5, 7, 14, and 28 days after. Repeated analysis of variance (ANOVA) and the Tukey honestly significant difference (HSD) test were used to compare the recorded values among the groups (α=.05).
In the P1 group, the casts stored at -20 °C exhibited the smallest overall size change, with a mean ±standard deviation volume of 99.42 ±0.04% compared with the original casts after 28 days of storage. This was followed by the casts stored at 4 °C, 20 °C, and 37 °C, with remaining volumes of 99.39 ±0.06% (P=.139), 99.14 ±0.08% (P<.001), and 98.96 ±0.03% (P<.001), respectively. For the P2 and P3 groups, casts stored at 4 °C retained the most volume at 99.82 ±0.01%, whereas those stored at -20 °C, 20 °C, and 37 °C underwent greater changes, with remaining volumes of 99.66 ±0.03%, 100.32 ±0.02%, and 100.44 ±0.02%, respectively (P<.001). The P3 group exhibited a similar trend to that of the P2 group, with the casts stored at 4 °C remaining closest to the original dimensions at 99.86 ±0.02%, while casts stored at -20 °C showed 99.73 ±0.03% of the original volume and those stored at 20 °C and 37 °C expanded with volumes of 100.37 ±0.03% and 100.48 ±0.03%, respectively (P<.001).
DLP printed casts stored at 4 °C exhibited the greatest overall dimensional stability, followed sequentially by those stored at -20 °C, 20 °C, and 37 °C. Additionally, the study confirmed that the posterior and anterior teeth regions of DLP printed casts respond differently to different storage temperatures.
尽管有研究专注于增材制造的准确性和尺寸稳定性，但关于存储条件对 3D 打印物体这些特性的影响的研究却很少。
本体外研究的目的是调查存储温度对数字光处理（DLP）打印牙模的尺寸稳定性的影响，并确定打印牙模的不同部位如何对不同的存储温度做出不同的反应。
使用桌面激光扫描仪对完全有牙的上颌模型进行数字化。随后，通过在模型的上颌中切牙和第一、第二磨牙上添加边长为 3 毫米的长方体，使用软件程序对模型进行修改。文件以标准 tessellation language（STL）格式保存。然后，通过桌面 DLP 打印机和光聚合树脂对修改后的数字化模型进行 DLP 技术打印处理。打印牙模 32 次，并储存在密封塑料袋中，避光，并置于 4 种不同的温度条件下（-20°C、4°C、20°C 和 37°C，每组 8 个）。中切牙上的长方体标记为 P1 组，第一磨牙标记为 P2 组，第二磨牙标记为 P3 组。5 次测量长方体之间的距离，在牙模生产后以及第 1、2、3、5、7、14 和 28 天立即记录结果。使用重复方差分析（ANOVA）和 Tukey Honestly 显著差异（HSD）检验来比较组间记录值（α=.05）。
在 P1 组中，储存于-20°C 的牙模体积变化最小，储存 28 天后的总体积变化率为 99.42±0.04%，与原始牙模相比。其次是储存在 4°C、20°C 和 37°C 的牙模，剩余体积分别为 99.39±0.06%（P=.139）、99.14±0.08%（P<.001）和 98.96±0.03%（P<.001）。对于 P2 和 P3 组，储存在 4°C 的牙模保留的体积最大，为 99.82±0.01%，而储存在-20°C、20°C 和 37°C 的牙模变化较大，剩余体积分别为 99.66±0.03%、100.32±0.02%和 100.44±0.02%（P<.001）。P3 组与 P2 组表现出相似的趋势，储存在 4°C 的牙模最接近原始尺寸，为 99.86±0.02%，而储存在-20°C 的牙模体积为 99.73±0.03%，储存在 20°C 和 37°C 的牙模体积分别膨胀至 100.37±0.03%和 100.48±0.03%（P<.001）。
DLP 打印牙模储存于 4°C 时表现出最大的总体尺寸稳定性，其次是储存于-20°C、20°C 和 37°C 的牙模。此外，研究证实 DLP 打印牙模的后牙和前牙区域对不同的储存温度有不同的反应。
