Statement of problem

Information on the dimensional changes in maxillary and mandibular dentures made by using computer-aided design and computer-aided manufacturing (CAD-CAM) techniques under uniform testing conditions is lacking.

Purpose

The purpose of this in vitro study was to evaluate the dimensional changes and reproducibility of maxillary and mandibular dentures by using CAD-CAM-milled and 3D-printed techniques.

Material and methods

Maxillary and mandibular edentulous models with wax occlusal rims were scanned, and dentures were designed by using a CAD software program and fabricated by using 2 techniques and materials: CAD-CAM-milled (CCM) and 3D-printed (3DP). The 3DP fabrications included 4 subgroups: dentures printed with a 90-degree build angle with UV light polymerization on the reference model (3DP 90M), dentures printed with a 90-degree build angle and light polymerization without the reference model (3DP 90), dentures printed with a 45-degree build angle with light polymerization on the reference model (3DP 45M), and dentures printed with a 45-degree build angle and light polymerization without the reference model (3DP 45). The preprocessing and postprocessing scan files of each denture produced by CCM and 3DP were superimposed by using a surface matching software program. Ten points each on maxillary and mandibular dentures were measured for deviations after processing. Additionally, for each denture, the widths were measured between the canines and molars, the anteroposterior plane from cusp tips between the canines and molars, and the vertical plane from the cusp tip of the canines to the marginal gingiva. They were then compared with those in the denture design CAD cast. The Kruskal-Wallis analysis of variance test was used for statistical analyses (α=.05).

Results

According to digital superimposition, CCM had the smallest values of deviation with no statistical difference (P>.05), indicating more uniform results from measurement points in both maxillary and mandibular dentures, followed by 3DP 90M, 3DP 90, 3DP 45M, and 3DP 45. Regarding the width measurements, CCM had the smallest values of deviation (P<.05). In 3DP, smaller deviation values were observed at the vertical plane from the tip of the canine to the marginal gingiva, and larger values were observed in the intermolar width (P<.05).

Conclusions

CCM exhibited smaller dimensional changes and better reproducibility among the tested techniques. In 3DP, the build angle and methods of light postprocessing influenced the dimensional stability. The 90-degree build angle with additional light polymerization on the cast improved the dimensional deviations.

中文翻译：

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研磨和打印技术制造的全口义齿的尺寸变化：一项体外研究

问题陈述

缺乏关于在统一测试条件下使用计算机辅助设计和计算机辅助制造 (CAD-CAM) 技术制作的上颌和下颌义齿尺寸变化的信息。

目的

这项体外研究的目的是通过使用 CAD-CAM 铣削和 3D 打印技术评估上下颌义齿的尺寸变化和再现性。

材料与方法

带蜡咬合的上下颌无牙颌模型扫描轮辋，并使用 CAD 软件程序设计假牙，并使用 2 种技术和材料制造：CAD-CAM 铣削 (CCM) 和 3D 打印 (3DP)。3DP 制造包括 4 个子组：在参考模型 (3DP 90M) 上以 90 度构建角和 UV 光聚合打印的义齿，在没有参考模型 (3DP 90) 的情况下以 90 度构建角和光聚合打印的义齿，在参考模型 (3DP 45M) 上以 45 度构建角和光聚合打印的义齿，以及在没有参考模型 (3DP 45) 的情况下以 45 度构建角和光聚合打印的义齿。使用表面匹配软件程序将 CCM 和 3DP 生成的每个义齿的预处理和后处理扫描文件叠加在一起。处理后测量上颌和下颌义齿上各十个点的偏差。此外，对于每个义齿，测量尖牙和磨牙之间的宽度、尖牙和磨牙之间的牙尖的前后平面，以及尖牙牙尖到边缘牙龈的垂直平面。然后将它们与那些在义齿设计 CAD 铸造。Kruskal-Wallis 方差检验分析用于统计分析 (α=.05)。

结果

数字叠加显示，CCM的偏差值最小，无统计学差异（P >.05），说明上下颌义齿测量点的结果更一致，其次是3DP 90M、3DP 90、3DP 45M和3DP 45. 关于宽度测量，CCM 的偏差值最小 ( P <.05)。在 3DP 中，在尖牙尖端到边缘牙龈的垂直面观察到较小的偏差值，在磨牙间宽度观察到较大的偏差值（P <.05）。

结论

CCM 在测试技术中表现出更小的尺寸变化和更好的重现性。在 3DP 中，构建角度和光后处理方法影响尺寸稳定性。90 度的成型角度和铸件上额外的光聚合改善了尺寸偏差。