Former Graduate Student, Graduate Prosthodontics, Faculty of Dentistry, University of British Columbia, Vancouver, Canada; Division of Prosthodontics, Dental Department, Security Forces Hospital, Riyadh, Saudi Arabia.
Professor Emeritus, University of British Columbia, Vancouver, Canada.
J Prosthet Dent. 2022 Mar;127(3):478.e1-478.e10. doi: 10.1016/j.prosdent.2021.09.033. Epub 2022 Feb 25.
Three-dimensional (3D) printing technology may improve the fit of partial removable dental prosthesis frameworks made by selective laser melting. Conventionally, the gaps between definitive casts and prostheses are evaluated by using clinical replicas, but digital evaluations may provide a better alternative.
The purpose of this in vitro study was to compare digital and conventional methods for evaluating the fit of partial removable dental prosthesis frameworks made by selective laser melting.
A printed resin definitive cast representing a Kennedy class II modification 2 design with 5 reference markers was made from a dentiform cast. Twelve cobalt-chromium partial removable dental prosthesis frameworks were fabricated by selective laser melting on this definitive cast with a digital design software program. The gaps between the frameworks and the cast were assessed by using the clinical replica method with a silicone impression material and measuring the thickness at each marker with calipers. Digital casts of each framework and the definitive cast were scanned and then registered with the CloudCompare software program to measure 3D gaps at the 5 reference markers and 3 occlusal rests. The results were analyzed individually for each technique by 1-way analysis of variance (ANOVA) with post hoc Bonferroni tests (α=.05).
For clinical registration, the mean gap between the frameworks and definitive cast was 13.9 ±7.6 μm. For digital registration, the root mean square gap was 70.7 ±24.2 μm. Statistically significant differences among the gaps for different markers were found for both approaches (P<.05). There were no significant differences among the gaps between the different frameworks. In both situations, the gap measurements were below the 300-μm clinically acceptable standard.
Both registration methods determined whether the fit of a framework fabricated by selective laser melting was within a clinically acceptable standard. The differences in the values produced most likely arose from the different registration methods.
三维（3D）打印技术可能会提高选择性激光熔化制作的局部可摘义齿框架的适配性。传统上，通过临床复制来评估最终模型和修复体之间的间隙，但数字评估可能是一个更好的选择。
本体外研究的目的是比较数字和传统方法评估选择性激光熔化制作的局部可摘义齿框架的适配性。
使用齿科模型制作一个带有 5 个参考标记的代表 Kennedy 类 II 改良 2 设计的 3D 打印树脂最终模型。使用数字设计软件程序，在这个最终模型上用选择性激光熔化技术制作 12 个钴铬局部可摘义齿框架。使用硅橡胶印模材料通过临床复制法评估框架与最终模型之间的间隙，并使用卡尺测量每个标记处的厚度。使用 CloudCompare 软件程序扫描每个框架和最终模型的数字模型，并进行注册，以测量 5 个参考标记和 3 个咬合休息处的 3D 间隙。使用单因素方差分析（ANOVA）对每个技术的结果进行单独分析，并进行事后 Bonferroni 检验（α=.05）。
对于临床注册，框架与最终模型之间的平均间隙为 13.9±7.6μm。对于数字注册，根均方根间隙为 70.7±24.2μm。两种方法都发现不同标记之间的间隙存在统计学差异（P<.05）。不同框架之间的间隙没有显著差异。在两种情况下，间隙测量值都低于 300μm 的临床可接受标准。
两种注册方法都确定了用选择性激光熔化制作的框架的适配性是否在临床可接受的标准范围内。产生的数值差异很可能是由于不同的注册方法所致。
