Assistant Professor, Department of Dentistry Services, Vocational School of Health Services, Ondokuz Mayıs University, Samsun, Turkey.
Associate Professor, Department of Prosthodontics, Faculty of Dentistry, Çukurova University, Adana, Turkey.
J Prosthet Dent. 2022 Jun;127(6):936.e1-936.e7. doi: 10.1016/j.prosdent.2022.04.003. Epub 2022 May 5.
Sintering-based computer-aided metal manufacturing strategies have been proposed as an alternative to hard metal milling. While these fabrication methods have been evaluated in terms of marginal and internal discrepancies and bond strength to porcelain, limited information on metal frameworks is available regarding their flexural yield strength.
The purpose of this in vitro study was to evaluate the flexural yield strength of 3-unit cobalt-chromium (Co-Cr) metal frameworks fabricated by hard metal milling (HMM), presintered soft metal milling (PSMM), and direct metal laser melting (DMLM) with 25-μm and 50-μm layer thicknesses.
Three-unit master metal die models were prepared. A total of 40 metal frameworks (n=10) were fabricated by using HMM (group HM), PSMM (group PSM), and DMLM with 25-μm (group LM25) and 50-μm layer thicknesses (group LM50). Metal frameworks were cemented to the master die and then subjected to a 3-point bend test. The flexural yield force was used to calculate the flexural yield strength. The data were statistically analyzed (α=.05). One metal framework from each group was evaluated with scanning electron microscopy for microstructural analysis.
The group LM50 exhibited the lowest significant (P<.001) flexural yield strength values. The group HM exhibited higher flexural yield strength values than the other groups. No significant difference was found between the groups LM25 and PSM (P=.954) or between the groups PSM and HM (P=.111).
The fabrication method significantly affected the flexural yield strength of metal frameworks. Metal frameworks fabricated by DMLM with a 50-μm layer thickness exhibited considerably lower flexural yield strength values.
基于烧结的计算机辅助金属制造策略已被提议作为硬金属铣削的替代方法。虽然这些制造方法已经在边缘和内部差异以及与瓷的结合强度方面进行了评估，但关于金属框架的信息有限，其抗弯屈服强度方面的信息有限。
本体外研究的目的是评估通过硬金属铣削（HMM）、预烧结软金属铣削（PSMM）和直接金属激光熔化（DMLM）制造的 3 单位钴铬（Co-Cr）金属框架的抗弯屈服强度，层厚分别为 25μm 和 50μm。
制备了三单位主金属模具模型。使用 HMM（组 HM）、PSMM（组 PSM）和 DMLM 制造了总共 40 个金属框架（n=10），层厚分别为 25μm（组 LM25）和 50μm（组 LM50）。将金属框架粘接到主模具上，然后进行 3 点弯曲试验。使用弯曲屈服力来计算弯曲屈服强度。对数据进行了统计学分析（α=.05）。从每个组中选择一个金属框架进行扫描电子显微镜评估，以进行微观结构分析。
组 LM50 表现出最低的显著（P<.001）抗弯屈服强度值。组 HM 表现出比其他组更高的抗弯屈服强度值。组 LM25 和 PSM 之间（P=.954）或 PSM 和 HM 之间（P=.111）没有发现显著差异。
制造方法显著影响金属框架的抗弯屈服强度。使用 50μm 层厚的 DMLM 制造的金属框架表现出相当低的抗弯屈服强度值。
