Department of Prosthodontics and Crown and Bridge, Bharati Vidyapeeth (Deemed to be University) Dental College and Hospital, Navi Mumbai, Maharashtra, India.
Indian J Dent Res. 2021 Oct-Dec;32(4):495-499. doi: 10.4103/ijdr.IJDR_1075_20.
For porcelain fused to metal restorations, computer-aided designing (CAD) / computer-aided manufacturing (CAM) systems claim to provide improved marginal fit than conventional casting systems.
The present in-vitro study was conducted to compare the marginal fit of cobalt-chromium alloy copings fabricated with milled wax/lost wax, CAD/CAM milling/sintering and direct metal laser sintering (DMLS) techniques.
A metal die simulating a prepared tooth was fabricated and scanned using an optical scanner. A standardized coping design was used to manufacture 30 alloy copings divided into three groups of ten copings each i.e., milled wax/lost wax, milling/sintering and DMLS. A modified replica technique was used to measure the silicone film thickness at four pre-designated points on the margin under a digital stereo-microscope.
The mean values for marginal gap were compared using one-way Analysis of Variance (ANOVA) followed by Tukey-Kramer test for all pair-wise comparisons.
The mean marginal gap values obtained by using milled wax/lost wax technique, milling/sintering technique and DMLS technique were 88.44 μm, 61.135 μm and 55.39 μm, respectively. One-way ANOVA showed a significant difference for marginal fit between the lost wax group and the other two test groups (P < 0.05).
The cobalt-chromium alloy copings fabricated using DMLS techniques displayed significantly better marginal fit than the milled wax/lost wax technique which may contribute to their improved clinical performance. DMLS technique produces restorations with an improved marginal fit and may be preferred by clinicians over milling and conventional casting techniques.
对于烤瓷熔附金属修复体，计算机辅助设计（CAD）/计算机辅助制造（CAM）系统声称比传统铸造系统提供更好的边缘适合性。
本体外研究旨在比较使用铣削蜡/失蜡、CAD/CAM 铣削/烧结和直接金属激光烧结（DMLS）技术制造的钴铬合金冠的边缘适合性。
制作了一个模拟制备牙齿的金属模具，并使用光学扫描仪进行扫描。使用标准化的牙冠设计制造了 30 个合金牙冠，分为三组，每组 10 个牙冠，即铣削蜡/失蜡、铣削/烧结和 DMLS。使用改良复制技术在数字立体显微镜下测量四个预定边缘点处的硅橡胶膜厚度。
使用单向方差分析（ANOVA）比较边缘间隙的平均值，然后使用 Tukey-Kramer 检验进行所有成对比较。
使用铣削蜡/失蜡技术、铣削/烧结技术和 DMLS 技术获得的平均边缘间隙值分别为 88.44μm、61.135μm 和 55.39μm。单向 ANOVA 显示，失蜡组和其他两个测试组之间的边缘拟合存在显著差异（P<0.05）。
使用 DMLS 技术制造的钴铬合金冠的边缘拟合明显优于铣削蜡/失蜡技术，这可能有助于提高其临床性能。DMLS 技术可生产出具有更好边缘拟合的修复体，并且可能比铣削和传统铸造技术更受临床医生的青睐。
