Dental Research Center, Dentistry Research Institute, Tehran University of Medical Sciences, Iran.
Department of Operative Dentistry, School of Dentistry, Tehran University of Medical Sciences, Iran.
Dent Med Probl. 2020 Oct-Dec;57(4):417-422. doi: 10.17219/dmp/125532.
Computer-aided design/computer-aided manufacturing (CAD/CAM) systems are widely used for the fabrication of porcelain-fused-to-metal (PFM) crowns.
This study was conducted to compare PFM crowns through triple scanning in terms of marginal discrepancy between the CAD/CAM and lost-wax fabrication techniques.
Twenty uniform resin dies of a prepared maxillary first molar were randomly divided into 2 groups: conventional lost-wax; and milling. Marginal discrepancy was evaluated at the framework and porcelain steps through triple scanning and direct visualization under a stereomicroscope. Then, the crowns were cemented to the related die and the marginal gap was measured with triple scanning, direct visualization under a stereomicroscope and scanning electron microscopy (SEM). The data was analyzed using the independent t test and the one-way analysis of variance (ANOVA). The significance level was set at 0.05.
Differences in the mean marginal gap were measured by the various evaluation methods. Triple scanning and stereomicroscopy identified increasing discrepancy during the fabrication process. According to the results of the independent t test, stereomicroscopy showed no difference after cementation between the CAD/CAM and lost-wax groups (p > 0.05), triple scanning showed higher fitness in the CAD/CAM group (p < 0.05), and SEM showed better adaptation in the lost-wax group (p < 0.05); however, there was a positive correlation between the findings of stereomicroscopy and SEM (p < 0.05).
The cobalt-chromium crowns had clinically acceptable marginal fitness from both the CAD/CAM and lost-wax techniques; however, the lost-wax group showed lower marginal discrepancy after cementation according to SEM.
计算机辅助设计/计算机辅助制造（CAD/CAM）系统广泛应用于烤瓷熔附金属（PFM）冠的制作。
本研究旨在通过三重扫描比较 CAD/CAM 和失蜡铸造技术制作的 PFM 冠的边缘差异。
将 20 个预备上颌第一磨牙的均匀树脂模具随机分为 2 组：常规失蜡法和铣削法。通过三重扫描和立体显微镜下直接观察评估基底和烤瓷阶段的边缘差异。然后，将冠体粘接到相关的模具上，通过三重扫描、立体显微镜下直接观察和扫描电子显微镜（SEM）测量边缘间隙。使用独立 t 检验和单因素方差分析（ANOVA）对数据进行分析。显著性水平设定为 0.05。
各种评估方法测量的平均边缘间隙存在差异。三重扫描和立体显微镜在制作过程中发现边缘差异逐渐增大。根据独立 t 检验的结果，立体显微镜在粘固后 CAD/CAM 组和失蜡组之间的差异无统计学意义（p>0.05），三重扫描显示 CAD/CAM 组的拟合度更高（p<0.05），SEM 显示失蜡组的适应性更好（p<0.05）；然而，立体显微镜和 SEM 的结果之间存在正相关（p<0.05）。
钴铬烤瓷冠从 CAD/CAM 和失蜡技术都具有临床可接受的边缘适配性；然而，根据 SEM，粘固后失蜡组的边缘差异较小。
