Associate Professor, Dental Prosthetics Technology, School of Health Services, Hacettepe University, Ankara, Turkey.
Professor, Department of Prosthodontics, Faculty of Dentistry, Near East University, Mersin, Turkey.
J Prosthet Dent. 2022 Dec;128(6):1358-1362. doi: 10.1016/j.prosdent.2021.11.032. Epub 2022 Jan 7.
The surface roughness (Ra) and wettability of complete denture base materials must meet certain clinical requirements. Although computer-aided design and computer-aided manufacturing (CAD-CAM) systems have recently become popular for the fabrication of complete dentures, the effects of the repeated usage of milling burs on the surface properties of CAD-CAM denture base acrylic resins have not yet been fully investigated.
The purpose of this in vitro study was to evaluate the effects of new and used burs on the Ra and contact angles (wettability) of a CAD-CAM polymethylmethacrylate (PMMA) denture base material.
A total of 40 Ø2×10-mm disks were fabricated from 1 brand of CAD-CAM PMMA resin (Polident). Half of the specimens (group N) were milled with a new tungsten carbide bur set, while the other half (group U) was milled with a used tungsten carbide bur set. Moreover, half of the specimens (groups NT and UT) were subjected to thermocycling before Ra and contact angle testing. Ra was tested by using a profilometer, and the surfaces were also examined by scanning electron microscopy (SEM). The contact angle was measured by using the sessile drop method. Data were analyzed with the Kruskal-Wallis and Dunn Pairwise Comparison tests (α=.05).
The mean contact angle was highest for group U (80 degrees) and lowest for group UT (66 degrees) (P<.05). Ra values were highest for group N (1.3 μm) and lowest for group U (0.93 μm) (P<.05).
Specimens milled with new tungsten carbide burs had lower mean contact angles and higher Ra values than specimens milled with used burs. The contact angles of CAD-CAM PMMA resin specimens milled with used burs decreased significantly after thermocycling. Regardless of whether or not thermocycling was performed, contact angle values decreased as Ra values increased.
全口义齿基托材料的表面粗糙度（Ra）和润湿性必须满足某些临床要求。尽管计算机辅助设计和计算机辅助制造（CAD-CAM）系统最近已广泛用于全口义齿的制作，但重复使用铣刀对 CAD-CAM 义齿基托丙烯酸树脂表面性能的影响尚未得到充分研究。
本体外研究的目的是评估新磨具和旧磨具对 CAD-CAM 聚甲基丙烯酸甲酯（PMMA）义齿基托材料 Ra 和接触角（润湿性）的影响。
从 1 种 CAD-CAM PMMA 树脂（Polident）共制备 40 个 Ø2×10-mm 圆盘。一半样本（组 N）用新的碳化钨磨具铣削，另一半（组 U）用旧的碳化钨磨具铣削。此外，一半样本（组 NT 和 UT）在进行 Ra 和接触角测试前进行热循环。使用轮廓仪测试 Ra，并用扫描电子显微镜（SEM）检查表面。通过静态液滴法测量接触角。用 Kruskal-Wallis 和 Dunn 两两比较检验（α=.05）分析数据。
组 U 的平均接触角最高（80 度），组 UT 的最低（66 度）（P<.05）。组 N 的 Ra 值最高（1.3μm），组 U 的最低（0.93μm）（P<.05）。
用新碳化钨磨具铣削的样本的平均接触角较低，Ra 值较高，而用旧磨具铣削的样本则相反。用旧磨具铣削的 CAD-CAM PMMA 树脂样本经过热循环后接触角显著降低。无论是否进行热循环，接触角值都随着 Ra 值的增加而降低。
