Bosch Gabriel, Ender Andreas, Mehl Albert
Research Assistant, Division for Computerized Restorative Dentistry, Center of Dental Medicine, University of Zürich, Zürich, Switzerland.
Research Assistant, Division for Computerized Restorative Dentistry, Center of Dental Medicine, University of Zürich, Zürich, Switzerland.
J Prosthet Dent. 2014 Dec;112(6):1425-31. doi: 10.1016/j.prosdent.2014.05.012. Epub 2014 Jul 1.
Milling is a central and important aspect of computer-aided design and computer-aided manufacturing (CAD/CAM) technology. High milling accuracy reduces the time needed to adapt the workpiece and provides restorations with better longevity and esthetic appeal. The influence of different milling processes on the accuracy of milled restorations has not yet been reviewed.
The purpose of this study was to investigate the influence of different milling processes on the accuracy of ceramic restorations.
Four groups of partial crowns were milled (each n = 17): Three groups in a 4-axial milling unit: (1) 1-step mode and Step Bur 12S (12S), (2) 1-step mode and Step Bur 12 (1Step), (3) 2-step mode and Step Bur 12 (2Step), and (4) one group in a 5-axial milling unit (5axis). The milled occlusal and inner surfaces were scanned and superimposed over the digital data sets of calculated restorations with specialized difference analysis software. The trueness of each restoration and each group was measured. One-way ANOVA with a post hoc Tukey test was used to compare the data (α = .05).
The highest trueness for the inner surface was achieved in group 5axis (trueness, 41 ± 15 μm, P<.05). The 4-axial milling unit exhibited trueness at settings ranging from 61 μm (2Step) to 96 μm (12S). For the occlusal surface, the highest trueness was achieved with group 5axis (trueness, 42 ± 10 μm). The 4-axial milling unit exhibited trueness at settings ranging from 55 μm (1Step) to 76 μm (12S).
Restorations milled with a 5-axial milling unit have a higher trueness than those milled with a 4-axial milling unit. A rotary cutting instrument with a smaller diameter results in a more accurate milling process. The 2-step mode is not significantly better than the 1-step mode.
铣削是计算机辅助设计与计算机辅助制造（CAD/CAM）技术的核心且重要的方面。高铣削精度可减少适配工件所需的时间，并为修复体提供更好的耐久性和美学吸引力。不同铣削工艺对铣削修复体精度的影响尚未得到综述。
本研究的目的是调查不同铣削工艺对陶瓷修复体精度的影响。
铣削四组部分冠（每组n = 17）：在四轴铣削单元中有三组：（1）一步模式和阶梯钻12S（12S），（2）一步模式和阶梯钻12（1步），（3）两步模式和阶梯钻12（2步），以及（4）在五轴铣削单元中有一组（5轴）。对铣削后的咬合面和内表面进行扫描，并使用专门的差异分析软件将其叠加在计算出的修复体的数字数据集上。测量每个修复体和每组的准确性。使用单因素方差分析和事后Tukey检验来比较数据（α = 0.05）。
5轴组内表面的准确性最高（准确性，41±15μm，P<0.05）。四轴铣削单元在61μm（2步）至96μm（12S）的设置下表现出准确性。对于咬合面，5轴组的准确性最高（准确性，42±10μm）。四轴铣削单元在55μm（1步）至76μm（12S）的设置下表现出准确性。
用五轴铣削单元铣削的修复体比用四轴铣削单元铣削的修复体具有更高的准确性。直径较小的旋转切割器械可实现更精确的铣削过程。两步模式并不明显优于一步模式。
