Division of Oral and Maxillofacial Surgery, Unit of Oral Surgery and Implantology, Department of Surgery, University of Geneva & University Hospitals of Geneva, Geneva, Switzerland.
Division of Fixed Prosthodontics-Biomaterials, University of Geneva, University Clinic of Dental Medicine, Geneva, Switzerland.
Dent Mater. 2017 Mar;33(3):294-308. doi: 10.1016/j.dental.2016.12.004. Epub 2017 Jan 12.
To assess surface/subsurface damage after grinding with diamond discs on five CAD-CAM restorative materials and to estimate potential losses in strength based on crack size measurements of the generated damage.
The materials tested were: Lithium disilicate (LIT) glass-ceramic (e.max CAD), leucite glass-ceramic (LEU) (Empress CAD), feldspar ceramic (VM2) (Vita Mark II), feldspar ceramic-resin infiltrated (EN) (Enamic) and a composite reinforced with nano ceramics (LU) (Lava Ultimate). Specimens were cut from CAD-CAM blocs and pair-wise mirror polished for the bonded interface technique. Top surfaces were ground with diamond discs of respectively 75, 54 and 18μm. Chip damage was measured on the bonded interface using SEM. Fracture mechanics relationships were used to estimate fracture stresses based on average and maximum chip depths assuming these to represent strength limiting flaws subjected to tension and to calculate potential losses in strength compared to manufacturer's data.
Grinding with a 75μm diamond disc induced on a bonded interface critical chips averaging 100μm with a potential strength loss estimated between 33% and 54% for all three glass-ceramics (LIT, LEU, VM2). The softer materials EN and LU were little damage susceptible with chips averaging respectively 26μm and 17μm with no loss in strength. Grinding with 18μm diamond discs was still quite detrimental for LIT with average chip sizes of 43μm and a potential strength loss of 42%.
It is essential to understand that when grinding glass-ceramics or feldspar ceramics with diamond discs surface and subsurface damage are induced which have the potential of lowering the strength of the ceramic. Careful polishing steps should be carried out after grinding especially when dealing with glass-ceramics.
评估使用金刚石盘研磨五种 CAD-CAM 修复材料后的表面/次表面损伤，并根据生成损伤的裂纹尺寸测量估计潜在的强度损失。
测试的材料有：锂硅玻璃陶瓷（e.max CAD）、透锂长石玻璃陶瓷（Empress CAD）、长石陶瓷（Vita Mark II）、长石陶瓷-树脂渗透（Enamic）和纳米陶瓷增强复合材料（Lava Ultimate）。从 CAD-CAM 块体上切割试件，并进行配对镜面抛光以进行键合界面技术。用分别为 75μm、54μm 和 18μm 的金刚石盘研磨顶面。使用 SEM 在键合界面上测量碎屑损伤。使用断裂力学关系，根据平均和最大碎屑深度估算断裂应力，假设这些深度代表受拉伸的强度限制缺陷，并计算与制造商数据相比的潜在强度损失。
使用 75μm 金刚石盘研磨在键合界面上产生临界碎屑，平均为 100μm，所有三种玻璃陶瓷（LIT、LEU、VM2）的潜在强度损失估计在 33%至 54%之间。较软的材料 EN 和 LU 不易产生碎屑，平均分别为 26μm 和 17μm，没有强度损失。使用 18μm 金刚石盘研磨仍然对 LIT 有很大的损害，平均碎屑尺寸为 43μm，潜在强度损失为 42%。
当使用金刚石盘研磨玻璃陶瓷或长石陶瓷时，必须了解会产生表面和次表面损伤，这有可能降低陶瓷的强度。在研磨后应进行仔细的抛光步骤，特别是在处理玻璃陶瓷时。
