Etman Maged K
Division of Prosthodontics, College of Dentistry, University of Saskatchewan, Saskatoon, Canada.
J Prosthodont. 2009 Oct;18(7):550-9. doi: 10.1111/j.1532-849X.2009.00447.x. Epub 2009 Mar 26.
The original ceramic surface finish and its microstructure may have an effect on crack propagation. The purpose of this study was to investigate the relation between crack propagation and ceramic microstructure following cyclic fatigue loading, and to qualitatively evaluate and quantitatively measure the surface and subsurface crack depths of three types of ceramic restorations with different microstructures using a Confocal Laser Scanning Microscope (CLSM) and Scanning Electron Microscope (SEM).
Twenty (8 x 4 x 2 mm(3)) blocks of AllCeram (AC), experimental ceramic (EC, IPS e.max Press), and Sensation SL (SSL) were prepared, ten glazed and ten polished of each material. Sixty antagonist enamel specimens were made from the labial surfaces of permanent incisors. The ceramic abraders were attached to a wear machine, so that each enamel specimen presented at 45 degrees to the vertical movement of the abraders, and immersed in artificial saliva. Wear was induced for 80K cycles at 60 cycles/min with a load of 40 N and 2-mm horizontal deflection. The specimens were examined for cracks at baseline, 5K, 10K, 20K, 40K, and 80K cycles.
Twenty- to 30-microm deep subsurface cracking appeared in SSL, with 8 to 10 microm in AC, and 7 microm close to the margin of the wear facets in glazed EC after 5K cycles. The EC showed no cracks with increasing wear cycles. Seventy-microm deep subsurface cracks were detected in SSL and 45 microm in AC after 80K cycles. Statistically, there was significant difference among the three materials (p < 0.05). Bonferroni multiple comparison of means test confirmed the ANOVA test and showed that there was no statistical difference (p > 0.05) in crack depth within the same ceramic material with different surface finishes.
The ceramic materials with different microstructures showed different patterns of subsurface cracking.
原始陶瓷表面光洁度及其微观结构可能会对裂纹扩展产生影响。本研究的目的是探讨循环疲劳载荷作用下裂纹扩展与陶瓷微观结构之间的关系，并使用共聚焦激光扫描显微镜（CLSM）和扫描电子显微镜（SEM）对三种具有不同微观结构的陶瓷修复体的表面和亚表面裂纹深度进行定性评估和定量测量。
制备了20个（8×4×2 mm³）全瓷（AC）、实验陶瓷（EC，IPS e.max Press）和Sensation SL（SSL）块体，每种材料各10个上釉的和10个抛光的。从恒牙切牙的唇面制作了60个对抗性牙釉质标本。将陶瓷磨损器连接到磨损机上，使每个牙釉质标本与磨损器的垂直运动呈45度角，并浸泡在人工唾液中。在60次/分钟的频率下施加40 N的载荷和2 mm的水平挠度，诱导磨损80K次循环。在基线、5K、10K、20K、40K和80K次循环时检查标本的裂纹情况。
5K次循环后，SSL中出现了20至30微米深的亚表面裂纹，AC中为8至10微米，上釉的EC在磨损面边缘附近为7微米。随着磨损循环次数的增加，EC未出现裂纹。80K次循环后，在SSL中检测到70微米深的亚表面裂纹，在AC中为45微米。统计学上，三种材料之间存在显著差异（p < 0.05）。均值的Bonferroni多重比较检验证实了方差分析检验的结果，并表明相同陶瓷材料不同表面光洁度下的裂纹深度无统计学差异（p > 0.05）。
具有不同微观结构的陶瓷材料表现出不同的亚表面裂纹模式。
