Objectives

Previous studies have shown that the fracture toughness of ceramics can be determined from the fractal dimensions (D) of their fracture surfaces and that the surface should be leveled to obtain an accurate D measurement. This study was to determine the effects of leveling operations and distance from the failure origin on the D values.

Methods

Twelve clinically failed zirconia implants from four different manufacturers: Axis Biodental (n = 7), Z-Systems (n = 3), Straumann (n = 1), and Swiss Dental Solutions (n = 1) were obtained from one of the authors and thoroughly cleaned. Epoxy replicas were made of three locations along the crack path in the center region of each fracture surface (near origin (O), hackle (H), and near compression curl (CC)) using a light body polyvinyl siloxane impression material. Surfaces were scanned in ScanAsyst mode with a scan size of 5 μm × 5 μm and a scan rate of 0.592 Hz using the atomic force microscope. The surface scans were then leveled using 1st order flattening operation in the AFM analysis software. The height data before and after the operation were imported into a custom MathCAD script, and FRACTALS software was used to determine the D value by Minkowski Cover algorithm, which was shown previously to be the algorithm with the highest precision. A Wilcoxon signed-rank test, two-way repeated-measures ANOVA, and one-way repeated-measures ANOVA were performed as detailed below.

Results

The data were not normally distributed (S-W p ≤ 0.05), so a non-parametric repeated measures test (Wilcoxon signed-rank test) was selected. The median D values before and after leveling were 2.161 and 2.174, respectively. There was a significant difference before and after leveling (p < 0.001). The two-way repeated-measures ANOVA showed no significant difference among the D values for different implant brands (p = 0.66) and scanning locations on the fracture surface (p = 0.83). After eliminating the implant brand as a factor, the data passed normality and equal variance tests (S-W p = 0.88, BF p = 0.15). The mean D values and standard deviations from the three locations (O, H, CC) were 2.183 ± 0.031, 2.179 ± 0.024, and 2.175 ± 0.018, respectively. One-way repeated measures ANOVA showed no significant effect of scanning location (p = 0.74).

Significance

The leveling operation successfully removed the tilt without decreasing surface tortuosity, as it increased the D values significantly. The fractal dimension was the same at the three locations on the fracture surfaces. This means that hackle and compression curl regions can be used to determine fracture toughness when the failure origin has been lost.

中文翻译：

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临床失败的氧化锆牙种植体不同位置的分形分析。

目标

以前的研究表明，陶瓷的断裂韧性可以从其断裂面的分形维数 (D) 确定，并且应将表面平整以获得准确的 D 测量值。本研究旨在确定调平操作和距故障原点的距离对D值的影响。

方法

来自四个不同制造商的十二个临床失败的氧化锆种植体：Axis Biodental ( n  = 7)、Z-Systems ( n  = 3)、Straumann ( n  = 1) 和 Swiss Dental Solutions ( n = 1) 从其中一位作者处获得并彻底清洁。使用轻质聚乙烯硅氧烷印模材料，环氧树脂复制品由沿每个断裂表面中心区域的裂纹路径的三个位置（近原点 (O)、裂纹 (H) 和近压缩卷曲 (CC)）制成。使用原子力显微镜以 ScanAsyst 模式扫描表面，扫描尺寸为 5 μm × 5 μm，扫描速率为 0.592 Hz。然后使用 AFM 分析软件中的一阶展平操作对表面扫描进行平整。将手术前后的高度数据导入到自定义的MathCAD脚本中，并使用FRACTALS软件通过Minkowski Cover算法确定D值，该算法是之前显示的精度最高的算法。Wilcoxon 符号秩检验，双向重复测量方差分析，

结果

数据不呈正态分布（SW p  ≤ 0.05），因此选择了非参数重复测量检验（Wilcoxon 符号秩检验）。调平前后的中位数 D 值分别为 2.161 和 2.174。调平前后有显着差异（p  < 0.001）。双向重复测量方差分析显示，不同种植体品牌 ( p  = 0.66) 和断面扫描位置 ( p  = 0.83)的D值无显着差异。剔除种植体品牌作为因素后，数据通过了正态性和等方差检验（SW p  = 0.88，BF p = 0.15)。三个位置（O、H、CC）的平均 D 值和标准偏差分别为 2.183 ± 0.031、2.179 ± 0.024 和 2.175 ± 0.018。单向重复测量方差分析显示扫描位置没有显着影响（p  = 0.74）。

意义

调平操作成功地消除了倾斜而不会降低表面曲折度，因为它显着增加了D值。断面上三个位置的分形维数相同。这意味着当失效起源消失时，可以使用起皱和压缩卷曲区域来确定断裂韧性。