运用分形几何检验失效的植入物和假体。
Using fractal geometry to examine failed implants and prostheses.
机构信息
Department of Biomedical Materials Science, University of Mississippi Medical Center, 2500 N State Street, Jackson, MS 39216, USA.
出版信息
Dent Mater. 2018 Dec;34(12):1748-1755. doi: 10.1016/j.dental.2018.09.007. Epub 2018 Sep 24.
OBJECTIVE
To develop a novel protocol that is precise and accurate for analyzing the fracture surfaces of ceramic specimens using fractal geometry and to demonstrate its use on both clinically retrieved specimens and standard test specimens.
METHODS
A MathCAD script was written to transfer data from atomic force microscope scans to the FRACTALS software of John Russ. This software provided six algorithms for analyzing surfaces, so an experiment was conducted to determine which algorithm provided the most precision in fractal dimensional increment (D*) values and to calibrate that algorithm on surfaces generated with known D* values. Physical specimens were then tested using the chosen algorithm. These included pure silica glass fractured in deionized water versus nominally identical specimens fractured in saliva. Light body polyvinysiloxane was used to make impressions of Y-TZP fracture surfaces, and replicas were casted using a low-viscosity, low-shrinkage epoxy. Clinically failed Y-TZP dental implants were also examined. In addition, the fracture toughness and D* values of four ceramic materials (silicon nitride, silica glass, Y-TZP, and lithium disilicate glass-ceramic) were tested using standard geometry flexure beam specimens (ISO 6872).
RESULTS
The Minkowksi Cover algorithm was the most precise algorithm, and it had a negative bias that was corrected. There was no difference in D* based on water vs. saliva environment (p>0.05), and D* values from the deionized water group had lower standard deviation. The mean D* value obtained from the epoxy replicas 2.247 (0.007) was the same as that obtained from the original Y-TZP specimens 2.245 (0.002) (p=0.43, paired t-test). All scanned areas of the dental implants were fractal in nature, and there was no difference in fractal dimension between the locations near the failure origin and those far from the origin (on the compression curl) (p=0.74, repeated measures ANOVA). There was little scatter in the data collected using the revised protocol on ISO 6872 specimens, and the regression models succeeded in passing through the origin while achieving a good fit to the data (R=0.99 and 0.95).
SIGNIFICANCE
The new protocol proved to be a powerful tool in analyzing fracture surfaces of dental ceramic materials.
目的
开发一种新的协议，该协议使用分形几何精确且准确地分析陶瓷标本的断裂表面，并展示其在临床回收标本和标准测试标本上的应用。
方法
编写了一个 MathCAD 脚本，用于将原子力显微镜扫描的数据传输到 John Russ 的 FRACTALS 软件中。该软件提供了六种用于分析表面的算法，因此进行了一项实验，以确定哪种算法在分形维数增量（D*）值方面提供了最高的精度，并在具有已知 D值的表面上校准该算法。然后使用所选算法对物理标本进行测试。这些包括在去离子水中断裂的纯二氧化硅玻璃与在唾液中名义上相同的玻璃断裂的标本。轻质聚二甲基硅氧烷用于对 Y-TZP 断裂表面进行印象，并用低粘度、低收缩环氧树脂对复制品进行铸造。还检查了临床上失败的 Y-TZP 牙种植体。此外，还使用标准几何弯曲梁标本（ISO 6872）测试了四种陶瓷材料（氮化硅、二氧化硅、Y-TZP 和二硅酸锂玻璃陶瓷）的断裂韧性和 D值。
结果
Minkowski 覆盖算法是最精确的算法，它具有负偏差，已进行了校正。水与唾液环境之间的 D值没有差异（p>0.05），去离子水组的 D值具有较低的标准偏差。从环氧树脂复制品中获得的平均 D*值为 2.247（0.007），与从原始 Y-TZP 标本中获得的 2.245（0.002）相同（p=0.43，配对 t 检验）。牙种植体的所有扫描区域均具有分形性质，在离失效原点较近的位置与离原点较远的位置（在压缩卷曲处）的分形维数没有差异（p=0.74，重复测量方差分析）。使用修订后的协议在 ISO 6872 标本上收集的数据分散较小，回归模型成功穿过原点，同时与数据拟合良好（R=0.99 和 0.95）。
意义
新协议被证明是分析牙科陶瓷材料断裂表面的有力工具。
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