Ilie Nicoleta
Department of Conservative Dentistry, University Hospital, Ludwig-Maximilians-University, Goethestr. 70, D-80336 Munich, Germany.
J Funct Biomater. 2025 Aug 12;16(8):290. doi: 10.3390/jfb16080290.
The mechanical behavior of dental composites depends on the sample size and stress configuration. This makes it difficult to extrapolate laboratory data to clinical restorations with significant variations in size and geometry. Intrinsic parameters, such as fracture toughness, are therefore of great importance, even if they are less common and more difficult to measure. The aim of this study was to apply principles of fractography and fracture mechanics to exploit the results obtained from a three-point bending test. The objectives include calculating a material-specific constant, validating the experimental findings, and establishing a correlation with fracture toughness. Forty representative composites with wide variation in filler quantity (65-83% by weight and 46.4-64% by volume), type (compact glasses and pre-polymerized), and composition were examined. Fracture toughness/K was evaluated in a notchless triangular prism test. Fracture type, origin, and mirror size were determined on 280 flexural fracture specimens ( = 20). The amount of filler strongly influences all measured parameters, with the effect strength varying in the sequence: mechanical work (η = 0.995), modulus of elasticity (η = 0.991), flexural strength (η = 0.988), fracture toughness (η = 0.979), and mirror constant (η = 0.965). Fracture surfaces allowed the delineation of the fracture mirror and the application of fracture mechanics approaches. The mirror constant was derived from the radius of the fracture mirror, measured in the direction of constant stress, using Orr's equation, and correlates well with K (0.81). Larger confidence intervals were observed for the mirror constant data, while for 5 of 14 materials, the mirror constant was overestimated compared to K. The overestimation was attributed to the lower refractive index of the urethane methacrylate composition.
牙科复合材料的力学行为取决于样本大小和应力配置。这使得将实验室数据外推至尺寸和几何形状存在显著差异的临床修复体变得困难。因此，诸如断裂韧性等固有参数非常重要，即便它们不太常见且更难测量。本研究的目的是应用断口分析和断裂力学原理来利用三点弯曲试验获得的结果。目标包括计算特定材料常数、验证实验结果，并建立与断裂韧性的相关性。研究了40种具有代表性的复合材料，这些复合材料在填料含量（重量百分比为65 - 83%，体积百分比为46.4 - 64%）、类型（致密玻璃和预聚合材料）和组成方面存在很大差异。在无缺口三棱柱试验中评估断裂韧性/K。在280个弯曲断裂试样（= 20）上确定断裂类型、起源和镜面大小。填料量强烈影响所有测量参数，影响强度按以下顺序变化：机械功（η = 0.995）、弹性模量（η = 0.991）、弯曲强度（η = 0.988）、断裂韧性（η = 0.979）和镜面常数（η = 0.965）。断口表面允许描绘断裂镜面并应用断裂力学方法。镜面常数由在恒定应力方向上测量的断裂镜面半径根据奥尔方程得出，并且与K（0.81）具有良好的相关性。观察到镜面常数数据的置信区间较大，而对于14种材料中的5种，与K相比，镜面常数被高估。高估归因于聚氨酯甲基丙烯酸酯组合物的较低折射率。
