Kucko Nathan W, Petre Daniela-Geta, de Ruiter Marjolein, Herber Ralf-Peter, Leeuwenburgh Sander C G
Department of Dentistry - Regenerative Biomaterials, Radboud University Medical Center, Philips van Leydenlaan 25, 6525 EX, Nijmegen, the Netherlands; CAM Bioceramics B.V., Zernikedreef 6, 2333 CL, Leiden, the Netherlands.
Department of Dentistry - Regenerative Biomaterials, Radboud University Medical Center, Philips van Leydenlaan 25, 6525 EX, Nijmegen, the Netherlands.
J Mech Behav Biomed Mater. 2020 Sep;109:103776. doi: 10.1016/j.jmbbm.2020.103776. Epub 2020 Apr 12.
Calcium phosphate cements (CPCs) are frequently used as synthetic bone substitute materials due to their favorable osteocompatibility and handling properties. However, CPCs alone are inherently brittle and exhibit low strength and toughness, which restricts their clinical applicability to non-load bearing sites. Mechanical reinforcement of CPCs using fibers has proven to be an effective strategy to toughen these cements by transferring stress from the matrix to the fibers through frictional sliding at the interface. Therefore, tailoring the fiber-matrix affinity is paramount in designing highly toughened CPCs. However, the mechanistic correlation between this interaction and the macromechanical properties of fiber-reinforced CPCs has hardly been investigated to date. The aim of this study was to tailor the fiber-matrix interface affinity by modifying the surface of poly(vinyl alcohol) (PVA) fibers and correlate their interfacial properties to macromechanical properties (i.e. fracture toughness, work-of-fracture and tensile strength) of CPCs. Results from single fiber pullout tests reveal that the surface modification of PVA fibers increased their hydrophilicity and improved their affinity to the CPC matrix. This observation was evidenced by an increase in the interfacial shear strength and a reduction in the critical fiber embedment length (i.e. maximum embedded length from which a fiber can be pulled out without rupture). This increased interface affinity facilitated energy dissipation during fracture of CPCs subjected to macromechanical three-point flexure and tensile tests. The fracture toughness also significantly improved, even for CPCs reinforced with fibers of lengths greater than their critical fiber embedment length, suggesting that other crack-arresting mechanisms also play an important role in mechanically reinforcing CPCs. Overall, these basic insights will improve the understanding of the correlation between micro- and macromechanical characteristics of fiber-reinforced CPCs.
磷酸钙骨水泥（CPCs）因其良好的骨相容性和操作性能，常被用作合成骨替代材料。然而，单纯的CPCs本质上是脆性的，强度和韧性较低，这限制了它们在非承重部位的临床应用。使用纤维对CPCs进行机械增强已被证明是一种有效的增韧策略，通过界面处的摩擦滑动将应力从基体传递到纤维，从而使这些骨水泥增韧。因此，在设计高度增韧的CPCs时，调整纤维与基体的亲和力至关重要。然而，迄今为止，这种相互作用与纤维增强CPCs宏观力学性能之间的机理相关性几乎未被研究。本研究的目的是通过修饰聚乙烯醇（PVA）纤维的表面来调整纤维与基体的界面亲和力，并将其界面性能与CPCs的宏观力学性能（即断裂韧性、断裂功和拉伸强度）相关联。单纤维拔出试验结果表明，PVA纤维的表面改性提高了其亲水性，并改善了其与CPC基体的亲和力。界面剪切强度的增加和临界纤维埋入长度的减小（即纤维在不破裂的情况下可以拔出的最大埋入长度）证明了这一观察结果。这种增加的界面亲和力促进了在宏观力学三点弯曲和拉伸试验中CPCs断裂过程中的能量耗散。即使对于用长度大于其临界纤维埋入长度的纤维增强的CPCs，其断裂韧性也显著提高，这表明其他止裂机制在机械增强CPCs中也起着重要作用。总体而言，这些基本见解将增进对纤维增强CPCs微观和宏观力学特性之间相关性的理解。
