Experimental and numerical analysis on bending and tensile failure behavior of calcium phosphate cements

Ali Paknahad,Nathan W Kucko,Sander C.G Leeuwenburgh,Lambertus J Sluys

doi:10.1016/j.jmbbm.2019.103565

Abstract

Since their discovery in the 1980s, injectable self-setting calcium phosphate cements (CPCs) are frequently used in orthopedic, oral and maxillofacial surgery due to their chemical resemblance to the mineral phase of native bone. However, these cements are very brittle, which complicates their application in load-bearing anatomical sites. Polymeric fibers can be used to transform brittle calcium phosphate cements into ductile and load-bearing biomaterials. To understand and optimize this process of fiber reinforcement, it is essential to characterize the mechanical properties of fiber-free calcium phosphate matrices in full detail. However, the mechanical performance of calcium phosphate cements is usually tested under compression only, whereas bending and tensile tests are hardly performed due to technical limitations. In addition, computational models describing failure behavior of calcium phosphate cements under these clinically more relevant loading scenarios have not yet been developed. Here, we investigate the failure behavior of calcium phosphate cements under bending and tensile loading by combining, for the first time, experimental tests and numerical modeling. To this end, a 3-D gradient-enhanced damage model is developed in a finite element framework, and numerical results are correlated to experimental three-point bending and tensile tests to characterize the mechanical properties of calcium phosphate cements in full detail. The presented computational model is successfully validated against experimental results and is able to predict the mechanical response of calcium phosphate cement under different types of loading with a unique set of parameters. This model offers a solid basis for further experimental and computational studies on the development of load-bearing bone cements.

Highlights

Calcium phosphate cements (CPCs) are highly valuable bone sub stitution materials that are frequently used in orthopedic, oral and maxillofacial surgery (Bohner et al, 2012; Zhang et al, 2014; Ginebra et al, 2010; Bohner, 2000; Habraken et al, 2016)
We experimentally studied the response of a CPC matrix under bending and tensile loading
We proposed an experimental pro tocol to perform the three-point bending and tensile test for a CPC ma trix

Summary

Introduction

Calcium phosphate cements (CPCs) are highly valuable bone sub stitution materials that are frequently used in orthopedic, oral and maxillofacial surgery (Bohner et al, 2012; Zhang et al, 2014; Ginebra et al, 2010; Bohner, 2000; Habraken et al, 2016). Calcium phos phate cements set in situ at body temperature and form a paste that is moldable which can be directly injected into bone defects (Comuzzi et al, 2002). This procedure provides intimate adaptation to the irreg ular shape of bone defects. CPCs represent attractive al ternatives to conventional types of bioceramics which are difficult to shape and machine due to their non-self-setting nature (Zhang et al, 2014)

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