Computational Study on Interfacial Interactions between Polymethyl Methacrylate-Based Bone Cement and Hydroxyapatite in Nanoscale

Hongdeok Kim,Kyujo Lee,Joonmyung Choi,Sol Lee,Byeonghwa Goh

doi:10.3390/app11072937

Hongdeok Kim, Kyujo Lee + Show 3 more

Open Access

https://doi.org/10.3390/app11072937

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Journal: Applied sciences	Publication Date: Mar 25, 2021
Citations: 3	License type: CC BY 4.0

Affiliation: Anyang University, Hanyang University

Abstract

Polymethyl methacrylate (PMMA)-based bone cement (BC) is a key material in joint replacement surgery that transfers external forces from the implant to the bone while allowing their robust binding. To quantitatively evaluate the effect of polymerization on the thermomechanical properties of the BC and on the interaction characteristics with the bone ceramic hydroxyapatite (HAp), molecular dynamics simulations were performed. The mechanical stiffness of the BC material under external loading increased gradually with the crosslinking reaction occurrence, indicating increasing load transfer between the constituent molecules. In addition, as the individual Methyl Methacrylate (MMA) segments were interconnected in the system, the freedom of the molecular network was largely suppressed, resulting in more thermally stable structures. Furthermore, the pull-out tests using HAp/BC bilayer models under different constraints (BC at 40% and 85%) revealed the cohesive characteristics of the BC with the bone scaffold in molecular detail. The stiffness and the fracture energy increased by 32% and 98%, respectively, with the crosslink density increasing.

Highlights

Among the Bone cement (BC) materials, poly (PMMA)-based organic BC is exceptionally light and flexible compared with inorganic cement materials, and its simple fabrication enables wide and universal applications
The results suggest that as the Methyl Methacrylate (MMA) liquid became covalently connected to the adjacent MMA and/or Polymethyl methacrylate (PMMA), the translational freedom of the molecular networks became highly suppressed
The thermomechanical properties of PMMA-based BC and the interaction features with a bioceramic material, HAp, were investigated using all-atom MD simulations

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. From the mechanical and structural perspectives, BC acts as an intermediate medium that transmits various everyday external loads from the bone to the implant Because it allows a uniform distribution of the applied load on the entire surface, the disadvantages of metallic implants, including periprosthetic fracture or tissue damage, can be effectively prevented [4]. For the BC, it is difficult to monitor quantitative changes in its physical properties according to the crosslinking rate variations, because such variations are dominated by atomic-level compositional details, making it difficult to identify in experimental approaches. Another issue associated with polymer crosslinking is the nature of the interactions with other materials. The bilayer model of the BC and hydroxyapatite (HAp) that a key bioceramic material of the bone scaffold was considered, and the fracture toughness as well as the cohesive strength at the BC/HAp interface were quantitatively characterized throughout the pull-out tests

BC Microstructures

Effect of the Crosslinking Reaction on the Thermo-Mechanical Properties

Conclusions