Bioactive Additives and Functional Monomers Affect on PMMA Bone Cement: Mechanical and Biocompatibility Properties

Abstract

The most common bone cement material used clinically today for orthopedic surgeries is poly methyl methacrylate (PMMA). In general, poly Methyl MethAcrylate (PMMA) beads are added to MMA monomer with bead and monomer ratio of 2:1 to prepare the PMMA bone cement. Conventional PMMA bone cement has several mechanical and biological disadvantages. To overcome these disadvantages, researchers investigated several bioactive additives to PMMA bone cement, such as MgO, hydroxyapatite (HAp), chitosan (CS). Additionally, functional monomer, such as glycidyl methacrylate (GMA) was used in addition or substitution to MMA to enhance the properties of PMMA bone cement. A comparative study is required to evaluate the effect that different bioadditives and monomers have on the mechanical and biological performances on PMMA bone cement. The goal of this study is to determine the most suitable additives and alternative monomer for PMMA bone cement that can enhance the mechanical and biological performances of PMMA bone cement. Cobalt™ HV bone cement (referred as CBC), a commercial orthopedic bone cement, was used in this study as PMMA bone cement. MgO, hydroxyapatite (HAp), chitin (CT), chitosan (CS), Barium sulfate (BaSO4) and Silica (SiO2) were mixed with PMMA beads to prepare CBC-MgO, CBC-HAp, CBC-CT, CBC-CS, CBC-BaSO4 and CBC-SiO2 specimens. Additives included CBC were referred as composite specimen. CBC and composite specimens were further grouped according to the application of GMA as replacement of MMA monomer. Two groups of CBC and composite specimen were prepared. In the first group, CBC and composite specimens were prepared using MMA monomer only, referred as without GMA specimen. In the second group, CBC and composite specimens were prepared using GMA and MMA monomers, referred as with GMA specimen. There are three general research questions: (1) Is there a significant difference in the mechanical and biological performances between CBC (control) and different composite specimens that contain GMA? (2) Is there a significant difference in the in the mechanical and biological performances between CBC (control) and different composite specimens that do not contain GMA? and (3) Is there a significant difference in the mechanical and biological performances between specimens mixed with and without GMA? Elastic and fracture properties of different CBC and composite cements were calculated from three point bend experiments. Osteoblast cell adhesion experiments were performed on different CBC and composite cement on a custom made well plate. This study found that flexural strength and fracture toughness of the CBC specimens that contain GMA is significantly greater than the flexural strengths of all other specimens that contain GMA. In contrast, flexural strength and fracture toughness of the CBC-SiO2 specimens that do not contain GMA is significantly greater than the flexural strengths of all other specimens that contain GMA. This study also found that cell adhesion on the MgO impregnated CBC specimens is significantly greater than the cell adhesion of all other specimens for samples that contain GMA or do not contain GMA.