title: The role of interfacial mechanics in the prediction of global mechanical behavior of a bioactive composite: an in vitro study.
abstract: A bioactive bone-tissue substitute, hydroxyapatite (HA)-polymethylmethacrylate (PMMA) with the addition of a copolymer coupling agent, was examined in vitro to determine the influence of the coupling agent on the local mechanical properties of the system before and after simulated biologic conditions. Nano-indentation of the cross-sectional interface between the HA and PMMA of the composite was studied. The fracture mechanism and position of each indent mark were analyzed at up to 5000x magnification under field-emission, environmental-scanning electron microscopy. The local interfacial results were compared with global quasistatic compression test results. It was found that nano-indentation of the interface could predict changes in global mechanical behavior of the composite. Both interfacial and global Young's moduli were reduced after immersion in the simulated biologic media. Although the coupling agent improved the interfacial and global mechanical properties before and after 24 hours in in vitro immersion, it did not affect the surface bioactivity of the system, as shown in the measurement of calcium and phosphate concentration uptake. Thus, nano-indentation is a sensitive technique for examining interfacial mechanics and mechanical consequences of biologic reactivity of composite materials.
authors.affiliation: Materials Science and Engineering Department at Drexel University, Philadelphia, Pa, USA.
authors.forename: Emily
authors.initials: E
authors.lastname: Ho
authors.forename: Michele
authors.initials: M
authors.lastname: Marcolongo
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry*; D018786:Bone Substitutes / Q000737:chemistry*; D003188:Composite Resins / Q000737:chemistry*; D019245:Compressive Strength; D001840:Dental Bonding; D003799:Dental Stress Analysis; D017886:Durapatite / Q000737:chemistry; D004548:Elasticity; D006244:Hardness; D008422:Materials Testing; D019563:Mechanics; D011109:Polymethacrylic Acids / Q000737:chemistry; D013499:Surface Properties
chemical_list: D001672:Biocompatible Materials; D018786:Bone Substitutes; D003188:Composite Resins; D011109:Polymethacrylic Acids; C038300:methylmethacrylate-methacrylic acid copolymer; D017886:Durapatite