A Microstructure Change and a Fracture Characteristic of Apatite Ceramics by an Organism Activity Function
Noriyuki HISAMORI Yuu NOJIRI and Kenichi TAKAI
Abstract:Biocompatible materials, such as bioactive ceramics and bioactive glasses can be effective in the repair of bone defects during orthopedics surgery. These materials have been found by observation to exhibit varying degrees of osteoconductive behavior. The hydroxyapatite ceramics and bioactive glass ceramics was known as a highly bioactive ceramics, and replacements of lost bone. However, it is to be inferior to a fracture characteristic in a weak point of apatite ceramics. In the present study, surface structural changes of apatite ceramics with the bioactive function and mechanical property in simulated body fluid were investigatedDSub-micrometer hydroxyapatite ceramics powder was used as starting materials for making hydroxyapatite ceramics. Pressure less sintering was preformed at 1300 in O2 atmosphere using the pre-sintered bodies. Fracture resistance (KQ) was evaluated by ASTM E399-90 method. And also, fracture resistance tests were performed using compact tension specimens. It has been confirmed by SEM observation, thin-film X-ray diffraction matter and FT-IR reflection spectroscopy that the apatite layer can be reproduced on the surface of the hydroxyapatite ceramic even in a cellular simulated body fluid with ion concentrations nearly equal to those of human blood plasma. As a result, corrosion degradation of hydroxyapatite ceramics were preferentially recognized on hydroxyapatite particle after short time immersion into simulated body fluid. The general tendency of drastic decrease in fracture resistance was recognized in these materials. The fracture resistance of the specimen was found to decrease with increasing corrosion degradation, especially after 3week immersion in simulated body fluid. This remarkable degradation in fracture resistance is considered to be caused by crack propagation through corroded pit. However, the specimens after 4week immersion into simulated body fluid showed improved fracture resistance compared with those of corroded hydroxyapatite ceramics. There improvements in fracture resistance may be brought about through the mechanics was shown to induce the apatite layer formation on itfs surface in some areas between 4 and 8week by simulated body fluid. Key Words:Apatite ceramics, Bioactive function, Fracture resistance, Microstructure, Simulate body fluid