Abstract
Background
Calcium phosphate cement (CPC) is a promising biomaterial which can be used in numerous medical procedures for bone tissue repairing because of its excellent osteoconductivity. An injectable preparation and relatively short consolidation time are particularly useful characteristics of CPC. However, the low strength of CPC and its brittleness restrict its use. One method for toughening brittle CPC is to incorporate fibrous materials into its matrix to create a composite structure. Fibers are widely used to reinforce matrix materials in a variety of areas.
Objective
We hypothesized that there must be an optimal fiber length and structure which can balance these conflicting aspects of fiber reinforcement. The purpose of this study is to prove our conjectures that adding a small amount of short fibers significantly improves the hardness and the toughness of CPC while maintaining its injectability with a syringe and that fiber morphologies that have crimps and surface roughness are favorable for reinforcing.
Material and Methods
We used 3 types of short fibers of approximately 20–50 micrometer in diameter and 2 mm in length in this study: crimpy wool, crimpy polyethylene and straight polyethylene fibers. All of the materials were prepared by mixing a solvent with CPC powder with or without fiber. We grouped as follow, the control group, the wool group, the crimpy polyethylene group, the straight polyethylene group. After soaking in 37 degrees Celsius Simulated Body Fluid∗∗∗∗∗ for 1, 3, or 7 days, they were tested for each period. Impact strength test by the falling weight and compression test were performed.
Result
In the impact strength test, after soaking for 1 day, impact resistance in the wool group was approximately 180 times greater than in the control group. When soaking for 3 days or more, impact resistance of wool group improve better than control group. The impact resistance of the wool group was the greatest among the four groups in soaking for 3 days. In the compression test, the yield strength and ultimate strength of the wool group were significantly higher than ultimate strength of the control group. The wool group has stress–strain curves that are typical of those of ductile materials, whereas the stress–strain curves of the control group resemble those of brittle materials. This indicates that fiber reinforcement drastically alters the physical properties of CPC converting it from brittle to ductile.
Conclusion
In the present study, we sought to develop a method for producing injectable fiber-reinforced CPC. We focused on morphology and surface roughness of fiber in the reinforcement of CPC. This study clearly showed that CPC was substantially strengthened and toughened by crimpy short fiber reinforcement. CPC reinforced with short fibers which have morphology similar to wool should be a promising tool for orthopedic surgeons.
