In vitro bioactivity evaluation (Immersion in simulated body solution SBF) This test is one of the most common tests being used to investigate the bioactivity and biodegradability of biomaterials. Considering the convenience of this test and also considering the fact that, it doesn’t need much equipment and facilities, it has lots of applications and is being used widely. This test is so simple. However, the results are very decisive for researches. Changing the concentrations of the ions present in solutions, it would be possible to reduce the test time. In this test, a calcium rich layer of amorphous calcium phosphate will be formed on the surface. Exactly after the formation of this layer, it would turn into an amorphous calcium phosphate poor in calcium and will be finally crystalized on the surface in the form of apatite.