**3.1 Bioglass implants**

For the first time, the bioglass implants were introduced by Hench's team at the late 1960s [88]. Because of the great bioactivity of bioglasses, they are one of the best biomaterials for renovation and bone repair. Moreover, to combine great mechanical strength and excellent bioactivity of bioglasses, they can be successfully used as coatings on inert substrates [89]. A bioactive surface can be considered as important agent to avoid many simultaneous reactions, which take place between the implant and the targeted tissue at the implant surface. **Figure 10** shows the interfacial reactions involved in forming a bond between bioactive glass and bone. As can be seen, the first five stages take place at the periphery of bioactive glass and involve release of alkali ions (bacterial growth is inhibited as a result of pH increase) along with the formation of crystallized hydoxycarbonate apatite (HCA). Hence, the implanted material fastens down with the tissue from step 6 to 11 in consequence of osteostimulation and bone growth.

The bioactive glass with its composite coatings can be classified as following categorization according to the coating structure:
