**4. Conclusions**

The hydrothermal method is particularly appropriate for the realization of good-quality crystals and allows tailored HA nanosized particles to be synthesized or characteristic of 3-D structures.

This chapter discussed about the most influencing variables in the hydrothermal synthesis of HA and their effects to prepare a wide range of crystal morphologies.

Among the considered variables, temperature and pH seem to be the most significant factors affecting the dimensional, geometry, and crystalline characteristics of HA nanoparticles, e.g., through face-selective interaction and anisotropic growth processes.

**Table 5** summarizes the process parameters discussed and their effects and contribution on the final structures, which can have the form of hexagonal prisms (rods, needles, wires), sheets, plates, whiskers, fine spherical-shaped, etc., of varying sizes.

This extensive range of morphologies may be useful for developing various and improved types of nanostructured biomaterials, which could have potential application for repairing bone defects and tissue regeneration.


### **Table 5.**

*Summary scheme of the hydrothermal parameters contribution on the final HA nanostructure.* 

*Synthesis of Nanostructured Hydroxyapatite via Controlled Hydrothermal Route DOI: http://dx.doi.org/10.5772/intechopen.85091* 
