Fabrication of porous blocks of calcium phosphate through hydrothermal processing under glycine coexistence

Porous hydroxyapatite (HA) and beta-tricalcium phosphate (β-TCP) blocks are well known biomaterials employed as bone substitutes. Control of the porosity and morphology of these ceramics are important in governing their biological properties upon implantation. One synthetic method, hydrothermal processing, produces porous ceramics with distinct morphologies. In the present study, porous calcium phosphate blocks with unique structures were produced from compacted powder mixtures of alpha-tricalcium phosphate (α-TCP) and glycine (Gly) treated by exposure to water vapor at 120, 160, and 200°C for 5 h. Hydrothermal treatment at 200°C for 5 h of mixtures of Gly/α-TCP with mass ratios of 50/50 and 67/33 could give the porous materials of single phase HA. The obtained porous HA blocks had micrometer-sized pores due to the entanglement of rod-shaped particles, and large-sized pores of over 100μm in diameter derived from Gly. After the heating at 900°C for 3 h in air, HA was converted to β-TCP with almost same microstructure in comparison with that of pre-heating one. The present methods provided insight into the production of porous blocks composed of rod-shaped calcium phosphate particles with both submicron-sized pores and large-sized pores of about 100μm in size.