Fabrication of interconnected porous β-tricalcium phosphate (β-TCP) based on a setting reaction of β-TCP granules with HNO₃ followed by heat treatment

β-Tricalcium phosphate [β-TCP] is the typical bone substitute due to its excellent osteoconductivity and bioresorbability. One of the keys to improve its potential as bone substitute is to introduce porous structure and its regulation. In this study, interconnected porous β-TCP blocks were fabricated through a setting reaction of β-TCP granules and subsequent heat treatment. First, β-TCP granules were mixed with HNO₃. Upon mixing, β-TCP granules were bridged with dicalcium phosphate dihydrate [DCPD: CaHPO₄·2H₂O] containing Ca(NO₃)₂. Then, the DCPD-bridged β-TCP was heated at 1100°C. During the heating process, DCPD containing Ca(NO₃)₂ transformed into β-TCP and bonded with β-TCP granules. As a result, an interconnected porous β-TCP block formed. The diametral tensile strength and porosity of the interconnected porous β-TCP block fabricated from 200–300-μm β-TCP granules and 5 N HNO₃ and then heated at 1,100°C were 1.4 ± 0.2 MPa and 57% ± 2%, respectively.