Fabrication of higher thermal stability doped β-tricalcium phosphate bioceramics by robocasting
Résumé
β-tricalcium phosphate (β-TCP) is one of the most attractive
biomaterials for bone repair since it shows an excellent biological
compatibility, osteoconductivity, and resorbability. It can be used
to produce bone implants serving as temporary supports for
bone regeneration.However, there are still some issues for β-TCP
porous scaffolds fabrication. Indeed, β-TCP cannot be used as
scaffolds in large bone defects or in load-bearing areas due to its
weak mechanical properties related to insufficient densification
level. Indeed, the sintering temperature is limited because of the
occurrence of a phase transition β to α-TCP at 1150°C with a large
lattice expansion causing microcracks and reducing shrinkage
during sintering. The thermal stability can be increased by the
incorporation of dopants inside the β-TCP lattice. Indeed, such
dopants like cations can replace the calcium inside the structure
and stabilize the β phase as well as improve the biological
properties. Thus, cationic substitution can allow reaching higher
relative density value.
In this work, doped β-TCP powders are synthetized by
coprecipitation of Ca(NO3)2 and (NH4)2HPO4 solutions in presence
of different cations in order to prevent the phase transformation
and increase the sintering temperature. Owing to the β-phase
stabilization, new rapid sintering techniques like microwave
sintering can be successfully applied with a limited grain growth.
The sintered samples are compared in terms of microstructural
and mechanical properties. In addition to the sintering and
thermal stability study, 3D-printable suspensions are prepared
from optimized doped powder to manufacture porous scaffolds by
robocasting.