Abstract
Different 3D printing techniques for orthopaedic ceramic implants fabrication were compared. Stereolithography of calcium-phosphate slurries makes possible to achieve pre-determined pore size (50 mkm and more) and porosity of 70–80%. For the first time ceramic implants based on double calcium alkali metal phosphates (rhenanites) with given architecture serving good osteoconductivity as well as high resorptivity and strength (up to 10 MPa) were obtained.
Development of biomaterials based on calcium phosphates for orthopaedics is an important area of modern materials science. Chemical, physical and mechanical compatibility of this materials is a primary goal for this field. An ideal implant should gradually dissolve and be replaced by the new bone tissue in the patience body.
Bone is a multilevel organic/inorganic composite and the main inorganic compound is hydroxyapatite (HA, Ca10(PO4)6(OH)2). Due to this, biomaterials based on HA are widely used, along with biomaterials based on tricalcium phosphate (TCP, Ca3(PO4)2); however, low solubility of HA (lowest soluble phosphate) as well as TCP does not meet all of the requirements that biomaterials should have.
In this work decreasing of the crystal lattice energy approach was used as a strategy of improving the solubility. Modifying the chemical composition by replacing Ca2+cation in the TCP structure by a singly charged alkali metal cation leads to structural changes from TCP to CaMPO4(M=Na, K) – rhenanite. This work focuses on using double calcium alkali metal phosphates Ca(3 – x)М2x(PO4)2(x = 0–1, М = Na, K) as bioresorbable osteoconductive ceramic implant.
Additive manufacturing techniques are the most competitive technology which has been applied in the medical field for the direct or indirect construction of scaffolds and hard or soft tissues. Different techniques were used to prepare ceramics with given structure based on double calcium alkali metals phosphates to improve its osteoconductive properties. High resolution stereolithography (SLA) of ceramic photocurable resins has a great potential in fabrication of high quality complex shaped ceramics. For the first time ceramic implants based on double calcium alkali metal phosphates (rhenanites) with pre-determined pore size (50 mkm and more) and porosity of 70–80% were obtained. Given architecture of scaffold is serving a good osteoconductivity as well as a high resorptivity and strength (up to 10 MPa).
High resolution SLA can be easily used for fabrication of a small size implants (3mm in diameter/height or less) for in vivo experiments, and it can be freely used to fit any shade in osteoconductive properties of ceramic materials designed for bone grafting.
Russian Science Foundation supported this study under Grant No. 14-19-00752. The authors acknowledge partial support from Lomonosov Moscow State University Program of Development.
