Indirect rapid prototyping of biphasic calcium phosphate scaffolds as bone substitutes: influence of phase composition, macroporosity and pore geometry on mechanical properties

Abstract

While various materials have been developed for bone substitute and bone tissue engineering applications over the last decades, processing techniques meeting the high demands of scaffold shaping are still under development. Individually adapted and mechanically optimised scaffolds can be derived from calcium phosphate (CaP-) ceramics via rapid prototyping (RP). In this study, porous ceramic scaffolds with a periodic pattern of interconnecting pores were prepared from hydroxyapatite, β-tricalcium phosphate and biphasic calcium phosphates using a negative-mould RP technique. Moulds predetermining various pore patterns (round and square cross section, perpendicular and 60° inclined orientation) were manufactured via a wax printer and subsequently impregnated with CaP-ceramic slurries. Different pore patterns resulted in macroporosity values ranging from about 26.0-71.9 vol% with pore diameters of approximately 340 μm. Compressive strength of the specimens (1.3-27.6 MPa) was found to be mainly influenced by the phase composition as well as the macroporosity, both exceeding the influence of the pore geometry. A maximum was found for scaffolds with 60 wt% hydroxyapatite and 26.0 vol% open porosity. It has been shown that wax ink-jet printing allows to process CaP-ceramic into scaffolds with highly defined geometry, exhibiting strength values that can be adjusted by phase composition and pore geometry. This strength level is within and above the range of human cancellous bone. Therefore, this technique is well suited to manufacture scaffolds for bone tissue engineering.

Calcium Orthophosphate-Based Bioceramics

“…The alternatives include use hierarchical bioactive scaffolds to engineer in vitro living cellular constructs for transplantation or use bioresorbable bioactive particulates or porous networks to activate in vivo the mechanisms of tissue regeneration [807,808]. Thus, the aim of calcium orthophosphates is to prepare artificial porous bioceramic scaffolds able to provide the physical and chemical cues to guide cell seeding, differentiation and assembly into 3D tissues of a newly formed bone [463,727,809,810,811,812,813,814,815,816,817]. Particle sizes, shape and surface roughness of the scaffolds are known to affect cellular adhesion, proliferation and phenotype [783,784,785,786,787].…”

Medical Application of Calcium Orthophosphate Bioceramics

“…The alternatives include use hierarchical bioactive scaffolds to engineer in vitro living cellular constructs for transplantation or use bioresorbable bioactive particulates or porous networks to activate in vivo the mechanisms of tissue regeneration [692,693]. Thus, the aim of calcium orthophosphate bioceramics is to prepare artificial porous scaffolds able to provide the physical and chemical cues to guide cell seeding, differentiation and assembly into 3D tissues of a newly formed bone [648,[694][695][696][697][698][699][700]. Particle sizes, shape and surface roughness of the scaffolds are known to affect cellular adhesion, proliferation and phenotype.…”

Periodontal repair following implantation of beta-tricalcium phosphate with different pore structures in class III furcation defects in dogs

“…Beta-tricalcium phosphate (β-TCP) belongs to the group of bioactive bioceramics of completely synthetic origin and has been used in periodontology as a bone graft substitute since the 1980s 1,[20][21][22][23] . At present, there are various types of β-TCP composed of macropores with small connecting area [24][25][26] . We devised a tunnel pipe structure that maintained a continuous pore of 300 μm.…”