Resorbable Dicalcium Phosphate Bone Substitutes Prepared by 3D Powder Printing

Abstract

Bioceramic bone substitutes with programmed architecture were manufactured at room temperature in this study using a novel 3D printing process that combined 3D powder printing with calcium phosphate cement chemistry. During printing, biphasic α/β‐tricalcium phosphate (Ca3(PO4)2, TCP) powder reacted with a liquid component consisting of phosphoric acid solution to form a matrix of dicalcium phosphate dihydrate (CaHPO4·H2O, DCPD, brushite) and unreacted TCP. Printed samples showed compressive strengths between 0.9–8.7 MPa after printing depending on the acid concentration. A further strength improvement to a maximum of 22 MPa could be obtained by additional hardening of the samples in phosphoric acid for three one minute washes. After this treatment, the samples mainly consisted of brushite with minor phases of unreacted TCP and a lesser amount of dicalcium phosphate anhydrate (CaHPO4, DCPA, monetite). Hydrothermal conversion of brushite to DCPA resulted in an increase of porosity of approximately 13 % and a decrease of strength to 15 MPa, however the resorption rate in vivo was increased as demonstrated after intramuscular implantation over 56 weeks. Major advantages compared with commonly used sintering techniques are the low processing temperature, which enables the fabrication of thermally instable and degradable matrices of secondary calcium phosphates.

Structural changes to resorbable calcium phosphate bioceramic aged in vitro

“…Previously published research on scaffolds printed in this way, using the same raw materials, suggests the presence of monetite within the structures. It was reported that hydrothermal conversion of brushite to monetite led to an increase in porosity of approximately 13 % [42]. Although monetite formation was not detected in the work presented here, the increase in porosity is suggestive of CaP dissolution, a process which may or may not reach equilibrium before the media are refreshed every 3 days.…”

Perfluorodecalin and bone regeneration

“…Tissue engineering with 3D printed bioceramics loaded with BM and O 2 loaded PFD 3D-printed CPCs offer a unique opportunity to treat complicated bone defects by designing the implant according to the specific required geometry (Gbureck et al, 2007a). In previous studies we have shown the osteconductive and osteoinductive potential of 3D printed CPCs on goat vertebrae (Habibovic et al, 2008), and we have also been able to augment craniofacial bones using this 3D printed materials (Tamimi et al, 2009a).…”

“…Tubular brushite ceramic blocks were 3D-printed as per the computer design (Fig. 1B-C), following a previously reported technique for cement printing (Gbureck et al, 2007a).…”

“…Bone cements are used as injectable biomaterials in different clinical applications, and set in vivo into hard functional materials (Gbureck et al, 2007a;Tamimi et al, 2009b). A cement paste consists of a suspension of solid particles in a liquid, and injectability of these materials is highly dependent on the stability of this suspension.…”

Bone formation ability of carbonate apatite-collagen scaffolds with different carbonate contents

“…Last century, sintered ceramics such as calcium phosphates were the most commonly used hard tissue biomaterials from the viewpoint of mechanical strength; however, they are fundamentally less biodegradable and not easy to process. To obtain better handling properties, apatite-collagen/ gelatin composites [7][8][9] in addition to various kinds of calcium phosphate cements [10][11][12] have been developed. Recently, tissue engineering has been developed.…”