Comparing physicochemical properties of printed and hand cast biocements designed for ligament replacement

Abstract

In order to combat the low regenerative capabilities of ligaments, full ‘bone to bone’ replacements are required, which will integrate with bone while providing a smooth transition to the replacement soft tissue (tissues surrounding organs in the body, not being bone). This study investigated the use of three-dimensional powder printing technology to form calcium phosphate brackets, previously used for forming bespoke scaffold geometries, to 95±0·1% accuracy of their original computer aided design. The surface and internal structures of the printed samples were characterised both chemically and morphologically and compared with hand moulded cements in the dry state and after 3 days of immersion in phosphate buffered saline. X-ray diffraction, Raman spectroscopy and SEM all showed the presence of brushite in the hand moulded samples and brushite and monetite within the printed samples. Furthermore, the printed structures have a higher level of porosity in the dry state in comparison to the hand moulded samples (36±2·2% compared to 24±0·7%) despite exhibiting a compressive strength of almost double the hand cast material. Although the compressive strength of the printed cements decreases after the 3 day immersion, there was no significant difference between the printed and hand moulded cements under the same conditions. Three-dimensional powder printing technology has enabled the manufacture of bespoke calcium phosphate brackets with properties similar to those reported for hand moulded cements.