Extrusion-Based 3D Printing of Calcium Magnesium Phosphate Cement Pastes for Degradable Bone Implants

Abstract

This study aimed to develop printable calcium magnesium phosphate pastes that harden by immersion in ammonium phosphate solution post-printing. Besides the main mineral compound, biocompatible ceramic, magnesium oxide and hydroxypropylmethylcellulose (HPMC) were the crucial components. Two pastes with different powder to liquid ratios of 1.35 g/mL and 1.93 g/mL were characterized regarding their rheological properties. Here, ageing over the course of 24 h showed an increase in viscosity and extrusion force, which was attributed to structural changes in HPMC as well as the formation of magnesium hydroxide by hydration of MgO. The pastes enabled printing of porous scaffolds with good dimensional stability and enabled a setting reaction to struvite when immersed in ammonium phosphate solution. Mechanical performance under compression was approx. 8–20 MPa as a monolithic structure and 1.6–3.0 MPa for printed macroporous scaffolds, depending on parameters such as powder to liquid ratio, ageing time, strand thickness and distance.

Comparison of degradation behavior and osseointegration of 3D powder-printed calcium magnesium phosphate cement scaffolds with alkaline or acid post-treatment

“…As previously described in studies on CMPCs with the application form of granules, pastes or cylindrical scaffolds (Wu et al, 2008b;Wei et al, 2010;Ewald et al, 2019;Fuchs et al, 2021;Götz et al, 2021;Kowalewicz et al, 2021), the CMPCs investigated in this study as well as TCP showed excellent clinical tolerability with physiological wound healing. No animal showed lameness or pain.…”

“…Due to their better mechanical properties as well as their faster degradation compared to CPCs, CMPCs have been increasingly researched in recent years in the form of cement pastes and granules ( Wu et al, 2008a ; Wu et al, 2008b ; Klammert et al, 2010a ; Jia et al, 2010 ; Wei et al, 2010 ; Vorndran et al, 2011 ; Zeng et al, 2012 ; Ewald et al, 2019 ; Fuchs et al, 2021 ; Götz et al, 2021 ). However, for the treatment of many bone defects, three-dimensional, dimensionally stable scaffolds are required, that can be produced patient-specifically.…”

Influence of 3D Printing Parameters on the Mechanical Stability of PCL Scaffolds and the Proliferation Behavior of Bone Cells

“…This is in agreement with the compressive strength found for the different strand spacings in this work, as well as in the previously published work by our group, which was in connection with inverse 3D printing with variations in the strand width of the resulting scaffolds for use as a bone replacement [ 45 ]. Götz et al [ 46 ] also described the decrease in compressive strength with increasing strand spacing. In their work, however, they investigated scaffolds made of calcium magnesium phosphate cement.…”

Biodegradable magnesium phosphates in biomedical applications

“…Since Mg is a common substitute for Ca in natural bone tissue, so Mg-based materials are often added into CaP cement to form MCP cement to increase their setting time and mechanical properties. 20,79,80…”