Bioactive glass-ceramic scaffolds by additive manufacturing and sinter-crystallization of fine glass powders

Abstract

Wollastonite (CaSiO 3)-diopside (CaMgSi 2 O 6) glass-ceramic scaffolds have been successfully fabricated using two different additive manufacturing techniques: powder-based 3D printing (3DP) and digital light processing (DLP), coupled with the sinter-crystallization of glass powders with two different compositions. The adopted manufacturing process depended on the balance between viscous flow sintering and crystallization of the glass particles, in turn influenced by the powder size and the sensitivity of CaO-MgO-SiO 2 glasses to surface nucleation. 3DP used coarser glass powders and was more appropriate for low temperature firing (800-900°C), leading to samples with limited crystallization. On the contrary, DLP used finer glass powders, leading to highly crystallized glass-ceramic samples. Despite the differences in manufacturing technology and crystallization, all samples featured very good strength-to-density ratios, which benefit their use for bone tissue engineering applications. The bioactivity of 3D-printed glass-ceramics after immersion in simulated body fluid and the similarities, in terms of ionic releases and hydroxyapatite formation with already validated bioactive glass-ceramics, were preliminarily assessed.

Comparative Analysis of Wollastonite‐Diopside Glass‐Ceramic Structures Fabricated via Stereo‐Lithography

“…Previous experiences had already evidenced the feasibility of samples, for both glasses, only with simple cubic cell architectures. WDE had been printed also with a Kelvin cell architecture .…”

“…Contrary to previously reported DLP experiments with both glasses, on cubic scaffolds, the experiments here reported were conducted with quite coarse powders (<45 μm, instead of <20 μm), in order to simplify the processing. WD and WDE glass particles were both mixed with an acrylate polymer resin (tripropylene glycol diacrylate, Robot Factory S.R.L., Mirano, Italy), obtaining suspensions with a total solid load of 41 vol%.…”

“…Unlike for 45S5 Bioglass, there is a relatively large gap between dilatometric softening temperature ( T d , a well‐recognized threshold for significant viscous flow sintering,) and crystallization temperature ( T c ), exceeding 150 °C. This means that a nearly full strut densification may be achieved, upon heating, before crystallization takes place . Several variants have shown a controlled ionic releases and good bioactivity properties, according to their ability to stimulate apatite formation, and biocompatibility, according to MTT (3‐(4,5‐dimethyl‐2‐thiazolyl)‐2,5‐diphenyl‐2H‐tetrazolium bromide) and LDH (lactate dehydrogenase) activity assays with human fibroblasts.…”

“…Several variants have shown a controlled ionic releases and good bioactivity properties, according to their ability to stimulate apatite formation, and biocompatibility, according to MTT (3‐(4,5‐dimethyl‐2‐thiazolyl)‐2,5‐diphenyl‐2H‐tetrazolium bromide) and LDH (lactate dehydrogenase) activity assays with human fibroblasts. In addition, the combination between the wollastonite and diopside phases enhances the mechanical properties . Highly porous wollastonite‐diopside glass‐ceramics were successfully obtained by different techniques, based sintering with concurrent crystallization, including digital light processing (DLP), with the manufacturing of scaffolds with simple cubic or Kelvin cells.…”

“…In addition, the combination between the wollastonite and diopside phases enhances the mechanical properties . Highly porous wollastonite‐diopside glass‐ceramics were successfully obtained by different techniques, based sintering with concurrent crystallization, including digital light processing (DLP), with the manufacturing of scaffolds with simple cubic or Kelvin cells.…”