A Comparison of Bioactive Glass Scaffolds Fabricated ‎by Robocasting from Powders Made by Sol–Gel and Melt-Quenching Methods

Abstract

Bioactive glass scaffolds are used in bone and tissue biomedical implants, and there is great interest in their fabrication by additive manufacturing/3D printing techniques, such as robocasting. Scaffolds need to be macroporous with voids ≥100 m to allow cell growth and vascularization, biocompatible and bioactive, with mechanical properties matching the host tissue (cancellous bone for bone implants), and able to dissolve/resorb over time. Most bioactive glasses are based on silica to form the glass network, with calcium and phosphorous content for new bone growth, and a glass modifier such as sodium, the best known being 45S5 Bioglass®. 45S5 scaffolds were first robocast in 2013 from melt-quenched glass powder. Sol–gel-synthesized bioactive glasses have potential advantages over melt-produced glasses (e.g., greater porosity and bioactivity), but until recently were never robocast as scaffolds, due to inherent problems, until 2019 when high-silica-content sol–gel bioactive glasses (HSSGG) were robocast for the first time. In this review, we look at the sintering, porosity, bioactivity, biocompatibility, and mechanical properties of robocast sol–gel bioactive glass scaffolds and compare them to the reported results for robocast melt-quench-synthesized 45S5 Bioglass® scaffolds. The discussion includes formulation of the printing paste/ink and the effects of variations in scaffold morphology and inorganic additives/dopants.

Evaluation of robocasting process in the layering of dental feldspathic porcelain in metal‐ceramic restorations

“…A similar result is difficult to achieve with other AM techniques such as powder bed printing. 9,35,36 Finally, regarding the yield stress, the pastes under study cover the aforementioned value (>200 Pa) as the yield stress was calculated to be 1105 and 1164 Pa for the enamel and dentine paste, respectively.…”

Robocasting of advanced ceramics: ink optimization and protocol to predict the printing parameters - A review

“…The importance of preventing bubbles when loading the ceramic ink in the syringe was highlighted by several authors. Indeed, bubbles trapped in the ink can result in critical printing defects, in particular internal porosity and printing gaps [ 22 , 49 , 99 ].…”

Effects of glass–ceramic produced by the sol–gel route in macrophages recruitment and polarization into bone tissue regeneration

“…These techniques aim to enhance biocompatibility and bioactivity for effective bone healing while minimizing the risk of biomaterial implantation failure. [9][10][11][12][13][14][15][16][17] Glass biomaterials are predominantly fabricated using either traditional solidification (BS) or sol-gel processes (BS), involving heating the bioactive glass beyond its crystallization temperature, typically ranging from 610 to 630 C. 18 Crystallization in melt-derived glasses results in a reduction of the parent glass's microstructure and porosity, leading to solidification and subsequent physical stress. 19 Sol-gel methods exhibit a distinct behavior upon liquid contact, with the biomaterial's porous structure absorbing a certain amount of liquid.…”

“…A myriad of processing techniques has been applied to the development of bioactive glasses and related glass‐ceramics. These techniques aim to enhance biocompatibility and bioactivity for effective bone healing while minimizing the risk of biomaterial implantation failure 9–17 . Glass biomaterials are predominantly fabricated using either traditional solidification (BS) or sol–gel processes (BS), involving heating the bioactive glass beyond its crystallization temperature, typically ranging from 610 to 630°C 18 .…”