Bioactive glass and glass-ceramic scaffolds for bone tissue engineering

Abstract

Traditionally, bioactive glasses have been used to fill and restore bone defects. More recently, this category of biomaterials has become an emerging research field for bone tissue engineering applications. Here, we review and discuss current knowledge on porous bone tissue engineering scaffolds on the basis of melt-derived bioactive silicate glass compositions and relevant composite structures. Starting with an excerpt on the history of bioactive glasses, as well as on fundamental requirements for bone tissue engineering scaffolds, a detailed overview on recent developments of bioactive glass and glass-ceramic scaffolds will be given, including a summary of common fabrication methods and a discussion on the microstructural-mechanical properties of scaffolds in relation to human bone (structure-property and structure-function relationship). In addition, ion release effects of bioactive glasses concerning osteogenic and angiogenic responses are addressed. Finally, areas of future research are highlighted in this review.

Robocasting of SiO2-Based Bioactive Glass Scaffolds with Porosity Gradient for Bone Regeneration and Potential Load-Bearing Applications

“…The Ca-to-P atomic ratio increases from 1.09 at 24 h to 1.33 at 1 week but remains below the theoretical value of stoichiometric HA (1.67). This is consistent with most of in vitro assessments reported in the literature on bioactive glasses that, upon being soaked in SBF, are typically coated by a layer of Ca-deficient HA [6,7].…”

“…Man-made materials for BTE are often produced as porous scaffolds, which should fulfill specific requirements in terms of biological features, porosity, and mechanical properties to achieve a good implant outcome [5]. Ideally, BSMs shall exhibit a hierarchical structure, with interconnected pores of different dimensions ranging from few micrometers (which promote cell adhesion) to 100–500 µm (which are key to enhance bone ingrowth and capillary vessel formation, avoiding poor vascularization) [6,7]. The total porosity is required to be at least equal to the minimum value of the trabecular bone (i.e., 50 vol.% [8]).…”

“…In order to avoid stress shielding and bone resorption due to low load transfer as well as provide structural support during the whole healing process, a properly designed BSM shall show mechanical properties (i.e., compressive strength, elastic and flexural moduli) similar to those of surrounding bone [5]. Accurate control of such parameters is not achievable, unfortunately, by means of conventional fabrication techniques, which were reviewed elsewhere [7,9,10].…”

Bioactive and inert dental glass‐ceramics

“…[146][147][148][149] Therefore, almost all commercial bioactive glass-ceramics and others under development 34 have been the subject of study for scaffold development using various fabrication techniques, including, for example, foam-replication methods, salt or sugar leaching, thermally induced phase separation, microsphere emulsification sintering, electrospinning to form nano-fibrous structures, freeze casting, additive manufacturing technologies, computer assisted rapid prototyping techniques, and so forth. [146][147][148][149] The results are inspiring, and it appears that in future, biomimetic regeneration of the complex structure of teeth demands 3D porous materials, and bioactive glassceramics are promising for this application. Research and development in this area might lead to the first bio-tooth development.…”

“…Comprehensive reviews on the state‐of‐the‐art in bioactive glass‐ceramic scaffolds have been published by numerous scientists who believe that glass‐ceramics have a combination of better properties, such as high strength and fracture toughness (due to their unique toughening mechanisms), for scaffold development compared with those of glasses . Therefore, almost all commercial bioactive glass‐ceramics and others under development have been the subject of study for scaffold development using various fabrication techniques, including, for example, foam‐replication methods, salt or sugar leaching, thermally induced phase separation, microsphere emulsification sintering, electrospinning to form nano‐fibrous structures, freeze casting, additive manufacturing technologies, computer assisted rapid prototyping techniques, and so forth . The results are inspiring, and it appears that in future, biomimetic regeneration of the complex structure of teeth demands 3D porous materials, and bioactive glass‐ceramics are promising for this application.…”