The key Features expected from a Perfect Bioactive Glass –How Far we still are from an Ideal Composition?

Bioactive Glasses and Glass-Ceramics for Healthcare Applications in Bone Regeneration and Tissue Engineering

“…The most salient features desired for bioactive glasses as listed above can be obtained while totally excluding the alkalis and by a rational combination of all the remaining pertinent glass components, as has been plenteously demonstrated by Ferreira et al in several works published since 2011 [77,135,151,275,277,279,280,281,282,283,284,285,298,299,300,303,304,305,306,307,308,309,310,311,312,313]. Following a completely different concept, the alkali-free bioactive glass compositions were based upon the compositions of minerals that are biocompatible and bioactive, such as diopside, fluorapatite, wollastonite, and tricalcium phosphate, in different combinations and proportions.…”

“…Therefore, the pertinence of the continuous research activities focused on high alkali-containing bioactive glasses is highly questionable. As reviewed above, such glass compositions hardly can meet the most salient features of an ideal bioactive glass, concerning not only the in vitro and in vivo performances, but also the thermal, physicochemical properties, and processing ability, which include [279]:Absence of cytotoxic effects (no harmful dissolution products and the resulting pH);Non-genotoxic—no damage to genes within a cell or DNA mutations;Biocompatible—absence of any foreign body reaction;Fast biomineralisation rate in vitro with the formation of a hydroxyl carbonated apatite (HCA);Osteoconductivity—bone readily grows and bonds on its surface;Osteoinductive properties—recruiting immature cells and stimulating them to develop into pre-osteoblasts, which are essential in any bone healing process;Osseointegration—stable anchorage of an implant achieved by direct bone-to-implant contact.For implant coatings, good matching of the coefficients of thermal expansion of the coating glass and the metallic substrate for a strong adhesion between applied films and metallic implants;Ease of scaffold fabrication by additive manufacturing techniques;Ability to release therapeutic and anti-infection ions at the implant site.…”

“…Following a completely different concept, the alkali-free bioactive glass compositions were based upon the compositions of minerals that are biocompatible and bioactive, such as diopside, fluorapatite, wollastonite, and tricalcium phosphate, in different combinations and proportions. The emphasis in this section is particularly put on alkali-free bioactive glasses and glass-ceramics as a smart way to overcome all the drawbacks mentioned above for high alkali containing compositions, as summarised elsewhere [279].…”

“…The decrease of SBG CTE can be accomplished by increasing the silica content (at the expenses of bioactivity) [362,380] or partially replacing (with MgO, B 2 O 3 , and/or CaF 2 [290,309,310,311]) or even removing alkalis [151]. Furthermore, the high concentration of Na 2 O that is characteristic of 45S5 Bioglass ® and S53P4 BonAlive ® classical SBG systems, is known to induce faster degradation rates [279,380], which conflicts with the concept of durable thin implant coatings with long-lasting performance.…”

Novel antimicrobial phosphate-free glass–ceramic scaffolds for bone tissue regeneration

“…45S5 Bioglass discovered by Hench in 1969 is the first example of a biomaterial belonging to the third generation since it was the first material to bond with bone, rather than be encapsulated by fibrous tissue. However, 45S5 Bioglass fabricated using the replication method was brittle with low fracture toughness and compressive strength 22 . In addition to the silicate BGs, many new compositions have been proposed for optimizing the body´s response according to the specific clinical applications as borate glasses, which stand out for their high dissolution rates and apatite-forming ability 23 , phosphate glasses with less bioactivity but high solubility and BGs with other cations within the glass network in order to confer additional beneficial properties 24 and also glass–ceramic.…”