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Objectives:\ud Antibiotic resistance is increasingly a growing global threat. This study aimed to investigate the potential use of newly developed scandium-doped phosphate-based glasses (Sc-PBGs) as an antibacterial and anticariogenic agent through controlled release of Sc3+ ions.\ud \ud Methods:\ud Sc-PBGs with various calcium and sodium oxide contents were produced and characterised using thermal and spectroscopic analysis. Degradation behaviour, ion release, antibacterial action against Streptococcus mutans, anti-matrix metalloproteinase-2 (MMP-2) activity, remineralisation potential and in vivo biocompatibility were also investigated.\ud \ud \ud Results:\ud The developed glass system showed linear Sc3+ ions release over time. The released Sc3+ shows statistically significant inhibition of S. mutans biofilm (1.2 log10 CFU reduction at 6 h) and matrix metalloproteinase-2 (MMP-2) activity, compared with Sc-free glass and positive control. When Sc-PBGs were mounted alongside enamel sections, subjected to acidic challenges, alternating hyper- and hypomineralisation layers consistent with periods of re- and demineralisation were observed demonstrating their potential remineralising action. Furthermore, Sc-PBGs produced a non-toxic response when implanted subcutaneously for 2 weeks in Sprague Dawley rats.\ud \ud Significance:\ud Since Sc3+ ions might act on various enzymes essential to the biological mechanisms underlying caries, Sc-PBGs could be a promising therapeutic agent against cariogenic bacteria.

Phosphate-based glasses are a very promising class of multifunctional biomaterials. Being bioresorbable, they are capable of inducing simultaneous regeneration of tissue and delivery of drugs/therapeutic molecules and ions. Therefore, they can be used both as temporary implants and as controlled local delivery systems. Biomaterial-related infections, often causing revision surgery, could be prevented by incorporating into the biomaterial device antimicrobial agents that will be slowly released as the implant degrades. To date, the conventional technique used to prepare phosphate-based glasses is the melt-quenching process, which requires the melting of oxide powders at high temperatures (1000–1200 °C) followed by rapid cooling. However, this method often leads to non-homogeneous, bulk glasses that cannot be used for hosting temperature-sensitive molecules and can lead to reduction of antibacterial ions. Composition is also difficult to control because of the loss of volatile phosphate species during heating. This chapter describes two in-solution techniques for the synthesis of phosphate-based glasses alternative to the melt-quenching one: sol–gel and coacervation. A review of the literature published so far on the topics and a summary of key results is presented.