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Multi-doped glasses with Mg2+ and Zn2+ ions in glass-ionomer cements
John Makanjuola1, Robert Hill2, Sadia Niazi3
1Centre for Oral, Clinical & Translational Sciences, Faculty of Dentistry, Oral & Craniofacial Sciences, King's College London, Guy's Hospital, London SE1 9RT, United Kingdom.
Objective:
To develop a new, biocompatible glass-ionomer cement (GIC) with improved antibacterial activity and physical properties through multiple ionic substitutions of strontium with magnesium and zinc.
Methods:
A fluoro-alumino-silicate glass (LG99Sr) with composition 4.5SiO₂-3Al₂O₃-1.5 P₂O₅-3SrF₂-2SrO was synthesized using the melt-quench technique. LG99Sr was modified by partially substituting SrO with MgO and ZnO, yielding a new composition 4.5SiO₂-3Al₂O₃-1.5 P₂O₅-3SrF₂-0.5SrO-1MgO-0.5ZnO (LG99Sr-Mg-Zn). Following glass characterization, GICs were prepared using Fuji IX (GC Corporation, Tokyo, Japan) as a reference. Physical properties, antimicrobial activity (against Streptococcus mutans, Streptococcus mitis/oralis, and Lactobacillus paracasei), and in vitro cytocompatibility were evaluated. Data were analysed using two-way ANOVA and Tukey-Kramer HSD post-hoc tests to determine the differences in properties between groups (p < 0.05).
Results:
The presence of magnesium and zinc in LG99Sr-Mg-Zn was validated via EDS analysis, with ICP-MS confirming their release upon immersion. All GICs demonstrated similar fluoride release profiles; notably, LG99Sr-Mg-Zn exhibited a higher initial fluoride release. Mechanical properties at 24 hours were comparable; however, LG99Sr-Mg-Zn and Fuji IX showed significant improvements (p < 0.05) post-maturation compared to LG99Sr. After 1-month maturation, compressive strength, flexural strength, and Vickers microhardness were significantly higher (p < 0.05) for Fuji IX and LG99Sr-Mg-Zn, and microhardness remained significantly higher at 90 days. Agar diffusion, biofilm inhibition, and XTT tests revealed enhanced antibacterial activity (p < 0.05) for LG99Sr-Mg-Zn. MTT and alamarBlue assays confirmed zinc concentration in LG99Sr-Mg-Zn was not cytotoxic.
Significance:
Ionic substitution of magnesium and zinc in fluoro-alumino-silicate glass significantly enhanced fluoride release and antibacterial properties, improved mechanical properties upon maturation, and maintained cell viability, making it a promising restorative material.
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