Antimicrobial efficacy of strontium and zinc glasses and glass ionomer cements against clinically relevant bacteria
Hawshan Mustafa1, Farah Raja2, Tony Worthington2, Delia Brauer1, Richard A Martin2.
1Otto Schott Institute of Materials Research, Friedrich Schiller University Jena, Germany.
2Aston Institute of Materials Research & Aston Centre for Healthy Ageing, Aston University, Birmingham, UK.
Dental caries, caused by bacteria, can lead to significant tooth demineralization. Dental materials/glass ionomer cements (GIC) with bioactive glasses, that inhibit bacteria /dental caries, have therefore been studied. The aim of this study was to evaluate the antimicrobial efficacy of novel glasses and glass ionomer cements based on the SiO2-Al2O3-P2O5-CaO-CaF2 (LG26) composition, where calcium is replaced by either strontium (LG26Sr) or zinc (LG26Zn). Glasses were prepared using a melt quench technique. Cement discs were prepared using glass powder (≤ 40 micrometer) + polyacrylic acid powder + 10% tartaric acid solution, (8.66 mm diameter and 1 mm thick). The antimicrobial efficacy was evaluated by agar diffusion, direct and indirect assays using Staphylococcus aureus (ATCC 6538) and Streptococcus sanguinis (ATCC 10556).
Agar diffusion assays showed that LG26Zn cements have inhibition zones larger than those observed for amoxicillin and gentamicin, while no inhibition was observed for (ciprofloxacin and trimethoprim), which means that strain is resistant to these two controls. Zinc ions therefore inhibited bacterial growth significantly more than the control antibiotics studied.
Indirect contact assays revealed that LG26 (glasses and cements) failed to demonstrate antibacterial activity compared to the control samples. Strontium cements exhibited a slight reduction (0.7 log reduction/24 hours). Zinc glasses exhibited a significant antimicrobial effect (~3 log reduction/24 hours), however zinc cements showed a reduced but still significant antimicrobial effect (1.5 log reduction/24 hours).
Our results showed that zinc ions are more antibacterial compared to strontium and are therefore an attractive prospect in the management of dental caries.