Developing a calcium silver zeolite with remineralising and antimicrobial properties

Objectives: To 1) develop a novel calcium silver zeolite, 2) assess its calcium and silver ion release kinetics and, 3) assess its antimicrobial effect on common oral pathogens.
Methods: Calcium silver zeolite (Ca-Ag-Zeo) was synthesized using calcium chloride, silver nitrate and Zeolite X and characterized by X-ray diffraction spectrum, scanning electron microscopy, transmission electron microscopy and energy dispersive spectroscopy, respectively. The calcium and silver ion release of Ca-Ag-Zeo were assessed by Inductive Coupled Plasma Emission Spectrometry for 12 weeks. The antimicrobial effects of the Ca-Ag-Zeo on common oral pathogens, including Streptococcus mutans, Lactobacillus acidophilus, Lactobacillus casei, Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis and Candida albicans were assessed by minimum bactericidal concentration (MBC) assay. Silver zeolite X (Ag-Zeo) and zeolite X (Zeo) were used as control.
Results: Ca-Ag-Zeo was synthesized and presented a hexagonal cage structure containing calcium and silver. The accumulated calcium ion release concentration (±SD in mg/L) at 12 weeks of Ca-Ag-Zeo, Ag-Zeo and Zeo were 2.2 ± 0.54, 0 and 0, respectively (Ca-Ag-Zeo > Ag-Zeo = Zeo; p<0.001). The accumulated silver ion release concentration (±SD in mg/L) at 12 weeks of Ca-Ag-Zeo, Ag-Zeo and Zeo were 42.5 ± 5.58, 41.8 ± 3.96 and 0, respectively (Ca-Ag-Zeo = Ag-Zeo > Zeo; p<0.001). The MBC (mg/ml) of Ca-Ag-Zeo, Ag-Zeo and Zeo were 32, 16 and > 256 against S. mutans; 32, 16, >256 against L. acidophilus; 16, 16, and 256 against L. casei; 1, 2, >256 against A. actinomycetemcomitans; 0.25, 0.125, >256 against P. gingivalis; and 2, 1, > 256 against C. albicans respectively.
Conclusions: A novel calcium silver zeolite was developed. It can release calcium ions and silver ions sustainably and inhibit the growth of common oral pathogens.