Ammonium hexafluorosilicate with antibacterial agents for the prevention of caries

Objective: Ammonium hexafluorosilicate (SiF: (NH₄)₂SiF₆) was prepared in order to overcome the tooth discoloration caused by diamine silver fluoride (AgF: (NH₃)₂AgF) application. However, the antibacterial activity of SiF seems to be inferior to AgF due to silver having a high antibacterial activity. To increase the antibacterial activity of SiF, various antibacterial agents were added to SiF solution for the prevention of dental caries. The aim of this study was to evaluate the acid resistance and antibacterial activity of the SiF solution with the addition of antibacterial agents.

Method: Four kinds of antibacterial agents, such as chlorhexidine (CHX), cetylpyridinium chloride (CPC), isopropyl methylphenol (IPMP), or epigallocatechin gallate (EGCG) were added to SiF solution. Demineralized depth of hydroxyapatite pellets after several SiF treatments were measured by surface roughness analyzer. Also, antibacterial activity of several SiF solutions was evaluated. Streptococcus mutans adhesion on hydroxyapatite pellets was examined. Hydroxyapatite pellets treated with several SiF solutions were immersed in BHI inoculated with S. mutans standardized suspension. The number of S. mutans cells adhered to each pellet was evaluated by SEM observation and calculating colony forming unit.

Result: SiF+CPC solution showed equivalent acid resistance compared to SiF and AgF treatment. In contrast, the original acid resistance activity of SiF solution was diminished by the addition of other antibacterial agents (CHX, IPMP and EGCG). SiF+CPC was the most effective for the reduction of S. mutans adherence and inhibiting the formation of biofilm as the same level of that of AgF, in contrast, the addition of other antibacterial agents to SiF reduced the original antibacterial activity of SiF solution.

Conclusion: These findings suggest that the addition of CPC to SiF solution significantly reduced bacterial adherence and biofilm development without reduction of acid resisitance of SiF, indicating that it may be useful for the prevention of dental caries.