Use of silver nanoparticles with sodium fluoride on caries prevention

Abstract

Silver nanoparticles have been added into dental materials because of their antimicrobial properties. This thesis starts with a literature review to provide an overview of the antibacterial mechanism of silver nanoparticles and their application in dentistry. Silver nanoparticles have ability to penetrate bacterial cell walls, change the structure of cell membranes and even result in cell death. Silver ions released from silver nanoparticles increase permeability of cell membranes, produce reactive oxygen species, and interrupt replication of deoxyribonucleic acid. Dental materials containing silver nanoparticles have been developed for prosthetic, restorative, endodontic, orthodontic, periodontal and implant treatment. A systematic review was performed to study the use of silver nanomaterials for caries prevention. The review catergorised the silver nanomaterials as silver nanoparticles, resin with silver nanoparticles, glass ionomer with silver nanoparticles, and nano silver fluoride. The review concluded that silver nanomaterials inhibit the growth of cariogenic bacteria and the adhesion of biofilm. Moreover, they inhibit collagenase activity and preserve the collagen matrix. Silver nanomaterials also hinder the demineralisation of enamel and dentine, in addition to preventing caries progression. However, some researchers have concern about synthesis-dependent cytotoxicity of silver nanomaterials. Thus, the biocompatibility of silver nanomaterials is very important. This thesis has four laboratory studies. The first study is to develop biocompatible silver nanoparticles with antibacterial effect using a reducing agent and a capping agent. The silver nanoparticles developed have lower cytotoxicity on human gingival fibroblasts and stem cells than silver nitrate, which is a commonly used antimicrobial agent in medical care. This biocompatible silver nanoparticles inhibit growth and adhesion of Streptococcus mutans. They also impede lactic acid and polysaccharide production of the Streptococcus mutans biofilm. The second study is to investigate the remineralising and staining effects of the developed silver nanoparticles with sodium fluoride on artificial dentine caries using a microbial model. The silver nanoparticles and sodium fluoride were separately applied on dentine caries. The results showed that silver nanoparticles with sodium fluoride reduced mineral loss of dentine and prevented collagen degradation without staining. The third study is to synthesize the stable and biocompatible fluoridated silver nanoparticles. The fluoridated silver nanoparticles developed is stable over 18 months with a low cytotoxicity to human gingival fibroblasts. It inhibits growth of Streptococcus mutans and may be used as an antibacterial agent for caries control. The fourth study is to investigate the remineralising and staining effects of the synthesized fluoridated silver nanoparticles on artificial dentine caries. The results showed that the synthesized fluoridated silver nanoparticles had similar effect with silver diamine fluoride on remineralising dentine caries and preventing degradation of collagen. Furthermore, fluoridated silver nanoparticles do not cause significant tooth staining. It can be a potential agent for caries management. Because the use of fluoridated silver nanoparticles is simple, low cost, non-invasive and it does not stain teeth, it could be well accepted by both patients and clinicians. This fluoridated silver nanoparticles thus offers tremendous benefits for dentistry.