Effect of silver and fluoride ions on enamel demineralization

Objective: To compare the effect of silver and fluoride ions on enamel demineralization. Materials and methods: Sound permanent premolars were collected, and the coronal parts were prepared into tooth blocks with intact occlusal fissures. Acid-resistant nail varnish was painted onto each tooth block to cover its surfaces, leaving small unpainted window areas in the occlusal surface (OW) and the flat mesial surface (FW). The tooth blocks were then randomly allocated into one of four groups and immersed in different solutions, Gp1 - 2.36mol/L silver fluoride, Gp2 - 2.36mol/L potassium fluoride, Gp3 - 2.36mol/L silver nitrate, and Gp4 – de-ionized water, for 5 minutes and then followed by 7-day immersion in a buffered demineralization solution at a pH of 4.4. Micro-CT scans were carried out for the tooth blocks. Average lesion depth was calculated and compared between groups. Results: Numbers of tooth blocks in Gp1 to Gp4 were 4, 5, 4, and 4, respectively. No demineralization lesion could be observed in the micro-CT images of tooth blocks in Gp1 and Gp2 for either OW or FW. Demineralized enamel lesions were observed in the images of tooth blocks in Gp3 and Gp4 for both OW and FW. Lesion in OW was similar to that in FW in each tooth block. Mean lesion depths in FW in Gp3 and Gp4 were 172.6±33.0 um and 193.4±51.2 um, respectively (p>0.05). Conclusions: Topical application of a 2.36M fluoride solution can inhibit demineralization of enamel while topical application of silver ions has little effect.