title: Inhibitory Effects of Zinc Ions on Enamel Demineralisation Kinetics in vitro.
abstract: Metal ions including zinc have the ability to influence enamel demineralisation. However, there is a paucity of data regarding reductions in demineralisation effected by zinc ions (Zn2+) in the literature. Therefore the aim was to measure the effects of zinc ion concentration ([Zn2+]) on the real-time in vitro demineralisation of enamel, during exposure to caries-simulating conditions, using scanning microradiography (SMR). Human enamel blocks were fixed in SMR environmental cells, through which acidic solutions (0.1 M acetic acid, pH 4.0) were circulated for periods of 50 h. SMR was used to quantitatively measure continuous mineral mass loss. Subsequently, the effects of sequentially increasing [Zn2+] (0.1-3,565 ppm) in the acidic solutions were measured on the rate of enamel demineralisation. This study demonstrated that Zn2+ even at low concentrations significantly reduces enamel demineralisation. There was a log-linear relationship between the mean percentage reduction in demineralisation and increasing [Zn2+] up to 3,565 ppm, i.e. the change in the overall percentage reduction in demineralisation was greater at lower concentrations than at higher concentrations, with 60% reduction at 36 ppm increasing to 90% at 3,565 ppm. In conclusion, SMR demonstrated the ability of Zn2+ to reduce the rate of enamel demineralisation under real-time in vitro acid conditions simulating dental caries. The results suggest that Zn2+ in the oral fluids could protect against enamel demineralisation during an acidic challenge. The log-linear relationship between [Zn2+] and demineralisation suggests that the reduction in enamel dissolution is limited by the saturation of surface sites on the enamel surface.
authors.affiliation: Dental Physical Sciences Unit, Centre for Oral Growth and Development, Barts and the London School of Medicine and Dentistry, Queen Mary University, London, UK.
authors.forename: Nasrine R
authors.initials: NR
authors.lastname: Mohammed
authors.forename: Richard J M
authors.initials: RJ
authors.lastname: Lynch
authors.forename: Paul
authors.initials: P
authors.lastname: Anderson
mesh_terms: D003731:Dental Caries; D003743:Dental Enamel; D006801:Humans; D007700:Kinetics; D017001:Tooth Demineralization; D015032:Zinc
chemical_list: D015032:Zinc