Effects of Ion-Releasing Tooth-Coating Material on Demineralization of Bovine Tooth Enamel

We compared the effect of a novel ion-releasing tooth-coating material that contained S-PRG (surface-reaction type prereacted glass-ionomer) filler to that of non-S-PRG filler and nail varnish on the demineralization of bovine enamel subsurface lesions. The demineralization process of bovine enamel was examined using quantitative light-induced fluorescence (QLF) and electron probe microanalyzer (EPMA) measurement. Ion concentrations in demineralizing solution were measured using inductively coupled plasma atomic (ICP) emission spectrometry and an ion electrode. The nail varnish group and the non-S-PRG filler group showed linear demineralization. Although the nail varnish group and the non-S-PRG filler group showed linear demineralization, the S-PRG filler group did not. Further, plane-scanning by EPMA analysis in the S-PRG filler group showed no changes in Ca ion distribution, and F ions showed peak levels on the surface of enamel specimens. Most ions in the demineralizing solution were present at higher concentrations in the S-PRG filler group than in the other two groups. In conclusion, only the S-PRG filler-containing tooth-coating material released ions and inhibited demineralization around the coating. 1. Introduction In recent years, oral health in developed countries has improved, with the majority of people keeping more sound teeth for longer duration [1–7]. In particular, considerable interest has been directed at detecting caries at early stages, with the development of the International Caries Detection and Assessment System (ICDAS) [8, 9] and quantitative light-induced fluorescence (QLF) method [10, 11]. In current daily dental practice and oral health care programs, the inhibition of initial tooth enamel demineralization and the promotion of remineralization are the most important targets [12–14]. Surface-reaction type prereacted glass-ionomer (S-PRG) filler [15, 16] has been reported to have biological efficacy in reducing dental plaque formation [17, 18], inhibition of dentin demineralization [19], fluoride release and recharge potential [20], and prevention of demineralization in surrounding orthodontic brackets [21]. These efficacies might be due to the ability of S-PRG filler to release various ion species (fluoride, strontium, aluminum, sodium, etc.) as well as its capacity as an acid buffer [22]. S-PRG filler can therefore be found in various dental products, such as composite resin, root canal sealer, orthodontic resin bonding systems, and denture base resin [19, 23–28]. We developed a novel ion-releasing tooth-coating material