Enamel Remineralization by Calcium-Sodium-Phosphosilicate (NovaMin®) Toothpaste Following Tooth Bleaching

Objectives: The study has been carried out to determine the effects of bleaching on enamel structure and the remineralization potential of commercial bioactive glass NovaMin® in two different toothpastes. Aspects considered were: extent and nature of enamel alterations after application of bleaching agents; extent of remineralization after application of two commercial toothpastes containing bioactive glass; whether or not there are differences between toothpastes in terms of their effectiveness in promoting remineralization. Methods: Fifteen human teeth were extracted; roots were cut off at the cemento-enamel junction, remnants of pulp discarded, coronal segments ultra-sonicated and polished. The teeth were divided in 3 groups [all groups were treated with Mirawhite®Pro bleaching agent (8 minutes, 7 sessions)]: group 1. control; group 2. treated with Nanosensitive® hca (5 minutes); group 3. treated with Mirawhite® tc (5 minutes). The teeth were cut by half longitudinaly: first half- gold-sputtered and analyzed under SEM; the other half- cast in resin, carbon coated, analyzed under SEM, scans of the enamel surface and linescans along the line that goes through the enamel into the resin were collected. Finally, quantitative EDX point analysis was performed on the enamel surface to determine elemental levels (%) of Sr, Na, Mg, Al, Si, P, Ca (ANOVA, Tukey's, p<0.05). Results: Application of a bleaching agent in the previously described manner causes distinct morphological changes to enamel surface (from mild to severe). Subsequent treatment with either of toothpastes containing NovaMin® resulted in formation of protective layer on the enamel surface, consisting of bioactive glass deposits, with only slight differences between the two brands. Application of these dentifrices caused increases in Ca and P content of enamel surface, returning it to that of undamaged enamel. Conclusion: Remineralizing toothpastes should be used after bleaching, in order to repair any damage to the mineral tissue caused by these procedures.