Evaluation of bleaching agent effects on color and microhardness change of silver diamine fluoride-treated demineralized primary tooth enamel: An in vitro study

BACKGROUND: The present study aimed to assess the impact of application of fluoridated- 10% carbamide peroxide (CP) with or without potassium iodide (KI) on silver diamine fluoride (SDF)-treated enamel surface in the primary teeth. METHODS: After stained-remineralized caries lesions (s-RCLs) creation, 96 teeth were randomly allocated to four experimental groups: Group 1:SDF-treated enamel followed by 8-h/day application of 10% CP for 2 weeks; Group 2: SDF-treated enamel followed by 15-min/day application of 10% CP for 3 weeks; Group 3: SDF + KI-treated enamel followed by 8-h/day application of 10% CP for 2 weeks; and Group 4: SDF + KI-treated enamel followed by 15-min/day application of 10% CP for 3 weeks. Enamel microhardness (EMH) test (n = 12) and spectrophotometric color assessment (n = 12) was performed at four stages: baseline (intact enamel), demineralized enamel, aged remineralized-stained enamel, and after final intervention. Sixteen samples were used for SEM evaluation. Data were analyzed with the paired t-test, one-way ANOVA, and Tukey’s post-hoc test (p < 0.05). RESULTS: EMH values in all groups showed significant decrease after demineralization (all, p < 0.00001). All samples showed complete recovery of EMH values (%REMH) after SDF application compared to demineralization (%REMH(SDF)) (p = 0.971). Bleaching caused a slight decrease in %REMH for all groups. However, the differences were not statistically significant (p = 0.979). SEM findings revealed no changes in enamel porosity after bleaching. Bleaching application ameliorated the discoloration in all groups (all, p < 0.00001). All samples in Groups 2 and 4 had significantly lighter color after 21 days as compared to 14-day exposure to the bleaching material (both, p < 0.00001). CONCLUSIONS: SDF application on demineralized primary tooth enamel completely recovered enamel microhardness. 10% carbamide peroxide effectively bleached SDF stain without causing significant decrease in EMH values. Color improvement was more evident with the use of KI immediately after SDF application. Both 15-min and 8-h application of fluoridated CP resulted in statistically similar color enhancement in primary teeth. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12903-022-02371-3.