Tabriz University of Medical Sciences Journal of Dental Research, Dental Clinics, Dental Prospects 2008-210X 19 4 2025 12 31 Effect of single and repeated potassium iodide applications versus glutathione on silver diamine fluoride-induced tooth discoloration in primary teeth: An in vitro comparative study 215 221 10.34172/joddd.025.43876 EN Maryam Hajiahmadi https://orcid.org/0000-0001-6840-5539 Samira SadighBatha https://orcid.org/0000-0002-6676-6952 Mohammad Javad Tarrahi https://orcid.org/0000-0001-7875-4572 Journal Article 10.34172/joddd.025.43876 2025 07 15 2025 10 16 Background. This study aimed to evaluate the effects of a single application of potassium iodide (KI), repeated daily applications of KI, and glutathione (GSH) on silver diamine fluoride (SDF)-induced tooth discoloration in primary canines. Methods. This in vitro study was performed on 36 extracted primary canines with dentinal caries, which were randomly assigned to four treatment groups: A (38% SDF alone), B (38% SDF+immediate single application of KI), C (38% SDF+repeated daily KI applications), and D (38% SDF+20% GSH). Color changes were measured at baseline and after 1, 14, and 30 days using a spectrophotometer and the CIEL*a*b* system. Statistical analysis included one-way ANOVA with post hoc Tukey tests for inter-group comparisons, and repeated-measures ANOVA with Bonferroni’s correction for intra-group comparisons. Results. Significant differences in tooth discoloration (ΔE) were observed between the study groups at all time intervals (P<0.001). Group A showed the highest discoloration, while group D exhibited the lowest. Among the KI-treated groups, group B showed progressive discoloration over time, while group C demonstrated minimal changes, with no statistically significant differences between time intervals (P=0.435). Although groups C and D both showed reduced discoloration compared to group B, the difference between them was not statistically significant on day 30 (P=0.073). Conclusion. Repeated daily applications of KI or GSH effectively reduced SDF-induced tooth discoloration in primary canines. GSH showed the most favorable esthetic outcomes, suggesting its potential as a promising adjunct to SDF.