Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 20 0 2023 07 26 1 8 Narges Panahandeh Dental Research Center, Research Institute for Dental Sciences, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran Shervin Mohammadkhani Private Practice, Tehran, Iran Shervin Sedighi Private Practice, Tehran, Iran Sogol Nejadkarimi Department of Operative Dentistry, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran Amir Ghasemi Dental Research Center, Research Institute for Dental Sciences, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran 2021 06 30 2022 06 08 Objectives: This study aimed to investigate the impact of three different bleaching protocols on tooth discoloration caused by tea. Materials and Methods: Forty extracted sound premolars were cleaned, disinfected, and their initial color parameters were measured (T1). The teeth were then immersed in boiled tea solution for 24 hours, and their color was measured again (T2). The samples were divided into four groups of 10 teeth each. Group A was treated with an in-office bleaching gel followed by 30 seconds of light curing. Groups B, C, and D were respectively treated with 0.24M oxalic acid followed by bleaching gel, 5.25% sodium hypochlorite followed by bleaching gel, and a combination of 0.24M oxalic acid, 5.25% sodium hypochlorite, and bleaching gel. The color was measured once more after the interventions (T3). Data were analyzed using two-way repeated measures ANOVA, paired sample t-test, and Tukey's test. Results: The mean color change (∆E2) between T2 and T3 was significantly higher in group D compared to group A (P<0.05). However, there was no significant difference in color change between groups A, B, and C. Additionally, there was no significant difference in color change between groups B, C, and D. The groups also showed significant differences in ∆L (P=0.007), with the only significant difference found between groups B and C (P=0.001). Conclusion: The combined use of sodium hypochlorite and oxalic acid followed by in-office bleaching gel is more effective than bleaching alone in correcting tooth discoloration caused by tea. This protocol can further reduce yellow coloration. https://fid.tums.ac.ir/index.php/fid/article/view/4119