AbstractAimTo evaluate the effectiveness of ultrasonic activation of bleaching agents during ex vivo internal bleaching.MethodologyFifty canine human teeth were artificially stained, root filled and divided into five groups (n = 10) that received SP – sodium perborate plus deionized water (control group), CP – 37% carbamide peroxide gel, CPUS – 37% carbamide peroxide gel plus ultrasonic application, HP – 35% hydrogen peroxide gel or HPUS – 35% hydrogen peroxide gel plus ultrasonic application. In groups CP and HP, the bleaching agent was left inside the pulp chamber for three applications of 10 min. In groups CPUS and HPUS, the same process was performed, but ultrasonic vibration was applied to the bleaching agent by an alloy tip for 30 s, with 30 s intervals. Two sessions were performed. The colour was measured initially and after each session by an intraoral dental spectrophotometer. The variation (Δ) of the colour parameters based on the CIELab system L*, a* and b*, and the colour alteration ΔE* were calculated after first and second section. Data were analysed by one‐way anova and Tukey's test.ResultsThere was no significant difference amongst groups for ΔL*, Δa* and ΔE*, but there was a significant difference for Δb* in the first and second sessions (P = 0.0006 and 0.0016, respectively). After the first session, Δb* was significantly greater for groups HP and HPUS, without a significant difference between them. For the second session, group HPUS had the greatest Δb* values, but they were similar to groups HP and SP; group CP had the lowest values, which were similar to groups CPUS and SP.ConclusionUltrasonic activation of bleaching agents during ex vivo internal bleaching was no more effective than conventional internal bleaching procedures, without activation.