RESUMO
OBJECTIVES: In-office bleaching is usually performed in 2-3 sessions with one-week interval. The impact of shorter interval times on tooth sensitivity has not been evaluated. This study aimed to compare the absolute risk of tooth sensitivity (TS) and colour change after in-office bleaching with a two- and seven-day intervals between sessions. METHODS: We selected for this randomized, single-blind study, 40 patients with colour C2 or darker. We performed two bleaching sessions with a 35% hydrogen peroxide gel with either a 1-week or 2-day interval. We recorded the TS up to 48 h with a VAS scale and the colour at baseline and 30 days after bleaching with a value-oriented shade guide and a spectrophotometer. The risk and intensity of TS were compared with the Fisher's exact test and two-way repeated measures ANOVA. Colour change (ΔSGU and ΔE) were evaluated by Student's t-test (alpha=5%). RESULTS: Approximately 60% of the participants reported TS (65% and 55% for the 7 and 2-day groups). A significant whitening of approximately 6 shade guide units was detected for both groups. No difference was detected between groups. CONCLUSIONS: The reduction of the interval between bleaching sessions from seven to two days reduced the treatment time without increasing the bleaching-induced TS (clinicaltrials.gov identifier: NCT1959789). CLINICAL SIGNIFICANCE: In-office bleaching with a 2-day interval did not increase the risk and intensity of bleaching-induced tooth sensitivity.