Clinical Evaluation of the Application Time of in-Office Bleaching Gel

Objectives: This study aimed to evaluate the bleaching efficacy and tooth sensitivity of an in-office bleaching gel applied just once for 15 min (1 x 15-min) or three times of 15 min (3 x 15-min) each. Methods: Thirty caries-free participants had their teeth bleached using 35% peroxide hydrogen gel (Whiteness HP/FGM). In one group (n=15), the patients received three 15-min applications while in the other group the patients received just one 45-min application. This protocol was repeated after 1 week. The color of the teeth was evaluated by two blinded calibrated evaluators at baseline and after each bleaching session using a value-oriented Vita shade guide. The patients recorded the tooth sensitivity on a 0-4 scale. The color changes at each week recall and the tooth sensitivity intensity were compared using Student's t-test (á=0.05). The percentage of patients with tooth sensitivity and its intensity were analyzed using the Fisher's exact test and the Student's t-test (á=0.05), respectively. Results: The use of one 45-min application decreased the bleaching efficacy (p<0.05). 80% and 100% of patients from the 3 x 15min and 1 x 45 min groups, respectively experienced tooth sensitivity (p=0.22). The intensity of sensitivity was statistically lower for the 3 x 15 min (p=0.04) group. Conclusions: The single 45-min application of a 35% peroxide hydrogen gel (Whiteness HP/FGM) negatively affects the bleaching efficacy and increase the intensity of tooth sensitivity.