Randomization, allocation concealment, and implementation
Using a split-mouth design, in this study, a simple randomization was performed via the website www.sealedenvelope.com to determine the sequence of application of the respective experimental groups. According to this randomization process, each specified group was enclosed in an opaque, sequentially numbered envelope. Consequently, each envelope had instructions detailing the order in which the experimental groups should be applied to a hemiarch. Given the split-mouth design, the second experimental group was consistently assigned to the second hemiarch.Throughout the study, the initial randomized group started the process with the right upper hemiarch, while simultaneously the left upper hemiarch underwent bleaching together with the second group. The allocation sequence was disclosed immediately before the bleaching procedure in the first session and this same allocation sequence was followed in the subsequent sessions (implementation). This procedure was conducted by a researcher who was not directly involved in any of the experimental phases.