Efectiveness of a Brief Protocol by a Low (6%) Concentration Gel Peroxide Hydrogen of Teeth Bleaching

This was a randomized, triple-blinded (patients, evaluator, and statistician), and split-mouth design (one hemiarcade was treated by 2 different protocol applications) following nonprobability sampling. The patients were invited to participate in the study through posters posted around the city or recruited from participants in other studies in the same department, who were contacted by email or phone.

A total of 155 patients were examined in a dental chair to check if they met the inclusion and exclusion criteria. The patients included in this study were over 18 years old and selected with the following inclusion criteria: anterior teeth without restorations, previous bleaching procedures, cervical lesions, or dental pain. Patients who were pregnant or lactating, had moderate or severe fluorosis, tetracycline stains, orthodontic treatment, periodontal disease, orofacial tumors, trauma, or tooth malformation, or were taking analgesic, anti-inflammatory, or antibiotic drugs were excluded.

Two trained operators (restorative dentistry professors) performed the bleaching treatments. A third participant that did not have contact with the patients was responsible for conducting the randomization. The allocation of the hemiarcade in the groups was performed by random drawing using Microsoft Excel 2010 (Microsoft, Redmond, Washington, USA) from coding assigned to each participant. There were two experimental groups: Group A acted as a control, and hydrogen peroxide whitening compound was applied at a concentration of 6% to the upper hemiarcade with a convetional protocol application of 3 times of 12 minutes. Group B was the experimental group, in which the other upper hemiarcade was treated with 6% and a reduce application protocol of 1 times of 36 minutes , the both hemiarcades were bleached with the same compound catalyzed by titanium oxide nanoparticles and activated by blue hybrid light and an infrared laser.

Sample size calculation The primary outcome of this study was the efficacy determined by color alteration (ΔE). Previous studies showed that the use of in-office bleaching agent containing hydrogen peroxide (HP35) with or without LED/Laser light leads to a ΔE value of 7.0-2.0 after two bleaching sessions. In order to have an 80% chance of detecting significance at the level of 5%, and considering an increase in the primary outcome measure from 7 in the control group to 5 in the experimental group, a minimum of 16 participants would be required in each group. Due to a higher dropout rate in the last two clinical studies of our research group, The investigators decided to add 80% more patients, which led to 30 patients in each group.

Bleaching protocol In each session, volunteers received prophylaxis with pumice powder and water. Then, gingival tissue was protected using a light-cured resin gum barrier applied according to the manufacturer's instructions (Lase Protect - DMC, São Carlos, SP, Brazil). The bleaching agent was prepared by mixing hydrogen peroxide and thickening compounds according to the manufacturer's instructions (with 3 peroxide drops for 1 drop of thickener). The resultant gel was distributed uniformly on the upper hemiarcade surfaces of the teeth. A total of 8 teeth between the first premolars were bleached for each patient. In each bleaching session, the bleaching gels were applied three times for 12 minutes each and the other hemiarcade only for a 36 minutes by session. In each application, the surface of the gel was light activated with continuous irradiance using LED/laser light with a total power of 1800 mW (Whitening Lase Plus - DMC Equipamentos, São Carlos, SP, Brazil). Three bleaching sessions were completed for the patients, and the interval between sessions was 2 days.