Efeito do método de aplicação em géis clareadores de alta concentração em dois frascos: penetração de peróxido de hidrogênio, quantidade de gel utilizada e eficácia do clareamento

Abstract

Objective: Evaluate the penetration of hydrogen peroxide (HP) into the pulp chamber, amount of gel expended and bleaching efficacy during in-office bleaching using brush vs. conventional spatula with different two-bottle in-office bleaching gels. Materials and Methods: One hundred and ten extracted human premolars were randomly distributed into eleven groups (n = 10) according to the application method: 1) Method of aplication: Brush or conventional spatula; and 2) in-office bleaching gels: DSP White Clinic 35% H2O2 (WC); Pola Office 35% (PO); Potenza Bianco PRO 35% (PB); Whiteness HP 35% (WH) or Whiteness HP Maxx 35% (WM). A group not exposed to bleaching agents was the negative control. The concentration (μg mL-1) of HP into the pulp chamber was measured using UV-Vis spectrophotometry. The bleaching gel expended was evaluated with a precision analytical digital balance. The bleaching efficacy (ΔEab, ΔE00, and ΔWID) was assessed with a digital spectrophotometer. The initial HP concentration (%) and pH were measured, respectively via titration and digital pH meter. Two-way ANOVA, Tukey's, and Dunnett' test were used to analyze pH, HP penetration and concentration, amount of gel expended and bleaching efficacy. Results: The hydrogen peroxide concentration in the bleaching gels remained stable before and after application (p > 0.05). Initial values ranged from 30.5 ± 0.2% to 34.5 ± 0.5%, and after 15 minutes they remained between 30.5 ± 0.9% and 34.3 ± 0.4%, with no significant differences between time points, even for agents containing concentrations lower than those recommended by the manufacturer. The pH of the agents was acidic (2,60 ± 0,012 e 6,62 ± 0,035) and unstable (2,63 ± 0,015 e 5,27 ± 0,021) during application (p < 0.05), except for PO, which remained highly acidic throughout the application period (p > 0.05), resulting in greater penetration into the pulp, regardless of the application method (p < 0.05). The other agents showed similar penetration, regardless of the method used (p > 0.05). Brush application resulted in significantly lower gel consumption across all bleaching gels (p < 0.05). All bleaching gels demonstrated similar bleaching efficacy regardless of the application method (p > 0.05). Conclusion: No significant differences were found in HP penetration into the pulp chamber between brush and spatula. However, brush application significantly reduced bleaching gel consumption without compromising bleaching efficacy. Clinical relevance: The use of brush application in two-bottle bleaching gels reduces material waste while maintaining bleaching effectiveness, thus offering a more profitable clinical protocol for professionals.