Is at-home bleaching more effective on the upper arch than the lower arch? A prospective cohort study.

OBJECTIVE: Teeth bleaching is one of the most popular aesthetic dental treatments, uses to address both extrinsic and intrinsic tooth discoloration. However, variations in bleaching efficacy between the upper and lower dental arches are commonly observed. Sublingual salivary glands may play a role in these differences by increasing saliva contamination of bleaching trays, which accelerates the degradation of bleaching gel and may reduce its effectiveness in the lower arch. This study aims is to evaluate and compare the effectiveness of bleaching treatments in the upper and lowe arches. METHODS: This study employed a prospective observational cohort design with a split-mouth approach. Thirty-two participants completed a three-week bleaching regimen using 16 % carbamide peroxide. Color changes were assessed using the CIELAB, CIEDE2000, and Whiteness Index for Dentistry (WID) formulas, with spectrophotometric measurements taken at baseline and weekly intervals. RESULTS: No statistically significant differences (p > 0.5) in bleaching efficacy for incisors between the two arches. However, upper canines demonstrated significantly greater bleaching effectiveness than lower canines by the second and third weeks (p < 0.05), as indicated by the CIELAB and CIEDE2000 formulas. No significant differences (p > 0.05) were observed using the WID formula. CONCLUSION: While the lower canines exhibited slightly reduced bleaching effectiveness, these differences were not clinically noticeable, affirming the overall efficacy of the treatment for both arches. CLINICAL SIGNIFICANCE: At-home bleaching treatment demonstrates equivalent effectiveness in both dental arches. While the lower canines may achieve a slightly reduced degree of bleaching, these differences are not clinically noticeable. Consequently, extending the duration of the bleaching treatment for the lower arch is unnecessary.