Abstract
This study aimed to evaluate the color change of teeth bleached with light activation using two different objective color measurement approaches after two years of clinical follow-up. A cross-sectional retrospective clinical study according to STROBE was followed including 30 participants. The 25% hydrogen peroxide gel (Philips Zoom) was applied with a supplementary LED light for 15 min in four cycles. Tooth color was assessed based on CIEL*a*b* values using a spectrophotometer (Spectroshade) at different time points (baseline, post bleaching, 1 week, 1 year, and 2 years). Standardized digital photographs were taken at each time point. The L*, a*, and b* values were measured from the digital photographs using Adobe Photoshop software. The color difference (ΔE) was separately calculated using the L*, a*, and b* values obtained with spectrophotometric and photographic analyses at each evaluation time. Data were analyzed with non-parametric tests (p < 0.05). A color regression was detected by both measurement approaches after 1 and 2 years (p < 0.05). Greater ΔE values were acquired with the spectrophotometer compared to the digital photographic analysis (p < 0.05). Although a greater color change was observed with the spectrophotometer, both approaches were able to detect the color rebound using the 25% hydrogen peroxide light-activated in-office system. Digital photographic analysis might therefore be used to assess color change after bleaching.