Color change
’ anterior teeth, incisors, tooth
Subjective and objective methods were used to evaluate tooth color. Only the evaluators were unaware of the groups to which the participants had been assigned. Two examiners were trained on shade determination of eight subjects’ anterior teeth in a pilot study. This calibration was performed using Vita shade guide units (A1-D4) and a digital spectrophotometer (Vita Easyshade, Germany) made in the middle third of the upper and lower anterior teeth (incisors and canines), three times. For this, a custom tray was made with an orifice, with a 3.0mm radius window, to standardize the location of the color measuring. The color measurements were performed on the lateral and central incisors and on the canines, in both arches, with 12 teeth being evaluated per patient. The subjective evaluation was initially performed, followed by the objective evaluation. For the subjective evaluation, scores from 1 (B1) to 16 (C4) were assigned.Both measurements were performed at baseline (T0), seven (T1), fourteen (T2), and twenty-one days (T3) of treatment and the mean color change between evaluated teeth (incisors and canines) was calculated. A measurement was performed fourteen days after the completion of the treatment (T4). The color of each tooth was measured using the CIEDE2000 parameters: variables such as L*, a*, b*, h*, and c* coordinates that address not only L* (brightness), a* ( red-green), and b* (yellow-blue) found in the previous formula, but also the saturation (c*), hue angle (h*), matrix rotation term (RT), compensation for neutral colors; lightness compensation (SL), chroma compensation (SC), and hue compensation (SH), allowing a better correlation between the observed colors and bringing this score closer to what can be seen by the human eye. The shade comparison at different periods (T0, T1, T2, T3, and T4) was based on the ΔE00, which was calculated by the following formula: