The aim of this study was to evaluate color longevity after a year of in-office bleaching with gel (6% hydrogen peroxide HP, LED blue/laser infrared activation system) compared to a 35% control concentration in a split-mouth study model. Thirty-one patients were initially treated. The bleaching procedure with 6% or 35% gel HP was performed randomly in the upper half arcade of each patient. The color was measured at baseline and at 1 week, 1 month, and 1 year using the spectrophotometer Vita Easyshade, Vita Bleached, and Vita classical Shade guide organized by value. During the 1-year recall, the color was assessed before and after dental prophylaxis. Only 27 patients were assessed in the 1-year recall. There was a significant difference in the ΔE between the two groups at all times assessed (P < .011). The ΔL, Δa, and Δb showed significant difference between both groups at all assessed times (P < .038). There was no significant difference between the ΔSGU at all times (P > .05) except for the Vita bleachedguide postprophylaxis comparison (P < .05). The two compounds remained effective at 1year. When objectively evaluated, color difference between groups was found, not seen when subjectively determined. A low concentration hydrogen peroxide bleaching agent can reach good clinical results at 1year of follow-up.