Tooth Color Change Following Bleaching with a Desensitizing Double-Layer Technique

This in vitro study evaluated the effect of incorporating a desensitizing layer between the tooth surface and bleaching gel on tooth color change and treatment time during in-office bleaching procedures. The novelty of this study lies in assessing whether a double-layer technique, previously proposed to modify the diffusion behavior of potassium nitrate and hydrogen peroxide, can maintain whitening efficacy while reducing overall application time. Sixty caries-free third molars were randomly assigned to three groups (n = 20). The CTRL group received 25% hydrogen peroxide (HP) for 30 and 45 min; the DL group received a double-layer application consisting of 5% potassium nitrate followed by 25% HP for the same time intervals; and the MIXED group received 3% potassium nitrate incorporated into 40% HP. Tooth color was measured with a digital spectrophotometer at the baseline and after each treatment interval. Repeated measures ANOVA and pairwise t-tests were used to evaluate differences among groups and treatment times. No significant differences in color change were found among the groups at either evaluation time. The ΔE values obtained with the double-layer technique at 30 min were not significantly different from those observed in the CTRL and MIXED groups at 45 min (p = 0.75 and p = 0.33, respectively). Within the limitations of this in vitro study, no significant differences in tooth color were detected between the double-layer technique and conventional bleaching approaches, though sufficient whitening outcomes were achieved in a shorter treatment time. These findings suggest that this technique may represent a clinically relevant strategy to improve the efficiency of in-office bleaching protocols without compromising whitening efficacy.