Influence of Different Protocols on In-Office Bleaching: Whiteness Difference and Hydrogen Peroxide Penetration

To evaluate whiteness difference (WI_D) and hydrogen peroxide (HP) penetration into the pulp chamber in extracted teeth subjected to various in-office application protocols.

A total of 154 human premolars were randomly assigned to 11 groups (n = 14). The groups were divided into: Pola Office+ and Pola Rapid (SDI), and the following protocols: three applications of 8 min (3 × 8), two applications of 8 min (2 × 8), one application of 8 min (1 × 8), one application of 16 min (1 × 16), and one application of 24 min (1 × 24). These protocols were selected based on manufacturer recommendations and the aim of exploring simplified and alternative approaches applicable to clinical practice. One group served as a negative control. WI_D was assessed using a digital spectrophotometer before and after two sessions. HP concentration in the pulp chamber was measured using UV-Vis spectrophotometry. ANOVA two-way and Tukey's and Dunnett's tests were used for data analysis.

Significant WI_D were observed after two sessions, with greater changes in the 2 × 8, 3 × 8, and 1 × 24 protocols (p < 0.001). Lower levels of peroxide penetration were found with shorter application, such as the 1 × 8 protocol, while higher levels were detected in the 3 × 8 protocol (p < 0.0001).

Among the evaluated protocols, the 2 × 8-min and 1 × 24-min applications provided the best balance between achieving significant whitening and minimizing hydrogen peroxide penetration into the pulp chamber, making them effective and safer alternatives for in-office bleaching.

Shorter application times (2 × 8 min) or a single prolonged application (1 × 24 min) provide effective alternatives for achieving excellent whitening index results. These protocols reduce hydrogen peroxide penetration into the pulp chamber while also shortening the overall procedure time, enhancing both safety and efficiency.