Enamel cracks and dental bleaching: does a gingival barrier reduce hydrogen peroxide penetration?

To evaluate hydrogen peroxide (HP) penetration into teeth with enamel cracks and to assess the effectiveness of a gingival barrier as a protective strategy. Additionally, the study examined whether the use of a gingival barrier affects bleaching efficacy.

Thirty human premolars (n = 10 per group) were allocated into three experimental groups: intact teeth, teeth with enamel cracks, and teeth with enamel cracks protected with a gingival barrier. Cracks were detected using transillumination and measured using ImageJ software. In the third group, the gingival barrier was applied directly over the cracks, and the buccal surface of all specimens was also isolated with a gingival barrier (6 mm radius) and light-cured for 30 s. Bleaching was performed with 35 % hydrogen peroxide in two 30-minute sessions, with a seven-day interval apart. HP penetration into the pulp chamber was quantified using UV-Vis spectrophotometry. Bleaching efficacy was assessed by digital spectrophotometry (ΔE₀₀ and ΔWI_D). Data were analyzed using one-way and two-way ANOVA (α = 0.05).

Teeth exhibited vertical cracks averaging 4.2 ± 1.3 mm in length. Cracked teeth demonstrated 35 % higher HP penetration compared to intact teeth (p < 0.05). Covering the cracks with a gingival barrier did not reduce HP penetration (p = 0.22). No significant differences were found in bleaching efficacy among the groups (p > 0.05).

Enamel cracks significantly increased HP penetration. The gingival barrier did not reduce diffusion but did not compromise bleaching efficacy.

Teeth presenting enamel cracks showed significantly increased hydrogen peroxide penetration. Alternative protective strategies should be explored, as gingival barriers alone appear insufficient to effectively seal enamel cracks.