Effect of an experimental desensitizer with a hydroxyapatite-capsaicin composite applied before in-office dental bleaching on hydrogen peroxide diffusion, color and surface changes.

Objective: To evaluate a prior application of an experimental desensitizer containing a hydroxyapatite-capsaicin composite (HAp-CAP) in different concentrations on hydrogen peroxide (HP) diffusion into the pulp chamber, bleaching efficacy (BE) and on physical and chemical alterations of the enamel surface after in-office bleaching.

Materials and methods: Forty sound premolars were randomized in five groups according to each experimental condition (n = 8): no bleaching (negative control), only bleaching (positive control), 0.1%, 1% and 5% of HAp-CAP. Four groups were submitted to in-office bleaching (HP 35%) post-desensitizer application. The HP concentration (µg/mL) on the pulp chamber was measured by UV-Vis spectrophotometer. The BE was measured by digital spectrophotometer (ΔE_ab, ΔE₀₀ and ΔWI_D) before and after 7 days bleaching. Enamel tooth fragments obtained from twenty molars were submitted to the same experimental conditions and analyzed using FE-SEM and EDS, Vickers microhardness (VHN), Raman spectroscopy, and nanoroughness (Ra) by AFM to evaluate morphologic and chemical changes on enamel surface. All data were submitted to statistical analysis (α = 0.05).

Results: The groups treated with HAp-CAP exhibited a lower concentration of HP in the pulp chamber compared to only bleaching group (p < 0.05). There were no significant differences observed in BE between HAp-CAP groups and only bleaching group (p > 0.05). Only HAp-CAP 5% showed no significant differences in VHN values when compared to no bleaching group (p > 0.05). There were no significant differences among any group in Ra values (p > 0.05). The groups submitted to HAp-CAP showed a higher mineral concentration when compared to only bleaching group (p < 0.05).

Conclusion: Desensitizers containing HAp-CAP up to 5% effectively reduce HP diffusion into the pulp chamber after in-office bleaching, without interfering to BE and Ra, as well as prevent enamel demineralization.

Clinical relevance: The use of desensitizers containing HAp-CAP during in-office bleaching treatments offers a promising approach to reduce the risk of pulp irritation caused by hydrogen peroxide diffusion, without compromising the bleaching effectiveness or causing surface roughness.