Effects of experimental bleaching gels containing co-doped titanium dioxide and niobium pentoxide combined with...

The objective of the study is to evaluate the bleaching potential of 6% hydrogen peroxide (6% HP) gels containing NF_TiO₂ or Nb₂O₅ irradiated with a violet LED light and the effects on enamel mineral content and surface morphology.

Particles were synthesized, and experimental gels were chemically analyzed by preliminary and accelerated stability tests, pH, and HP decomposition rate. Bovine enamel blocks were treated with 6% HP gels containing (n = 10): 5% NF_TiO₂, 5% Nb₂O₅, 2.5% NF_TiO₂ + 2.5% Nb₂O₅ or without particles (6% HP), irradiated or not with LED, and the control was treated with 35% HP. Color (∆E₀₀) and whitening index (∆WID) variations, surface microhardness (SH), average roughness (∆Ra), Ca-P concentration (EDS), and enamel morphology (SEM) were assessed. Bleaching was performed in 3 sessions of 30 min and 7-day intervals. Data were submitted to two- (pH, decomposition rate, ∆E₀₀, and ∆WID) or three-way ANOVA and Bonferroni (SH), Kruskal-Wallis (∆Ra), and Dunnet tests (α = 0.05).

No changes in the gel's color, odor, or translucency were observed. The pH (6 to 6.5) remained stable over time, and light irradiation boosted the HP decomposition rate. NF_TiO₂ and Nb₂O₅-containing gels displayed higher ∆E₀₀ and ΔWID when light-irradiated (p < 0.05). Nb₂O₅ and Nb₂O₅ + NF_TiO₂ decreased enamel SH (p < 0.05), but no SH changes were found among groups (p > 0.05). No differences among groups were noted in ∆Ra, Ca-P content, and enamel morphology after treatments (p > 0.05).

Experimental light-irradiated 6% HP gels containing NF_TiO₂ or Nb₂O₅ were chemically stable and exhibited bleaching potential comparable with 35% HP.

Low-concentrated HP gels containing NF_TiO₂ or Nb₂O₅ and light-irradiated stand as a possible alternative to in-office bleaching.