Characterization and effects on enamel of low-concentration bleaching gels containing hyaluronic acid, NF_TiO nanoparticles and irradiated with violet LED light.

OBJECTIVE

To characterize and evaluate experimental in-office bleaching gels containing hyaluronic acid (HA) or carbomer 940 (CAR), enriched with NF_TiO₂ nanoparticles and irradiated with a violet LED, assessing their effects on the physicochemical properties of enamel.

MATERIALS AND METHODS

Bovine enamel-dentin discs were treated according to the parameters: thickener (HA or CAR), HP concentration (1.5% or 6%), and irradiation (with or without LED), resulting in 9 experimental groups (n = 10/group). An additional control group (35%HP-commercial) was adopted, and three sessions were conducted (30 min each, with a 7-day interval). Gels were evaluated for pH, particle size, polydispersity index, zeta potential and rheological behavior. Samples were assessed for color change (ΔE), whiteness index (ΔWI), Ca/P ratio (EDS), surface microhardness (KHN), roughness (ΔRa), and surface morphology (SEM). Data were analyzed using ANOVA three-way and Tukey/Bonferroni (α = 5%).

RESULTS

pH remained stable above 6.0. Hyaluronic-based gels exhibited higher particle size and polydispersity, but lower zeta potential and less viscous rheological behavior compared to the carbomer-based ones (p < 0.05). LED light significantly increased ΔE and ΔWI for all gels, with HA-1.5%HP and HA-6%HP + LED achieving comparable ΔWI to 35%HP-commercial (p > 0.05). Hyaluronic-based gels groups irradiated with LED increased Knoop microhardness (p < 0.05). No significant changes were found in ΔRa, Ca/P ratio, or enamel morphology (p > 0.05).

CONCLUSION

Experimental hyaluronic or carbomer bleaching gels incorporated with NF_TiO nanoparticles and irradiated with violet LED showed minimal variations in physicochemical properties, effective bleaching even at low HP concentrations, and no enamel damage.

CLINICAL RELEVANCE

Innovative bleaching gel formulations incorporating hyaluronic acid, NF_TiO₂ nanoparticles, and violet LED light irradiation exhibit high efficacy even at low hydrogen peroxide concentrations, thereby minimizing enamel damage and potentially mitigating post-operative sensitivity.