Carbamide peroxide nanoparticles for dental whitening application: Characterization, stability and in vivo/in situ evaluation.

Carbamide peroxide is the popular home dental whitening agent. However, it has critical stability. Nanoparticles have been applied to develop products with advantages properties as better efficacy and stability increase. The aim of this study was the characterization of carbamide peroxide polymeric nanoparticles, their bleaching efficacy, effects on pulp damage and stability evaluation. Particle size demonstrated a spherical morphology and bimodal distribution (11 and 398 nm). Nanoparticles presented high entrapment efficiency (98.94%) and the zeta potential value was slightly positive (+10.26 mV). Regardless of the zeta potential, the steric effect may contribute to carbamide peroxide nanoparticle stabilization. The stability studies conducted at room temperature suggested that carbamide peroxide nanoparticles could maintain all the parameters evaluated (size, polydispersity index, zeta potential, entrapment efficiency, pH and content) for at least 90 days. Instability index was determined by dispersion analyzer (LUMiSizer ®), was 0.018, and the light transmission profile did not present sedimentation. Carbamide peroxide nanoparticles were able to prevent thermal degradation and photostability. Clinical efficacy of the whitening gels was obtained by color change in the spectrophotometer and the results showed that all the evaluated gels containing the nanoparticles (0, 1, 2 and 5% of real carbamide peroxide) were effective at bleaching after 2 h of home whitening treatment (during 30 days). After the treatment, the extracted teeth showed no in situ pulp damage by histological evaluation. The nanotechnology strategy of converting carbamide peroxide into polymeric nanoparticles revealed a new product with improved stability, a good approach for carbamide peroxide delivery.