RESUMEN
This study evaluated the effects of acid etching of the enamel and the combination of different light sources (halogen light, light-emitting diodes [LEDs], and LED/Laser) and the bleaching product on color change, penetration of hydrogen peroxide (H2O2), and cytotoxicity over time. The color change (ΔE) and the amount of H2O2 that permeated the tooth tissue were analyzed using a spectrophotometer. Cell metabolism and morphology were evaluated using the methylthiazol tetrazolium assay and scanning electron microscopy, respectively. The ΔE values and H2O2 permeation were not significantly different under any of the experimental conditions. Tooth whitening significantly reduced cell metabolism, regardless of whether a light source was used. Preconditioning the enamel did not influence the cellular metabolism in any group. In conclusion, combining the bleaching product with different light sources and/or preconditioning the enamel resulted in few significant changes in color, transenamel and transdentinal penetration of H2O2, or cytotoxicity and cell morphology.
Asunto(s)
Blanqueadores Dentales , Blanqueamiento de Dientes , Color , Esmalte Dental , Peróxido de HidrógenoRESUMEN
AIM: To evaluate the transenamel and transdentinal cytotoxicity of bleaching gels based on carbamide peroxide (CP) on odontoblast-like cells after different contact times of the products with enamel. METHODOLOGY: Enamel/dentine discs were obtained from bovine incisors and placed in artificial pulp chambers. Bleaching gels containing 10% or 16% CP were applied for 8 h day(-1) on the enamel side of the discs during periods of 1, 7 or 14 days. Deionized water and artificial saliva served as controls. The extracts (culture medium plus bleaching gel products that diffused through the discs) were collected and applied on previously cultured MDPC-23 cells for 1 h. Cell metabolism was evaluated by the MTT assay, and the data were analysed statistically by one-way anova and Tukey's test (α=0.05). Cell morphology was analysed by SEM. RESULTS: There was no significant difference (P>0.05) between the controls and the groups bleached with 10% CP gel. In the groups bleached with 16% CP gel, however, cell metabolism decreased significantly (P<0.05) by 40.32%, 30.16% and 26.61% at 1, 7 and 14 days, respectively. There was no significant difference (P>0.05) between 1, 7 or 14 applications of the gels for either of the CP concentrations. CONCLUSION: Regardless of the number of applications on an enamel surface, the 10% CP bleaching gel did not cause transenamel and transdentinal cytotoxicity to the MDPC-23 cell cultures. However, diffusion of products from the 16% CP gel through enamel and dentine and cytopathic effects to the pulp cells occurred even after a single application of this product on enamel.