Abstract
This in vitro study evaluated the potential protective effect of vitamin E alpha-tocopherol (α-T) isomer against the toxicity of hydrogen peroxide (HP) applied on dental pulp cells. Odontoblast-like MDPC-23 cells were seeded on 96-well plates for 72 h, treated with different concentrations of α-T (1, 3, 5, and 10 mM) for different times (1, 4, 8, and 24 h) and then exposed or not to a 0.018% HP solution for 30 min. In positive and negative control groups, cells were exposed to HP or culture medium (DMEM containing 5% DMSO), respectively. Cell viability was assessed by the MTT assay and the absorbance numeric data, expressed as percentage values, were subjected to the statistical analysis by Kruskal-Wallis and Mann-Whitney tests (α=5%). Considering the cells in the negative control as having 100% of cell viability, all combinations of α-T concentrations and pretreatment times showed a protective effect against HP cytotoxicity. Significant reduction of cell viability (59%) was observed in the positive control compared with the negative control. The highest values of pulp cell viability were obtained after pretreatment with 1 and 3 mM α-T concentrations for 24 h followed by exposure to HP (126% and 97% of cell viability, respectively). Under the tested conditions, the most effective cell protection against the cytotoxic effects of HP was provided by the lowest concentrations of α-T (1 and 3 mM) applied for 24 h.
Highlights
Hydrogen peroxide (HP) is a molecule with a well-known oxidant intracellular activity during the biologic process of cellular respiration
There is a consensus on vital tooth bleaching research that HP and its byproducts released from bleaching agents may diffuse through the mineralized dental tissues and reach the pulp space (3,4)
In contact with the pulp cells, HP and the reactive oxygen species (ROS) resulting from its degradation produce a direct oxidative damage and may generate a secondary oxidative stress due to the imbalance between the amount of ROS and intracellular antioxidants (1)
Summary
Hydrogen peroxide (HP) is a molecule with a well-known oxidant intracellular activity during the biologic process of cellular respiration. The use of these bleaching gels has been shown to cause postoperative tooth sensitivity (2) and side effects on dental pulp tissue, ranging from acute inflammatory response to the formation of areas of necrosis (3,4), as a result of HP diffusion through the dentinal tubules, reaching the pulp chamber (5) and causing an oxidative stress to pulp cells (6). It is known that the antioxidant action of VE is mediated by its alpha-tocopherol (α-T) isomer, which has the capacity to incorporate to the cell membrane and stop lipid peroxidation propagation (11). Several researchers have assessed the protective effect of α-T and confirmed its capacity to prevent oxidative stress propagation, stabilize the cell membrane, enhance cell viability and increase the amount of endogenous antioxidants (12-17)
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