Increased whitening efficacy and reduced cytotoxicity are achieved by the chemical activation of a highly concentrated hydrogen peroxide bleaching gel

Abstract Objective This study was designed for the chemical activation of a 35% hydrogen peroxide (H2O2) bleaching gel to increase its whitening effectiveness and reduce its toxicity. Methodology First, the bleaching gel - associated or not with ferrous sulfate (FS), manganese chloride (MC), peroxidase (PR), or catalase (CT) - was applied (3x 15 min) to enamel/dentin discs adapted to artificial pulp chambers. Then, odontoblast-like MDPC-23 cells were exposed for 1 h to the extracts (culture medium + components released from the product), for the assessment of viability (MTT assay) and oxidative stress (H2DCFDA). Residual H2O2 and bleaching effectiveness (DE) were also evaluated. Data were analyzed with one-way ANOVA complemented with Tukey's test (n=8. p<0.05). Results All chemically activated groups minimized MDPC-23 oxidative stress generation; however, significantly higher cell viability was detected for MC, PR, and CT than for plain 35% H2O2 gel. Nevertheless, FS, MC, PR, and CT reduced the amount of residual H2O2 and increased bleaching effectiveness. Conclusion Chemical activation of 35% H2O2 gel with MC, PR, and CT minimized residual H2O2 and pulp cell toxicity; but PR duplicated the whitening potential of the bleaching gel after a single 45-minute session.

Influência do gluconato de cálcio sobre a citotoxicidade trans-amelodentinária de um agente clareador com 20% de peróxido de hidrogênio / Influence of calcium gluconate on the trans-enamel and trans-dentinal cytotoxicity of a bleaching agent with 20% hydrogen peroxide

Objetivo: Avaliar a citotoxicidade de um agente clareador contendo 2% de gluconato de cálcio (GC) sobre células pulpares humanas (HDPCs). Materiais e Métodos: Discos de esmalte-dentina adaptados em câmaras pulpares artificiais (CPAs) foram posicionados em compartimentos de forma que a dentina permaneceu imersa em meio de cultura, enquanto que o esmalte foi submetido ao clareamento com géis a 20% de H2O2 contendo ou não GC, durante 1x 45, 1x15 ou 1x5 minutos. No controle positivo foi realizado clareamento com 35% de H2O2 aplicado por 1x 45 minutos, sendo que no controle negativo nenhum tratamento foi realizado sobre o esmalte. A viabilidade celular (teste do MTT) e a difusão trans-amelodentinária de H2O2 (violeta leuco- -cristal/peroxidase) foram avaliadas (ANOVA/Tukey α = 5%; n = 8). Resultados: Foi observada redução significativa na viabilidade celular em todos os grupos clareados quando comparados ao controle negativo (p < 0,05); no entanto, os grupos expostos aos géis contendo 20% de H2O2, com ou sem GC, apresentaram valores de viabilidade celular significativamente superiores ao controle positivo (p < 0,05). A redução da viabilidade celular e a difusão de H2O2 residual para os grupos clareados com 20% de H2O2 foi proporcional ao tempo de contato dos produtos com a superfície dental, sendo que a presença de GC resultou em minimização significativo do efeito tóxico/difusão de H2O2 para os protocolos 1x 15 e 1x 5 min (p < 0,05). Conclusão: A presença de 2% de GC nos géis com 20% de H2O2 resulta em redução da difusão de H2O2 residual pela estrutura dental e do efeito citotóxico sobre células pulpares humanas, quando o produto é aplicado por curtos períodos sobre a superfície dental.

Objective: To evaluate the cytotoxicity of a bleaching agent containing 2% calcium gluconate (CG) on human pulp cells (HDPCs). Materials and Methods: Enamel-dentin disks adapted in artificial pulp chambers (CPAs) were placed in compartments so that dentin remained immersed in culture medium, while the enamel was subjected to bleaching with 20% H2O2 gels containing or not CG for 1x 45, 1x15 or 1x5 minutes. In the positive control, bleaching was performed with 35% H2O2 applied for 1x 45 minutes, and in the negative control no treatment was performed on the enamel. Cell viability (MTT test) and transenamel and trans-dentinal diffusion of H2O2 (leuco-crystal violet / peroxidase) were evaluated (ANOVA / Tukey α = 5%, n = 8). Results: A significant reduction in cell viability was observed in all bleached groups when compared to the negative control (p <0.05); However, groups exposed to gels containing 20% H2O2, with or without CG, had significantly higher values of cell viability than the positive control (p <0.05). The reduction of cell viability and the diffusion of residual H2O2 to the bleached groups with 20% H2O2 was proportional to the contact time of the products with the dental surface, and the presence of CG resulted in a significant minimization of the toxic /diffusion effect of H2O2 For the 1x15 and 1x5min protocols (p <0.05). Conclusion: The presence of 2% GC in gels with 20% H2O2 results in reduction of residual H2O2 diffusion by dental structure and cytotoxic effect on human pulp cells when the product is applied for short periods on the dental surface.

Bioestimulação de células pulpares humanas expostas a sinvastatina / Biostimulation of human pulp cells exposed to simvastatin

O objetivo desse estudo foi avaliar o potencial bioativo da sinvastatina (SV), aplicada por diferentes períodos sobre células da polpa dental humana (HDPCs). Para isto, HDPCs em 80% de confluência (n=6) foram tratadas com meio osteogênico suplementado com 0,01 µM de SV pelos períodos de 24 h, 72 h ou continuamente por até 21 dias. No controle negativo, as células foram mantidas em meio osteogênico. A viabilidade celular (MTT) foi avaliada em períodos de 1, 3, 7, 14 e 21 dias, e a deposição de matriz mineralizada (alizarin red) após 14 e 21 dias de cultivo celular. Os dados foram submetidos aos testes ANOVA e Tukey (α=5%). Foi observado que nos períodos de 1, 3, 7 e 14 dias não houve diferença significativa na viabilidade das células submetidas aos tratamentos com SV em comparação ao controle (p<0,05); no entanto, redução tardia foi observada aos 21 dias para as células tratadas com SV por 72 h ou de modo contínuo (p<0,05). Em contrapartida, aumento na deposição de matriz mineralizada foi observado para o tratamento contínuo com SV aos 21 dias, quando comparado ao controle (p<0,05). Foi possível concluir que o tratamento contínuo de células pulpares humanas com 0,01µM de SV foi capaz de bioestimular a deposição de matriz mineralizada in vitro.

The objective of this study was to evaluate the bioactive potential of simvastatin (SV), applied during different periods on human dental pulp cells (HDPCs). For this, HDPCs at 80% confluency (n = 6) were treated with osteogenic medium supplemented with 0.01 µM SV for periods of 24 h, 72 h or continuously up to 21 days. In the negative control group, the cells were cultivated in osteogenic medium. The cell viability (MTT) was evaluated after 1, 3, 7, 14 and 21 days, and the mineralized matrix deposition (alizarin red) was assessed at 14 and 21 days of cell culture. Data were submitted to ANOVA and Tukey's test (α=5%). No significant difference in cell viability was observed at 1, 3, 7 and 14 days for the cells exposed to SV compared to negative control (p<0.05); however, significant reduction was observed at 21 days for cells treated with SV during 72 h or continuously (p<0.05). On the other hand, increase in mineralized matrix deposition at 21 days was observed for cells treated continuously with SV when compared to control (p<0.05). It was possible to conclude that the continuous treatment of human pulp cells with 0.01 µM of SV was able to biostimulate mineralized matrix deposition in vitro.