Effect of Fluoride-Treated Enamel on Indirect Cytotoxicity of a 16% Carbamide Peroxide Bleaching Gel to Pulp Cells

The aim of this study was to evaluate the possibility of fluoride solutions applied to enamel to protect pulp cells against the trans-enamel and transdentinal cytotoxicity of a 16% carbamide peroxide (CP) bleaching gel. The CP gel was applied to enamel/dentin discs adapted to aicial pulp chambers (8 h/day) during 1, 7 or 14 days, followed by fluoride (0.05% or 0.2%) application for 1 min. The extracts (culture medium in contact with dentin) were applied to MDPC-23 cells for 1 h, and cell metabolism (MTT assay), alkaline phosphatase (ALP) activity and cell membrane damage (flow cytometry) were analyzed. Knoop microhardness of enamel was also evaluated. Data were analyzed statistically by ANOVA and Kruskal-Wallis tests (α=0.05). For the MTT assay and ALP activity, significant reductions between the control and the bleached groups were observed (p<0.05). No statistically significant difference occurred among bleached groups (p>0.05), regardless of fluoride application or treatment days. Flow cytometry analysis demonstrated 30% of cell membrane damage in all bleached groups. After 14 days of treatment, the fluoride-treated enamel presented significantly higher microhardness values than the bleached-only group (p<0.05). It was concluded that, regardless of the increase in enamel hardness due to the application of fluoride solutions, the treated enamel surface did not prevent the toxic effects caused by the 16% CP gel to odontoblast-like cells.

Resumo O objetivo do presente estudo foi avaliar o possível efeito protetor de soluções fluoretadas aplicadas sobre o esmalte dentário frente à citotoxicidade trans-amelodentinária de um gel clareador com 16% de peróxido de carbamida (PC). O gel de PC foi aplicado sobre discos de esmalte/dentina adaptados a câmaras pulpares aiciais (8 h/dia) durante períodos de 1, 7 ou 14 dias, seguido de aplicação de soluções fluoretadas (0,05% ou 0,2%) durante 1 min. Os extratos (meio de cultura em contato com a dentina) foram aplicados sobre células MDPC-23 durante 1 h, seguido de análise do metabolismo celular (teste do MTT), atividade de fosfatase alcalina (ALP) e danos à membrana celular (citometria de fluxo). A microdureza Knoop do esmalte dental foi avaliada. Os dados foram analisados pelos testes de ANOVA e Kruskal-Wallis. Para o teste do MTT e atividade de ALP, redução significante entre os grupos controle e clareados foram observados (p<0,05). Nenhuma diferença entre os grupos clareados foi observada (p>0,05), independente da aplicação das soluções fluoretadas ou tempo de tratamento. A análise por citometria de fluxo demonstrou lesão à membrana celular em torno de 30% para todos os grupos clareados. Após 14 dias de tratamento, os espécimes clareados e fluoretados apresentaram aumento significante na microdureza do esmalte (p<0,05). Pôde-se concluir que apesar do aumento na dureza do esmalte decorrente da aplicação das soluções fluoretadas, este tratamento não preveniu os efeitos tóxicos causados pelo gel com 16% de PC sobre as células odontoblastóides. .

Biochemical and Mitochondrial Changes Induced by Cd, Fe and Zn in Limnodrillus hoffmeisteri / Cambios Bioquímicos y Mitocondriales Inducidos por Cd, Fe y Zn en Limnodrillus hoffmeisteri

The effects of sublethal concentrations of cadmium (0.64 µg/L), iron (0.043 mg/L) and zinc (0.31 mg/L) and a mixture of these metals on succinate dehydrogenase (SD) and alkaline phosphatase (AP) activity and on structural changes in the mitochondria of epithelium cells of the digestive tract were examined in the oligochaete Limnodrillus hoffmeisteri after 96 h of exposure in artificial sediments. SD activity was significantly inhibited, particularly in treatments with Cd alone (92.57 percent), while AP increased its activity with Cd alone (73.23 percent). However, when this metal was mixed with Fe and Zn, the inhibition of SD activity was lower (67.82 percent) than with Cd alone, showing an antagonistic effect and AP increased its activity (73.26 percent). Mitochondria were structurally damaged by exposure to Cd alone. However, in the metal mixtures, the toxic effects may exert interactive effects eliciting a less structural damage in the mitochondria of epithelium cells of the digestive tract than when Cd is alone.

Se estudió el efecto de las concentraciones subletales de Cd (0,64 µg/L), Fe (0,043 mg/L) y Zn (0,31 mg/L) en forma aislada y en mezcla sobre la actividad de la succinato deshidrogenasa (SD) y la fosfatasa alcalina (AP) en las mitocondrias de las células epiteliales del tracto digestivo en el oligoqueto Limnodrillus hoffmeisteri después de 96 h de exposición en sedimentos artificiales. La SD se inhibió significativamente, particularmente en los tratamientos con Cd en forma aislada (92,57 por ciento), mientras que la AP se incrementó con Cd en forma aislada (73,23 por ciento). Sin embargo, cuando este metal se mezcló con Fe y Zn, la inhibición de la SD fue menor (67,82 por ciento) que con Cd en forma aislada, lo que mostró un efecto antagonístico y la AP incrementó su actividad (73,23 por ciento). Sin embargo, cuando este metal estaba en mezcla con Fe y Zn, la inhibición de la SD fue menor (67,82 por ciento) que con Cd en forma aislada, mostrando un efecto antagonístico y un incremento en la actividad de la AP (73,26 por ciento). Las mitocondrias fueron dañadas estructuralmente por exposición al Cd en forma aislada. Sin embargo, con los metales en mezcla, los efectos tóxicos pudieron ejercer efectos interactivos provocando un menor daño estructural en la mitocondria de las células del epitelio del tracto digestivo que cuando el Cd estaba en forma aislada.

Toxicity of chlorhexidine on odontoblast-like cells

Chlorhexidine gluconate (CHX) is recommended for a number of clinical procedures and it has been pointed out as a potential cavity cleanser to be applied before adhesive restoration of dental cavities. OBJECTIVE: As CHX may diffuse through the dentinal tubules to reach a monolayer of odontoblasts that underlies the dentin substrate, this study evaluated the cytotoxic effects of different concentrations of CHX on cultured odontoblast-like cells (MDPC-23). MATERIAL AND METHODS: Cells were cultured and exposed to CHX solutions at concentrations of 0.06 percent, 0.12 percent, 0.2 percent, 1 percent and 2 percent. Pure culture medium (á-MEM) and 3 percent hydrogen peroxide were used as negative and positive control, respectively. After exposing the cultured cells to the controls and CHX solutions for 60 s, 2 h or 60 s with a 24-h recovery period, cell metabolism (MTT assay) and total protein concentration were evaluated. Cell morphology was assessed under scanning electron microscopy. CHX had a dose-dependent toxic effect on the MDPC-23 cells. RESULTS: Statistically significant difference was observed when the cells were exposed to CHX in all periods (p<0.05). Significant difference was also determined for all CHX concentrations (p<0.05). The 60-s exposure time was the least cytotoxic (p<0.05), while exposure to CHX for 60 s with a 24-h recovery period was the most toxic to the cells (p<0.05). CONCLUSION: Regardless of the exposure time, all CHX concentrations had a high direct cytotoxic effect to cultured MDPC-23 cells.

Efecto de la aspirina, cafeina y diazepam sobre la actividad de la glucosa 6 fosfatasa, succinico deshidrogenasa y beta galactosidasa acida en la placenta humana / Effect os aspirin, caffeine and diazepam on glucose 6-phosphatase, succinic dehydrogenase, and acid-galactosidase in human placenta

Se estudio "in vitro" la actividad enzimatica de la beta galactosidasa acida, glucosa 6 fosfatasa y succinico deshidrogenasa para determinar si se afectaban en presencia de aspirina, cafeina y diazepam en homogeneizado total de placenta humana. Se utilizaron dosis de 10, 50 y 100 /ml de cada farmaco, y se determino si existia diferencia significativa en ausencia de los farmacos y en presencia de los mismos mediante la prueba t de Student para series apareadas. En todas las concentraciones de los tres farmacos la beta galactosidasa acida presento un aumento altamente significativo. La glucosa 6 fosfatasa y la succinico deshidrogenasa tuvieron una disminucion altamente significativa, aunque en esta ultima la disminucion fue solosignificativa con la dosis mas pequena. Se concluye que la presencia de aspirina, cafeina y diazepam produce alteraciones en la actividad de las enzimas estudiadas que pueden provocar trastornos del metabolismo placentario

Effect of metal mixtures on activity of two respiratory enzymes and their recovery in Oreochromis mossambicus (Peters).

Effects of sublethal doses of metal (Cu, Cd, Zn) mixtures on the activities of key respiratory enzymes (succinate dehydrogenase, SDH and glyceraldehyde dehydrogenase, GDH) and their recovery following withdrawal of treatments were studied in the freshwater fish O. mossambicus. On the basis of 96 hr LC50 Cu was highly toxic followed by Zn and Cd, and the trimetal combination (Cu+Zn+Cd) was extremely toxic than any other combination; combination of Zn+Cd was least toxic. A significant gradual decrease in SDH with a concomitant increase in GDH activity observed in liver, brain, muscle and gill of animals exposed to metal suggest a metabolic shift from aerobiosis to anaerobiosis due to metal action. Exposed individuals when transferred to metal impoverished water showed an improvement in SDH activity and decline in GDH activity suggesting slow reversal to aerobic metabolism. O. mossambicus needs more time for complete recovery.