Cytotoxicity and genotoxicity of sodium percarbonate: a comparison with bleaching agents commonly used in discoloured pulpless teeth.

AIM: To evaluate the cytotoxicity and genotoxicity of sodium percarbonate (SPC) in comparison with bleaching agents used on discoloured pulpless teeth. METHODOLOGY: The cytotoxicity and genotoxicity of bleaching agents were evaluated both in their pure form as well as at concentrations commonly used in clinical practice. Hydrogen peroxide (HP), carbamide peroxide (CP), sodium perborate (SP) and SPC were diluted in Dulbecco's modified Eagle's medium (DMEM) in series. To evaluate the cytotoxicity, the survival of 3T3/NIH mouse fibroblasts was measured photometrically using an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay after a 24 h-exposure period. Genotoxicity was indicated by micronuclei (MN) formation, and modification of the normal cell was analysed by light microscopy (400x). Statistical analysis was performed by one-way anova, followed by a multiple-comparison Tukey post hoc test (P < 0.05). RESULTS: All groups exhibited a dose-dependent cytotoxicity. However, CP showed a similar cytotoxic effect when compared with DMEM-untreated control (UC) group. HP and SPC were significantly more cytotoxic than SP. The genotoxicity test showed that SPC and SP had an intermediate rate of MN frequency when compared with the UC group. The mean rate of MN frequency for HP was higher and statistically more significant than for the other groups tested. No difference was observed when CP and UC groups were compared. CONCLUSIONS: Sodium percarbonate showed cytotoxicity and genotoxicity similar to those of the other products tested. However, before SPC is used clinically, studies should be conducted to confirm its safety in vivo.

Cytotoxicity of polycarbonate orthodontic brackets

Aim: To assess the cytotoxicity of polycarbonate orthodontic brackets. Methods: Polycarbonate brackets from two different manufacturers, namely, Composite bracket (Morelli™) and Silkon Plus bracket (American Orthodontics™), were assessed. In addition to these two experimental groups, other three control groups were included: Positive Control Group (C+) consisting of amalgam cylinders, Negative Control Group (C-) consisting of glass rods, and Cell Control Group (CC) consisting of cells not exposed to any material. All brackets were previously sterilized under ultra-violet light (UV) and, then, immersed in Eagle’s minimum essential media (MEM) for 24 hours, after which the supernatants were removed and placed into contact with L929 fibroblast cells. Cytotoxicity was evaluated at 24, 48, 72 and 168 hours. After contact with MEM, the cells were further incubated at 37oC for 24 hours and 100 mL of 0.01% neutral red dye were added. The cells were incubated again at 37ºC for three hours to incorporate the dye. After this period, the cells were fixed and viable cell counting was performed by spectrophotometry at 492 nm wavelength. Results: No statistically significant difference was found between the experimental groups (1 and 2) and the negative and cell control groups (p > 0.05). The Positive Control Group exhibited high cytotoxicity throughout experimental period are differed significantly from the other groups (p < 0.05). Conclusions: Polycarbonate orthodontic brackets were found not to be cytotoxic within the evaluated experimental period.

Protective effect of high alkalinity against the deleterious effects of chronic waterborne cadmium exposure on the detection of alarm cues by juvenile silver catfish (Rhamdia quelen).

The objective of the present study was to analyze the effect of chronic cadmium (Cd) exposure at two alkalinity levels (63 and 92 mg l(-1) CaCO(3)) on the antipredatory behavior of juvenile silver catfish (Rhamdia quelen) exposed to conspecific skin extract and predator odor. At an alkalinity of 63 mg l(-1) CaCO(3), 30 days of exposure to either 4.5 or 8.0 microg l(-1) Cd impaired the catfish's antipredatory response to alarm cues. However, silver catfish exposed to 4.5 microg l(-1) Cd at an alkalinity of 92 mg l(-1) CaCO(3) responded to skin extract and predator odor. In catfish exposed to 8.0 microg l(-1) Cd at the same alkalinity, only the number of feeding bites decreased, and this occurred only for specimens exposed to predator odor. Our results show that higher alkalinity protected against the deleterious effects of Cd on alarm cue detection but only in the larvae exposed to the lowest waterborne Cd level.

Neurotoxicologia clinica: los plaguicidas / Clinical neurotoxicology: pesticides

Los plaguicidas son compuestos quimicos de gran utilidad principalmente en la agriculatura. Su uso incorrecto e indiscriminado ha llevado a cuadros clinicos de neurotoxicidad importantes, en especial de Encefalopatia y Neuropatia Periferica. Se actualizan las diversas manifestaciones clinicas neurologicas en las intoxicaciones por Organofosforados, Organoclorados, Carbonatos, herbicidas como el Paraquat y los Repelentes de insectos