nÃo hà / Na prÃtica odontolÃgica vÃrios fÃrmacos sÃo utilizados com diversas finalidades incluindo-se, entre eles, os agentes capeadores das polpas de dentes decÃduos. O formocresol à o composto mais utilizado em pulpotomias de dente decÃduos na diluiÃÃo de 1:5 da formulaÃÃo de Buckley. A seguranÃa clÃnica do formocresol tem sido questionada em virtude de possuir na sua composiÃÃo o formaldeÃdo, composto sabidamente tÃxico e carcinogÃnico. O presente trabalho tem como objetivo, estimar o potencial genotÃxico do formocresol em diferentes diluiÃÃes a partir da amostra comercializada. Esse estudo foi avaliado pelos ensaios de curta duraÃÃo in vivo e in vitro. Os animais foram tratados com o formocresol nas diluiÃÃes de 1:50, 1:100, 1:500 e 1:1000, e apÃs 24h e 48h sacrificados, sendo posteriormente a medula Ãssea extraÃda, e o material submetido Ãs observaÃÃes de perdas cromossÃmicas (micronÃcleos) em eritrÃcitos policromÃticos (PCE), alÃm disso, os fÃgados dos animais tratados (grupo 24h) foram submetidos à anÃlise histolÃgica. No ensaio in vitro o formocresol nas diluiÃÃes de 1:750, 1:1000 e 1:2000 foram incubados em cultura de linfÃcitos humanos por 45 min., sendo em seguida submetido ao procedimento de anÃlise do teste cometa. Na avaliaÃÃo da incidÃncia de micronÃcleo, no grupo 24h, nÃo houve diferenÃa quando da comparaÃÃo entre as diluiÃÃes de 1:50, 1:100, 1:500 e controle negativo, apenas quando comparada à diluiÃÃo de 1:1000 em relaÃÃo Ãs demais houve diferenÃa significativa (p < 0,001). PorÃm, quando a diluiÃÃo de 1:1000 foi comparada à ciclofosfamida, nÃo existiu diferenÃa significativa (p > 0,50). Enquanto a diluiÃÃo 1:1000 e da ciclofosfamida diferiram estatisticamente do controle negativo, no grupo 24h (p < 0,01). Entretanto, na observaÃÃo do grupo 48h, apenas a ciclofosfamida apresentou incidÃncia de micronÃcleos, diferindo estatisticamente dos grupos tratados e controle (p< 0,001). Jà no estudo histolÃgico do fÃgado, foi observado hepatotoxicidade nos animais tratados do grupo 24h. Na anÃlise do cometa, foi observado que em todas as diluiÃÃes do formocresol utilizadas houve a formaÃÃo de crosslinks no DNA, fator esse determinante para inferir o potencial genotÃxico do formocresol. ConcluÃmos que o formocresol à tÃxico e, quando diluÃdo atà 1000 vezes, à potencialmente genotÃxico e mutagÃnico. / In odontology practice, many drugs used have different purposes, such as primary teeth pulp covers. The Formocresol is the medicine most used in pulpotomy of primary teeth in 1:5 dilution of Buckleyâs formulation. The clinical safety of Formocresol has been questioned since its formulation is composed by formaldehyde, which is known as a toxic and carcinogenic compound. The present study has the objective of estimate the genotoxic potential of Formocresol in different dilutions using the commercialized sample. This study was evaluated by short period trials in vivo and in vitro. The animals were treated with Formocresol in the dilutions of 1:50, 1:100, 1:500 and 1:1000, and after 24h and 48h, they were sacrificed afterwards with the medulla extraction. This material was submitted to chromosomal damage observations (micronuclei) in polychromatic erythrocytes (PCE). The liver of the animals treated (24h group) were also submitted to histological analysis. In in vitro trial, the 1:750, 1:1000 and 1:2000 dilutions of Formocresol were incubated in human lymphocyte culture for 45 min and to comet test analysis next. There was no difference in micronuclei incidence evaluation when compared to 1:50, 1:100 and 1:500 dilutions and to negative control, in the 24h group. The difference appeared only when compared the 1:1000 dilution to the others, with a significant difference of p<0.001. However, when the dilution of 1:1000 was compared to the cyclophosphamide there was no significant difference (p>0.50). Meanwhile, the dilution of 1:1000 and of cyclophosphamide was statistically different from the negative control, in the 24h group. However, in the 48h group observations, only the cyclophosphamide presented micronuclei incidence, statistically differing from the treated groups and control (p<0.001). In the liver histological study it was observed hepatotoxicity in the animal treated in the 24h group. In comet analysis it was observed that in all used dilutions there was DNA crosslinks formation, which was an important factor to give a genotoxic potential to Formocresol. It was concluded that Formocresol is toxic and when diluted to 1:1000 is potentially genotoxic and mutagenic