RESUMO ABSTRACTObjeti vo: Analisar, in vitro, através da Microscopia Eletrônica de Varredura, o efeito do EDTA nas concentrações de 3%, 5%, 10% e 17%, na remoção da camada residual e na desobstrução dos túbulos denti nários, nos tempos de 1 e 3 minutos. Método: Da amostra consti tuída de 80 dentes, foram selecionadas, randomicamente, oito unidades para compor o grupo controle negati vo (GC1) e 8 para consti tuírem o grupo controle positi vo (GC2 Objecti ve: To analyze, in vitro, by scanning electron microscopy (SEM), the eff ect of EDTA at concentrati ons of 3%, 5%, 10% and 17% for 1 and 3 minutes, on the removal of the smear layer and opening of denti nal tubules. Method: Eighty teeth were randomly assigned to groups as follows: 8 specimens were allocated to the negati ve control group (CG1), 8 to the positi ve control group (GC2), and the other 64 were distributed to 8 experimental groups (ExpG). Aft er root canal instrumentati on, fi nal irrigati on was done with the EDTA soluti ons, which were left in contact with the denti n surfaces for 1 and 3 minutes. Results: The analysis of the SEM micrographs at ×2,000 magnifi cati on revealed that 10% and 17% EDTA soluti ons were the most eff ecti ve, regardless of the applicati on ti me. Conclusion: Regarding the smear layer removal and denti nal tubule opening, the effi cacy of EDTA is not altered with the increase of the applicati on ti me from 1 to 3 minutes.