Objectives: The purpose of this study was to compare the apical seal in root canals obturated with EndoRez and different gutta-percha techniques using a dye penetration model. Methods: Forty extracted single rooted incisors were endodontically prepared using the Hero 642 system. Root length was determined by insertion of a #10 file into the canal until it appeared at the apex. Working length was recorded 1 mm shorter. The teeth were randomly assigned to four experimental groups of ten each: A: single cone technique, B: lateral condensation, C: warm vertical condensation, D: Thermafil. After root canal filling, the teeth were coated with nail varnish, leaving the apical foramen exposed and stored in 5% methylene blue solution for seven days. Roots were sectioned transversally at each millimetre. The distribution of filling material in each canal was assessed by stereomicroscopic examination of four cross-sections on each tooth. Areas of gutta-percha (G), sealer (S) and voids (V) were measured on the digital images. Results: The total area of gutta-percha was not statistically different among the groups B, C, D (pConclusions: Within the limitations of an in vitro investigation Thermafil and vertical condensation produce a similar apical seal. Keywords: apical sealing, obturation, sealer