Objective: To assess the efficacy of two sealants to preserve the apical seal after root canal preparation and cementation of posts at 24 h or 72 h after endodontic treatment. Study design: Sixty human single-root teeth were instrumented and obturated using lateral compaction technique with EndoFill® [30] or AH-Plus® [30] and were prepared in one of three ways, leaving a 3 mm gutta percha remnant in all cases: without cast post preparation, with preparation after 24 h or after 72 h. After cementing the posts, the specimens were thermal cycled at 5 and 55?C in water baths, submerged in 2% methylene blue dye for 72 h, embedded in acrylic resin and cut transversally into three 1-mm apical sections. Dye leakage was quantitatively assessed as the percentage leaked area. Results and conclusion: Comparison of the apical sections showed significant differences in leakage with both sealers among the three preparation groups (p<0.001). No significant differences between sealers were found in any preparation group or in the same sections.