The aim of this study was to observe the penetration of an aqueous solution into the root canal dentin under sonic activation and ultrasonic activation. Materials and Method: This study consisted of experimental in vitro research. In order to achieve a closed system, the apex of 45 single-rooted teeth was sealed with wax. The step-back technique was manually performed using a K50 apical master file and 3 groups were organized according to the protocol of the final irrigant activation: Group I: non-activated Chinese ink for 30 seconds, Group II: Chinese ink sonically activated with EndoActivator for 30 seconds, and Group III: Chinese ink ultrasonically activated with Varios 350 equipment for 30 seconds. Teeth were sectioned longitudinally, and the samples obtained were observed under a stereomicroscope at 1X magnification in order to be photographed and scanned to calculate the penetration area using the Image J software. The tinted radicular area was evaluated in relation to the total area of the root dentin. The Tukey’s post-hoc test and ANOVA were used for the statistical analysis (p<0.05). Results: Group I and II obtained 9.13% and 9.42% penetration respectively, while in group III the highest degree of dye infiltration was achieved (13.9%), being statistically significant (p<0.001). Conclusions: Ultrasonic activation produced a significantly higher penetration of the dye when compared to conventional activation and sonic activation.