Penetration effect of sodium hypochlorite activated by the NSKVarios 370 ultrasonic system and the EQ-S sonic system in singlerooted premolars

Abstract

The effectiveness of endodontic disinfection largely depends on the ability of sodium hypochlorite (NaOCl) to penetrate deeply into dentinal tubules, particularly in the apical third, where the anatomy is more complex and mechanical access is limited. Sonic and ultrasonic activation techniques have been proposed to enhance this penetration by generating dynamic fluid movement. Aim: To evaluate and compare the depth of penetration of 5.25% NaOCl into dentinal tubules using passive ultrasonic irrigation (PUI; NSK Varios 370) and sonic activation (SIM; EQ-S Metabiomed), in comparison to conventional needle irrigation. Materials and Method: thirty-six extracted human single-rooted premolars were instrumented to working length with ProTaper Gold F3. The teeth were randomly assigned to three groups (n = 12): PUI, SIM, and control. A standardized final irrigation protocol was performed, followed by the application of 1% methylene blue, activated or not, according to the group. Three transverse sections were obtained from each tooth (coronal, middle, and apical), and penetration depth was measured using ImageJ image analysis. Data were analyzed with nonparametric tests (Mann–Whitney U; p < 0.05). Results: Both PUI and SIM showed significantly greater penetration depths than the control group in all three thirds of the canal (p < 0.05). No significant difference was found between PUI and SIM (p > 0.05). The greatest penetration was observed in the coronal third, followed by the middle and apical thirds in all groups. Conclusions: Ultrasonic and sonic activation techniques produced greater marker penetration into dentinal tubules compared to conventional irrigation. Furthermore, the EQ-S system yielded similar results to those obtained with ultrasonic activation, with no statistically significant difference between the two systems.