Effect of Different Irrigation Activation Methods on the Dentinal Tubule Penetration of Dyed Sodium Hypochlorite: Rhodamine B vs. Fluorescein Sodium Salt

Background: This study aimed to observe the penetration of sodium hypochlorite (NaOCl) into the dentinal tubules (DTs) with confocal laser scanning microscopy (CLSM) using fluorescein sodium salt (FSS) and Rhodamine B. Methods: Six groups of 120 freshly extracted human maxillary central incisors were randomly divided. Both FSS and Rhodamine B were used in 3 groups (n: 20): control group, sonic irrigation (SI), and passive ultrasonic irrigation (PUI). The irrigation solution amounts and total duration were the same in all groups. Using CLSM, transverse sections (2-, 4-, and 6 mm distances to the root apex) were examined. Both the percentage (%) and maximum depth (µm) of NaOCl penetration were calculated. Results: There was no statistically significant difference in penetration percentage (PP) and maximum depth of penetration (MPD) between Rhodamine B and FSS (P=.635, and P= .869, respectively). The maximum PP of NaOCl was seen in the 6-mm sections across all groups, including both Rhodamine B and FSS. In the same sections with 2 dyes, however, no statistically significant changes were seen between the irrigation groups. In the SI and PUI groups, a significantly higher MPD was detected with Rhodamine B in 4-mm sections than 2-mm sections. The SI group exhibited significantly more MPD than control group in the 4-mm section with Rhodamine B and FSS. Conclusion: The FSS can be safely used in penetration studies into the DT. The SI and PUI did not significantly enhance the irrigation solution’s penetration into the DT compared to conventional endodontic irrigation. Cite this article as: Yalçın TY, Gökyay SS. Effect of different irrigation activation methods on the dentinal tubule penetration of dyed NaOCl: rhodamine B vs. fluorescein sodium salt. Essent Dent. 2025; 4, 0037, doi: 10.5152/EssentDent.2025.25037.