Effect of Different Irrigation Solutions on the Diffusion of MTA Cement into the Root Canal Dentin

(1) Aim: This study aims to analyze the in vitro infiltration of a silicate root canal sealer into dentinal tubules after using different endodontic irrigating solutions. (2) Methods: Twenty-nine teeth with single roots were separated into three groups according to the final irrigation protocol: G1 n = 10) = 17% EDTA (ethylenediaminetetraacetic acid) + 3.0% sodium hypochlorite (NaOCl), G2 (n = 10) = 17% EDTA + 2.0% chlorhexidine and G3 (Control group, n = 9) = 17% EDTA + saline solution. Root canals were filled using cold lateral compaction technique with MTA Fillapex sealer and gutta-percha. The sealer was labeled with rhodamine B. The teeth were segmented at the middle and third apical sections, which were visualized using 10× confocal laser microscopy to determine the sealer penetration percentage. (3) Results: In the apical section, no statistically significant differences were found between the groups regarding sealer penetration. In the middle section, Group 1 obtained the highest percentage, and Group 2 the lowest (p = 0.004). Group 1 also presented statistically significant differences in the Control Group (p = 0.031) and had close sealer penetration values. Meanwhile, the Control Group (p = 0.023) and Group 2 (p = 0.029) revealed a significant decrease of sealer penetration between the apical and middle sections. (4) Conclusion: The obtained results support that final irrigation with NaOCl promoted similar sealer penetration in the apical and middle sections. On the other hand, a significant decrease in the sealer penetration of the middle section was observed for the chlorhexidine and saline groups. Compared to other irrigant solutions, NaOCl promotes more uniform sealer penetration, which can correlate with better sealing and, consequently, higher endodontic treatment success.