Comparative Dentinal Tubule Penetration of Three Calcium Silicate-Based Sealers Under Conventional and Sonic-Activated Final Irrigation Protocols: An In Vitro Confocal Microscopy Study

Background: Successful root canal treatment depends on achieving an effective three-dimensional seal and limiting microbial persistence and reinfection. Dentinal tubule penetration may enhance sealing by increasing sealer–dentin contact and micromechanical retention. This study compared the dentinal tubule penetration of BioRoot RCS, NeoSealer Flo, and TotalFill BC Sealer with AH Plus using the calcium-sensitive fluorophore Fluo-3 and evaluated the effect of sonic activation of final irrigation. Methods: 128 extracted human single-rooted teeth were allocated to four sealer groups and subdivided according to final irrigation protocol: non-activated final irrigation (NAFI) or sonic-activated final irrigation (SAFI). Sealers were labeled with 0.1% Fluo-3, and canals were obturated using the single-cone technique. Root sections obtained at 3, 5, and 8 mm from the apex were analyzed by CLSM. Penetration area and depth percentages were calculated and statistically compared (p < 0.05). Results: All sealers penetrated dentinal tubules. For overall penetration, under NAFI, BioRoot RCS and NeoSealer Flo showed significantly greater penetration area than AH Plus and TotalFill BC Sealer, while BioRoot RCS showed significantly greater penetration depth than AH Plus and TotalFill BC Sealer. Under SAFI, BioRoot RCS and NeoSealer Flo showed significantly greater penetration area than TotalFill BC Sealer, whereas NeoSealer Flo showed significantly greater penetration depth than all other sealers (p < 0.05). Sonic activation significantly increased penetration in selected sealers and root thirds; for NeoSealer Flo, penetration depth increased from 37.55% to 49.15% in the coronal third and from 33.10% to 48.73% in the middle third, while AH Plus also showed increased penetration apically and no significant effect was observed for BioRoot RCS. Penetration was generally greatest coronally and lowest apically. Conclusions: Dentinal tubule penetration was influenced by sealer type, final irrigation protocol, and root third. Sonic activation improved penetration under specific conditions but did not produce a uniform effect across all sealers or root thirds.