Exploring the Impact of Ultrasonic Activation on the Antimicrobial Activity of Root Canal Sealers: A Year‐Long Ex Vivo Investigation Into Bacterial Survival

AIM: This study investigated the long-term survival of bacteria in root canals obturated using two endodontic sealers-AH Plus Jet (AHP) and BioRoot RCS (BCS)-while also assessing the influence of ultrasonic agitation on their antimicrobial effectiveness. METHODOLOGY: One hundred human single-rooted teeth were contaminated for 21 days with dual-species biofilms of Enterococcus faecalis and Streptococcus oralis. Samples were collected at various treatment stages: initial (S1), post-instrumentation (S2), and after filling removal (S3), with additional samples after 7 days (S4). Groups were categorized by sealer type, incubation duration (30 days and 12 months), and ultrasonic agitation (UA): AHP, AHP/UA, BCS, BCS/UA, and a control group (CON) without a sealer. Bacterial survival was assessed through colony-forming unit (CFU) counts, and viability was visualized via confocal laser scanning microscopy (CLSM). RESULTS: Bacterial counts immediately after root filling removal (S3) remained comparable to those observed before obturation (S2) but significantly increased after 7 days of nutritional exposure (S4) in all groups (p < 0.05). CLSM corroborated the CFU findings, indicating that bacteria remained viable within dentinal tubules after 30 days and 12 months. The use of UA enhanced the antimicrobial effectiveness of the sealers during the 30-day period (p < 0.05). After 12 months, AHP exhibited lower bacterial growth, particularly for E. faecalis, compared with BCS (p < 0.05). CONCLUSIONS: Ultrasonic agitation reduced the ability of residual bacteria to recolonize the root canal space during the initial 30-day period. However, viable bacteria persisted even after 12 months of obturation, irrespective of the sealer and obturation technique used.