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Nanobubbles enhance the effects of low-concentration sodium hypochlorite on root canal irrigation
Haoyu Liu1, Nguyen Nhat Thu Le2, Jianfeng Wu2
1Department of Cariology and Endodontology, Peking University School and Hospital of Stomatology & National Center for Stomatology & National Clinical Research Center for Oral Diseases & National Engineering Research Center of Oral Biomaterials and Digital Medical Devices & Beijing Key Laboratory of Digital Stomatology & NHC Key Laboratory of Digital Stomatology & NMPA Key Laboratory for Dental Materials, No.22, Zhongguancun South Avenue, Haidian District, Beijing, 100081, P.R. China.
Objectives:
To evaluate whether nanobubbles (NBs) enhance the antibiofilm efficacy of low-concentration sodium hypochlorite (NaClO) and enable smear layer removal.
Materials And Methods:
Enterococcus faecalis biofilms were established on dentin discs and in root canals. Biofilms on dentin discs were treated with pure water, nanobubble water (NBW), 0.01% NaClO, 0.01% NaClO + NB, or 0.1% NaClO, then observed by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Residual biomass was quantified by colony forming unit (CFU) counting. Root canals were irrigated with pure water, 0.5% NaClO, 0.5% NaClO + NB, or 3% NaClO. Antibacterial effects were evaluated by CLSM and CFU counting. Smear layer removal was evaluated by SEM. Solution penetration was evaluated by crystal violet bleaching.
Results:
Compared with 0.01% NaClO, 0.01% NaClO + NB caused more dead bacteria (P < 0.05) and disrupted biofilm structure. Bacteria with cell wall perforations were observed exclusively in NB-containing groups. In root canals, 0.5% NaClO + NB resulted in more dead bacteria than 0.5% NaClO alone at all examined depths (P < 0.05), and was comparable to 3% NaClO at 100 μm depth into the dentinal tubules in coronal third and 100-200 μm depth in middle third (P > 0.05). NaClO + NB group exhibited the lowest residual biomass on canal walls, enabled effective smear layer removal, and enhanced solution penetration (P < 0.05).
Conclusions:
NBs enhanced antibiofilm efficacy and enabled smear layer removal, thereby improving the performance of low-concentration NaClO in root canal irrigation.
Clinical Relevance:
Adding NBs to low-concentration NaClO offers a promising strategy to enhance root canal irrigation efficacy.