Nanobubble-Enhanced Antimicrobial Agents: A Promising approach For Regenerative Endodontics.

AIM In this study, we investigated the properties of nanobubble (NB) water and its effect on smear layer removal and strengthening the efficiency of disinfecting agents used in regenerative endodontic treatment. METHODOLOGY NB water was generated in a NB Generator. The NB size, concentration, and pH were measured. Porcine teeth were enlarged to size 60 using hand-files and irrigated with either NB water, 17% EDTA or received no further irrigation. The ability of irrigants to remove the smear layer was evaluated using a scanning electron microscope (SEM) (9 roots/group). Other Samples (6 roots/group) were subjected to Vickers hardness test to determine the dentin microhardness. Autofluorescent-tetracycline mixed with distilled water or NB water was placed inside the root canal space of porcine teeth, and the depth of medicament penetration into the dentinal tubules was visualized using fluorescent stereomicroscope (5 roots/group). For the disinfection experiment, human roots were prepared, autoclaved, and inoculated with Enterococcus faecalis for 3 weeks. Canals were then disinfected by (1) standard needle irrigation (SNI) with 5.25% NaOCl, (2) 5.25% NaOCl with ultrasonication (US), (3) 5.25% NaOCl + XP finisher (XP), (4) SNI with 1.5% NaOCl, or (5) SNI with 1.5% NaOCl in NB water; (5 roots/group). Teeth were split open and stained with LIVE/DEAD BackLight and visualized using confocal laser scanning microscope (CLSM) at the coronal, middle, and apical thirds of the canal. The ratio of dead/total bacteria in the dentinal tubules at various depth levels (50 μm, 100 μm, and 150 μm) was calculated. RESULTS NB water was more effective in removing smear layer than 17% EDTA and could allow infiltration of tetracycline into the dentinal tubule more than 1 mm. NB water did not alter the dentin microhardness compared to 17% EDTA (P 0.05), i.e., these groups had stronger bacterial killing than 1.5% NaOCl (P 0.05). CONCLUSIONS NB water can allow smear layer removal and enhance tubular penetration of medicaments without changing dentin microhardness. In large canal models, NB water appears to improve the tubular disinfection capacity of lower concentration of NaOCl up to 50 μm. The use of irrigation activation (US or XP), on the other hand, did not provide any added disinfection into the dentinal tubules compared to standard needle irrigation. These results suggest that NB water may be a promising adjunct to endodontic irrigants and medicaments.