(PR118) Removal of E. Faecalis in Dentinal Tubules with Combined NaOCl, Nanobubble Water and ErCr:YSGG Biolase

Objective: To determine whether combination of NaOCl mixed in nanobubble water (NB) and ErCr:YSGG laser (Biolase) plus Ca(OH)2 treatments can eliminate dentinal tubule colonization by E. Faecalis (Ef).

Methods: 24 single-canaled teeth were instrumented to 40/.04 then autoclaved followed by Ef inoculation and cultivation at 37°C for ~4 weeks. Teeth were randomly divided into 4 groups (Grp): Grp-I as control, not disinfected. Grp-II 6.25% NaOCl; Grp-III 1.25% NaOCl in regular H2O; Grp-IV 1.25% NaOCl in NB; and subjected to NaOCl/NB/Biolase/Ca(OH)2 disinfection. Canal contents were collected before and after disinfection for MTT assays. Teeth received two rounds (4x10 sec cycles) of standard Biolase canal disinfection. Teeth were then filled with Ca(OH)2 for 9 days and subjected to another cycle of disinfection followed by Confocal Laser Scanning Microscopy (CLSM) to detect live/dead (green/red fluorescence) Ef in the dentinal tubules. Data analyzed by ANOVA.

Results: MTT assays showed below detectable Ef activities of all groups. CLSM showed significant difference between Grp-I and remaining groups in different segments (coronal, middle, apical) and different depth into the dentin (50, 100, 150 nm) (p <.05). No difference was found between Grps-II-IV (p>.05). Grps-III&IV had weaker fluorescence signals overall compared to Grps-I&II. Possible extensive destruction of Ef beyond fluorescence detectability, although sporadic green fluorescence signals were observable in Grps-III&IV.

Conclusion: 1.25% NaOCl with Biolase is as effective as 6.25% NaOCl with Biolase. Our extensive disinfection protocol reduced dentinal tubule infection drastically. Whether NB further enhances Ef killing in dentinal tubules under this disinfection protocol requires further investigation.