In vitro comparison of passive and continuous ultrasonic irrigation in simulated lateral canals of extracted teeth.

Introduction: Complete endodontic system disinfection
requires the removal of vital and necrotic pulp
tissue, microorganisms, and toxins. The purpose of
this study was to compare the effects of 2 ultrasonic irrigation
techniques on the penetration of sodium hypochlorite
into the main canal and simulated lateral
canals of extracted teeth. Methods: Two simulated
lateral canals each were created 2, 4, and 6 mm from
the working length in 60 single-rooted teeth (6 canals/
tooth, n = 360). To resemble the clinical situation,
a closed system was created in each tooth. The teeth
were randomly assigned to 3 experimental irrigation
groups: group 1 (n = 20), positive pressure irrigation
(PPI); group 2 (n = 20), passive ultrasonic irrigation
(PUI); and group 3 (n = 20), continuous ultrasonic irrigation
(CUI). Samples were evaluated by direct observation
of still images recorded under a dental operating
microscope. To examine irrigating solution penetration,
20% Chinese ink (Sanford Rotring GmbH, Hamburg,
Germany) was added to a 5% sodium hypochlorite solution
and delivered into the root canals. Results: The
results showed a significantly higher (P < .05) penetration
of irrigant into the lateral canals in the CUI group.
PUI and CUI did not differ significantly in solution penetration
into the apical thirds of the main canals. The PPI
group showed a significantly lower penetration of
sodium hypochlorite into the main and lateral canals
compared with the CUI and PUI groups. Conclusions:
CUI as a final rinse significantly increased the penetration
of irrigating solution into