The use of calcium hydroxide pastes as intracanal medication with an aqueous or viscous vehicle, as propylene glycol, can be useful, since all formulations of the tested pastes resulted in great bacterial reduction inside root canals.

Objectives: The objective of the present work was to evaluate the ultrasonic agitation, time and vehicle (propylene glycol or distilled water) on the antimicrobial potential and penetrability of calcium hydroxide pastes on infected dentin by means of Confocal Laser Scanning Microscopy (CLSM) and microbiological culture (MC). Materials and methods: Dentin specimens were infected with Enterococcus faecalis using a new contamination protocol of 5 days. The specimens were divided into eight groups and dressed with the pastes for 7 or 15 days: G1) calcium hydroxide (CH) + propylene glycol (prop)/7 days (d), G2) CH + prop/7d + ultrasonic agitation (U), G3) CH + distilled water (dw)/7d, G4) CH + dw/7d + U, G5) CH + prop/15d, G6) CH + prop/15d + U, G7) CH + dw/15d, G8) CH + dw/15d + U. The ultrasonic activation was made for 1 min in both directions with a plain point insert. After medications removal, the images obtained by CLSM showed the viable (green) and dead (red) bacteria with Live and Dead dye. By the MC, the dentinal wall debris obtained by burs were collected for colony counts. For the penetration test, the Rodamine B dye was added to the CH pastes and analyzed by CLSM. Results: The 7 and 15-days CH + prop+U pastes performed better antimicrobial efficacy, followed by the CH + dw+U/15d paste. Conclusions: All pastes demonstrated better penetration and antimicrobial activity against E. faecalis when agitated with ultrasound, even in periods of up to seven days. The propylene glycol vehicle showed better results. Clinical relevance: Agitation of the dressing that remains for less time inside the root canal can optimize the decontamination of endodontic treatment.