The Effect of Passive Ultrasonic Activation of 2% Chlorhexidine or 5.25% Sodium Hypochlorite Irrigant on Residual Antimicrobial Activity in Root Canals

Abstract

Ninety-four single-canal roots were prepared using the step-down technique. Forty-two canals were irrigated with 2% chlorhexidine, 42 canals with 5.25% sodium hypochlorite (NaOCl), and 10 control canals with phosphate-buffered saline (PBS). The chlorhexidine and NaOCl groups were each then equally divided into a final irrigation group and a 1-min passive ultrasonic irrigation group. Canals were enlarged with a Parapost drill. The apical 3-5 mm was covered with nail polish. Canals were rinsed with PBS, dried, refilled with PBS, and stored. At 6 h, 20 microl of fluid was pipetted from each canal and placed into wells on agar plates, which were inoculated with Streptococcus sanguinis. The plates were incubated, and zones of inhibition were measured. Sampling was repeated at 24, 48, 72, 96, 120, 144, and 168 h. Residual antimicrobial activity with 2% chlorhexidine was statistically significantly superior to 5.25% NaOCl with irrigation alone and with final passive ultrasonic activation (p < 0.001). Chlorhexidine experimental groups demonstrated residual antimicrobial activity for as long as 168 h.

Bacteriologic investigation of the effects of sodium hypochlorite and chlorhexidine during the endodontic treatment of teeth with apical periodontitis

“…62 Chlorhexidine exhibits substantivity to dentin and consequently may present residual antimicrobial effects for days to weeks and help prevent root canal reinfection. 52,[63][64][65][66][67][68][69] This seems to be an important advantage over NaOCl. Nevertheless, one important disadvantage of chlorhexidine is that it lacks tissue-dissolving ability, which is one of the obvious benefits of NaOCl.…”

Direct and indirect antibacterial effects of various concentrations of triple antibiotic pastes loaded in a methylcellulose system

“…However, a trend of lower percentages of live cells within the biofilm was observed in dentin treated with 1.5% NaOCl, which may indicate a limited residual antibacterial effect. Previous studies have also suggested limited residual antibacterial properties of NaOCl (29,34). Few endodontic regeneration case reports have demonstrated successful root canal disinfection using irrigation solutions without supplementary inter-appointment medicaments (5,6).…”

The use of calcium hydroxide, antibiotics and biocides as antimicrobial medicaments in endodontics

“…56,[96][97][98][99][100][101] The positively-charged molecules of CHX can adsorb onto dentine and prevent microbial colonization on the dentine surface for some time beyond the actual medication period 101 -this may inhibit re-infection of the canal subsequent to treatment 98 during that time period. CHX is retained in root canal dentine in levels sufficient to exert antimicrobial effects for at least 12 weeks.…”