Antimicrobial activity of root canal filling pastes used in pediatric dentistry

This study evaluated the antimicrobial activity of root canal filling pastes commonly used in primary teeth: iodoform paste, zinc oxide-eugenol (ZOE), and analytical grade calcium hydroxide (Ca[OH]₂). The materials were evaluated in the following 6 combinations: iodoform paste (Rifocort [prednisolone + rifampicin] + iodoform + camphorated paramonochlorophenol); zinc oxide + eugenol in a proportion of 1:3; zinc oxide + eugenol in a proportion of 1:5; Ca(OH)₂ + water; iodoform paste + ZOE (1:3) + Ca(OH)₂; and ZOE (1:3) + Ca(OH)₂. Chlorhexidine gel (0.2%) served as the positive control. A commercial strain of Enterococcus faecalis (ATCC 25175) was plated in petri dishes containing 10 mL of brain-heart infusion agar culture medium with a hole in the center. The filling pastes (3 g) were manipulated and inserted in the hole. The plates were incubated at 37°C for 48 hours, and then the inhibition zone associated with each paste was measured. The experiments were carried out in triplicate (n = 3 per group). The data were submitted to analysis of variance and Tukey tests (P < 0.05). Iodoform paste resulted in the largest mean (SD) inhibition zone, 7.06 (0.74) mm. The smallest was obtained with Ca(OH)₂ + water, the mean (SD) of 0.00 (0.00) mm indicating that these specimens did not form an inhibition zone. The ZOE pastes in proportions of 1:3 and 1:5 resulted in statistically similar mean (SD) inhibition zones of 1.86 (0.50) and 1.30 (0.18) mm, respectively (P > 0.05). Of the test materials, the combination of iodoform paste + ZOE + Ca(OH)₂ presented the second largest inhibition zone, 6.27 (3.08) mm, significantly different from that of the non-iodoform pastes (P < 0.05). It can be concluded that iodoform paste, alone or in combination with ZOE + Ca(OH)₂, demonstrates high antimicrobial activity, while the combination of ZOE + Ca(OH)₂ demonstrates moderate activity.