Antimicrobial activity of root canal filling materials for primary teeth

Objective: to evaluate “in vitro” the antimicrobial activity of five root filling materials for primary teeth against five standard microorganisms' strains. Methods: The following root canal filling pastes were evaluated: CTZ (chloramphenicol, tetracycline, zinc oxide and eugenol), ZOE (zinc oxide and eugenol), L&C^® (calcium hydroxide), Guedes-Pinto (iodoform, camphorated fenol and Rifocort^®) and 3Mix (metronidazole, ciprofloxacin and minociclyne). Agar diffusion method (ADM) and broth-dilution technique (BDT) were performed to determine the inhibition zone and the minimum inhibition concentration (MIC). Test microorganism strains used were: Enterococcus faecalis ATCC 29212(G1), Staphylococcus aureus ATCC 25923(G2), Streptococcus mutans ATCC 25175(G3), Escherichia coli ATCC 25922(G4) and Pseudomonas aeruginosas ATCC 27593(G5). For ADM, bacterial suspensions were spread with a swab on Mueller-Hinton agar plates and freshly mixed filling pastes were placed into 4mm wells punched in the agar. The plates were incubated (37°C, 48h). The diameters of the inhibition zones around the filling materials were measured. For BDT, 0.1ml of each paste was diluted in 5 ml of Mueller-Hinton broth and tested in a two-fold dilution series ranging from 1/2 to 1/128. The MIC was determined after 24h incubation. Results: A statistically significant association between the diameters of the inhibition zones and the type of filling material was found for all tested microorganisms (Kruslkall-Wallis test, p values: G1=0.003; G2=0.005; G3=0.013; G4=0.004 e G5=0.004). The pastes containing antibiotics, 3Mix and CTZ, showed the largest inhibition zones and the lowest MIC for all bacterial strains. Using ADM and BDT, no antimicrobial activity was detected for L&C^®. The ZOE and Guedes-Pinto pastes inhibited the growth of all test organisms at various levels. Conclusion: All tested materials, with the exception of the calcium hydroxide paste, possess antimicrobial activity but CTZ and 3 Mix were more potent bacterial growth inhibitors.