Antibiotic Resistance Decreases the Efficacy of Endodontic Filling Pastes for Root Canal Treatment in Children's Teeth

The antibacterial efficacy of antimicrobial filling pastes (AFP) used in the root canal treatment of primary teeth has been widely reported. However, antibiotic resistance as an emerging global problem could impact their current efficacy. This study aimed to evaluate the efficacy of two common AFP on susceptible or resistant bacteria isolated from primary necrotic molars. Microbiological samples were obtained and cultured from the root canals of 34 children. In total, 96 colony-forming units were obtained to determine their resistance to tetracycline, rifampicin, and chloramphenicol. They were identified as S. mutans or E. faecalis using polymerase chain reaction. The antimicrobial activity of CTZ paste (chloramphenicol, tetracycline, zinc oxide, and eugenol) and Guedes-Pinto modified (GPM) paste (rifampicin, prednisolone, iodoform, and camphorated paramonochlorophenol) were tested against the identified and selected microorganisms. Larger size inhibition zones were observed in both species when the tested strains were susceptible to the antibiotics in the AFP preparation. The efficacy of AFP containing antibiotics depends on the antibiotic resistance profile of the strain. Antibiotic resistance and its effect on the AFP were shown, which calls into question the use of simplified endodontic techniques that depend on antibiotics, since in these cases these techniques could not clinically eliminate resistant bacteria from the root canal.