Antimicrobial efficacy of alternative root canal disinfection strategies: An evaluation on multiple working models

Researching disinfection strategies is pivotal because effectively eliminating bacteria and their byproducts during root canal treatment (RCT) remains a challenge. This study investigated the antimicrobial efficacy of natural antimicrobial compounds, propolis (PRO) and copaiba oil-resin (COR), compared to conventional agents in Endodontics. Antimicrobials were tested against endodontic pathogens via macrodilution with standardized inoculums to determine the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). Biofilm killing efficacy were performed using two dual-species biofilms: Enterococcus faecalis (ATCC 29212) and Streptococcus mutans (ATCC 20523) and Streptococcus oralis (J22) and Actinomyces naeslundii (T14V-J1) grown on dentine discs. At the intratubular level (dentine cylinders), dentine tubule contamination was performed with E. faecalis and S. mutans. The specimens were exposed to antimicrobials to simulate their use at different sets of RCT and bacterial viability was quantified using Live/Dead staining via confocal laser scanning microscopy (CLSM). Biofilm characteristics and immediate removal of S. oralis and A. naeslundii biofilm model were evaluated employing optical coherence tomography (OCT) and CFU/mL counting. Statistical tests were applied according to data distribution for each analysis (α=0.05). Macrodilutions showed different effects against endodontic pathogens. Direct contact and intratubular analysis showed that PRO and COR promoted disinfection like conventional agents (p > 0.05). According to OCT analysis, PRO and COR showed similar biofilm reduction after immediate contact (p < 0.05). CFU/mL counting showed decontamination (p < 0.05) after using natural and conventional agents. PRO and COR showed antimicrobial effects, indicating their suitability as complementary approaches in RCT to eliminate as much microbial load as possible.