Comparative Antimicrobial and Oxidative Damage of Indocyanine Green, Methylene Blue, and Curcumin on Dual-Species Biofilms of Enterococcus faecalis and Candida albicans

Failure of the endodontic treatment is often associated with persistent polymicrobial biofilms, particularly those involving <i>Enterococcus faecalis</i> (<i>E. faecalis)</i> and <i>Candida albicans</i> (<i>C. albicans</i>), which display synergistic pathogenicity and resistance to standard disinfection methods. This in vitro study compared the antimicrobial activity and oxidative damage induced by indocyanine green (ICG)-mediated laser ablation (LA) with that produced by antimicrobial photodynamic therapy (aPDT) using methylene blue (MB) or curcumin (CUR) in root canals infected with dual-species biofilms. The samples were divided into five experimental groups (n = 20): Group A-Methylene Blue + Red Laser (RL), Group B-Curcumin + Blue LED (BL), Group C-Indocyanine Green + Infrared Diode Laser (DL), Group D-saline solution (Negative Control-NC), Group E-2.5% sodium hypochlorite (Positive Control-PC). One hundred treated bovine incisors (20 per group) were analyzed for microbial viability (colony-forming unit (CFU/mL)), the metabolic functionality of biofilms was assessed through the 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium hydroxide (XTT) based reduction method, and oxidative stress markers, including Thiobarbituric Acid Reactive Substances (TBARS), protein carbonyl content, total oxidant capacity (TOC), and total protein levels. All experimental treatments significantly reduced microbial load compared to the negative control (<i>p</i> < 0.05), with ICG achieving the greatest reduction. ICG also induced the highest levels of oxidative stress across all parameters (<i>p</i> < 0.05). These findings suggest that LA with ICG is more effective than aPDT with MB or CUR, achieving disinfection outcomes comparable to those of 2.5% sodium hypochlorite, and warrant further investigation in complex clinical models.