Antimicrobial Efficacy and Dentinal Tubule Penetration of the Photosensitizer Acai ( <i>Euterpe Oleracea</i> Martius): A New Approach in Antimicrobial Photodynamic Therapy in Endodontics

<b><i>Objectives:</i></b> This study evaluated in vitro the antimicrobial efficacy and penetration depth of acai as a photosensitizer (PS) using or not using passive ultrasonic irrigation (PUI). <b><i>Background:</i></b> Acai extracts have attracted attention as potential photosensitizing molecules, especially because of their natural origin. <b><i>Methods:</i></b> A total of 150 mandibular molars were instrumented with the ProTaper Next system. Ninety canals were inoculated with standard strains of <i>Enterococcus faecalis</i> for 21 days and randomly divided into six groups (<i>n</i> = 15): AC: acai; MB: methylene blue; BL: blue laser irradiation; RL: red laser irradiation; AC+BL: acai irradiated with blue laser; and MB+RL: methylene blue irradiated with red laser. Microbiological samples were collected from the canals before (no treatment group) and after the procedures described for each group. Dentinal tubule penetration was assessed in the remaining 60 canals, randomly divided into four groups (<i>n</i> = 15): MB; MB+PUI; AC; and AC+PUI. The PSs MB and acai were placed into the canals and agitated or not with an ultrasonic tip. The roots were sectioned and analyzed under a stereomicroscope. The results were analyzed using the Kruskal-Wallis test and analysis of variance (Tukey's test). <b><i>Results:</i></b> The greatest reduction in microbial counts occurred in the MB+RL, AC+BL, and AC groups (<i>p</i> < 0.0001). The amount of bacteria after the procedures in log colony forming units (CFU)/mL was MB+RL: 3.59, AC+BL: 5.32, and AC: 5.24. There was no significant difference in penetration depth between MB and acai, using or not using PUI, in the coronal, middle, or apical thirds (<i>p</i> > 0.05). <b><i>Conclusion:</i></b> Acai can be used as an antimicrobial agent for disinfection of the root canal, showing similar results when photoactivated or not.