## 1 Introduction  
The oral cavity naturally contains various species of microorganisms that can invade the root canal system and cause endodontic infections [1]. These infections are associated with pulp necrosis resulting from caries, trauma, iatrogenic damage, and periodontal disease, known as primary infections, or they may occur in teeth that have undergone previous root canal treatment, known as secondary/resistant infections [2]. At least 500 microbial species, mostly bacteria, are linked to endodontic infections, including primary, secondary, persistent, and extraradicular infections. Some fungal species are also present [3]. Microorganisms can organize into a biofilm that adheres to the dental walls of the root canal system [4]. In biofilm form, bacteria become more resistant than their planktonic counterparts [5]. Around 20 to 30 species of oral microorganisms are frequently found in primary infections, the majority being strict anaerobic and Gram-negative bacteria, along with some Gram-positive bacteria. In secondary and persistent infections, microbial diversity is more restricted if the previous endodontic treatment was adequate. However, if the treatment was inadequate, the microbiota resembles that of a primary infection in both load and diversity [1]. _Enterococcus faecalis_ is a Gram-positive, facultative anaerobic, fermentative coccus. Its shape is ovoid, ranging from 0.5 to 1 \(\upmu\)m in diameter [6]. The presence of E. faecalis is strongly associated with secondary/persistent root canal infections, being the most prevalent bacterium in cases of apical periodontitis in previously treated teeth [7]. Its ability to survive in the root canal system despite conventional antimicrobial protocols is attributed to several key mechanisms. One of the primary factors is its ability to invade dental tubules and adhere to collagen, allowing it to persist in areas inaccessible to irrigants and mechanical instrumentation. Additionally, it has the capacity to withstand inhospitable conditions, such as nutrient scarcity and the highly alkaline environment of the root canal following endodontic treatment [8]. This resistance is partly due to its proton pump activity, which helps maintain intracellular pH homeostasis. _E. faecalis_ was detected in different types of endodontic infections, including chronic asymptomatic periapical lesions, acute apical periodontitis, acute dentoalveolar abscesses, and teeth requiring retreatment due to chronic asymptomatic periapical lesions. Furthermore, _E. faecalis_ was significantly more associated with asymptomatic cases, and was present in 33% of asymptomatic periadicular lesions and 67% of retreatment cases with persistent infections, highlighting its strong association with failed endodontic treatments [9]. Commonly, sodium hypochlorite (NaOCI) is used as an endodontic irrigant, it exhibits antimicrobial efficacy against _E. faecalis_, antiendotoxin activity against its lipoteichoic acid (LTA), and dissolving capacity [10]; however, it has serious contraindications in endodontics represented by its cytotoxicity, genotoxicity, and the potential for allergic reactions in some patients [10]. Thus, the search for alternative irrigants in endodontics is constant. The use of herbal medicines is increasing as these are valuable sources of bioactive molecules with antimicrobial properties and biocompatibility [11]. Studies have reported synergistic effects when combining herbal medicines, revealing promising potential for new therapeutic products [12; 13; 14]. _Nasturtium officinal W.T. [PERSON]_, commonly known as watercress, is a perennial plant from the Brassicaceae family, native to West Asia, Europe, India, and Africa, but cultivated in various regions worldwide [15]. _N. officinal_ contains flavonoids, phenolic acids, and glucosinolates, which, through natural hydrolysis by the enzyme myrosinase, produce isothiamate (ITC) compounds [16]. It was added to calcium hydroxide to improve its efficiency against _Candida albicans_ as intracanal predicament, and it was effective [17].