# Evaluation of pH and Optical Properties of Dual Ringe HEDP Irrigating Solution
## 4 Discussion  
As previously noted, irrigation presents a crucial step in endodontic procedures that ensures the successful outcome of the treatment [1,2]. It usually involves the alternating use of antiseptic and chelating solutions to ensure antimicrobial and tissue-dissolving effects together with the removal of the smear layer. Considering potential chemical interactions, some of which are deemed potentially dangerous, care should be taken to prevent the mixing of different solutions by intercepting the procedure with saline or distilled water [32]. In 2005, the concept of continuous chelation emerged, introducing the possibility of combining NaCl with a weak chelating agent, such as HEDP [12]. Dual Rinse HEDP presents a versatile endodontic irrigation product of etidronic acid. It can be dissolved in distilled water to create a 9% HEDP solution, acting as a mild chelator. Alternatively, when dissolved in NaCl, it yields a solution with both antiseptic and chelating properties, suitable for continuous chelation and simplifying the irrigation procedure [13]. While the combination of NaCl and HEDP has shown promising results in terms of antimicrobial and chelating effects, it is noteworthy that certain aspects of this innovative irrigating solution, such as its pH values, remain relatively unexplored. Understanding the pH characteristics is crucial as it directly influences the chemical environment within the root canal. Additionally, the optical properties of Dual Rinse HEDP in combination with NaCl are of significant interest, particularly in the context of laser irrigation. However, limited information is currently available on these aspects, warranting further investigation to comprehensively assess the irrigants' properties and potential implications for clinical use. The null hypothesis of the study is partially rejected. Although there were differences in pH values between all irrigating solutions, optical characteristics were significantly different only between Dual Rinse HEDP solutions and some of the other tested irrigants at specific wavelengths. The pH of endodontic irrigants is a critical parameter that directly impacts their efficacy in dissolving tissue, removing the smear layer, providing antimicrobial action, ensuring biocompatibility, preserving dentin, and contributing to overall treatment success [16]. Clinicians should carefully consider the pH of irrigants as part of the decision-making process when selecting and using these solutions during endodontic procedures. The mechanism of action of NaCl involves its hydrolysis to hypochlorous acid and its further dissociation into mainly hypochlorite and hydrogen ions. This reaction is reversible and is highly dependent on the pH of the solution [33]. The antimicrobial effectiveness of NaCl is primarily attributed to its elevated pH. At high pH, it disrupts the integrity of the cytoplasmic membrane, resulting in irreversible enzymatic inhibition, disturbances in cellular metabolism, and the degradation of phospholipids through lipid peroxidation processes [34]. Our findings align with previous research regarding the highly alkaline nature of NaCl, supporting its well-established role as an effective antimicrobial agent in endodontics [34]. Another antimicrobial agent in the focus of our study was CHX. CHX is a wide-spectrum antiseptic that, due to its cationic nature, is capable of binding to the negatively charged surfaces. It can bind to bacteria, damaging the outer layers of the cell wall, or to surfaces of the oral mucosa or hydroxyapatite of dentine, leading to substantive antimicrobial activity [35]. In our study, CHX presented a pH of 6.25, which is in range for its optimal antimicrobial activity (the range of 5.5 to 7.0) reported previously [36]. While both EDTA and CA achieve their mechanisms of action through the chelation of calcium ions from dentine, they differ in pH levels. Specifically, the CA in our study possessed a highly acidic nature with a pH of 1.5.