# Evaluation of pH and Optical Properties of Dual Ringe HEDP Irrigating Solution
## 4 Discussion
Electronic transitions involve the movement of electrons between different energy levels within atoms or molecules, typically induced by the absorption of photons. These transitions may result from the excitation of electrons from the non-bonding n and bonding \(\pi\) orbitals to the \(\pi^{\star}\) antibonding orbitals, leading to the absorption of photons with wavelengths corresponding to the UV range [48]. Interestingly, HEDP demonstrated comparable absorption to EDTA and CA, while the combination of HEDP + NaOCl presented a complex absorption profile, similar to that of NaOCl. This complexity in the absorption profile may arise from the interaction between the molecules of HEDP and NaOCl, leading to changes in the electronic structure and resulting in a unique absorption spectrum. NaOCl was observed to cause molecular electronic transitions when mixed with other substances, as previously shown in combination with EDTA [49]. In the UVB region, most solutions showed decreasing absorption values, except NaOCl and CHX, which maintained high absorption coefficients. Previous research reported that CHX absorbs light with the wavelength of 280 nm (UVB range), while it does not absorb light in the UVA range of the spectrum [50]. In fact, most solutions, including CHX, generally exhibited low absorption in the UVA region in our study. The only exceptions were NaOCl and HEDP + NaOCl, which displayed higher absorption values around 316 nm. High absorption values for NaOCl have been shown previously in wavelengths between 250 nm and 350 nm, with peak values at around 300 nm [31; 51]. These absorption peaks can be attributed to specific electronic transitions occurring within the hypochlorite ion, leading to the absorption of photons in the UV region. Specifically, transitions involving the oxygen-chlorine bond within the hypochlorite ion and transitions from n orbitals to \(\pi^{\text{e}}\) orbitals may contribute to the observed absorption peaks [48]. However, absorption is inversely related to the decomposition of NaOCl, as products of its reduction, such as hydroxyl ions, do not absorb energy in this spectral region [51]. In clinical settings, NaOCl decomposes in the presence of organic matter, inflammatory exudate, tissue remnants, and microbial biomass in the root canal [35]. This implies that the absorption profiles of solutions can be different in clinical settings when both irrigants and lasers interact with other constituents of the root canal, necessitating further research. Excimer lasers such as argon fluoride, krypton fluoride, and xenon chloride operate in the UV spectrum at wavelengths of 193, 248, and 308 nm [52; 53; 54]. They have been studied for various applications, including refractive eye surgery [55], dermatological procedures [56], and dentistry [54], because of their ability to ablate tissues with minimal heat. The effects of excimer lasers are achieved when high-energy UV photons are absorbed by the target material, which leads to the formation of excited states and the generation of reactive chemical species through a photochemical process. Reactive chemical species contribute to the breaking of molecular bonds and the removal of material, resulting in ablation. Excimer lasers are also known for low absorption in water [57]. Conversely, our findings suggest high absorption values for NaOCl, HEDP + NaOCl, and CHX in all wavelengths utilized by excimer lasers, making them potential candidates for use in LAI. However, one limitation could be the reported degradation of chemical compounds by UV light [58], thus leaving the use of excimer lasers in LAI, and their effects on irrigating solutions, to be studied in the future. Our study revealed that all tested irrigating solutions, as well as DW, showed little to no absorption in the VL range of spectrum. These results are in line with the previous findings of [PERSON] et al. [31] and [PERSON] et al. [59]. However, unlike in our study, [PERSON] et al.