# Evaluation of pH and Optical Properties of Dual Ringe HEDP Irrigating Solution
## 3 Results
### Spectral Analysis
#### 3.2.2 Spectral Properties of Endodontic Irrigants  
As shown in Figure 2, the transmission values of the different irrigating solutions in the VL and NIR ranges mostly followed that of DW, with similar decrease and increase curves in the NIR range from 915 nm to 1100 nm. The most notable differences were  
Figure 2: Transmission values of distilled water, NaOCl, EDTA, Dual Rinse HEDP, Dual Rinse HEDP + NaOCl, citric acid, and chlorohexidine at different wavelengths of ultraviolet, visible light, and near-infrared regions. Abbreviations: UV—ultraviolet; VL—visible light; NIR—near infrared; C—ultraviolet C; B—ultraviolet B; A—ultraviolet A DW—distilled water; NaOCl—sodium hypochlorite; EDTA—ethylenediamineiterate acid; HEDP—1-hydroxyethylidene 1,1-disphosphonate; HEDP + NaOCl—1-hydroxyethylidene 1,1-disphosphonate + sodium hypochlorite; CA—citric acid; CHX—chlorohexidine digluconate. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Irrigating Solution**} & \multicolumn{5}{c}{**Wavelength Region of the Spectrum**} \\ \cline{2-6}  & **UVC** & **UVB** & **UVA** & **VL** & **NIR** \\ \hline DW & 0.14 \(\pm\) 0.33 \({}^{\ddagger}\) & 0.22 \(\pm\) 0.04 \({}^{\ddagger}\) & 0.34 \(\pm\) 0.02 \({}^{\ddagger}\) & 0.39 \(\pm\) 0.04 \({}^{\ddagger}\) & 1.11 \(\pm\) 0.65 \({}^{\ddagger}\) \\ NaOCl & 24.66 \(\pm\) 13.85 \({}^{\ast}\) & 38.67 \(\pm\) 0.84 \({}^{\ast}\) & 12.51 \(\pm\) 14.56 \({}^{\ast,\ddagger}\) & 0.04 \(\pm\) 0.05 \({}^{\ast,\ddagger}\) & 0.73 \(\pm\) 0.65 \({}^{\ast}\) \\ HEDP & 27.52 \(\pm\) 12.81 \({}^{\ast,\ddagger}\) & 0.47 \(\pm\) 0.10 \({}^{\ast,\ddagger}\) & 0.11 \(\pm\) 0.08 \({}^{\ast,\ddagger}\) & 0.02 \(\pm\) 0.03 \({}^{\ast,\ddagger}\) & 0.66 \(\pm\) 0.63 \({}^{\ast}\) \\ HEDP + NaOCl & 20.98 \(\pm\) 14.18 \({}^{\ast,\ddagger}\) & 9.49 \(\pm\) 1.27 \({}^{\ast,\ddagger}\) & 1.43 \(\pm\) 1.70 \({}^{\ddagger,\ddagger}\) & 0.04 \(\pm\) 0.04 \({}^{\ast,\ddagger}\) & 0.68 \(\pm\) 0.63 \({}^{\ast}\) \\ EDTA & 28.85 \(\pm\) 14.13 \({}^{\ast}\) & 0.40 \(\pm\) 0.15 \({}^{\ast,\ddagger}\) & 0.10 \(\pm\) 0.06 \({}^{\ast,\ddagger}\) & 0.02 \(\pm\) 0.04 \({}^{\ast,\ddagger}\) & 0.71 \(\pm\) 0.63 \({}^{\ast}\) \\ CA & 24.59 \(\pm\) 16.20 \({}^{\ast}\) & 0.31 \(\pm\) 0.12 \({}^{\dagger}\) & 0.05 \(\pm\) 0.04 \({}^{\ast,\ddagger}\) & 0.02 \(\pm\) 0.04 \({}^{\ast,\ddagger}\) & 0.68 \(\pm\) 0.59 \({}^{\ast}\) \\ CHX & 39.40 \(\pm\) 1.20 \({}^{\ast}\) & 35.55 \(\pm\) 7.31 \({}^{\ddagger}\) & 0.70 \(\pm\) 1.84 \({}^{\ast,\ddagger}\) & 0.03 \(\pm\) 0.04 \({}^{\ast,\ddagger}\) & 0.75 \(\pm\) 0.65 \({}^{\ast}\) \\ \hline \hline \end{tabular}  
* indicates statistically significant difference (\(p<0.05\)) compared to distilled water; \({}^{\daggeragger}\) indicates statistically significant difference (\(p<0.05\)) compared to ethylenediamineiterateacid. Abbreviations: UV—ultraviolet; VL—visible light; NIR—near infrared; DW—distilled water; NaOCl—sodium hypochlorite; EDTA—ethylenediamineiterate acid; HEDP—1-hydroxyethylidene 1,1-disphosphonate; HEDP + NaOCl—1-hydroxyethylidene 1,1-disphosphonate + sodium hypochlorite; CA—citric acid; CHX—chlorohexidine digluconate.  
\end{table} 
Table 3: Mean values of absorption coefficients (\(\alpha\)) of distilled water and endodontic irrigants at different wavelengths of ultraviolet, visible light, and near-infrared regions. Results are presented as mean \(\pm\) standard deviation (SD). observed in UV regions, with all solutions showing significantly lower transmission values at different ranges of the UV spectrum compared to DW. Each endodontic irrigating solution presented a high absorption coefficient in the UVC range of the spectrum, with the mean \(\alpha\) values showing a statistically significant difference to DW (Table 3; \(p<0.05\)). NaOCl presented peak absorption at the start of the spectrum around 205 nm (\(\alpha\) = 39.21 cm\({}^{-1}\)), followed by a strong decrease at 230 nm (\(\alpha\) = 3.62 cm\({}^{-1}\)) and an increase to a second peak at 270 nm (\(\alpha\) = 39.59 cm\({}^{-1}\)).