# Evaluation of pH and Optical Properties of Dual Ringe HEDP Irrigating Solution
## 3 Results
### Spectral Analysis
#### 3.2.2 Spectral Properties of Endodontic Irrigants
Similar absorption values were observed for Dual Rinse HEDP at the beginning of the UVC range with peak absorption at 210 nm (\(\alpha\) = 34.32 cm\({}^{-1}\)); however, going to the UVB range of the spectrum, a strong decrease was observed. HEDP showed no statistical difference to EDTA and CA (\(p>0.05\)) but presented statistically significant higher mean \(\alpha\) values compared to DW and NaOCl (\(p<0.05\)). HEDP + NaOCl presented high absorption at the start of the spectrum, reaching a peak around 210 nm (\(\alpha\) = 39.21 cm\({}^{-1}\)), followed by strong decrease reaching the lowest absorption at 255 nm (\(\alpha\) = 4.46 cm\({}^{-1}\)), after which the absorption coefficient rose to the end of the UVC region. The mean \(\alpha\) values for HEDP + NaOCl showed a statistically significant difference to DW and EDTA (\(p<0.05\)) but no difference to NaOCl (\(p>0.05\)). EDTA and CA showed similar \(\alpha\) values to each other and statistically significant higher absorption values compared to DW (\(p<0.05\)), with major peaks at around 240 nm for EDTA (\(\alpha\) = 39.59 cm\({}^{-1}\)) and around 230 nm for CA (\(\alpha\) = 39.21 cm\({}^{-1}\)). After initial high absorption, both solutions presented decreased absorption values going to the UVB range of spectrum. Unlike all previous solutions, CHX presented constant high absorption values throughout the UVC region (mean \(\alpha\) = 39.40 cm\({}^{-1}\)) with only minor oscillations. The UVB region of the spectrum was characterized by decreasing absorption values for all endodontic solutions, except NaOCl and CHX, which remained constantly high throughout (mean \(\alpha\) = 38.67 cm\({}^{-1}\) and \(\alpha\) = 35.56 cm\({}^{-1}\), respectively). All endodontic irrigants, except CA, presented statistically significant higher \(\alpha\) values compared to DW (\(p<0.05\)). However, both EDTA and HEDP, while not showing a statistical difference between them, showed statistically significant lower absorption values in the UVB region compared to NaOCl (\(p<0.05\)). On the contrary, HEDP + NaOCl showed significantly higher absorption values compared to EDTA (\(p<0.05\)), with a peak value of \(\alpha\) = 10.72 cm\({}^{-1}\) at around 290 nm. Still, its absorption coefficient was significantly lower to that of NaOCl (\(p<0.05\)). It should be noted that CHX presented a significant decrease in absorption at the end of the UVB region of the spectrum. In the UVA region, the absorption coefficients were low in almost all tested solutions, with the mean \(\alpha\) values being lower than in DW. Only considerably higher absorption values were observed at the beginning of the UVA spectrum for NaOCl and HEDP + NaOCl, showing values of \(\alpha\) = 39.21 cm\({}^{-1}\) and \(\alpha\) = 6.32 cm\({}^{-1}\) at 316 nm, respectively, and dropping to \(\alpha\) = 0.24 cm\({}^{-1}\) and \(\alpha\) = 0.12 cm\({}^{-1}\) at 400 nm. The trend of low-to-no absorption of the irrigant solutions was continued through the VL range of the spectrum. All tested solutions presented significantly lower absorption values (mean values of \(\alpha\leq 0.04\) cm\({}^{-1}\)) compared to DW (\(p<0.05\)). Only minor peaks were observed at 757 nm for NaOCl (\(\alpha\) = 0.11 cm\({}^{-1}\)), at 738 nm for HEDP (\(\alpha\) = 0.06 cm\({}^{-1}\)), at 737 nm for HEDP + NaOCl (\(\alpha\) = 0.10 cm\({}^{-1}\)), at 738 nm for EDTA (\(\alpha\) = 0.11 cm\({}^{-1}\)), at 739 nm for CA (\(\alpha\) = 0.06 cm\({}^{-1}\)), and at 741 nm for CHX (\(\alpha\) = 0.12 cm\({}^{-1}\)). All tested solutions showed significantly lower mean absorption values compared to DW (\(p<0.05\)) and no statistically significant difference between them (\(p>0.05\)) in the NIR region of the spectrum. Interestingly, all tested solutions presented a strong increase in absorption from around 940 nm, all reaching a similar peak absorption at 975 nm followed by a decrease in higher wavelengths.