# Characterization and Crystallinity of Two Bioactive Sealers: Qualitative and Quantitative Analysis
## 4 Discussion
However, it was only detected in Cerafil after immersion in PBS and was at a very low intensity in AH-26 (Figure 1C,D). Similarly, Endosequence had a significantly greater value of the PO4\({}^{3-}\)/Amide I FTIR ratio, which was increased by immersion either in water or PBS in both Endosequence and Cerafil. However, the CO3\({}^{2-}\)/PO4\({}^{3-}\)\({}_{\text{FIR}}\) ratio decreased in both Endosequence and Cerafil after immersion, particularly in PBS. This may be attributed the increase in the phosphate amount by PBS and/or the decrease in the amount of carbonate by the immersion solution. This was confirmed by XRD, as the calcium phosphate percentage was greater in Endosequence (30.6%) than in Cerafil (11.7). After immersion in PBS, the formed hydroxyapatite percentage was greater in Endosequence (32.4.7%) than Cerafil (21.4%), but none was detected in AH-26 (Figure 4). It was found that the increase in the surface carbonated phase would increase the material's brittleness [42] and wearing property. Calcium carbonate (calcite) is formed during the CaSi hydration process in the presence of water. Although it is essential for obtaining alkaline pH through the activation of portlandite (CaHO) formation, the greatest carbonate phase may lead to the formation of the decalcification of C-S-H with a poor calcium phase [43]. It was confirmed by XRD that the calcite percentage was greater in Endosequence (11.2%) after immersion than in Cerafil (4.9%). So, the carbonate phase may reduce the crystallinity index of Endosequence more than that of Cerafil. The crystallinity of materials was influenced by their crystal size in [33], and the intensity of the crystalline phase percentage was related to the amorphous phases that can be calculated from the XRD spectra [27]. The crystal size has a critical role in setting time and, in turn, crystal precipitation after the setting reaction. It was suggested that smaller or fine particles can adhere well to each other, forming a crystalline structure [44]. After immersion in PBS, the ClXRD of Cerafil was significantly greater than that of Endosequence. This may be attributed to their smaller particle size. However, AH-26 had a significantly larger particle size, so it decreased its ClXRD (Figure 6B,C). This finding is confirmed by SEM images, as the precipitated cauliflower-like hydroxyapatite crystals induced by Cerafil were bigger than those of Endosequence (0.06-0.07 and 0.05-0.06 \(\upmu\)m, respectively), while the latter was separated by small spaces and collagen-like structure (Figure 2(EP)). The crystal size and degree of crystallinity are indicative of the Ca/P ratio, which is also influenced by CaCO\({}_{3}\)[45]. The crystallinity of hydroxyapatite can be calculated based on several parameters: from Raman spectra, based on an FWHM of 960 cm\({}^{-1}\) (CI\({}_{\text{Raman}}\)) [27]; from XRD (CI\({}_{\text{XRD}}\)), based on the highest intensity of the most crystalline phase; and from FTIR, based on split doublet \(v_{4}\) phosphate bands at \(\approx\)600 and 560 cm\({}^{-1}\) (CI\({}_{\text{FTIR}}\)) [28; 29; 30]. Due to the various parameters, the result may be different. In XRD spectra, the difference in intensity is related to the sharpness of the peaks, which corresponds to the crystalline phase of the sample. Samples with sharp peaks showed a high content of crystalline phase, and the sample with a less sharp peak showed a high content of amorphous phase. After immersion in PBS, there was no significant difference between the CI\({}_{\text{Raman}}\) and CI\({}_{\text{FTIR}}\) of both sealers, while the greatest significant value of Cl\({}_{\text{XRD}}\) was recorded in Cerafil. All parameters for crystallinity indices were dependent on phosphate peaks in all spectra, particularly after hydroxyapatite precipitation. It was detected in both bioceramic sealers, but it was not detected in AH-26. As the crystal size of hydroxyapatite increases, the \(v_{4}v\text{PO}_{4}\text{{}^{3-}}_{\text{FTIR}}\) (603 and 565 cm\({}^{-1}\)) peak increases [46].