# Characterization and Crystallinity of Two Bioactive Sealers: Qualitative and Quantitative Analysis
## 4 Discussion
In a previous study, the physical properties of Cerafil in relation to its clinical application, including setting time, solubility, pH, and surface structure, were compared with those of Endosequence as a function of bioactivity after immersion in PBS. Although both sealers successfully formed hydroxyapatite, Endosequence gained more weight than Cerafil. Furthermore, both sealers had different Ca/P ratios, which may be attributed to their variable calcium and phosphate content. It was previously reported in a former study that the Ca/P ratio was decreased after immersion in PBS, with an insignificant difference between Cerafil (2.06 \(\pm\) 0.43) and Endosequence (2.1 \(\pm\) 0.04) [11]. This finding may be attributed to the high phosphate content of the surrounding solution (PBS). This result may affect the hardness and crystallization of hydroxyapatite formation. For this reason, this study was focused on the factors affecting the crystallization of both Cerafil and Endosequence. The degree of hardness and density of the material after bioactivity can be evaluated based on several parameters, including the degree of crystallinity and mineral maturity, that affect the perfection of the formed layer. The literature is limited in this area, and further studies are required to evaluate this characteristic concept in root canal sealers. This study is the first publication that focuses on the crystallinity characterization of Cerafil compared with Endosequence after bioactivity in qualitative and quantitative assessments. Concerning the qualitative evaluation, the chemical composition groups were identified by Raman and FTIR spectroscopy, while the phase composition was identified by XRD analysis. It was revealed that both raw Cerafil and Endosequence have a relatively similar composition with varying percentages. The difference in their composition was detected using their XRD spectra; raw Cerafil contained calcium sulfate anhydrite, and in contrast, the raw Endosequence spectra contained calcium di-aluminum oxide. This finding was supported by previous EDX analysis, whereby Cerafil showed sulfur, while Endosequence showed aluminum [11]. Both sulfur and aluminum are considered during the setting reaction phase to accelerate the hydration reaction of calcium silicate [40]. The setting reaction and material composition can affect the mineral maturity and crystallinity of the full set material. The setting reaction of Cerafil was faster than that of Endosequence [11]; however, Endosequence may undergo incomplete setting before immersion [8]. Furthermore, the crystallinity can be affected by the amount of calcium silicate hydrate (C-S-H). XRD revealed greater C-S-H in Cerafil (26.3%) than in Endosequence (20.2%). Wollastonite (CaOSSi), which was detected in both bioceramic sealers, is a structure rich in calcium chains and can form an outer layer containing CaO/PO, identical to a hydroxyapatite-like material, that can be identified by XRD [23]. It was suggested that the AL2O3 addition of Endosequence to CaSi promotes stability in the set material and increases its crystallinity [41], despite its deficient (incomplete) setting reaction before immersion [8; 16]. Regarding the quantitative evaluation, mineral maturity can be calculated based on the area ratio of the apatite/non-aquitic phosphate band of the Raman spectra (1030/1110\({}_{\text{Raman}}\) cm\({}^{-1}\)), PO4/Amide I FTIR and CO3\({}^{2-}\)/PO4\({}^{3-}\)\({}_{\text{FIR}}\)[19; 26; 28]. The area ratio of 1030/1110\({}_{\text{Raman}}\) cm\({}^{-1}\) had the greatest significant values for Endosequence, while the lowest significant values were recorded for AH-26. This finding may be attributed to the decrease in the intensity of the non-aquitic band (1110 cm\({}^{-1}\)) in the bioceramics after immersion (Figure 1A-C). Moreover, an apatite phosphate band at 1030 cm\({}^{-1}\) was present, in the raw Endosequence spectra, which became more intense after immersion in PBS (Figure 1B).