# Characterization and Crystallinity of Two Bioactive Sealers: Qualitative and Quantitative Analysis
## 4 Discussion  
When discussing the biological properties of dental materials, there is some terminology to consider. \"A material's capacity to work in a particular application with a suitable host response\" is the definition of biocompatibility. The Endosequence bioceramic-based root canal sealer was first introduced in endodontics as a pre-mixed injectable calcium silicate sealer containing tri- and dicalcium silicate, calcium phosphate, calcium hydroxide, and zirconium oxide [34]. Tantalum oxide was also detected by previous studies [13,14]. Figure 6: XRD phase composition of AH-26 root canal sealers. (**A**) Raw material (**a**) and after a 30-day immersion period in water (**b**) and PBS (**c**). (**B,C**) The mean \(\pm\) standard deviation of crystal size and crystalline index, respectively, for all sealers in the three tested environments (dry or immersion status). The symbol (*) refers to the greatest significant mean at \(p<0.001\), the symbol (\(\dagger\)) refers to the lowest significant mean at \(p<0.001\), and the symbol (\(\
eq\)) indicates that there was no significant difference between the sealers of the same symbol at \(p>0.05\). This was confirmed by the current XRD spectra, as it detected calcium silicate; wollastonite-2M, alite, and dicalcium silicate; and calcite, tricalcium phosphate, calcium hydroxide, and zirconium oxide. In the presence of water, it sets and forms calcium silicate hydrate and calcium hydroxide, resulting in an alkaline medium that enhances antibacterial and biological potential [14]. Furthermore, it is biocompatible and bioactive, as it reacts with the phosphates of the tissue fluids forming hydroxyapatite [13]. Endosequence had a prolonged setting time and a high degree of solubility that jeopardized its sealing ability in [6; 17]. Several improvements were attempted by the manufacturer to solve the prolonged setting times and solubility of biocearamics. New versions of biocearamic-based sealers were introduced, including fast-set Endosequence and Cerafil. According to manufacturer's instructions, Endosequence is aluminum-free; however, calcium di-aluminum oxide was detected by XRD, and previously, the Al element was also detected by EDX [11]. It seems that aluminum was added for the improvement of its delayed setting time, in turn, reducing its solubility property. There is no information on Cerafil's composition except the manufacturer's instructions [21], and only one publication explains the effect of bioactivity on reducing its solubility [11]. According to manufacturer's brochure, Cerafil is composed of calcium silicate, calcium phosphate, zirconium oxide, calcium oxide, glasses, accelerators, filler, and thickening agents [21]. The resulting XRD data of set Cerafil compositions reported a similar composition (calcium silicate, calcite, lime, tricalcium phosphate, calcium sulfate anhydrite, zirconia oxide, and bismite). In recent years, the term \"bioactivity\" has been widely used to refer to a property of biocearamic materials, such as the material's ability to form hydroxyapatite when in contact with simulated tissue fluid, like PBS [19; 35]. This hydroxyapatite layer is chemically equivalent to the tooth structure. It can provide the host with interfacial union [23] and improve the material's physical properties. The main drawback of biocearamic sealers is their solubility [6; 16; 17], which has been mitigated by increasing their bioactivity [11]. Several publications have determined hydroxyapatite precipitation on Endosequence's surface after immersion in PBS [34; 36; 37]. The precipitation was successfully formed due to the reaction of the calcium content of the sealers with the phosphate content of the PBS [38]. Accordingly, PBS was used in this study, since its composition is similar to simulated body fluid [39].