## 1 Introduction  
In endodontics, a successful treatment plan requires strict control to avoid bacterial leakage during root canal treatment (RCT). However, bacteria can still survive after chemo-mechanical procedures and root canal filling. The root canal system is considered a three-dimensional (3D) apparatus. It is composed of the main canal and many lateral canals with ramifications, isthmuses, loops, deltas, and denntal tubules. Therefore, cleaning and shaping should be accomplished in a 3D manner to ensure the penetration of irrigants into all the pulp tissues and bacteria in the complex root anatomy [1]. In addition, endodontic infections are considered polymicrobial [2]. Recent studies revealed that the leading cause of endodontic treatment failure and persistent root canal infections is the presence of several bacterial species, prominently _Enterococcus faecalis_ (_E. faecalis_) [3]. Infection may happen due to bacterial leakage through the gaps between the endodontic sealers and either the gutta-percha or the internal canal wall [4]. To tackle this issue, several types of sealers with multiple chemical compositions, such as calcium hydroxide, zinc oxide, glass ionomer, and resin sealers, are used nowadays in endodontics [5]. Resin-based sealers have been the most used sealers for many years due to their easy handling, good wettability, dental tubule-penetrating properties, and potential to form a monoblock between the filling material and dentinal wall. The monoblock phenomenon indicates the formation of a single cohesive bond between the core material, sealing agent, and root canal dentin [6]. However, if misused, they might have some shrinkage during setting and form voids, which might increase the possibility of microbial leakage [7; 8]. Significant efforts were made to achieve successful RCT using the latest revolution in root canal-sealing materials. Bio-ceramic sealers were introduced and attracted many clinicians' attention owing to their biocompatibility and alkaline pH. Bio-ceramic sealers are also considered bio-active and non-toxic [9]. An example of a bio-ceramic sealer is MTA Fillapex (Angelus, Londrina, Brazil). MTA Fillapex is characterized by a high flowability rate. Moreover, MTA Fillapex permeates quickly through the lateral and accessory tooth canals as it has a minimal film thickness. Notably, MTA Fillapex includes salicate resin in its chemical composition for its bio-compatible and antimicrobial properties [10]. Another clinical advantage of MTA Fillapex is its low solubility and expansion as well as its high radiopacity and cement regeneration with good sealing [11]. The calcium ion (Ca\({}^{2+}\))-releasing ability of MTA Fillapex is a useful tool that assists in tissue regeneration and healing processes. MTA Fillapex also has excellent antibacterial properties due to its high pH (9.5-10.4) [12]. Another example of a Ca\({}^{2+}\) silicate bio-ceramic sealer is CeraSeal (META BIOMED, Cheongju, Korea). CeraSeal provides an antimicrobial effect and high bio-compatibility due to its high pH (12.73). In addition, it has an excellent radiopacity (8 mm Al), provides good sealing ability, and can be used with single cone obturation [13], which employs a single gutta-percha cone, while the sealer thickness inside the canal mainly depends on the adaptation of the single gutta-percha cone to the canal walls [14]. This technique has become more popular among practitioners owing to its ability to complete RCT in a short time and with good results [15]. Recent literature has reported on the sealing ability of the relatively new bio-ceramic sealers [16]. The main mechanism involves tricalcium silicate and dicalcium silicate particles which, when in contact with humidity, develop Ca\({}^{2+}\) silicate and Ca\({}^{2+}\) hydroxide needles in the hydrate phase, which slowly release Ca\({}^{2+}\) and hydroxyl (OH\({}^{-}\)) ions in the presence of phosphate-containing fluids.