## 1 Introduction  
The removal of intracanal posts, excessive instrumentation, past endodontic treatment, internal root resorption, and/or dehydration from the use of irrigating solutions can all result in the thinning or weakening of root canal walls [1]. Consequently, this will make teeth less resistant to functional loads and more prone to fracture, resulting in tooth loss [2]. Vertical root fracture (VRF) is a root-canal treatment complication [3] that is considered the third main cause of extraction among root-canal-treated teeth, after caries and periodontal disease [4]. The frequency of extracted vertically fractured teeth among endodontically treated patients ranges from 11% to 20%. VRFs were detected in 10.9% of removed endodontically treated teeth (ETT) in the root canal system [5]. Endodontically treated premolars have the lowest survival rates due to the high frequency of vertical root fracture [6] because of their roots with a cross-section of a smaller mesiodistal diameter and with a deep oval or flattened shape [7]. The comparatively small size of their crown and the high occlusal forces they are subjected to explain their fragility [8] Therefore, one of the primary objectives of endodontic treatment is to strengthen the remaining tooth structure with root canal filling materials following chemical and mechanical preparation [9]. It is reported that the use of gutta percha (GP) as a core material along with root canal sealers are considered the standard root filling of endodontically treated teeth (ETT) [10]. However, since the GP has a lower elastic modulus than dentine, it has a little effect in reinforcing roots after root canal treatment [11]. Furthermore, GP cannot fill the whole three-dimensional canal space due to the existence of lateral canals, accessory canals, canal irregularities and small discrepancies that present between root dentinal walls and the obturating material [12]. Consequently, when selecting root canal sealers, some factors must be considered to seal the gap between the dentinal wall and the obturating material and to reinforce the remaining structure of the teeth [9]. It has been suggested that sealers with stable adhesion to the radicular dentine and have a Young modulus of elasticity similar to dentine will strengthen the remaining tooth structure, thus contributing to the long-term success of an ETT [9]. The epoxy resin-based AH Plus has been considered the \"gold-standard\" endodontic sealer [13; 14] because of its low solubility and excellent flow, apical seal, biocompatibility, and adhesion to root dentine [15]. When compared to other sealers, AH Plus has shown promising outcomes. It demonstrated the lowest weight loss among the various root canal sealers in water and artificial saliva with varying pH values, regardless of the solubility medium used. In addition, compared to traditional sealers, AH Plus demonstrated the highest level of solution durability [16]. However, it has drawbacks, including the possibility of mutagenicity, cytotoxicity, and an inflammatory reaction. Furthermore, due to its hydrophobicity, the hydrophilic channel is unable to completely fill with fluid. Retained dental moisture, in particular, can cause problems in AH Plus adhesion to canal walls [17]. Thus, sealers or endodontic obturation materials providing higher fracture resistance and improved seal have been developed. Sealers based on calcium silicates have recently gained popularity due to their favorable biological properties. They are biocompatible and non-cytotoxic, are dimensionally stable, chemically bond to root dentin, produce an alkaline pH, have antimicrobial properties, and promote enhanced root strength after obturation [18]. BioRoot RCS which exists in both liquid and powder form, is one of the calcium silicate-based root canal sealers. The primary ingredients of the powder, according to the manufacturer, are tricalcium silicate, povidone (a sticky agent), and zirconium dioxide (a contrast medium).