## 2 Requirement Properties for Root Canal Sealer in the Treatment of Teeth with Periapical Lesions  
Biocompatibility is the response of a material to live cells; it encompasses cytotoxicity, cytogenicity, genotoxicity, and carcinogenicity. One of the primary requirements for an endodontic root canal sealer is that it be non-toxic and immunologically suitable for the tissue. Due to the fact that they may come into close contact with tissues, the biocompatibility of root canal sealers is crucial for the clinical efficacy of endodontic therapy, especially when the sealer extends the apical foramen and comes into contact with surrounding periapical tissues for a prolonged period [15]. In other words, a material is biocompatible when in contact with a tissue and does not induce undesirable reactions such as toxicity, irritation, inflammation, or hypersensitivity [16]. The majority of biocearamic-based root canal sealers are biocompatible. Theirbiocompatibility is due to the calcium phosphate present in the sealer itself. Calcium phosphate is also the principal inorganic constituent of hard tissues (teeth and bone). Many bioceramic sealers have the ability to stimulate bone regeneration if accidentally extruded through the apical foramen during root canal filling or root perforation repairs [17]. The biological compatibility of sealers is typically determined by evaluating fibroblasts' vitality in the material's presence [17]. In a perfect situation, one would have some leeway in one's schedule while the sealer in root canals sets. However, a slow setting period might cause tissue irritation, as the majority of root canal sealers are poisonous until they are entirely set. According to the producers of bioceramic sealers, the setting reaction is catalyzed by the presence of moisture in the dentinal tubules, which is particularly significant when treating teeth with apical resorption. The normal setting time is four hours, although patients with extremely dry canals may require a significantly longer setting time [18]. Flow is a feature that allows the sealer to enter inaccessible places such as the thin irregularity of the dentin, the isthmus, accessory canals, and the gaps between the master and accessory cones of gutta-percha [19]. According to the International Standards Organization (ISO 6786/2001), a root canal sealer should have a flow rate of no less than 20 mm [20]. The flow rate of the sealer is affected by particle size, temperature, shear rate, and time spent forming the mix. When calculating the flow rate using a rheometer, the tubes' inner diameter and insertion rate are considered [15]. Material mass loss for a predetermined amount of time immersed in water is known as solubility. According to ISO 6876 and American Dental Association (ADA) specification No. 7, the sealer's solubility should not be greater than 3%. Sealers with a high solubility always permit the formation of space between the interfaces--sealer, dentin and GP points. This provides avenues for leakage from the oral cavity and periapical tissues [15]. The sealer used in root canals needs to be sufficiently radiopaque and distinct from surrounding anatomical structures [21]. This enables the radiographic inspection of the root canal filling to assess its quality. In accordance with ISO 6876/2001, the minimum radiopacity for root canal sealers is based on a reference standard of 3 mm aluminum. According to the literature, root canal sealers' basic antibacterial effects are linked to their alkalinity and calcium ion release, which promote healing by encouraging the formation of mineralized tissue [22]. Root canal sealers are evaluated for antimicrobial activity using two tests--agar diffusion and direct contact [23]. _Enterococcus faecalis_ is a particularly widespread intra-radicular microbe isolated from teeth with periapical changes and is used as a modified contact test to test the antimicrobial activity of endodontic sealers [24; 25].