## 1 Introduction  
Endodontic therapy, generally focused on root canal treatment, has a major goal directed to the cure or prevention of perriadicular periodontitis. Orthograde endodontic treatment includes cleaning and shaping of the root canal system, preparing it for the subsequent filling, with the aim of maintaining disinfection and preventing reinfection. The latter is achieved by a core--most often gutta-percha--and an endodontic sealer, under well-defined criteria of length and density. The treatment is completed by an adequate coronal restoration [1]. A dentin sealer's adhesion is its ability to adhere to the root canal's walls and promote the union of the filling materials to dentin. Different sealers and filling techniques (e.g., single cone, lateral compaction, or thermoplastic obturation) have been reported to produce an impact in the penetration of the sealer into dental tubules, thereby influencing dentin sealers' adhesion [2]. Optimal adhesion of the root filling to the intraradicular dentin leads to fewer gap-containing regions, which would allow fluid infiltration within either sealer-dentin or sealer-core-filling material interfaces [3]. Consequently, it also avoids sealer dislodgment during operative procedures, increasing endodontic treatment success rates [3]. It is widely accepted that sealing ability is of utmost importance to successful outcomes of root canal treatments [3]. A great variety of endodontic sealers are available commercially. They are divided into different groups according to their chemical composition, properties, or therapeutic additives, which influence their performance [4]. Studies have also shown that the sealers' bond strength to dentin may be affected by the pretreatment of canal walls and the type of sealer used [5]. The physicochemical properties of sealers interfere with their ability to adhere to dentin [6]. The epoxy-resin-based sealer AH Plus (Dentsply DeTrey GmbH, Konstanz, Germany) is the gold-standard sealer due to its extensively studied physical properties, such as its high bond strength to dentin [6]. This advantage has been justified by epoxy-resin-based sealers' chemical bonding to exposed collagen and their great capacity to form smooth and compact tags inside dental tubules [6; 7]. MTA Fillapex is composed of a salicate-resin matrix filled with MTA, natural resin, bismuth oxide, and silica [8]. This sealer's composition is primarily resin, which raises doubts concerning its classification as a true calcium-silicate-based sealer or MTA-based sealer [4]. Nevertheless, it is reported that the set sealer releases calcium and hydroxyl ions. When the material comes into contact with phosphate-containing fluids, these ions cause the formation of apatite, which may deposit within collagen fibrils, promoting controlled mineral nucleation on dentin, seen as the formation of an interfacial layer with tag-like structures [7; 8]. MTA Fillapex's low bond strength could be due to the low adhesion capacity of these tag-like structures [9]. Calcium-silicate-based sealers, such as BioRoot RCS and Endosequence BC, have become popular in endodontics, mainly due to their biocompatibility and bioactivity [10]. These sealers have the potential to adhere chemically to dentin through the production of hydroxyapatite during setting [6]. Although they have undergone great development to improve their performance, there is still a lack of consensus regarding their bond strength to intraradicular dentin [6; 11]. Plasma, considered to be the fourth state of matter, is an electrically conductive medium that responds to electric and magnetic fields and is also a source of large quantities of highly reactive species such as electrons, ions, electronically excited neutrons, and free radicals [12]. Plasmas are generally classified as thermal and non-thermal (or cold plasma), based on the relative temperatures and energy of the different plasma species (electrons, ions, and neutrons) [12].