## 1 Introduction  
Contemporary endodontics offers a wide span of materials for root canal filling, which leads to an improved endodontic treatment success rate, as novel materials exhibit better biocompatibility, bioactivity, and sealing properties [1, 2]. An appropriate bond strength at the material-dentin interface is crucial to ensure a proper seal of the root canal system, with the ultimate goal of preventing or minimizing microleakage [3, 4, 5]. Mineral trioxide aggregate (MTA) was the first hydraulic cement successfully introduced in endodontics due to its biocompatibility, low solubility, radiopacity, hard-tissueinductive and conductive activity, ability to set in a wet environment, and ability to imprison bacteria as a result of its in situ precipitation [1; 6; 7; 8]. MTA presents a suitable biomaterial for an extensive range of clinical applications, including vital pulp therapy [9], regenerative endodontic procedures [10], apexification, perforation and resorption repair, as well as root-end and root canal filling [11; 12; 13]. However, this calcium silicate-based cement presents some well-known drawbacks, including its long setting time, challenging handling properties, potential for tooth discoloration, and high cost [12; 14]. Aiming to overcome MTA shortcomings, several newly developed hydraulic materials were launched. Biodentine(tm) (Septodont, Saint-Maur-des-Fosses Cedex, France) shows mechanical properties and clinical applications comparable with MTA [15]. Conversely, this bioactive dentin substitute material presents a shorter setting time (approximately 12 min) due to the inclusion of calcium chloride as a setting accelerator within its composition alongside improved handling properties [16; 17]. Moreover, Biodentine(tm) is associated with better esthetic outcomes, as it demonstrates superior color stability compared with MTA [14]. More recently, Endosequence Root Repair Material (ERRM; Brasseler USA, Brasseler USA, Savannah, GA) became commercially available and is now present in Europe as TotalFill(r) (FKG, La Chaux-de-Fonds, Switzerland), a pre-mixed and ready-to-use material provided in both scoopable or injectable versions. This biomaterial presents reasonably good handling properties and a fast initial setting time of 2 h [18]. Besides being hydrophilic, radiopaque, and having a high pH level, excellent physical and biological properties have been reported in previous studies, with data confirming its biocompatibility, cytotoxicity levels, and antibacterial properties similar to MTA [19; 20; 21]. Bioactive materials can be subjected to functional load or forces resulting from restorative material placement. Therefore, a proper bond between the material and the dentin surface is essential to resist dislodgement and guarantee long-term success [22; 23; 24]. However, blood contamination has been identified as one potential factor affecting MTA's physical properties and retention to root dentin, consequently jeopardizing its sealing ability [25; 26; 27]. In contrast, some studies found that blood did not negatively impact bond strength [4; 28; 29]. Since blood exposure is likely to occur in various clinical situations in which calcium silicate-based materials are used, it becomes fundamental to render data concerning the influence of blood on the bond strength obtained with more recently introduced materials, namely Biodentine(tm) and TotalFill(r) BC Putty. Furthermore, considering the discrepancy of results found in literature regarding the impact of blood contamination on the adhesion of different biomaterials to root dentin, it becomes crucial to provide additional data on the topic. Push-out bond strength tests allow assessment of the bond strength inherent to the biomaterial-root canal dentin adhesive interface [30]. The present study aims to evaluate the effect of blood contamination on the push-out bond strength obtained with three different biomaterials (ProRoot(r) MTA, Biodentine(tm), and TotalFill(r) BC Putty) to root canal dentin.