## 1 Introduction  
Endodontic treatment aims to prevent apical and coronal infiltration and microorganisms' proliferation by eliminating root canal infection and filling the dental pulp space [1; 2; 3; 4]. Thus, the obturation of root canal systems is one of the most important steps of endodontic treatment [1]. Since endodontic sealers used to fill the root canals are applied in direct contact with the periapical tissues, such as the periodontal ligament, it is very important to evaluate the cellular effects of these materials [5; 6]. In this context, minimal invasive endodontics enters as an approach to root canal treatment that emphasizes preserving the natural tooth structure as much as possible while effectively treating the infection or inflammation within the tooth. Thus, the removal of healthy tooth structure is minimized and consequently the long-term success of the treatment is enhanced while the patient discomfort is reduced [7]. The bioactivity, alongside with other properties of the sealers used in the endodontic treatment will imply the long-term success of the treatment.  
There are several types of sealers, with different physical, chemical, and biological characteristics, which translate into different sealing abilities, adhesive properties, antimicrobial efficacy, radiodensity, and biocompatibility [8]. sealers are categorized according to their main chemical constituents: zinc oxide eugenol, calcium hydroxide, glass ionomer, silicone, resin, and bioceramic-based sealers [9; 10]. AH Plus (Dentsply DeTrey GmbH, Konstanz, Germany), an epoxy-resin-based sealer, is considered a gold standard due to its high bond strength to the dentin and physical properties, being one of the most used in clinical practice [6; 11]. However, this endodontic sealer does not present bioactive properties [6]. Bio MTA+ (PPH [PERSON], Stalowa Wola, Poland), one of the most recent sealers, is a silico-calcium-based material that contributes to tissue regeneration after perforation of the canal wall. In vitro studies have shown that mineral trioxide aggregate (MTA), in general, has good biocompatibility, nonmutagenic sealing ability, and bioinductive properties [12]. Bio MTA+, a similar material to the conventional MTA, with decreased-sized grains and the insertion of nanoceramic particles and hydroxyapatite, provides higher penetration of calcium ions to the demineralized tissue, and increased sealing process [12; 13].  
Bio C sealer (Angelus Industria de Produtos Odontologicos S/A, Londrina, PR, Brazil) is a novel bioeramic, nonresin sealer, composed of calcium silicates, calcium aluminate, calcium oxide, zirconium oxide, iron oxide and silicon oxide and its bioactivity is also related to the release of calcium ions that stimulates periapical healing [8; 11]. This endodontic sealer has presented adequate flow and radiopacity, low volumetric change, and good biocompatibility, resulting in the allowance of the rapid regression of inflammatory reaction [6; 14].  
Our study aimed to compare the biocompatibility of Bio MTA+ and Bio C sealer with the most used sealer in clinical practice, AH Plus. Thus, a comprehensive evaluation of the biocompatibility of these three root canal sealers, AH Plus, Bio MTA+, and Bio C sealer, from cytotoxicity to genotoxicity, was performed on immortalized human gingival fibroblasts, at different concentrations and over 24 and 72 h, using two different methodologies. Cell viability and proliferation, as well as the cytotoxicity of compounds, may be assessed by the 3-(4,5-dimethylthiazol-2-yl) bromide-2,5-diphenyltetrazolzolium (MTT) assay [15], which measures the mitochondrial activity of cells, and the Sulforhodamine B (SRB) assay [16] that allows cell density determination, based on the quantification of cellular protein content. In this study, both methodologies were used as complementary methods.