Introduction: Reparative dentinogenesis can be stimulated through a direct capping on pulp tissues with biomaterials. Objectives: The aim is to evaluate the cytotoxicity of three materials: Life®, WhiteProRoot®MTA and Biodentine™. Materials and methods: The MDPC-23 cell line was exposed to medium conditioned (ISO10993-5). Metabolic activity was assessed by the MTT assay, viability by the SRB assay, and the type of death and cell cycle by flow cytometry. Differentiation was assessed by expression of alkaline phosphatase (AP) and dentin sialoprotein (DSP) by immunocytochemistry. The mineralization was evaluated with the AlizarinRedS assay. Results: WhiteProRoot®MTA and Biodentine™ have similar results, with decreases in metabolic activity and cell viability at 24 hours and increase in the following times. Life® shows a decrease in metabolic activity and viability, with an increase in cell death and changes in the cycle. The evaluation of differentiation and mineralization indicates a marked increase in the expression of AP and DSP and of the formation of calcium deposits with Biodentine™ when compared to WhiteProRoot®MTA. Conclusions and clinical implications: The results of WhiteProRoot®MTA confirm their indication for these therapies, justifying their recognition as a 'gold standard'. Biodentine™ can be an alternative, since it presents superior results in the phases of differentiation and mineralization, and its clinical manipulation is simplified by its short cure time. Funding: GAI 2013 (Faculty of Medicine, University of Coimbra); FCT, Portugal (Strategic Project PEst-C / SAU / UI3282 / 2013 and UID / NEU / 04539/2013), COMPETE-FEDER. Keywords: Biomaterials. cytotoxicity, pulp capping, reparative dentinogenesis, therapy