['To evaluate the transdentinal cytotoxicity of resin-based luting cements (RBLCs), with no HEMA in their composition, to odontoblast-like cells.', "Human dentine discs 0.3\xa0mm thick were adapted to artificial pulp chambers (APCs) and placed in wells of 24-well plates containing 1\xa0mL of culture medium (DMEM). Two categories of HEMA-free RBLCs were evaluated: group 1, self-adhesive Rely X Unicem (RU; 3M ESPE), applied directly to the dentine substrate; and group 2, Rely X ARC (RARC; 3M ESPE), applied to dentine previously acid-etched and treated with a bonding agent. In group 3 (control), considered as representing 100% cell metabolic activity, no treatment was performed on dentine. The APC/disc sets were incubated for 24\xa0h or 7\xa0days at 37\xa0°C and 5% CO2 . Then, the extracts (DMEM + dental materials components that diffused through dentine) were applied to cultured odontoblast-like MDPC-23 cells for 24\xa0h. After that, the cell viability (MTT assay), cell morphology (SEM), total protein production (TP) and alkaline phosphatase (ALP) activity were assessed. Data from MTT assay and TP production were analysed by Kruskal-Wallis and Mann-Whitney tests (α\xa0=\xa05%). Data from ALP activity were analysed by one-way anova and Tukey's test (α\xa0=\xa05%).", 'In group 1, a slight reduction in cell viability (11.6% and 16.8% for 24-h and 7-day periods, respectively) and ALP activity (13.5% and 17.9% for 24-h and 7-day periods, respectively) was observed, with no significant difference from group 3 (control) (P\xa0>\xa00.05). In group 2, a significant reduction in cell viability, TP production and ALP activity compared with group 3 (control) occurred (P\xa0<\xa00.05), regardless of incubation time. Alteration in MDPC-23 cell morphology was observed only in group 2.'] Does cytocompatibility of HEMA-free resin-based luting cement according to application protocols on dentine surfaces?