A multifunctional dendrimer for BPA-free dental adhesives: Polymerization behavior and cytotoxic profile of G-IEMA

To determine whether substituting Bis-GMA for dendritic macromer G-IEMA in a universal adhesive alters real-time cure/post-cure performance and in-vitro cytotoxicity. Polymerization kinetics of five neat monomers (Bis-GMA, G-IEMA, UDMA, TEGDMA, HEMA) and four adhesives, two commercial controls (Scotchbond Universal, Futurabond M+) and two experimental formulations differing only in the base monomer, EXP-BIS vs. EXP-G, with 25 wt% of Bis-GMA or G-IEMA, respectively, were monitored by real-time ATR-FTIR for 20 min cure/post-cure (n = 3). Key outputs were final degree of conversion (DC_max), maximum polymerization rate (Rp_max) and half-time (t_0.5). Cytocompatibility was assessed on primary human dental-pulp cells via 24 h MTT and propidium-iodide (PI) assays using extracts of polymerized and non-polymerized specimens (n = 12). Among homopolymers, DC_max did not differ (one-way ANOVA, p = 0.24) while R_p,_max did (p < 0.0001), with G-IEMA and TEGDMA faster than Bis-GMA; t₀.₅ was similar (p = 0.15). Across adhesives, DC_max (p = 0.06), Rp_max (p = 0.89) and t₀.₅ (p = 0.27) were comparable; EXP-GI reached the highest DC_max (≈89 %). G-IEMA was less cytotoxic than Bis-GMA in both assays: MTT +20 % and +51 % in non-polymerized and polymerized extracts, respectively; PI −40 % and −54 % (all pairwise p < 0.01). For adhesive extracts, MTT showed a main effect of adhesive (two-way ANOVA, p < 0.001) but no treatment effect/interaction; relative to Scotchbond, EXP-GI supported +6.7 % (non-polymerized) and +18.2 % higher metabolic activity, while all adhesives remained below the control (p < 0.001). After polymerization, EXP-GI exhibited 17 % lower apoptosis than Scotchbond (p = 0.049) and 11 % lower than Futurabond (p < 0.05). G-IEMA can replace Bis-GMA without compromising cure efficiency or increasing acute cytotoxicity, supporting its use in BPA-free universal adhesives.