Comparative study of DMOT and DMPT accelerators in PMMA-based bone cement: Implications on polymerization, strength, porosity, and cytocompatibility

Cranioplasty requires durable and biocompatible materials to restore cranial defects. This study investigated the influence of powder-to-liquid (P/L) ratio and activator type—N,N-Dimethyl-o-toluidine (DMOT) and N,N-Dimethyl-p-toluidine (DMPT)—on the properties of polymethyl methacrylate (PMMA)-based bone cement containing zirconium dioxide (ZrO₂) as a radiopaque agent and Calendula sp. extract as a bioactive additive. The formulations were evaluated for radiopacity (X-ray), microstructure (SEM–EDX), mechanical strength (compressive test), and cytocompatibility. DMOT-based formulations with higher powder content demonstrated superior mechanical stability, achieving compressive strengths of 135.9 MPa and 124.1 MPa after 30 and 60 days of immersion, respectively, in accordance with ASTM F451 standards. In contrast, DMPT-based cements showed faster polymerization, greater porosity, and lower mechanical strength. SEM analysis confirmed pore formation in DMPT systems, while EDX mapping verified uniform Zr dispersion across all samples. Radiopacity increased proportionally with ZrO₂ concentration. Qualitative MTT results indicated cell viability above 90 %, confirming cytocompatibility. Overall, the findings emphasize that activator selection and formulation balance are key factors for optimizing the mechanical integrity and biocompatibility of PMMA bone cement for cranioplasty applications.