Development of bio-compatible isosorbide-based polyurethanes exhibiting eucalyptol solubility for advanced root canal...

Gutta-percha (GP) has long been the standard root canal filling material, but its poor removability, limited mechanical properties, and potential cytotoxicity restrict clinical performance. To address these shortcomings, this study aimed to develop bio-based D-isosorbide thermoplastic polyurethanes (IPUs) with improved removability in eucalyptol oil, superior mechanical performance, and enhanced cytocompatibility, providing a potential alternative to GP.

D-isosorbide-based IPUs were synthesized from polycarbonate polyol and D-isosorbide via catalyst-free, two-step polymerization. Four formulations with different hard segment contents (HS10-HS40) were prepared and evaluated for thermal stability (thermogravimetric analysis and differential scanning calorimetry), mechanical properties (tensile testing), solubility in eucalyptol oil, and cytocompatibility (CCK-8 and LDH assays), compared with GP.

All IPUs showed high thermal stability (T₅d > 270 °C) and melting transitions between 44 and 48 °C, similar to GP. Among the formulations, IPU-30 demonstrated optimal performance, achieving a tensile strength of 11.8 ± 1.0 MPa and elongation at break of 721 ± 144 %, markedly surpassing GP. Solubility in eucalyptol increased with D-isosorbide content, with IPU-40 exhibiting up to 13 % mass loss. In cytocompatibility assays, IPU-30 displayed lower early-phase cytotoxicity and maintained higher cell viability than GP over 6 days.

D-isosorbide-based IPUs combine favorable thermal and mechanical properties with partial solubility in eucalyptol, enabling easier and safer retreatment. Their excellent cytocompatibility further supports their potential as sustainable and clinically viable alternatives to GP in root canal obturation.