CO2-derived non-isocyanate urethane based self-etching dental adhesive system

Abstract

This study reports the synthesis and comprehensive evaluation of a novel maleated self-etch urethane monomer (MAUM) designed to enhance dental adhesive performance. Adhesive formulations containing 0–25 phr MAUM were assessed for polymerization kinetics, mechanical properties, etching efficacy, bonding strength, water sorption, and cytotoxicity. Photo-DSC and FTIR analyses revealed that methacrylate conversion increased from 76% to 89% with MAUM addition, despite a 25% decrease in total polymerization enthalpy, attributed to the maleate groups’ lower reactivity and delayed vitrification from flexible side chains. Mechanical testing showed that fracture toughness improved by up to 40% at 20 phr MAUM, while flexural strength (109–130 MPa) and modulus (2250–2690 MPa) remained statistically unchanged. SEM imaging confirmed ductile fracture surfaces and effective etching of enamel and dentin, facilitating hybrid layer formation. Microshear bond strength (μSBS) increased significantly from 5.68 MPa (5% MAUM) to 15.49 MPa (20% MAUM), matching the commercial adhesive benchmark (15.76 MPa). Water sorption measurements showed a reduction from 30.2 μg/mm³ in the control to 24.5 μg/mm³ in 20 phr MAUM adhesives, indicating improved hydrolytic stability. Cytotoxicity tests with L929 fibroblasts demonstrated >85% cell viability for both 0 phr and 20 phr formulations, surpassing commercial adhesives that often fall below 60% viability. Collectively, these results demonstrate that MAUM enhances polymer network quality, mechanical resilience, adhesive performance, and biocompatibility, while reducing water uptake, supporting its promise for durable and safe dental adhesives.