Smart Nano-Hydrogels for Self-Healing Dental Restorations: Synthesis, Characterisation, and In Vitro Performance Evaluation

Abstract

Dental restorations often fail prematurely due to secondary caries, marginal microleakage, and mechanical fatigue. Smart nano-hydrogels offer a promising solution by integrating self-healing polymer networks with controlled drug release and enhanced mechanical properties. This study aimed to design and synthesize four novel poly (2-hydroxyethyl methacrylate) (pHEMA) and poly (tetraethylene glycol dimethacrylate) (pTEGDMA)-based nano-hydrogels, evaluating their physicochemical characteristics, pH-responsive swelling, drug release kinetics, self-healing efficiency, antibacterial activity against key cariogenic pathogens, and in vitro cytotoxicity per ISO 10993-5. Marginal integrity and bond strength of restorations were tested under simulated thermocycling. Five experimental groups NH-Ctrl, NH-HEMA, NH-TEGDMA, NH-Ag, and NH-Dual were characterized via dynamic light scattering, FTIR, SEM, and TGA. Swelling was assessed at pH 4.0–7.4, and drug release was modeled using Korsmeyer–Peppas, Higuchi, and zero-order kinetics. NH-Dual demonstrated optimal performance: particle size 155 ± 5 nm, zeta potential −27.9 mV, swelling ratio 183.5% at pH 7.4, Korsmeyer–Peppas exponent 0.55, self-healing efficiency 96.3%, and antibacterial zone of inhibition 21.4 ± 1.1 mm. Cell viability remained above 87.6%, and bond strength after 5,000 thermocycles was 22.1 ± 1.8 MPa. These findings highlight the potential of dual-network, silver-loaded nano-hydrogels for advanced self-healing dental restorations.