Preparation and characterization of Bis-GMA-free dental composites with dimethacrylate monomer derived from 9,9-Bis[4-(2-hydroxyethoxy)phenyl]fluorene

Abstract

Objective: Synthesize a new BPA-free monomer for use in methacrylate-based materials and evaluate critical properties of resin and composite materials based on the monomer.

Methods: Bis-EFMA was synthesized through reaction between 9,9-bis[4-(2-hydroxyethoxy)-phenyl]fluorene and 2-(methacryloyloxy)ethyl isocyanate. Experimental Bis-EFMA-based resin (Bis-EFMA/TEGDMA=50/50, wt./wt.) and composite were prepared. Critical properties were investigated according to standard or referenced methods Bis-GMA/TEGDMA (50/50, wt./wt.) resin system, Bis-GMA-based composite and 3M ESPE Filtek™ Z250 were used as controls.

Results: FT-IR and ¹H NMR spectra confirmed the structure of Bis-EFMA monomer. Cured resin materials: Bis-EFMA-based and Bis-GMA-based resins had nearly the same degree of conversion (p>0.05); Bis-EFMA-based resin had significantly lower shrinkage, water sorption and solubility, and cytotoxicity than Bis-GMA-based resin (p<0.05); flexural properties of Bis-EFMA-based resin were all higher than those of Bis-GMA-based resin (p<0.05). Cured composite materials: There was no significant difference in conversion (p>0.05); Bis-EFMA-based composite had significantly lower shrinkage and solubility (p<0.05); water sorption of Bis-EFMA-based composite and Z250 were similar (p>0.05), but lower compared to Bis-GMA-based composite (p<0.05); Bis-EFMA-based composite had the deepest curing depth (p<0.05); Before water immersion, there was no significant difference in flexural strength between Bis-EFMA-based composite and each control composite (p>0.05), while FS became lower than that of Z250 (p<0.05), but higher than that of Bis-GMA-based composite (p<0.05) after water immersion; Flexural modulus of Bis-EFMA-based composite and Z250 were nearly the same (p>0.05), higher than that of Bis-GMA-based composite (p<0.05); Bis-EFMA-based composite showed less cytotoxicity than Bis-GMA-based composite and Z250 (p<0.05).

Significance: Bis-EFMA has potential as a substitute for Bis-GMA to prepare Bis-GMA-free dental composites.

Keywords: Bis-GMA-free; Bisphenol A; Conversion; Dental composite material; Flexural properties; Polymerization shrinkage cytotoxicity; Resin matrix; Solubility; Water sorption.