Novel guaiacol-based high-performance dimethacrylate containing fluorenyl cardo structure for dental restorative resins.

Abstract

In dentistry, the use of bisphenol A glycidyl methacrylate (Bis-GMA) is being questioned since bisphenol A is regarded as an endocrine disruptor. As alternative candidates to Bis-GMA, bio-based dental resins face the crucial challenge of low mechanical strength and high water sorption. In this study, a novel guaiacol-based dimethacrylate containing fluorenyl cardo-structure was developed to effectively improve the hydrophobicity, enhance the mechanical properties, and reduce the polymerization shrinkage of bio-based dental restorative resins. Therefore, 9, 9-bis(3-methoxy-4-glycerolate methacrylate)fluorene (BMHF-GMA) was synthesized from a new guaiacol-based bisphenol, 9, 9-bis(3-methoxy-4-phenol)fluorene (BMHF), which is a lower estrogenic activity bisphenol monomer than commercial bisphenols from the results of cell proliferation test. The experimental dental resin (5 MHMA5T) was prepared containing BMHF-GMA and triethylene glycol dimethacrylate in a 1:1 ratio. The control group (5B5T) replaced BMHF-GMA completely with Bis-GMA. Evaluation of both dental resins revealed that 5 MHMA5T possessed comparable double bond conversion (>50 % in 20 s), better volumetric polymerization shrinkage (7.19 ± 0.09 %), shrinkage stress (0.92 ± 0.01 MPa in 1200 s), water sorption (39.9 ± 0.52 μg mm^-3), water solubility (0.99 ± 0.04 μg mm^-3) and lower cytotoxicity compared with 5B5T. 5 MHMA5T had superior mechanical properties (flexural strength: 122.30 ± 5.00 MPa; flexural modulus: 3.49 ± 0.02 GPa; Vickers hardness number: 25.21 ± 0.56 HV). Especially, after water immersion, it still maintained adequate mechanical properties (flexural strength: 97.34 ± 5.00 MPa; flexural modulus: 2.92 ± 0.02 GPa; Vickers hardness number: 19.33 ± 0.61 HV). Therefore, the new dimethacrylate BMHF-GMA shows great potential in complex and wet oral environments and offers a promising alternative to Bis-GMA in dental restorative resins.