Organosilica nanoparticle-reinforced resin-based dental composites: synthesis, characterisation, and evaluation of physicochemical properties

Abstract

Dental nanocomposites have recently gained significant attention in the scientific community due to their ability to improve the aesthetic outcomes of dental restorations, thereby improving appearance. Despite extensive research efforts, developing dental nanocomposites that meet both mechanical and aesthetic standards remains a challenging issue. Although nanoparticles are effective at enhancing dental nanocomposite materials, they also have drawbacks. The higher surface-to-volume ratio of silica particles, combined with their hydrophilic nature, increases water absorption and can cause the resin to dry, leading to nano- or micro-leakage. The study investigates the effect of a hydrophobic organo-silica shell framework on nanocomposite performance and the mechanical properties of a dental filler-based nanocomposite. Inorganic SiO₂ nanoparticles were coated with 1,2-bis(triethoxysilyl)ethane (BTEE) to improve hydrophobicity and promote liquid-phase mixing. Core-shell organosilica nanoparticles (csOS NPs) and solid silica core nanoparticles (sSiO₂ NPs) were conjugated with 3-(trimethoxysilyl)propyl methacrylate (γ-MPS), creating csOS-MA and sSiO₂-MA nanoparticles with methyl methacrylate (MA) groups for better filler-resin binding. Characterization techniques included scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), and Fourier transform infrared spectroscopy (FTIR). Single-weight amounts of sSiO₂-MA and csOS-MA nanoparticles were used as fillers in composites tested for compressive strength (CS), modulus, and flexural strength (FS), polymerisation shrinkage (PS), and degree of conversion (DC). The findings revealed that the organosilica shell has a significant impact on the mechanical characteristics and DC of the nanocomposite. The study examined the water sorption (WSP) and water solubility (WSL) of nanoparticles prior to and following surface modification. The findings indicated that the addition of an organosilica shell significantly reduced both WSP and WSL while also improving the overall physical properties of the nanoparticles.The findings show that incorporating an organosilica shell on the surface of an inorganic silica core significantly enhances the design of dental restorative materials for nanocomposite filling restorations.