Influence of Surface Treatment on the Interfacial and Mechanical Properties of Short S‑Glass Fiber-Reinforced Dental Composites

The influence of interfacial shear strength (IFSS) between processed short S-glass fibers (250 and 350 μm in length, 5 μm in diameter) and the dental resin (a mixture of urethane dimethacrylate and triethylene glycol dimethacrylate monomers) on the mechanical properties has been studied experimentally. The surface profile of short S-glass fibers was modified using a selective atomic level metal etching process and simple silanization process to enhance the interfacial properties. The S-glass fibers were etched in acid solutions to increase the surface roughness and selectively remove Al3+ and Mg2+ ions, which promoted the mechanical and chemical interfacial bonding reactions. The single glass fiber tensile and microdroplet pull-out tests were performed to investigate the effects of interfacial properties on the flexural strength of the resultant composites. The surface modified S-glass fibers showed an increase of 11–40% in IFSS compared to untreated glass fibers. Composites reinforced with 350 μm length glass fibers (AR-70), which were treated in piranha solution for 4 h, showed the highest improvement in overall mechanical properties, flexural strength (34.2%), modulus (9.7%), and breaking energy (51.9%), compared to the untreated fiber-reinforced composites. The modified Lewis–Nielsen equation was developed using the effective fiber length factor to accurately predict the modulus of the short fiber-reinforced composites and validated with experimental results.