Comparative Effect of Different Nanoparticles with Different Concentrations on Fracture Toughness and Elastic Modulus of Restorative Dental Composite Resin

Background/Objective: Resin-based composite (RBC) gained wide popularity in dentistry due to its excellent biocompatibility, superior aesthetics, and good bonding to enamel and dentine. However, they have several shortcomings, including mechanical insufficiency and shrinkage tendency. Many researchers have utilized nanoparticles (NPs) as a reinforcing filler for RBCs. This article focused on assessing the impact of three different nanoparticles, ZrO₂, TiO_2, and SiO_2, with concentrations of 3 wt% and 7 wt%, on the elastic modulus (E) and fracture toughness (K_IC) of one commercial light-activated dental resin composite. Methods: 140 rectangular specimens were constructed according to ISO 4049 with dimensions (25 × 2 × 5 ± 0.03 mm) and (25 × 2 × 2 ± 0.03 mm) for fracture toughness and elastic modulus, respectively. Specimens were categorized into four main groups based on nanofiller types. Control: plain without filler (CC) and three modified ones with ZrO₂ (ZC), TiO₂ (TC), and SiO₂ (SC). Furthermore, modified groups were divided into two subgroups according to nanofiller concentration, 3 and 7 wt% (ZC3, ZC7, TC3, TC7, SC3, and SC7), n = 10. Mechanical testing for fracture toughness was completed using a single-edge notched beam, while a three-point bending test was used for elastic modulus. Analysis of data was based on two-way ANOVA and Bonferroni post hoc (α = 0.05). Results: ZrO₂ provided the most substantial improvement in both E and K_IC, with the optimal performance observed at 3 wt% for stiffness and 7 wt% for toughness. TiO₂ groups also enhanced these properties at both concentrations; however, the gains were less pronounced compared to ZrO₂. SiO₂ improved mechanical performance at 3 wt%, but a higher loading of 7 wt% resulted in reduced values. Conclusions: Resin-based composite modified with 3 wt% of NPs tends to possess higher fracture toughness and modulus of elasticity. Fracture toughness enhancement was concentration-dependent with ZrO₂ NPs, where the best result was obtained with 7 wt%. Nanoparticle-reinforced composite, particularly ZrO₂, may be suitable for prosthodontic applications.