Effect of Amorphous Silica Nanoparticle Size and Content on fracture toughness of a Highly-Filled Dental Composite

Dental composites are of a crucial importance in restorative dentistry; however, these materials present poor mechanical properties such as low resistance against fracture and high wear rate. As a result, further studies on mechanical properties of dental composites, such as research presented this paper, is essential. The reported research was aimed to evaluate the effect of particulate filler content and size on fracture toughness of experimental dental composites.
The study was done experimentally and laboratory. Initially, amorphous silica nanoparticles (ASN) with the mean particle sizes of 12 nm (ASN12) and 40 nm (ASN40) were selected. Then, silica nanoparticles were modified using silane coupling agent γ-MPS. The surface modification was also examined by FTIR and TGA tests. For this purpose, composites with different weight percentages of the filler were prepared in ten groups.
Composites containing nanoparticles were evaluated in term of fracture toughness. Moreover, the distribution of the filler particles within the polymer matrix was studied using SEM and TEM respectively. The collected data were analyzed and compared by ANOVA and Tukey’s HSD tests at a significance level higher than 0.05.
The results of the tests indicated an increase in fracture toughness due to increased filler content. This increase has an optimum, and then the fracture toughness decreases. The results also showed that fracture toughness in composites containing 12 nm nanoparticles is better than fracture toughness in composites containing 40 nm nanoparticles.(p-0.03)
The results showed an increase in the fracture toughness with increasing the filler content up to an optimum loading. The filler size seemed to affect fracture toughness of the composites and smaller filler sizes tend to render the material tougher.