Impact of Nanoparticles Additions on the Strength of Dental Composite Resin

This study aimed to evaluate the effect of nanoparticles, zirconium dioxide (ZrO₂), titanium dioxide (TiO₂), and silicon dioxide (SiO₂), on flexural strength (FS), hardness, and wear resistance of light cured dental composite resin.

210 rectangular and disc-shaped composite resin specimens were fabricated with dimensions (25 × 2 × 2 ± 0.03 mm) and (6×4 ± 0.03 mm) for FS, hardness, and wear resistance, respectively (70/test). Specimens of each test were divided according to nanofillers into four groups, unmodified as control, ZrO₂ (Z), TiO₂ (T), and SiO₂ (S) groups; each one was further subdivided into two subgroups according to nanoparticles concentration, 3wt.% and 7wt.% (Z3, Z7, T3, T7, S3, and S7), 10 specimens of each subgroup. A3-point bending test and Vickers hardness test were used for FS and hardness measurements, respectively. Wear resistance was evaluated by the differences in surface roughness of tested specimens before and after wear test. Two-way and 1-way ANOVA and Bonferroni's post hoc tests were done for data analysis (α = 0.05).

Two-way ANOVA for FS and wear resistance showed that there was a significant interaction between type of nanoparticles and concentration of nanoparticles (p < 0.001) while two-way ANOVA for hardness showed that both type of nanoparticles and concentration of nanoparticles had a significant effect (p < 0.001), while the effect of their interaction was not statistically significant (p=0.142). 1-way-ANOVA test showed significant increase in FS and wear resistance for all tested groups (p < 0.001 and p < 0.001, respectively) except T7 and S7. Also, there was a significant enhancement in hardness for all tested groups (p < 0.001).

Modification of light cured composite resin with certain amounts of nanoparticles (3% and 7% of ZrO₂ and 3% of TiO₂ and SiO₂) can be beneficial in improving flexural strength and wear resistance while hardness of composite resin was increased with all NPs additions.