Objective. This study aimed to investigate the effects of nanoparticles (zirconium dioxide (ZrO2), titanium dioxide (TiO2), and silicon dioxide (SiO2)) on the flexural strength, impact strength, hardness, and wear resistance of the acrylic resin denture base material. Materials and Methods. Acrylic resin specimens were fabricated in dimensions according to American Dental Association (ADA) specifications per test. Specimens were divided according to nanofiller into four groups; unmodified as control, ZrO2 (Z), TiO2, (T), and SiO2 (S) groups. Each one was subdivided into two subgroups according to nanoparticle concentrations; 3% and 7% (Z3, Z7, T3, T7, S3, and S7). A 3-point bending test, Charpy impact test, and Vickers hardness test were used for flexural strength, impact strength, and hardness measurements, respectively. Wear resistance was measured by the differences in surface roughness of tested specimens before and after the wear test. A scanning electron microscope was used to assess nanoparticle specifications and distributions and for fracture surfaces analysis. ANOVA, Bonferroni’s post hoc test, and the Kruskal–Wallis test were applied for data analysis (α = 0.05). Results. Regarding the flexural and impact strength, there was a statistically remarkable increase for all tested groups compared with the control group, except for the T7 and S7 groups ( P value <0.001, effect size = 0.893) and ( P value <0.001, effect size = 0.759), respectively. There was a statistically significant improvement in the hardness of all tested groups compared with the control group ( P value <0.001, effect size = 0.67) except T3 and S3. Regarding wear, a statistically significant enhancement was noticed in the wear resistance of all tested groups ( P value <0.001, effect size = 0.685), except for the T7 and S7 groups. Conclusion. The flexural strength, impact strength, and wear resistance improved with both concentrations of ZrO2 and low TiO2 and SiO2 concentrations. The hardness increased with both concentrations of ZrO2 and high TiO2 and SiO2 concentrations.

Background. The effect of beverages on nanocomposite denture base materials is neglected. Therefore, this study aimed to investigate the influence of different beverages (coffee, tea, cola, and mineral water) on the color stability of nanoparticles-modified denture base materials (DBMs). Materials and Methods. A total of 280 specimens (n = 10/group) were prepared from heat-polymerized acrylic resin modified with different concentrations (3% and 7%) of zirconium dioxide (nano-ZrO2), titanium dioxide (nano-TiO2), and silicon dioxide (nano-SiO2) nanoparticles, while 0% was taken as a control. Color change (∆E) of the specimens was evaluated after simulating 6-month immersion time in four commonly used beverages, coffee, tea, cola, and mineral water, as experimental groups. Color stability was measured using a spectrophotometer, and then values were converted to National Bureau of Standards units (NBS units). The one-way ANOVA test was applied to compare color change (ΔE) results followed by Bonferroni’s post hoc test (α = 0.05). Results. The results showed that the heat-polymerized acrylic resin modified with different types of nanoparticles showed lower color changes after being immersed in beverage solutions compared to the unmodified group ( P  < 0.001), so the color stability of heat-polymerized acrylic resin was significantly enhanced by the addition of several nanoparticles; nano-ZrO2 showed the lowest ΔE followed by nano-TiO2 and then nano-SiO2. Regardless of the filler type, 3% concentration showed lower mean ΔE than 7% concentration. Regarding the beverage solutions, the greatest color change was found in the coffee group followed by tea and cola, while water showed the least changes. Conclusion. Modification of heat-polymerized acrylic resin with certain amounts of nano-ZrO2, nano-TiO2, and nano-SiO2 may be useful in improving color stability.

Objective. 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. Materials and Methods. 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). Results. 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 ). Conclusion. 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.

To evaluate the effect of beverages (coffee, tea, Cola-Cola, and mineral water) on the color stability of resin-based composite (RBC) materials modified with different nanoparticles (NPs). The specimens (70/beverage) were fabricated from light-cured RBCs and divided according to NPs into four groups: one control, unmodified (N0); and three experimental—ZrO2 (Zr), TiO2 (Ti), and SiO2 (Si) groups. Each experimental group was further subdivided into two subgroups according to NP concentrations: 3 wt.% and 7 wt.% (n = 10). A spectrophotometer was used to assess the color change (∆E) before and after six months of immersion. Data were analyzed and compared using one-way-ANOVA followed by Bonferroni’s post-hoc test (α = 0.05) and subsequently ∆E value conversion to National Bureau of Standards (NBS) units. The modified light-cured RBCs with ZrO2, TiO2, and SiO2 demonstrated smaller color changes after immersion in the beverages than the unmodified group (p < 0.001). Zr groups showed the lowest ΔE, followed by Ti and Si groups; a 3% concentration resulted in a lower mean ΔE than the 7% concentration. NBS findings showed that coffee and tea produced marked unacceptable color changes (NBS units were >3), and Coca-Cola resulted in noticeable color changes (NBS units between 1.5 and 3), while water produced slight color changes (NBS ≤ 1). Modification of RBCs with both concentrations of ZrO2, as well as 3% of TiO2 and SiO2, may improve its color stability. Based on NBS results, RBCs immersed in mineral water and Coca-Cola showed clinically acceptable color changes, while those immersed in coffee and tea were clinically unacceptable.

No abstract