The Effect of Silica and Prepolymer Nanoparticles on the Mechanical Properties of Denture Base Acrylic Resin.

PURPOSE

To evaluate how hydrophobic nanoparticle silica and prepolymer affect the flexural strength, surface hardness, surface roughness, and resilience of a denture base acrylic resin.

MATERIALS AND METHODS

A total of 40 denture base acrylic resin specimens with dimensions 65 × 10 × 3 mm were fabricated in this study. Specimens were divided into five experimental groups (n = 8) according to surface-treated silica and prepolymer concentration incorporated into the acrylic resin (weight %) prior to polymerization: G1 acted as control, no fillers were used in this group. G2: 1 wt% 12 nm silica nanoparticles; G3: 5 wt% 12 nm silica nanoparticles; G4: 1 wt% 12 nm prepolymer nanoparticles; G5: 5 wt% 12 nm prepolymer nanoparticles were added into the acrylic mixture. Acrylic specimens were polymerized according to the manufacturer's instructions. Three-point bending test was performed to evaluate the flexural strength and the resilience of the specimens. Then, a digital profilometer was used to determine the surface roughness of the specimens. Surface hardness was conducted by a digital Shore D hardness testing machine. Surface analysis of one specimen in each group was performed with a scanning electron microscopy (SEM) to observe the fracture surfaces of specimens. ANOVA and Tukey tests were used for the statistical analysis (p < 0.05).

RESULTS

Statistical analysis revealed significant differences among the groups. All groups showed poor flexural strength as compared with the control (p < 0.05). Regarding resilience, silica 5% showed the highest value whereas silica 1% showed the lowest value. Regarding Shore D hardness, silica 1% had the lowest hardness whereas polymer addition did not significantly influence the hardness of the acrylic resin (p < 0.05). Furthermore, silica 1% presented the highest roughness as compared with the other groups (p < 0.05). SEM images indicated some porosity and voids on fracture surfaces.

CONCLUSIONS

Both the silica and prepolymer incorporation into acrylic resin adversely affected the flexural strength of the acrylic resin compared to control group. In all concentrations, prepolymer incorporation resulted in increased flexural strength of acrylic resins compared to silica addition. The greater concentrations of the fillers resulted in increased mechanical properties of the acrylic resin.