Biaxial Flexural Strength of Nanocomposites

Signature Grand, Davie, Florida, USA

Objective. To evaluate the bi-axial flexural strength of 5 nanocomposites vs. 1 universal composite (control). Methods. Cylindrical discs with a diameter of 9 mm and thickness of 1.2 mm were made using a custom-made stainless steel mold. Six specimens were prepared for each material. Specimen's surface was covered with mylar strips and polymerized in between 2 glass slabs to achieve consistent surface finish. Specimens were immersed in distilled water for 72 hrs. The strength test was carried out using a universal mechanical testing system (Instron 8841, Instron Corp., Canton, MA). In the biaxial fixture, the specimens were supported by three stainless steel ball bearings with diameter of 1.6 equally spaced inside the fixture. A mylar strip was placed on top of each specimen to more uniformly distribute the load from the piston. The specimen was loaded at a crosshead speed of 0.5 mm/min until failure. Statistical analysis was performed with ANOVA and Student-Newman-Keuls (SNK) at p < 0.05. Results. (figure a) ;The results, in MPa ± SD are shown in the Table, Filtek Z250 had a statistically significantly higher value than all other composites. TPH3 was no different than Premise and Simile. Simile was no different than Simile or Filtek Supreme. Filtek Supreme was statistically higher than Premise (p < 0.05). Grandio was statistically higher than Premise, TPH3, and Simile. Grandio and Z250 had similar values. Conclusions. Grandio showed a statistically significantly higher biaxial flexural strength (p < 0.05) than all other nanocomposites tested, except for Filtek Supreme, which had similar values.