The main deficiency of dental composites is the inability to withstand the functional stress imposed which limits their use as posterior restorative materials. Objective: To evaluate the elastic moduli of eight experimental unfilled resins, sixteen experimental composites as well as two commercial composites. Methods: Two silane-treated glass fillers of strontium and barium borosilicate glasses were incorporated into eight resins containing different proportions of BISGMA / TEGDMA / UDMA / BISEMA / HEMA. The total filler content including fumed silica was 80 weight percent. Disc specimens (16mm diameter x 1.5mm thickness) were made and soaked in deionised water @ 37ºC for 21 days prior to testing. The water sorption of the resins (n=10) was evaluated by weight gain. The density of the specimens (n=3) was determined by water displacement method. The dynamic Young's, shear, bulk moduli and Poisson's ratio (n=3) were determined by an ultrasonic method using lithium niobate crystals at 10MHz resonant frequency. Statistical analysis of the data was conducted using ANOVA and a Student-Knewman-Keuls rank order test. Results: The water sorption for the unfilled resins ranged from 22.15 to 81.52µg/cm³. The dynamic Young's shear and bulk moduli of the experimental resins and composites ranged from 4.97 to 24.17GPa, 2.24 to 9.79GPa and 6.59 to 16.58GPa respectively. The dynamic Young's, shear and bulk moduli for Surefil and charisma F were (18.86±0.87, 18.14±0.94Gpa), (7.86±0.36, 7.19±0.34GPa) and (10.45±0.48, 12.67±0.95GPa) respectively. Conclusions: Resins containing HEMA exhibited significantly higher water sorption at p=0.05. The elastic moduli of experimental composites containing strontium glass fillers were higher than the ones containing barium glass fillers at p=0.05. The experimental composites containing HEMA exhibited significantly higher elastic moduli than all other experimental materials (p=0.05). Ten experimental composites exhibited significantly higher mechanical properties than Surefil and Charisma F at p=0.05.

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