Methods: Fourteen recent resin composites of different resin matrices of Bis-GMA and TEGDMA, different filler loading (41-64%) and sizes (ranging 5nm-20µm) were studied using Bohlin rheometer. It conducted steady shear sweep test in order to measure the composites viscosity. The geometry used in this test was an aluminium parallel plate 20mm in diameter. Composite paste was placed on the rheometer lower plate, after which the upper plate was lowered to adjust the gap to 250µm. After residual normal stress was relieved, a frequency sweep test was completed over the angular frequency range of ω=0.1–100 rad/s. Data was analysed using one way ANOAV, Bonferroni post-hocand t-independent tests (p<0.05).
Results: All composites exhibited pseudoplasticity. The viscosity increased as the percentage of filler loading (by volume) was increased, but decreased with increasing temperature (25°C to 37°C). For similar filler volumes, as the filler size decreased, viscosity increased. Statistically significant differences in viscosity presented between the materials at 25°C and 37°C (p<0.05). Viscosity ranged 0.05-349.33 KPas at 25°C and 0.03-132.00 KPas at 37°C. Filtek Supreme XTE exhibited the highest viscosity at both temperatures (p<0.05). Filtek Bulk Fill on the other hand, showed the lowest viscosity at both temperatures (p<0.05). Viscosity significantly decreased with the increase in the temperatures for all materials (p<0.05). The reduction ranged from 40.81% (for Venus Diamond Flow) to 92.22% (for Spectrum TPH3).
Conclusion: Composite resin rheological properties are significantly affected by the composite resin matrices composition, filler content (size and loading), and temperature. Filtek Supreme XTE and Filtek Bulk Fill exhibited the highest and lowest viscosities respectively (p<0.05). Viscosity significantly decreased with the increase in the temperatures for all materials (p<0.05).