Rheological properties of contemporary nanohybrid dental resin composites: The influence of preheating

Abstract

Preheating of dental composites enhances their flowability and can improve marginal adaptation and decrease voids leading to more successful restorations. The aim of this research is to study the influence of preheating temperature on the rheological properties of four contemporary nanohybrid dental resin composites. The rheological measurements on the four preheated nanohybrid resin-based composites [Herculite Ultra (Kerr), Tetric EvoCeram (Ivoclar Vivadent), Filtek Supreme Ultra (3 M) and Grandio (Voco)] were conducted utilizing a parallel-plate shear rheometer. The composites were placed on the lower plate, and the upper plate was lowered until it gently touched the surface of the sample at a gap distance of 0.5 mm. Measurements were obtained at three different temperatures 25, 37 and 60 °C. The shear rate varied linearly in ramp mode from 0.1 to 10 s− 1. All dental resin composites tested in this research showed a significant reduction in shear viscosity with increasing temperature. Additionally, all dental resin composites were pseudoplastic, indicating a disproportionate reduction in complex viscosity (η*) with enhancing frequency (shear rate; shear-thinning effects). There is a variation in shear modulus of elasticity (G′) between the four contemporary nanohybrid dental resin composites at low shear rates. Preheating the composite material resulted in enhanced flow and greater adaptability, as evident by decreasing G’ values with increasing shear rate which did not occur with samples that were not preheated. The results demonstrated that regardless of the resin composite material, it was found that preheating the nanohybrid dental composites considerably improves their flowability and can improve clinical placement and adaptation. Finally, the obtained results could be employed as a guideline for material behavior to form the desired consistency or compare commercially available preheating devices.