title: A comparison of viscoelastic properties of three root canal sealers.
abstract: OBJECTIVE
  Handling of endodontic sealers is greatly dependent on their elasticity and flow ability. We compared the viscoelastic properties of three root canal sealers.
  
  
  METHODS
  AH Plus (Dentsply, De Trey, Konstanz, Germany), Endofill (Dentsply Hero, Petrópolis, Rio de Janeiro, Brazil) and AH26 (Dentsply, De Trey, Konstanz, Germany) were mixed according to the manufacturers' instructions. The resulted pastes were placed on the plate of a rheometer (MCR 300, Anton-Paar, Graz, Austria). The experiments were performed at 25°C and 37°C. Viscoelastic properties of the sealers including loss modulus (G″), storage modulus (G') and complex viscosity (η*) were studied using dynamic oscillatory shear tests. The shear module versus frequency (from 0.01 to 100 S(-1)) curves were gained using frequency deformation sweep test. Three samples of each material were examined at each temperature. The mean of these three measurements were recorded.
  
  
  RESULTS
  The storage modulus of AH plus was higher than its loss modulus at two temperatures. Endofill exhibited a crossover region in which the storage modulus crosses the loss modulus in both temperatures. At 25°C the loss modulus of AH26 was higher than the storage modulus (G″>G'). In contrast, at 37°C G' was greater than G″ (G'>G″). Both shear modules of AH Plus and Endofill decreased as the temperature raised from 25°C to 37°C. On the contrary, the loss modulus and storage modulus of AH26 increased at 37°C.
  
  
  CONCLUSIONS
  In both test temperatures, AH Plus behaved like viscoelastic solids and Endofill exhibited a gel-like viscoelastic behavior. AH26 at 25°C behaved like liquids, while at 37°C it was an elastic solid-like material.
authors.affiliation: Dental Research Center, Dentistry Research Institute, Department of Endodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran ; Researcher, Iranian Center for Endodontic Research, Tehran, Iran.
authors.forename: Sedigheh
authors.initials: S
authors.lastname: Khedmat
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Momen-Heravi
authors.forename: Malihe
authors.initials: M
authors.lastname: Pishvaei
keywords: Endodontics; Rheology; Sealer