title: The effect of storage temperature on mechanical properties of gutta-percha and resilon.
abstract: OBJECTIVE
  To compare the mechanical properties of Resilon and gutta-percha cones after storing at three different temperatures.
  
  
  METHODS
  One-hundred standardized size 40/02 gutta-percha cones and 100 Resilon cones were randomly divided into four groups. The first group of the materials were tested immediately after receipt as the control group. The other three were stored in their packages at -12°C, 4± 1°C and 22± 2°C for three months. Then, obturating cones were loaded by a tensile force at the rate of 5mm/min. Physical integrity of gutta-percha and Resilon cones were also evaluated according to ISO6877. The data were analyzed by one-way analysis of variance, post hoc and t-test. A p-value <0.05 was considered significant.
  
  
  RESULTS
  The elasticity modulus of gutta-percha reduced significantly after three months storage at -12°C, while storage at 4±1°C and 22± 2°C had no effect on its modulus of elasticity. In addition, the tensile strength of gutta-percha did not change after three months of storing. The modulus of elasticity of Resilon reduced significantly in all storage conditions; however, its tensile strength did not change. The storage conditions did not have a significant effect on the elongation rate of gutta-percha and Resilon. Eighty percent of gutta-percha cones lost their physical integrity after storage in 4 °±1C and 22±2°C. However, storage conditions had no impact on the physical integrity of Resilon cones.
  
  
  CONCLUSIONS
  Storing gutta-percha at -12°C can benefit its properties, while keeping Resilon at both refrigerated and room conditions can preserve its mechanical properties.
authors.affiliation: Dental Research Center Dentistry Research Institute, Department of Endodontics, School of Dentistry, Tehran University of Medical Sciences, and Iranian Center for Endodontic Research, Tehran, Iran.
authors.forename: Sedigheh
authors.initials: S
authors.lastname: Khedmat
authors.affiliation: Department of Dental Biomaterials, School of Dentistry, Dental Research Center Dentistry Research Institute, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Farzaneh
authors.initials: F
authors.lastname: Aghajani
authors.affiliation: Undergraduate Student, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Shabnam
authors.initials: S
authors.lastname: Zaringhalam
keywords: Elastic Modulus; Gutta-Percha; Mechanical Phenomena; Tensile Strength