title: Shear modulus and thermal properties of gutta percha for root canal filling.
abstract: The purpose of this investigation was to investigate the rheological properties of four commercially available gutta perchas for root canal filling. The relaxation modulus [Gr(0): instantaneous shear modulus] and specific volume of their materials were examined. In addition, the quantity of heat was also studied by differential scanning calorimeter. In a lower temperature range than the first-order transition temperature (melting point), the Gr(0) values of each material were almost identical. A marked decrease of Gr(0) was observed at the melting point, and the range of the first-order transition temperature at heating was from 42.0 to 60.0 degrees C. At higher temperatures than the first-order transition temperature of each material, a considerable difference in Gr(0) values was observed. The transition temperatures obtained by the results of the Gr(0), specific volume and quantity of heat agreed with one another. A marked specific volume change was observed at the first-order transition temperature. The technique using melted gutta percha may not be favourable compared with the conventional lateral condensation technique because melted gutta percha undergoes a large amount of shrinkage during setting.
authors.affiliation: Department of Operative Dentistry and Endodontology, Kagoshima University Dental School, Kagoshima, Japan. tsukada@dentb.hal.kagoshima-u.ac.jp
authors.forename: G
authors.initials: G
authors.lastname: Tsukada
authors.forename: T
authors.initials: T
authors.lastname: Tanaka
authors.forename: M
authors.initials: M
authors.lastname: Torii
authors.forename: K
authors.initials: K
authors.lastname: Inoue
mesh_terms: D006171:Gutta-Percha; D006801:Humans; D008422:Materials Testing; D012212:Rheology; D012387:Root Canal Filling Materials
chemical_list: D012387:Root Canal Filling Materials; D006171:Gutta-Percha