title: Effect of compression load and temperature on thermomechanical tests for gutta-percha and Resilon®.
abstract: OBJECTIVE
  To analyse a method used to evaluate the thermomechanical properties of gutta-percha and Resilon(®) at different temperatures and compression loads.
  
  
  METHODS
  Two hundred and seventy specimens measuring 10 mm in diameter and 1.5 mm in height were made from the following materials: conventional gutta-percha (GCO), thermoplastic gutta-percha (GTP) and Resilon(®) cones (RE). After 24 h, the specimens were placed in water at 50 °C, 60 °C or 70 °C for 60 s. After that, specimens were placed between two glass slabs, and loads weighing 1.0, 3.0 or 5.0 kg were applied. Images of the specimens were digitized before and after the test and analysed using imaging software to determine their initial and final areas. The thermomechanical property of each material was determined by the difference between the initial and final areas of the specimens. Data were subjected to anova and SNK tests at 5% significance. To verify a possible correlation between the results of the materials, linear regression coefficients (r) were calculated.
  
  
  RESULTS
  Data showed higher flow area values for RE under all compression loads at 70 °C and under the 5.0 kg load at 60 °C (P < 0.05). Regarding gutta-percha, GTP showed higher flow under loads weighing 3.0 and 5.0 kg, at 60 and 70 °C (P < 0.05). GCO presented higher flow at 70 °C with a load of 5.0 kg. Regression analyses showed a poor linear correlation amongst the results of the materials under the different experimental conditions.
  
  
  CONCLUSIONS
  Gutta-percha and Resilon(®) cones require different compression loads and temperatures for evaluation of their thermomechanical properties. For all materials, the greatest flow occurred at 70 °C under a load of 5.0 kg; therefore, these parameters may be adopted when evaluating endodontic filling materials.
authors.affiliation: Department of Restorative Dentistry, Araraquara Dental School, São Paulo State University - UNESP, Araraquara, Brazil. tanomaru@uol.com.br
authors.forename: M
authors.initials: M
authors.lastname: Tanomaru-Filho
authors.forename: G F
authors.initials: GF
authors.lastname: Silveira
authors.forename: J M S N
authors.initials: JM
authors.lastname: Reis
authors.forename: I
authors.initials: I
authors.lastname: Bonetti-Filho
authors.forename: J M
authors.initials: JM
authors.lastname: Guerreiro-Tanomaru
mesh_terms: D000704:Analysis of Variance; D019245:Compressive Strength; D003799:Dental Stress Analysis; D006171:Gutta-Percha / Q000737:chemistry*; D006358:Hot Temperature; D006801:Humans; D008422:Materials Testing; D012212:Rheology; D012387:Root Canal Filling Materials / Q000737:chemistry*; D018709:Statistics, Nonparametric; D013314:Stress, Mechanical
chemical_list: D012387:Root Canal Filling Materials; C486892:resilon sealer; D006171:Gutta-Percha