title: Thermal analysis and stability of commercially available endodontic obturation materials.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the thermal stability of 23 commercially-available endodontic obturation materials.
  
  
  METHODS
  Specimens (n = 10) were sealed in aluminum differential scanning calorimetry (DSC) crucibles and subjected to thermal scan series consisting of a 25 to 70 °C at 5 °C/min followed by a rapid increase to 230 °C, followed by a second scan from 25 to 70 °C at 5 °C/min. The first scan evaluated the materials as-received followed by a worse-case-scenario thermal challenge simulating temperatures involved with warm vertical condensation obturation techniques. The second thermal scan observed any phase changes from the high temperature challenge. This two-scan process was repeated twice to observe changes encountered by repeat high heat exposure during obturation. Mean thermal enthalpies were analyzed with Kruskal-Wallis and Games-Howell post-hoc test. (p = 0.05).
  
  
  RESULTS
  Thermal behavior was material dependent. During the first thermal scan, materials typically demonstrated broad endothermic enthalpy curves suggesting either a gutta-percha phase mixture and/or an alpha crystalline phase. The first high-heat challenge produced definitive alpha/beta thermal phase signatures usually associated with gutta-percha. Changes in beta-phase enthalpies were noted with Therarmafil Plus and UltraFil Firmset while increase in alpha-phases was observed with GuttaCore, K3, Lexicon, and Schein Accessory Points.
  
  
  CONCLUSIONS
  Commercial endodontic gutta-percha obturation materials displayed thermal characteristics that were material dependent. However, all demonstrated stability at temperatures in excess to that experienced during warm vertical condensation techniques.
  
  
  CONCLUSIONS
  The gutta-percha obturation materials evaluated in this evaluation can be used successfully in warm vertical condensation techniques without fear of degradation.
authors.affiliation: Graduate Dental Research, 81 Dental Squadron, 606 Fisher Street, Keesler Air Force Base, Biloxi, MS, 39534, USA. Howard.roberts@us.af.mil.
authors.forename: H W
authors.initials: HW
authors.lastname: Roberts
authors.affiliation: Advanced Education in Endodontics, 81 Dental Squadron, Keesler Air Force Base, Biloxi, MS, USA.
authors.forename: T C
authors.initials: TC
authors.lastname: Kirkpatrick
authors.affiliation: Advanced Education in Endodontics, Georgia Regents University School of Dental Medicine, Augusta, GA, USA.
authors.forename: B E
authors.initials: BE
authors.lastname: Bergeron
mesh_terms: D002151:Calorimetry / Q000379:methods; D006171:Gutta-Percha / Q000737:chemistry*; D006358:Hot Temperature; D008422:Materials Testing; D012387:Root Canal Filling Materials / Q000737:chemistry*; D012389:Root Canal Obturation / Q000295:instrumentation*; D013499:Surface Properties
chemical_list: D012387:Root Canal Filling Materials; D006171:Gutta-Percha
keywords: Differential scanning calorimetry (DSC); Gutta-percha; Thermal analysis; Thermal stability