Thermal analysis and stability of commercially available endodontic obturation materials

The purpose of this study was to evaluate the thermal stability of 23 commercially-available endodontic obturation materials. Specimens (n = 10) were sealed in aluminum differential scanning calorimetry (DSC) crucibles and subjected to thermal scan series consisting of a 25 to 70 A degrees C at 5 A degrees C/min followed by a rapid increase to 230 A degrees C, followed by a second scan from 25 to 70 A degrees C at 5 A degrees 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). 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. 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. The gutta-percha obturation materials evaluated in this evaluation can be used successfully in warm vertical condensation techniques without fear of degradation.