title: Ultrasonic condensation of gutta-percha: the effect of power setting and activation time on temperature rise at the root surface - an in vitro study.
abstract: OBJECTIVE
  To determine the effect of power setting and duration of activation on the temperature rise at the root surface during root canal obturation by ultrasonic condensation of gutta-percha.
  
  
  METHODS
  A human maxillary canine was used in an in vitro split tooth model to allow repeated obturation of the root canal system using an ultrasonic device to thermocompact gutta-percha. Combinations of power settings (1, 3 and 5) and durations of activation (4, 10 and 15 s) were used to test their effect on temperature rise at the root surface using eight K-type thermocouples at the mid-root and apical levels. At the end of each obturation, the tooth was disassembled to remove the gutta-percha in preparation for the next obturation (n = 10 for each combination). Multiple linear regression models were used to investigate the effects of power setting, duration of activation and thermocouple location on the maximum temperature rise recorded.
  
  
  RESULTS
  Only one combination of power setting (5) and duration of activation (15 s) resulted in temperature rise in excess of 10 degrees C. The maximum temperature rise at the mid-root level was significantly (P < 0.001) greater than that recorded apically. It is also significantly affected by the combination of power setting and duration of activation.
  
  
  CONCLUSIONS
  Temperature rises at the root surface during ultrasonic condensation of gutta-percha in excess of 10 degrees C were evident in only one combination of power (5) and time (15 s) settings at the mid-root level.
authors.affiliation: Unit of Endodontics, Eastman Dental Institute for Oral Health Care Sciences, University College London, London, UK. rerootx@aol.com
authors.forename: G C
authors.initials: GC
authors.lastname: Bailey
authors.forename: S A
authors.initials: SA
authors.lastname: Cunnington
authors.forename: Y-L
authors.initials: YL
authors.lastname: Ng
authors.forename: K
authors.initials: K
authors.lastname: Gulabivala
authors.forename: D J
authors.initials: DJ
authors.lastname: Setchell
mesh_terms: D001831:Body Temperature; D003481:Cuspid; D006171:Gutta-Percha; D006358:Hot Temperature; D006801:Humans; D016018:Least-Squares Analysis; D016014:Linear Models; D012389:Root Canal Obturation / Q000295:instrumentation / Q000379:methods*; D013814:Thermal Conductivity; D013997:Time Factors; D014465:Ultrasonics
chemical_list: D006171:Gutta-Percha