title: Post space preparation timing of root canals sealed with AH Plus sealer.
abstract: OBJECTIVE
  To determine the optimal timing for post space preparation of root canals sealed with epoxy resin-based AH Plus sealer in terms of its polymerization and influence on apical leakage.
  
  
  METHODS
  The epoxy polymerization of AH Plus (Dentsply DeTrey) as a function of time after mixing (8, 24, and 72 hours, and 1 week) was evaluated using Fourier transform infrared (FTIR) spectroscopy and microhardness measurements. The change in the glass transition temperature (Tg) of the material with time was also investigated using differential scanning calorimetry (DSC). Fifty extracted human single-rooted premolars were filled with gutta-percha and AH Plus, and randomly separated into five groups (n= 10) based on post space preparation timing (immediately after root canal obturation and 8, 24, and 72 hours, and 1 week after root canal obturation). The extent of apical leakage (mm) of the five groups was compared using a dye leakage test. Each dataset was statistically analyzed by one-way analysis of variance and Tukey'spost hoctest (α = 0.05).
  
  
  RESULTS
  Continuous epoxy polymerization of the material with time was observed. Although theTgvalues of the material gradually increased with time, the specimens presented no clearTgvalue at 1 week after mixing. When the post space was prepared 1 week after root canal obturation, the leakage was significantly higher than in the other groups (p< 0.05), among which there was no significant difference in leakage.
  
  
  CONCLUSIONS
  Poor apical seal was detected when post space preparation was delayed until 1 week after root canal obturation.
authors.affiliation: Department of Dental Science, Graduate School, Kyungpook National University, Daegu, Korea.
authors.forename: Hae-Ri
authors.initials: HR
authors.lastname: Kim
authors.affiliation: Department of Conservative Dentistry, Kyungpook National University, Daegu, Korea.
authors.forename: Young Kyung
authors.initials: YK
authors.lastname: Kim
authors.affiliation: Department of Dental Biomaterials, School of Dentistry, Kyungpook National University, Daegu, Korea.; Institute for Biomaterials Research and Development, Kyungpook National University, Daegu, Korea.
authors.forename: Tae-Yub
authors.identifier: 0000-0002-9998-3099
authors.initials: TY
authors.lastname: Kwon
keywords: AH Plus; Polymerization; Post and core technique; Root canal preparation