title: [Evaluation of the efficiency of different instrumentation for root canal retreatment using micro-computed tomography].
abstract: OBJECTIVE
  To establish the three-dimensional model of human permanent premolars based on Micro-computed tomography (Micro-CT) data, and evaluate the efficiency quantitatively of two different instrumentations for root canal retreatment.
  
  
  METHODS
  Forty extracted permanent premolars for the reason of orthodontic treatment were collected, prepared by using ProTaper Ni-Ti files and filled by cold gutta pertscha lateral condensation technique. The subjects were scanned by Micro-CT. Forty teeth were randomly divided into two groups and retreated by K-Flexo files and ProTaper Universal retreatment system respectively. Then all subjects were scanned again, and the mean percentage of remaining filling materials and the scores of remaining filling materials presented in upper, middle and apical 1/3 of the canal were calculated.
  
  
  RESULTS
  Mean percentage of the remaining filling materials by K-Flexo files was lower than that by ProTaper Universal retreatment system (P=0.005). The scores demonstrated that K-Flexo files had greater efficiency than ProTaper Universal retreatment system when retreating the apical 1/3 of canal (P<0.05).
  
  
  CONCLUSIONS
  This study shows that both techniques could not remove filling materials completely.
authors: Dept. of Endodontics, School of Stomatology, Shandong University, Jinan 250012, China.
authors: Jing
authors: J
authors: Guo
authors: Kaifeng
authors: K
authors: Yin
authors: Haibing
authors: H
authors: Yang
authors: Xuan
authors: X
authors: Han
authors: Yan
authors: Y
authors: Wang
mesh_terms: D003722:Dental Alloys; D003786:Dental Pulp Cavity; D006171:Gutta-Percha; D006801:Humans; D009532:Nickel; D019233:Retreatment; D012387:Root Canal Filling Materials; D018915:Root Canal Preparation; D012390:Root Canal Therapy; D014025:Titanium; D055114:X-Ray Microtomography
chemical_list: D003722:Dental Alloys; D012387:Root Canal Filling Materials; C040654:titanium nickelide; D009532:Nickel; D006171:Gutta-Percha; D014025:Titanium