title: Apically extruded debris and irrigant with two Ni-Ti systems and hand files when removing root fillings: a laboratory study.
abstract: OBJECTIVE
  To compare the amount of apically extruded debris and irrigant produced by two Ni-Ti instruments and hand files when removing root fillings, and to compare two experimental models.
  
  
  METHODS
  Sixty single straight root canals in human mandibular premolars were prepared with K-files and filled with gutta-percha and AH Plus sealer. The teeth were randomly divided into three groups of 20 for removal of the root filling material with Reciproc files (Group 1, RP), Mtwo retreatment files (Group 2, MR) or hand files (Group 3, H). Each group was then equally divided into experimental subgroups: A, with 1.5% agar gel model (AG); B, with empty tube model (ET). Apically extruded debris and irrigant was quantified by subtracting the initial weight of the test apparatus without a tooth from its weight after the root canal retreatment. Comparative analysis of the amount of apically extruded debris and irrigant for each of the instruments and the experimental models was performed. Time for gutta-percha removal was recorded. Data were statistically analysed using one-way analysis of variance.
  
  
  RESULTS
  Removal of root fillings with two Ni-Ti instruments produced less apically extruded debris and irrigant than hand files in both experimental models (P < 0.05). More apically extruded debris and irrigant was produced with Reciproc files than Mtwo retreatment files using the 1.5% agar gel model (P > 0.05). Significantly more apically extruded debris and irrigant was produced with Reciproc files than Mtwo retreatment files using the empty tube model (P < 0.05). The time required to remove the root fillings followed Reciproc<Mtwo R<hand files (P < 0.05).
  
  
  CONCLUSIONS
  All the instruments produced apically extruded debris and irrigant. The two Ni-Ti instruments produced less apically extruded debris and irrigant than hand files. A 1.5% agar gel can provide resistance to apically extruded debris and irrigant and may represent the clinical situation better than the empty tube model.
authors.affiliation: State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu.
authors.forename: Y
authors.initials: Y
authors.lastname: Lu
authors.forename: R
authors.initials: R
authors.lastname: Wang
authors.forename: L
authors.initials: L
authors.lastname: Zhang
authors.forename: H L
authors.initials: HL
authors.lastname: Li
authors.forename: Q H
authors.initials: QH
authors.lastname: Zheng
authors.forename: X D
authors.initials: XD
authors.lastname: Zhou
authors.forename: D M
authors.initials: DM
authors.lastname: Huang
mesh_terms: D004853:Epoxy Resins; D006171:Gutta-Percha; D006801:Humans; D009532:Nickel; D011897:Random Allocation; D012387:Root Canal Filling Materials; D012389:Root Canal Obturation; D007507:Therapeutic Irrigation; D014025:Titanium
chemical_list: D004853:Epoxy Resins; D012387:Root Canal Filling Materials; C534916:epoxy resin-based root canal sealer; C040654:titanium nickelide; D009532:Nickel; D006171:Gutta-Percha; D014025:Titanium
keywords: Mtwo retreatment files (Mtwo R); Reciproc; apically extruded debris and irrigant; gutta-percha; root canal retreatment