title: Confocal microscopy assessment of filling material remaining on root canal walls after retreatment.
abstract: OBJECTIVE
  The percentage of Endofill remaining on canal walls after retreatment with different techniques was evaluated using confocal microscopy and qualitative analysis of the interface between the filling material/dentine.
  
  
  METHODS
  Sixty-four root canals of incisors were prepared with ProTaper, filled with gutta-percha and Endofill mixed with 0.1% rhodamine B. The roots were thermocycled and distributed into groups according to the method of evaluation: GI - direct viewing (DV) and GII - operating microscope (OM) and according to the removal technique: A) ProTaper retreatment (PR), B) PR/xylol, C) ultrasound and D) ultrasound/xylol. The root canals were then refilled with gutta-percha and AH Plus with 0.1% fluorescein and sectioned at 2, 4 and 6 mm from the apex. The percentage of remaining Endofill was analysed by confocal microscopy. Additionally, 16 roots were prepared with a ProTaper F5 instrument and were filled with Endofill + 0.1% rhodamine B/gutta-percha (negative control group) (n = 8), and the positive control group (n = 8) were filled with AH Plus with 0.1% fluorescein/gutta-percha.
  
  
  RESULTS
  Three-way anova demonstrated differences in the method of evaluation, removal techniques and their interaction (P < 0.05). OM (26.15 ± 12.16%) had a smaller percentage of remaining sealer than DV (32.77 ± 14.47%). The Tukey's test revealed that ultrasound/xylol (15.77 ± 7.15%) led to lower percentages of remaining sealer, significantly different from the PR group (35.25 ± 13.63%), PR/xylol (33.03 ± 11.64%) and ultrasound (33.79 ± 11.71%), which were similar (P > 0.05). Qualitative analysis detected that ultrasound had lower remaining Endofill than PR, particularly when combined with xylol. Operating microscope resulted in lower residual sealer, regardless of the removal technique.
  
  
  CONCLUSIONS
  None of the protocols was associated with complete removal of the filling material; however, the use of ultrasound/xylol under an OM provided better results.
authors.affiliation: School of Dentistry, University of Ribeirão Preto, UNAERP Ribeirão Preto, SP, Brazil.
authors.forename: F A
authors.initials: FA
authors.lastname: Rached-Júnior
authors.forename: M D
authors.initials: MD
authors.lastname: Sousa-Neto
authors.forename: J F B
authors.initials: JF
authors.lastname: Bruniera
authors.forename: M A H
authors.initials: MA
authors.lastname: Duarte
authors.forename: Y T C
authors.initials: YT
authors.lastname: Silva-Sousa
mesh_terms: D006171:Gutta-Percha; D006801:Humans; D066298:In Vitro Techniques; D007180:Incisor; D018613:Microscopy, Confocal; D009532:Nickel; D019233:Retreatment; D012387:Root Canal Filling Materials; D018915:Root Canal Preparation / Q000295:instrumentation*; D013499:Surface Properties; D014025:Titanium
chemical_list: D012387:Root Canal Filling Materials; C074417:Endo-Fill; D009532:Nickel; D006171:Gutta-Percha; D014025:Titanium
keywords: Ni-Ti instruments; confocal microscopy; endodontics; residual sealer; root canal retreatment; ultrasonic tips