title: Comparison of the efficacy of nickel-titanium rotary systems with or without the retreatment instruments in the removal of gutta-percha in the apical third.
abstract: BACKGROUND
  The purpose of this study was to compare the efficacy of nickel-titanium rotary systems with or without the retreatment instruments in the removal of gutta-percha from the apical third.
  
  
  METHODS
  The systems compared were as follows: ProTaper Universal (PT), ProTaper Universal Retreatment (PTr), Mtwo (M2) and Mtwo Retreatment (M2r). Sixty extracted mandibular incisors were treated with a crown-down technique and filled with gutta-percha and sealer. The apical diameter was standardized in 0.30 mm, 1 mm from the apex. The teeth were distributed into 4 experimental groups: PT, PTr, M2 and M2r. In PTr and M2r groups, filling materials were removed by PTr/M2r followed by root canals preparation up to a PT F4/M2 40; in groups PT/M2, the filling materials were removed and the root canals were prepared by PT up to a PT F4/M2 up to a M2 40. The roots were split and photomicrographing. The percentage of clean area in the apical 5 mm was calculated using software. Data were analyzed with the Kruskal-Wallis test.
  
  
  RESULTS
  Remaining material was found in all hemisections and there was no statistically significant difference between the groups (p = 0.09). Considering the surface of the canal walls of all teeth, the mean of the percentage of clean area was 54%.
  
  
  CONCLUSIONS
  Considering the applied methodology, remaining filling material was found in all hemisections, regardless of the retreatment technique and PT or M2 were as effective as PTr/PT or M2r/M2.
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Estácio de Sá University, Av, Alfredo Baltazar da Silveira, 580/cobertura, Recreio dos Bandeirantes, Rio de Janeiro, RJ 22790-710, Brazil. flavioferreiraalves@gmail.com.
authors.forename: Flávio Rodrigues Ferreira
authors.initials: FR
authors.lastname: Alves
authors.forename: Thiago Oliveira
authors.initials: TO
authors.lastname: Ribeiro
authors.forename: Jaime Omar
authors.initials: JO
authors.lastname: Moreno
authors.forename: Hélio Pereira
authors.initials: HP
authors.lastname: Lopes
mesh_terms: D003722:Dental Alloys / Q000737:chemistry*; D003786:Dental Pulp Cavity / Q000648:ultrastructure*; D004867:Equipment Design; D006171:Gutta-Percha / Q000737:chemistry*; D006801:Humans; D006813:Humidity; D009532:Nickel / Q000737:chemistry*; D019233:Retreatment; D012387:Root Canal Filling Materials / Q000737:chemistry*; D012388:Root Canal Irrigants / Q000627:therapeutic use; D018915:Root Canal Preparation / Q000295:instrumentation*; D012399:Rotation; D012973:Sodium Hypochlorite / Q000627:therapeutic use; D013193:Stainless Steel / Q000737:chemistry; D013499:Surface Properties; D013696:Temperature; D013995:Time; D014025:Titanium / Q000737:chemistry*; D019227:Tooth Apex / Q000648:ultrastructure*; D019415:Torque; D016896:Treatment Outcome; D015035:Zinc Oxide-Eugenol Cement / Q000627:therapeutic use
chemical_list: D003722:Dental Alloys; D012387:Root Canal Filling Materials; D012388:Root Canal Irrigants; D015035:Zinc Oxide-Eugenol Cement; C040654:titanium nickelide; D013193:Stainless Steel; D009532:Nickel; D006171:Gutta-Percha; D014025:Titanium; D012973:Sodium Hypochlorite