title: Analysis of apical root transportation associated with ProTaper Universal F3 and F4 instruments by using digital subtraction radiography.
abstract: BACKGROUND
  The aim of this study was to assess the occurrence of apical root transportation after the use of ProTaper Universal rotary files sizes 3 (F3) and 4 (F4).
  
  
  METHODS
  Instruments were worked to the apex of the original canal, always by the same operator. Digital subtraction radiography images were produced in buccolingual and mesiodistal projections. A total of 25 radiographs were taken from root canals of human maxillary first molars with curvatures varying from 23-31 degrees. Quantitative data were analyzed by intraclass correlation coefficient and Wilcoxon nonparametric test (P = .05).
  
  
  RESULTS
  Buccolingual images revealed a significantly higher degree of apical transportation associated with F4 instruments when compared with F3 instruments in relation to the original canal (Wilcoxon test, P = .007). No significant difference was observed in mesiodistal images (P = .492).
  
  
  CONCLUSIONS
  F3 instruments should be used with care in curved canals, and F4 instruments should be avoided in apical third preparation of curved canals.
authors.affiliation: School of Dentistry, Universidade Luterana do Brasil (ULBRA), Canoas, RS, Brazil. g.kunert@click21.com.br
authors.forename: Gustavo Golgo
authors.initials: GG
authors.lastname: Kunert
authors.forename: Vania Regina
authors.initials: VR
authors.lastname: Camargo Fontanella
authors.forename: Abílio Albuquerque Maranhão
authors.initials: AA
authors.lastname: de Moura
authors.forename: Fernando Branco
authors.initials: FB
authors.lastname: Barletta
mesh_terms: D003786:Dental Pulp Cavity / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D006801:Humans; D008422:Materials Testing; D008963:Molar / Q000000981:diagnostic imaging; D009811:Odontometry; D019252:Radiography, Dental, Digital / Q000379:methods*; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods; D013382:Subtraction Technique; D019227:Tooth Apex / Q000033:anatomy & histology / Q000000981:diagnostic imaging*