title: Effect of canal length and curvature on working length alteration with WaveOne reciprocating files.
abstract: BACKGROUND
  This study evaluated the working length (WL) modification after instrumentation with WaveOne Primary (Dentsply Maillefer, Ballaigues, Switzerland) reciprocating files and the incidence of overinstrumentation in relation to the initial WL.
  
  
  METHODS
  Thirty-two root canals of permanent teeth were used. The angles of curvature of the canals were calculated on digital radiographs. The initial WL with K-files was transferred to the matched WaveOne Primary reciprocating files. After glide paths were established with PathFile (Dentsply Maillefer, Ballaigues, Switzerland), canals were shaped with WaveOne Primary referring to the initial WL. The difference between the postinstrumentation canal length and the initial canal length was analyzed by using a fiberoptic inspection microscope. Data were analyzed with a balanced 2-way factorial analysis of variance (P < .05).
  
  
  RESULTS
  Referring to the initial WL, 24 of 32 WaveOne Primary files projected beyond the experimental apical foramen (minimum-maximum, 0.14-0.76 mm). A significant decrease in the canal length after instrumentation (95% confidence interval ranging from -0.34 mm to -0.26 mm) was detected. The canal curvature significantly influenced the WL variation (F(1) = 30.65, P < .001). The interaction between the initial canal length and the canal curvature was statistically significant (F(2) = 4.38, P = .014).
  
  
  CONCLUSIONS
  Checking the WL before preparation of the apical third of the root canal is recommended when using the new WaveOne NiTi single-file system.
authors.affiliation: Department of Endodontics, University of Turin Dental School, Turin, Italy.
authors.forename: Elio
authors.initials: E
authors.lastname: Berutti
authors.forename: Giorgio
authors.initials: G
authors.lastname: Chiandussi
authors.forename: Davide Salvatore
authors.initials: DS
authors.lastname: Paolino
authors.forename: Nicola
authors.initials: N
authors.lastname: Scotti
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Cantatore
authors.forename: Arnaldo
authors.initials: A
authors.lastname: Castellucci
authors.forename: Damiano
authors.initials: D
authors.lastname: Pasqualini
mesh_terms: D003722:Dental Alloys / Q000737:chemistry; D003786:Dental Pulp Cavity / Q000473:pathology*; D004867:Equipment Design; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D007180:Incisor / Q000473:pathology; D008963:Molar / Q000473:pathology; D009532:Nickel / Q000737:chemistry; D009811:Odontometry / Q000379:methods; D055100:Optical Fibers; D019252:Radiography, Dental, Digital / Q000379:methods; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods; D014025:Titanium / Q000737:chemistry; D019227:Tooth Apex / Q000473:pathology
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium