title: A Micro-computed Tomography Evaluation of the Shaping Ability of Two Nickel-titanium Instruments, HyFlex EDM and ProTaper Next.
abstract: BACKGROUND
  The aim of this study was to evaluate and compare, by means of micro-computed tomography imaging, the shaping ability of ProTaper Next (PTN) and the novel HyFlex EDM (HFEDM) instruments.
  
  
  METHODS
  Forty teeth were randomly divided into 2 groups and prepared with PTN or HFEDM. Root canal transportation and centering ratio were evaluated in mesiodistal and buccolingual directions at 5 levels (at the midpoint of the apical, middle, and coronal thirds and at the boundaries between them). Variations in volume, surface, and cross-sectional shape were measured for the apical, middle, and coronal thirds. The null hypotheses were that no differences existed between the 2 groups. The D'Agostino-Pearson test (α = .05) was conducted to assess the normality of the data sets. The distributions were compared by using the Mann-Whitney test (α = .05).
  
  
  RESULTS
  Statistically significant differences (P < .005) were recorded only for buccolingual canal transportation and centering ratio at the section between the middle and coronal thirds, where HFEDM files were superior.
  
  
  CONCLUSIONS
  HFEDM and PTN files were similarly effective, and both safely prepared the root canals, respecting their original anatomies. HFEDM files performed better in terms of buccolingual canal transportation and centering ratio at the section between the middle and coronal thirds.
authors.affiliation: School of Dental Medicine, University of Milano-Bicocca - San Gerardo Hospital, Monza, Monza and Brianza, Italy. Electronic address: piermatteovenino@icloud.com.
authors.forename: Pier Matteo
authors.initials: PM
authors.lastname: Venino
authors.affiliation: School of Dental Medicine, University of Milano-Bicocca - San Gerardo Hospital, Monza, Monza and Brianza, Italy.
authors.forename: Claudio Luigi
authors.initials: CL
authors.lastname: Citterio
authors.affiliation: School of Dental Medicine, University of Milano-Bicocca - San Gerardo Hospital, Monza, Monza and Brianza, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Pellegatta
authors.affiliation: School of Dental Medicine, University of Milano-Bicocca - San Gerardo Hospital, Monza, Monza and Brianza, Italy.
authors.forename: Marta
authors.initials: M
authors.lastname: Ciccarelli
authors.affiliation: School of Dental Medicine, University of Milano-Bicocca - San Gerardo Hospital, Monza, Monza and Brianza, Italy.
authors.forename: Marcello
authors.initials: M
authors.lastname: Maddalone
mesh_terms: D000497:Alloys; D003786:Dental Pulp Cavity / Q000000981:diagnostic imaging / Q000601:surgery; D006801:Humans; D018915:Root Canal Preparation / Q000295:instrumentation; D012390:Root Canal Therapy / Q000295:instrumentation*; D055114:X-Ray Microtomography
chemical_list: D000497:Alloys; C013616:nitinol
keywords: Centering ratio; HyFlex EDM; M-wire; ProTaper Next; controlled memory; microcomputed tomography; root canal preparation; transportation