title: Increased apical enlargement contributes to excessive dentin removal in curved root canals: a stepwise microcomputed tomography study.
abstract: BACKGROUND
  To determine whether increased apical enlargement would result in a complete preparation of curved canals and to progressively assess shaping quality using multiple microcomputed tomography (MCT) scans.
  
  
  METHODS
  Ninety root canals with a curvature of 25° to 50° were selected. Five MCT scans, 1 preoperative and 4 postoperative, were acquired from each canal. Canal preparation was performed up to size 50 using 3 techniques, nickel-titanium (NiTi) hand files, Mtwo (VDW, Munich, Germany), and ProTaper (Maillefer, Ballaigue, Switzerland), by experienced operators in a dental mannequin so as to simulate the clinical conditions. At a level of 1 mm short of the working length, 2 parameters were evaluated in each of the 4 postoperative acquisitions: the percentage of the prepared outline and the amount of dentin removed (the prepared area).
  
  
  RESULTS
  Statistically, there was no significant difference between the 3 systems used regarding the prepared outline. The maximum prepared outline was achieved by the use of NiTi hand files (63%; confidence interval [CI], 54%-73%), whereas Mtwo and ProTaper amounted to 58% (CI, 50%-66%) and 60% (CI, 51%-70%), respectively. In contrast, the dentin area removed by ProTaper was significantly higher than that of Mtwo and NiTi hand files.
  
  
  CONCLUSIONS
  Increased apical enlargement of curved canals did not result in a complete apical preparation, whereas it did lead to the unnecessary removal of dentin.
authors: Division of Endodontology, Department of Conservative Dentistry, School of Dental Medicine, University of Tübingen, Tübingen, Germany. Ashraf.ElAyouti@med.uni-tuebingen.de
authors: Ashraf
authors: A
authors: Elayouti
authors: Eleftheria
authors: E
authors: Dima
authors: Martin S
authors: MS
authors: Judenhofer
authors: Claus
authors: C
authors: Löst
authors: Bernd J
authors: BJ
authors: Pichler
mesh_terms: D003722:Dental Alloys; D003786:Dental Pulp Cavity / Q000000981:diagnostic imaging*; D003804:Dentin; D004867:Equipment Design; D006801:Humans; D009532:Nickel; D018915:Root Canal Preparation / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods*; D018709:Statistics, Nonparametric; D014025:Titanium; D019227:Tooth Apex / Q000000981:diagnostic imaging; D055114:X-Ray Microtomography / Q000379:methods*
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium