title: Root-canal preparation with FlexMaster: canal shapes analysed by micro-computed tomography.
abstract: OBJECTIVE
  To evaluate the relative performance of FlexMaster nickel-titanium instruments shaping maxillary molar root canals in vitro.
  
  
  METHODS
  Extracted human maxillary molars were scanned, before and after root-canal shaping, with FlexMaster, employing micro-computed tomography (microCT) at a resolution of 36 microm. Canals were three-dimensionally reconstructed and evaluated for volume, surface area, 'thickness' (diameter), canal transportation and prepared surface. Based on median canal volume, the canals were divided into 'wide' and 'constricted' groups. Comparisons were made between mesiobuccal (mb), distobuccal (db) and palatal (p), as well as 'wide' and 'constricted' canals, using anova and Scheffé post-hoc tests.
  
  
  RESULTS
  Volume and surface area increased significantly and similarly in mb, db and p canals, and no gross preparation errors were found. Mean root-canal diameters, 5 mm coronal to the apex, increased from 0.45 to 0.65 mm, from 0.41 to 0.56 mm and from 0.79 to 0.85 mm for mb, db and p canals, respectively. Apical canal transportation ranged from 0.01 to 0.29 mm and was independent of canal type; 'wide' canals had a significantly higher (P < 0.05) proportion of unprepared surfaces than 'constricted' canals had.
  
  
  CONCLUSIONS
  FlexMaster instruments shaped curved and narrow root canals in maxillary molars to sizes 40 and 45 without significant shaping errors. Canal anatomy had an insignificant impact on preparation, indicating that FlexMaster instruments were able to shape 'constricted' canals as well as 'wide' ones.
authors.affiliation: Department of Preventive Dentistry, Periodontology and Cariology, Division of Endodontology, University of Zürich, Switzerland.
authors.forename: W
authors.initials: W
authors.lastname: Hübscher
authors.forename: F
authors.initials: F
authors.lastname: Barbakow
authors.forename: O A
authors.initials: OA
authors.lastname: Peters
mesh_terms: D000704:Analysis of Variance; D003722:Dental Alloys; D003786:Dental Pulp Cavity / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008852:Microradiography; D008963:Molar; D009532:Nickel; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods; D014025:Titanium; D014057:Tomography, X-Ray Computed / Q000379:methods*; D019227:Tooth Apex; D019228:Tooth Crown
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium