title: Effects of root canal preparation on apical geometry assessed by micro-computed tomography.
abstract: BACKGROUND
  Previous micro-computed tomography analyses of root canal preparation provided data that were usually averaged over canal length. The aim of this study was to compare preparation effects on apical root canal geometry.
  
  
  METHODS
  Sixty extracted maxillary molars (180 canals) used in prior studies were reevaluated for analyses of the apical 4 mm. Teeth were scanned by using micro-computed tomography before and after canal shaping with FlexMaster, GT-Rotary, Lightspeed, ProFile, ProTaper, instruments or nickel-titanium K-files for hand instrumentation. Apical preparation was to a size #40 in mesiobuccal and distobuccal and #45 in palatal canals except for GT (#20) and ProTaper (#25 in mesiobuccal and distobuccal and #30 in palatal canals, respectively). Data for canal volume changes, the structure model index (quantifying canal cross sections), and untreated surface area were contrasted by using analysis of variance and Scheffé tests.
  
  
  RESULTS
  Mean mesiobuccal, distobuccal, and palatal canal volumes increased after preparation (P < .05), but differences were noted for preparation techniques. GT rendered the smallest (0.20 +/- 0.14 mm(3)); K-files and ProFile showed the largest volume increases (0.51 +/- 0.20 mm(3) and 0.45 +/- 021 mm(3), P < .05). All canals were slightly rounder in the apical 4 mm after preparation indicated by nonsignificant increases in structure model index. Untreated areas ranged from 4%-100% and were larger in mesiobuccal and palatal canals than in distobuccal ones. Preparation with GT left significantly larger untreated areas in all canal types (P < .05); among root canal types, distobuccal canals had the least amounts of untreated surface areas.
  
  
  CONCLUSIONS
  Apical canal geometry was affected differently by 6 preparation techniques; preparations with GT instruments to an apical size #20 left more canal surface untouched, which might affect the ability to disinfect root canals in maxillary molars.
authors: Division of Endodontology, University of Zurich Dental School, Zurich, Switzerland. frank.paque@zzmk.uzh.ch
authors: Frank
authors: F
authors: Paqué
authors: Daniel
authors: D
authors: Ganahl
authors: Ove A
authors: OA
authors: Peters
mesh_terms: D003722:Dental Alloys; D003762:Dental Instruments; D003786:Dental Pulp Cavity / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D004867:Equipment Design; D006801:Humans; D008963:Molar; D009532:Nickel; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods; D014025:Titanium; D019227:Tooth Apex / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D055114:X-Ray Microtomography
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium