title: An anatomic investigation of the mandibular first molar using micro-computed tomography.
abstract: BACKGROUND
  The mandibular first molar is the most frequently endodontically treated tooth and is extremely anatomically challenging. The purpose of this micro-computed tomographic evaluation was to quantitatively investigate the morphology of the mandibular first molar to improve both orthograde and retrograde treatment.
  
  
  METHODS
  Twenty-two mandibular first molars were scanned, reconstructed, and subjected to various linear measurements. The average, standard deviation, and standard error of the mean of each linear measurement were calculated, and the mode for each nominal data category was determined.
  
  
  CONCLUSIONS
  The furcal aspect of the entire mesial root should be considered a "danger zone." Mesial canals were found to be much more variable than distal canals in morphology, whereas the relative position of the orifices of the mesial canals was relatively consistent at 1.5 mm from the pulpal floor. Root-end resection of 3 mm would remove the majority of lateral canals and apical ramifications.
authors.affiliation: Division of Endodontics, University of Minnesota School of Dentistry, Minneapolis, Minnesota. Electronic address: harr1284@umn.edu.
authors.forename: Samantha P
authors.initials: SP
authors.lastname: Harris
authors.forename: Walter R
authors.initials: WR
authors.lastname: Bowles
authors.forename: Alex
authors.initials: A
authors.lastname: Fok
authors.forename: Scott B
authors.initials: SB
authors.lastname: McClanahan
mesh_terms: D019412:Anatomy, Cross-Sectional; D003782:Dental Pulp / Q000000981:diagnostic imaging; D003786:Dental Pulp Cavity / Q000000981:diagnostic imaging; D003804:Dentin / Q000000981:diagnostic imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008334:Mandible / Q000000981:diagnostic imaging*; D008963:Molar / Q000000981:diagnostic imaging*; D009811:Odontometry / Q000379:methods; D019227:Tooth Apex / Q000000981:diagnostic imaging; D019228:Tooth Crown / Q000000981:diagnostic imaging; D014092:Tooth Root / Q000000981:diagnostic imaging; D055114:X-Ray Microtomography / Q000379:methods*
keywords: Canal anatomy; danger zone; isthmus; mandibular first molar