title: Micro-computed tomography study of the internal anatomy of mesial root canals of mandibular molars.
abstract: BACKGROUND
  The aim of this study was to determine the mesiodistal and buccolingual diameter, apical volume, and the presence of isthmuses at the apical level of mesial root canals of mandibular molars.
  
  
  METHODS
  Sixty extracted first and second mandibular molars were scanned by using a SkyScan 1076 micro-computed tomography system with a voxel size of 18 μm. The apical thirds of the samples were reconstructed to allow a perpendicular section of the apical third by using the multiplanar reconstruction tool of the OsiriX software. The mesiodistal and the buccolingual distances of root canals were measured between the 1- to 4-mm levels. The type of root canal isthmuses present at these levels was classified by using modified criteria of Hsu and Kim. The volume of the root canal anatomy between the 1- to 3-mm apical levels was obtained by using the CTAN-CTVOL software.
  
  
  RESULTS
  The medians of the mesiodistal diameter at the 1-, 2-, 3-, and 4-mm levels in the mesiobuccal and mesiolingual canals were 0.22 and 0.23 mm, 0.27 and 0.27 mm, 0.30 and 0.30 mm, and 0.36 and 0.35 mm, respectively. The buccolingual lengths at the 1-, 2-, 3-, and 4-mm levels were 0.37-0.35 mm, 0.55-0.41 mm, 0.54-0.49 mm, and 0.54 and 0.60 mm, respectively. The presence of isthmuses was more prevalent at the 3- to 4-mm level. However, 27 cases presented complete or incomplete isthmuses at the 1-mm apical level. The mean of the volume of the apical third was 0.83 mm(3), with a minimum value of 0.02 and a maximum value of 2.4 mm(3).
  
  
  CONCLUSIONS
  Mesial root canals of mandibular molars do not present a consistent pattern. A high variability of apical diameters exists. The presence of isthmuses at the apical third was not uncommon even at the 1-mm apical level.
authors.affiliation: Department of Endodontics, Bauru Dental School, University of São Paulo, Bauru, São Paulo, Brazil.
authors.forename: Marcelo Haas
authors.initials: MH
authors.lastname: Villas-Bôas
authors.forename: Norberti
authors.initials: N
authors.lastname: Bernardineli
authors.forename: Bruno Cavalini
authors.initials: BC
authors.lastname: Cavenago
authors.forename: Marina
authors.initials: M
authors.lastname: Marciano
authors.forename: Aldo
authors.initials: A
authors.lastname: Del Carpio-Perochena
authors.forename: Ivaldo Gomes
authors.initials: IG
authors.lastname: de Moraes
authors.forename: Marco H
authors.initials: MH
authors.lastname: Duarte
authors.forename: Clovis M
authors.initials: CM
authors.lastname: Bramante
authors.forename: Ronald
authors.initials: R
authors.lastname: Ordinola-Zapata
mesh_terms: D003786:Dental Pulp Cavity / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008334:Mandible / Q000000981:diagnostic imaging*; D008963:Molar / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D009811:Odontometry / Q000379:methods; D019227:Tooth Apex / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D055114:X-Ray Microtomography / Q000379:methods*