title: The radix entomolaris and paramolaris: a micro-computed tomographic study of 3-rooted mandibular first molars.
abstract: BACKGROUND
  The morphology of the supernumerary third root (radix) in mandibular first molars was examined by micro-computed tomography (μCT) scanning.
  
  
  METHODS
  Nineteen permanent mandibular first molars with radix were scanned in a μCT device to evaluate their morphology with respect to root length, root curvature direction, location of radix, apical foramen, accessory canals and apical deltas, and distance between canal orifices as well as 2- and 3-dimensional parameters of the canals (number, area, roundness, major/minor diameter, volume, surface area, and structure model index). Quantitative data were analyzed by 1-way analysis of variance and the Tukey test (α = 0.05).
  
  
  RESULTS
  The mean length of the mesial, distal, and radix roots was 20.36 ± 1.73 mm, 20.0 ± 1.83 mm, and 18.09 ± 1.68 mm, respectively. The radix was located distolingually (n = 16), mesiolingually (n = 1), and distobuccally (n = 2). In a proximal view, most radix roots had a severe curvature with buccal orientation and a buccally displaced apical foramen. The spatial configuration of the canal orifices on the pulp chamber floor was mostly in a trapezoidal shape. The radix root canal orifice was usually covered by a dentinal projection. The radix differed significantly from the mesial and distal roots for all evaluated 3-dimensional parameters (P < .05). The radix canal had a more circular shape in the apical third, and the mean size of the minor diameter 1 mm short of the foramen was 0.25 ± 0.10 mm.
  
  
  CONCLUSIONS
  The radix root is an important and challenging anatomic variation of mandibular first molars, which usually has a severe curvature with a predominantly distolingual location, and a narrow root canal with difficult access.
authors.affiliation: Department of Restorative Dentistry, Dental School of Ribeirão Preto, University of São Paulo, São Paulo, Brazil.
authors.forename: Luis Eduardo
authors.initials: LE
authors.lastname: Souza-Flamini
authors.affiliation: Department of Restorative Dentistry, Dental School of Ribeirão Preto, University of São Paulo, São Paulo, Brazil.
authors.forename: Graziela Bianchi
authors.initials: GB
authors.lastname: Leoni
authors.affiliation: Department of Restorative Dentistry, Dental School of Ribeirão Preto, University of São Paulo, São Paulo, Brazil.
authors.forename: Jardel Francisco Mazzi
authors.initials: JF
authors.lastname: Chaves
authors.affiliation: Department of Restorative Dentistry, Dental School of Ribeirão Preto, University of São Paulo, São Paulo, Brazil.
authors.forename: Marco Aurélio
authors.initials: MA
authors.lastname: Versiani
authors.affiliation: Department of Restorative Dentistry, Dental School of Ribeirão Preto, University of São Paulo, São Paulo, Brazil.
authors.forename: Antônio Miranda
authors.initials: AM
authors.lastname: Cruz-Filho
authors.affiliation: Department of Restorative Dentistry, Dental School of Ribeirão Preto, University of São Paulo, São Paulo, Brazil.
authors.forename: Jesus Djalma
authors.initials: JD
authors.lastname: Pécora
authors.affiliation: Department of Restorative Dentistry, Dental School of Ribeirão Preto, University of São Paulo, São Paulo, Brazil. Electronic address: sousanet@forp.usp.br.
authors.forename: Manoel Damião
authors.initials: MD
authors.lastname: Sousa-Neto
mesh_terms: D063405:Anatomic Variation; D019412:Anatomy, Cross-Sectional / Q000379:methods; D003782:Dental Pulp / Q000000981:diagnostic imaging; D003786:Dental Pulp Cavity / Q000000981:diagnostic imaging; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008334:Mandible / Q000000981:diagnostic imaging; D008963:Molar / Q000000981:diagnostic imaging*; D009811:Odontometry / Q000379:methods; D019227:Tooth Apex / Q000000981:diagnostic imaging; D019237:Tooth Cervix / Q000000981:diagnostic imaging; D014092:Tooth Root / Q000000981:diagnostic imaging*; D055114:X-Ray Microtomography / Q000379:methods*
keywords: Micro–computed tomographic imaging; radix; root canal anatomy