title: Morphologic micro-computed tomography analysis of mandibular premolars with three root canals.
abstract: BACKGROUND
  This study aimed to describe the anatomy of mandibular premolars with type IX canal configuration by using micro-computed tomography.
  
  
  METHODS
  Mandibular premolars with radicular grooves (n = 105) were scanned, and 16 teeth with type IX configuration were selected. Number and location of canals, distances between anatomic landmarks, occurrence of apical delta, root canal fusion, and furcation canals, as well as 2-dimensional (area, perimeter, roundness, major and minor diameters) and 3-dimensional (volume, surface area, and structure model index) analysis were performed. Data were statistically compared by using analysis of variance and Kruskal-Wallis tests (α = 0.05).
  
  
  RESULTS
  Overall, specimens had 1 root with a main canal that divided into mesiobuccal, distobuccal, and lingual canals at the furcation level. Mean length of the teeth was 22.9 ± 2.06 mm, and the configuration of the pulp chamber was mostly triangle-shaped. Mean distances from the furcation to the apex and cementoenamel junction were 9.14 ± 2.07 and 5.59 ± 2.19 mm, respectively. Apical delta, root canal fusion, and furcation canals were present in 4, 5, and 10 specimens, respectively. No statistical differences were found in the 2-dimensional and 3-dimensional analyses between root canals (P > .05).
  
  
  CONCLUSIONS
  Type IX configuration of the root canal system was found in 16 of 105 mandibular premolars with radicular grooves. Most of the specimens had a triangle-shaped pulp chamber. Within this anatomic configuration, complexities of the root canal systems such as the presence of furcation canals, fusion of canals, oval-shaped canals in the apical third, small orifices at the pulp chamber level, and apical delta were also observed.
authors: Department of Endodontics, Bauru Dental School, University of São Paulo, Bauru, São Paulo, Brazil. ronaldordinola@usp.br
authors: Ronald
authors: R
authors: Ordinola-Zapata
authors: Clóvis Monteiro
authors: CM
authors: Bramante
authors: Marcelo Haas
authors: MH
authors: Villas-Boas
authors: Bruno Cavalini
authors: BC
authors: Cavenago
authors: Marco Húngaro
authors: MH
authors: Duarte
authors: Marco Aurélio
authors: MA
authors: Versiani
mesh_terms: D059925:Anatomic Landmarks / Q000000981:diagnostic imaging; D063405:Anatomic Variation; D001641:Bicuspid / Q000000981:diagnostic imaging*; D003786:Dental Pulp Cavity / Q000000981:diagnostic imaging*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D008334:Mandible / Q000000981:diagnostic imaging; D009811:Odontometry / Q000379:methods; D009929:Organ Size; 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: Complex root canal system; dental anatomy; mandibular premolars; micro-computed tomography