title: Prevalence of C-shaped Configurations in the Mandibular First and Second Premolars: A Cone-beam Computed Tomographic In Vivo Study.
abstract: BACKGROUND
  The mandibular premolar C-shaped anatomy has been presented as a complex morphology to be treated. The objective of this retrospective observational study was to evaluate and characterize, in in vivo conditions, the incidence of these morphologies using cone-beam computed tomographic (CBCT) technology.
  
  
  METHODS
  Mandibular premolar CBCT samples were collected from a preexisting database. All teeth were analyzed in 3 planes (axial, coronal, and sagittal), and the C-shape classification was performed at 3 different axial levels (coronal, middle, and apical). C-shape presence and configuration were recorded as well as the number of roots, the presence of a radicular groove, and Vertucci classification. The Z test for proportions was used to analyze the differences between independent groups. Intraobserver reliability was tested using the Cohen kappa test.
  
  
  RESULTS
  Two thousand twelve mandibular premolars were included in this study. A prevalence of C-shaped morphologies was noted in 2.3% and 0.6% of mandibular first and second premolars, respectively. This clinical condition was mostly unilateral. The C-shaped configuration (C1 and C2) was found mainly in the middle axial level. Its presence was uncommon in the apical level and null in the coronal level; 61.5% of all mandibular first premolar C shapes were identified in Vertucci type V roots. Differences were observed among sex, teeth, and Vertucci root configuration at P < .05.
  
  
  CONCLUSIONS
  Although the mandibular premolar C-shaped anatomy has a low prevalence ratio, a clinician should be aware of its existence, mainly when treating roots with Vertucci type V configuration. The prevalence was statistically higher in first premolars and males.
authors.affiliation: Department of Endodontics, Faculdade de Medicina Dentária, Universidade de Lisboa, Lisbon, Portugal. Electronic address: jnr_martins@yahoo.com.br.
authors.forename: Jorge N R
authors.initials: JNR
authors.lastname: Martins
authors.affiliation: Department of Oral Surgery, Faculdade de Medicina Dentária, Universidade de Lisboa, Lisbon, Portugal.
authors.forename: Helena
authors.initials: H
authors.lastname: Francisco
authors.affiliation: Bender Division of Endodontics, Albert Einstein Medical Center, Philadelphia, Pennsylvania.
authors.forename: Ronald
authors.initials: R
authors.lastname: Ordinola-Zapata
mesh_terms: D001641:Bicuspid / Q000002:abnormalities* / Q000000981:diagnostic imaging; D054893:Cone-Beam Computed Tomography; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008334:Mandible; D008875:Middle Aged; D015995:Prevalence; D012189:Retrospective Studies; D014071:Tooth Abnormalities / Q000000981:diagnostic imaging / Q000453:epidemiology*; D014092:Tooth Root / Q000002:abnormalities* / Q000000981:diagnostic imaging
keywords: Cone-beam computed tomography; morphology; premolar; prevalence studies