title: Anomalous mandibular premolars: a mandibular first premolar with three roots and a mandibular second premolar with a C-shaped canal system.
abstract: OBJECTIVE
  To describe unusual variations in the root morphology and root canal systems of mandibular first and second premolar teeth extracted for orthodontic reasons.
  
  
  CONCLUSIONS
  Normally mandibular first and second premolar teeth have single roots with single canals. A 15-year-old patient presented for orthodontic treatment and two mandibular premolar teeth were examined post-extraction. The mandibular first premolar exhibited three distinct, separate roots and the mandibular second premolar exhibited a C-shaped root canal system. The coronal morphology of each of the mandibular premolars revealed dimensions and anatomy within normal limits. The incidence of a three-rooted mandibular first premolar is approximately 0.2%.
  
  
  CONCLUSIONS
  * Thorough clinical and radiographic interpretation is important in recognizing anomalous root and root canal systems. * The most common forms of root and canal systems and its aberrations must be understood to realize variations from normal do occur. * Successful root canal treatment requires an accurate diagnosis of the root canal system using all available aids. * Value of microcomputed tomography in the study of anatomy ex vivo and cone-beam tomography in clinical endodontics of complex premolar cases is increasing.
authors.affiliation: Faculty of Dentistry, Department of Dental Clinical Sciences, Dalhousie University, Halifax, NS, Canada. blaine.cleghorn@dal.ca
authors.forename: B M
authors.initials: BM
authors.lastname: Cleghorn
authors.forename: W H
authors.initials: WH
authors.lastname: Christie
authors.forename: C C S
authors.initials: CC
authors.lastname: Dong
mesh_terms: D000293:Adolescent; D001641:Bicuspid / Q000002:abnormalities*; D003786:Dental Pulp Cavity / Q000002:abnormalities*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008297:Male; D008310:Malocclusion / Q000628:therapy; D008334:Mandible; D019252:Radiography, Dental, Digital; D012690:Serial Extraction; D014092:Tooth Root / Q000002:abnormalities*; D055114:X-Ray Microtomography