title: Prevalence of C-shaped mandibular molars in the Portuguese population evaluated by cone-beam computed tomography.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the prevalence of first and second C-shaped mandibular molars in a Western European population of Portuguese Caucasians.
  
  
  METHODS
  Patients having both routine panoramic radiograph and presurgical cone-beam computed tomography (CBCT) exams were selected. The CBCT examination was performed at five different axial levels and the mandibular molars were classified as C-shape according to the Fan criteria. Differences between genders, age groups, left and right side, type of tooth, and root concavity side were determined. The molars were classified as nonfused roots (NFRI-II), FRI-III, or single root with single canal (SS) groups, using the panoramic radiograph. The prevalence of C-shaped anatomy was calculated to each group.
  
  
  RESULTS
  A total of 1783 teeth (695 first molars and 1088 second molars) from 792 patients were included in the study. The prevalence of C-shaped configurations was 0.6% and 8.5% to mandibular first and second molars, respectively. The differences between gender, teeth, and root concavity direction were considered statistically significant (P< 0.05). The FR had a significantly higher rate of C-shapes when compared to NFR (P< 0.05). Intrarater reliability was 93.6%.
  
  
  CONCLUSIONS
  The FR radiographic appearance may be considered a predictor of this anatomy. Second mandibular molars and females had a higher incidence ratio. Apparently, the mandibular C-shaped anatomy is more common in the population of this study than that has been previously reported for the European population.
authors.affiliation: Department of Endodontics, Implantology Institute, Lisbon, Portugal.
authors.forename: Jorge N R
authors.initials: JNR
authors.lastname: Martins
authors.affiliation: Department of Biology, New York University, New York, USA.|Department of Oral Biology, School of Dental Medicine, Lisbon University, Lisbon, Portugal.|Oral Biology and Biochemistry Group, Biomedical and Oral Sciences Research Unit (FCT Unit 4062)- Evidence Based Dentistry Center, Lisbon University, Lisbon, Portugal.
authors.forename: António
authors.initials: A
authors.lastname: Mata
authors.affiliation: Oral Biology and Biochemistry Group, Biomedical and Oral Sciences Research Unit (FCT Unit 4062)- Evidence Based Dentistry Center, Lisbon University, Lisbon, Portugal.|Department of Anatomy and Physiology, School of Dental Medicine, Lisbon University, Lisbon, Portugal.
authors.forename: Duarte
authors.initials: D
authors.lastname: Marques
authors.affiliation: Department of Implantology, School of Dental Medicine, Lisbon University, Lisbon, Portugal.
authors.forename: João
authors.initials: J
authors.lastname: Caramês
keywords: C-shaped root canal; Cone-beam computed tomography; dental morphology; mandibular molars; panoramic radiography