title: Incidence of four canals in root-canal-treated mandibular first molars in a Saudi Arabian sub-population.
abstract: OBJECTIVE
  The aim of this in-vivo study was to assess the incidence of three roots and four root canals in clinical cases of root-treated mandibular first molars in a Saudi Arabian population.
  
  
  METHODS
  A clinical study of 251 root-canal treated permanent mandibular first molars was conducted. The teeth were examined clinically and radiographically.
  
  
  RESULTS
  The results showed that 5.97% of the examined teeth had three roots, 57.76% had four root canals (two mesial and two distal) and 42.3% had three root canals (two mesial and one distal).
  
  
  CONCLUSIONS
  The occurrence of four root canals in the mandibular first molar of a Saudi Arabian subpopulation was high.
authors.affiliation: Department of Restorative Dental Science, College of Dentistry, King Saud University, Riyadh, Saudi Arabia.
authors.forename: S
authors.initials: S
authors.lastname: al-Nazhan
mesh_terms: D018912:Arabs; D003786:Dental Pulp Cavity / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D008297:Male; D008963:Molar / Q000033:anatomy & histology*; D012529:Saudi Arabia; D012727:Sex Characteristics; D014092:Tooth Root / Q000033:anatomy & histology*