title: The incidence of four canals in maxillary first molars: a clinical determination.
abstract: BACKGROUND
  The authors conducted an in vivo study to report the incidence of fourth root canals located and treated in maxillary first molars during a seven-month period in a postgraduate endodontic program.
  
  
  METHODS
  In this retrospective study, the authors determined the number of canals treated by postgraduate students in an endodontic program. The attending postgraduate endodontic faculty member supervising the case verified the number of canals in the teeth. The authors then collected the data from each resident and compiled them.
  
  
  RESULTS
  The residents treated a total of 121 maxillary molars, 85 (70.2 percent) of which met the criterion of having four or more canals treated. Approximately 99 percent of the fourth canals were located in the mesiobuccal root.
  
  
  CONCLUSIONS
  Overall, 70 percent of the maxillary first molars contained at least four canals that required instrumentation.
  
  
  CONCLUSIONS
  The results of this study demonstrate that it is imperative for any dentist performing root canal therapy on maxillary first molars to examine carefully the pulpal floor to locate all canals, especially the second mesiobuccal canal. Performing thorough examinations may increase the chance of treatment success.
authors.affiliation: Department of Endodontics, University of Medicine and Dentistry Of New Jersey, New Jersey Dental School, Newark, NJ 07101 USA.
authors.forename: Gary
authors.initials: G
authors.lastname: Hartwell
authors.forename: Craig M
authors.initials: CM
authors.lastname: Appelstein
authors.forename: William W
authors.initials: WW
authors.lastname: Lyons
authors.forename: Mary E
authors.initials: ME
authors.lastname: Guzek
mesh_terms: D003786:Dental Pulp Cavity / Q000033:anatomy & histology*; D006801:Humans; D008437:Maxilla; D008963:Molar / Q000033:anatomy & histology*; D009811:Odontometry; D012189:Retrospective Studies; D018915:Root Canal Preparation / Q000295:instrumentation; D014092:Tooth Root / Q000033:anatomy & histology