title: A six-canal maxillary first molar: case report.
abstract: OBJECTIVE
  The aim of this case report is to describe an unusual six-canal maxillary first molar tooth.
  
  
  METHODS
  The maxillary left first molar of a young African-American male was treated as an emergency at the first visit. At the second visit, the five canals (MB1 and 2, Pal1 and 2 and DB) were easily identified at high magnification of 16-25 under an operating microscope. The canals were then instrumented and filled using the Microseal technique. A careful radiographic examination of the final fill indicated that there was a third canal in the palatal root as suggested by a slight extrusion of the filling material between the two canals. At the third visit, the fillings of the palatal canals were removed and the apical 4mm was re-examined. The existence of a third palatal canal exiting between the two apices was verified and subsequently instrumented and obturated.
  
  
  CONCLUSIONS
  It should be assumed that all molar teeth have more than the traditionally expected three canals. The location of root canals should be identified at high magnification under the microscope. Careful radiographic re-examination of the fillings should be done in order to identify possibly missed canals.
authors.affiliation: Department of Endodontics, School of Dental Medicine, University of Pennsylvania, 4001 Spruce Street, Philadelphia, PA 19104, USA.
authors.forename: F
authors.initials: F
authors.lastname: Maggiore
authors.forename: Y T
authors.initials: YT
authors.lastname: Jou
authors.forename: S
authors.initials: S
authors.lastname: Kim
mesh_terms: D000328:Adult; D003786:Dental Pulp Cavity / Q000002:abnormalities* / Q000000981:diagnostic imaging; D006171:Gutta-Percha / Q000627:therapeutic use; D006801:Humans; D008297:Male; D008437:Maxilla; D008866:Microsurgery; D008963:Molar / Q000002:abnormalities* / Q000000981:diagnostic imaging; D011671:Pulpitis / Q000628:therapy; D011859:Radiography; D012387:Root Canal Filling Materials / Q000627:therapeutic use; D012389:Root Canal Obturation / Q000379:methods; D018915:Root Canal Preparation / Q000379:methods; D019227:Tooth Apex / Q000002:abnormalities / Q000000981:diagnostic imaging; D015035:Zinc Oxide-Eugenol Cement / Q000627:therapeutic use
chemical_list: D012387:Root Canal Filling Materials; D015035:Zinc Oxide-Eugenol Cement; D006171:Gutta-Percha