title: Persistent periapical radiolucencies of root-filled human teeth, failed endodontic treatments, and periapical scars.
abstract: OBJECTIVE
  This report describes 6 cases that demonstrate persistent periapical radiolucent lesions after conventional root canal treatment.
  
  
  METHODS
  Six teeth that had conventional root canal treatment or re-treatment with nonresolving periapical radiolucencies underwent periapical surgery. Biopsies were obtained and analyzed descriptively by correlative light and transmission electron microscopy for general features and microbial findings.
  
  
  RESULTS
  Three findings were identified: periapical lesions with persisting infection in the apical root canal system (2 cases); a cyst (1 case); and periapical healing by scar tissue formation (2 cases).
  
  
  CONCLUSIONS
  These results confirm previous observations that associated factors in the failure of endodontic treatment include persistent intraradicular infection and periapical cysts. In addition, unresolved periapical radiolucencies may occasionally be due to healing by scar tissue, which may be mistaken as a sign of failed endodontic treatment.
authors.affiliation: Department of Oral Structural Biology, Center for Dental and Oral Medicine, University of Zurich, Switzerland.
authors.forename: P N
authors.initials: PN
authors.lastname: Nair
authors.forename: U
authors.initials: U
authors.lastname: Sjögren
authors.forename: D
authors.initials: D
authors.lastname: Figdor
authors.forename: G
authors.initials: G
authors.lastname: Sundqvist
mesh_terms: D000328:Adult; D002921:Cicatrix / Q000000981:diagnostic imaging / Q000601:surgery; D003786:Dental Pulp Cavity / Q000382:microbiology; D019232:Dental Restoration Failure; D005260:Female; D006094:Gram-Positive Bacteria / Q000302:isolation & purification; D006801:Humans; D007180:Incisor; D008297:Male; D008854:Microscopy, Electron; D008875:Middle Aged; D010483:Periapical Diseases / Q000000981:diagnostic imaging* / Q000382:microbiology* / Q000601:surgery; D011859:Radiography; D019233:Retreatment; D012184:Retrograde Obturation