Microbiologic analysis of teeth with failed endodontic treatment and the outcome of conservative re-treatment.

By : Sundqvist G, Figdor D, Persson S, Sjögren U



(1) to determine the success rate of retreatment and identify factors that might influence the prognosis.

(2) to obtain data on the composition of the microbial flora in previously root-filled teeth with persisting periapical lesions.

N= 54 teeth (5 with 2 canals and 49 with single canal).

Inclusion: teeth that had been previously RCT 4 to 5 years ago, asymptomatic, and showed radiographic evidence of periapical lesions.


• Rubber dam was applied and the teeth surfaces were disinfected before access.

• Access prepared, Gutta-percha removed mechanichally without use of chemical solvent & irrigation done by saline.

• The canals were left empty and the accesses were sealed with temporary filling.

• Three bacterial samples were taken by soaking up the fluid (liquid thioglycolate medium) in the canals with paper points.(1) after removal of GP (2) at a 2nd visit 7 days later (3) at a 3rd visit after 7 days of CaOH2  medicament.

• Patients were recalled yearly and up to 5 years if complete healing had not taken place earlier.

Most highlighted Results: 

  • The microbial flora that recovered was mainly single species of predominantly gram-positive organisms.
  • The isolates most commonly recovered were bacteria of the species E.faecalis (38% of the cases with recovered bacteria).
  • The overall success rate of re-treatment was 74% . In the cases from which E. faecalis was isolated,it was lower: 66%.
  • Two factors had a negative influence on the prognosis: presence of bacteria at the time of root filling (+ve 3rd sample): 33% vs. 80%  for -ve 3rd sample and the size of PA lesion.

 Clinical significance: 

E. faecalis was the most frequently detected bacteria in re-treatment cases and appears to be highly resistant to antibacterial effect of irrigants and intracanal medicaments commonly used.