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Alternatives after failure of endodontic treatment

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Failed endodontic treatment

Parameters for the assessment of treatment success

Since neither microbiological examination of the root canal nor histological examination of periradicular tissue are possible, the following parameters are used to assess the success of endodontic treatment in clinical practice:
  • presence of clinical signs such as swelling or fistulae, and particularly pain
  • radiological criteria
    (quality of obturation of the root canal achieved with the filling material, regularity and anatomical form of the mechanical preparation , condition of the periapical tissue)
Since clinical symptoms may be absent regardless of possible endodontic infection (Pekruhn 1986), the assessment of treatment success is based almost exclusively on radiological examination.

In clinical practice, not only objective criteria such as pain and swelling are used to assess the endodontic treatment success (Reit 1998) but failure of endodontic treatment measures will also be defined individually using subjective criteria (Thiele et al. 2003).

The most important subjective criteria include (Thiele et al. 2003):
  • apparent severity of endodontic infection (presence and size of radiologically visible periapical translucency)
  • accessibility of the root canal (e.g. periapical changes in a tooth held together with a prosthodontic pin are not considered suitable for orthograde access to treatment, though teeth without pin retained restorations are suitable)
  • risk assessment regarding later clinical complaints
  • overall therapeutic concept
  • overall clinical situation (e.g. presence of severe systemic disease)
  • preference of the individual dentist
  • patient's expectations
  • costs etc.
Treatment success should be assessed based on objective criteria.
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Definition of treatment failure

According to Strindberg's definition, endodontic treatment has failed if, after a sufficiently long period for healing, there is a residual, persistent, or progressive radiological translucency in periapical tissue (Strindberg 1956). Furthermore, any kind of clinical complaint is to be considered an appropriate criterion for unsuccessful root canal treatment. Strindberg considers re-assessment at four-yearly intervals sufficient.

According to Reit (1987), if there are no clinical complaints, the first radiological check following endodontic treatment should be after one year. If radiological findings are essentially normal, this can be considered a treatment success. If there are pathological changes, another radiological re-assessment is due after 3 years. Primary root canal treatment has failed should pathological findings persist (Reit 1987).

In their most recent statement, the endodontic advisory board of the DGZ [Deutsche Gesellschaft für Zahnerhaltung - German Society for the Preservation of Teeth] recommend clinical and radiological checks of success of root canal treatment for the DGZMK [German Society of Dental, Oral and Craniomandibular Sciences] for a period of at least 4 years in intervals of 6 months, 1, 2, and 4 years (Hülsmann and Schäfer 2005).

However, bacteria remaining in the root canal can also cause recurrence of periapical inflammation later on (Siqueira 2001).

Causes of endodontic treatment failure

Causes of endodontic treatment failure may be fractures of dental hard tissues, insufficient techniques used in root canal treatment or, in most cases, persistent or recurrent endodontic infection (intraradicular or extraradicular).

The most frequent causes of endodontic treatment failure include (Thiele et al. 2003):
  • insufficient apical obturation
  • insufficient coronal obturation
  • insufficient disinfection of the root canal (ramification, aberrant dentin tubes)
  • specific microbial infection (enterococcus faecalis and candida albicans, for instance, are very slightly susceptible to the effects of calcium hydroxide.)
  • protracted course of treatment
  • iatrogenic damage of integrity of the tube's anatomy (excessive use of instruments/excessive filling/false route)
According to Ray and Trope (1995), good apical and coronal closure resulted in 91.4% of cases in complete resolution of the endodontic infection. If only good apical obturation is guaranteed but a tight coronary closure is refrained from, the rate of success is reduced to 44.1%.

Strategies for endodontic revision

There are two options following unsuccessful primary endodontic treatment:
  1. conservative revision of the root canal with repeated filling
  2. apicectomy
In a review, Hepworth and Friedman stated a rate of success of 66% for orthograde revision and 59% for apical surgery (1997).
Kvist and Reit (1999) compared 95 cases of unsuccessful primary endodontic treatment which were revised at random by surgery or conservatively. The patients had clinical and radiological follow-ups. Over a period of 4 years, the patients were re-examined; the period of time for follow-ups was critical for the final assessment. Teeth revised by surgery exhibited significantly quicker healing of periapical bone. After 24 months, no differences were observed regardless of whether a conservative approach or surgical treatment measures had been used.

Surgical treatment of relapse using retrograde apical closure results in the separation of the infection from vital tissue, the former being responsible for the failure. However, the infection will persist. Therefore, surgical treatment of relapse should only be considered if orthograde treatment of the root canal is no longer possible; conservative revision is then recommended prior to the surgical revision within a short period of time, if possible.



  • Hepworth MJ, Friedman S (1997) Treatment outcome of surgical and non-surgical management of endodontic failures J Can Dent Assoc 63:364-71
  • Hülsmann M, Schäfer E (2005), „Good clinical practice“: Die Wurzelkanalbehandlung, Stellungnahme des Endodontiebeirats der DGZ, Gemeinsame Stellungnahme der DGZ und der DGZMK, Stand 23.07.2007, Dtsch Zahnärztl Z 60:8
  • Hülsmann R, Weiger R (2004) Revision einer Wurzelkanalbehandlung, Stellungnahme der DGZMK, Dtsch Zahnärztl Z 59
  • Kvist T, Reit C (1999) Results of endodontic retreatment: a randomized clinical study comparing surgical and nonsurgical procedures Endod. 1999 Dec;25(12):814-7
  • Pekruhn RB (1986) The incidence of failure following single-visit endodontic therapy J Endod 12:68-72
  • Ray HA, Trope M (1995) Periapical status of endodontically treated teeth in relation to the technical quality of the root filling and the coronal restoration Int Endod J. 1995 Jan;28(1):12-8
  • Reit C (1987) Decision strategies in endodontics: on the design of a recall program Endod Dent Traumatol 3:233-9
  • Reit C, Kvist T (1998) Endodontic retreatment behaviour: the influence of disease concepts and personal values Int Endod J. 1998 Sep;31(5):358-63
  • Siqueira Junior JF (2001) Aetiology of root canal treatment failure: why well-treated teeth can fail. Int Endod J 34:1-10
  • Strindberg LZ (1956) The dependence of the results of pulp therapy on certain factors Acta Odontol Scand 14 (Suppl 21):1-175
  • Strindberg LZ (1956) The dependence of the results of pulp therapy on certain factors Acta Odontol Scand 14 (Suppl 21):1-175
  • Thiele L, Hickel R, Folwaczny M (2003) Der endodontische Misserfolg - von der Definition zur Strategie. Dtsch Zahnärztl Z 58:144-50