How often does root canal treatment fail? (Statistics) -

Success and failure rates of endodontic therapy reported by research studies. | How incidence rates are affected by tooth type or provider (dentist vs. endodontist).

How likely is your tooth's root canal therapy to fail?

  • Before you choose the option of having endodontic therapy performed for your tooth, it only makes sense that you'd like to have an idea of its chances of success.
  • And of course, if you've had a tooth that's experienced failure, you no doubt would like to know how unique that type of event is.

As you'll find out from reading this page, the issue of endodontic therapy success rates has been investigated extensively by researchers. And in general terms, the statistics they report are in consensus with each other.

As such, they confirm that root canal therapy can be expected to provide a lasting outcome for a tooth and therefore typically (per your dentist's recommendation) makes a good choice.


A) Root canal treatment success rates.

For our reporting on this issue, we've chosen to cite statistics from three research studies who collectively have evaluated the outcomes of literally millions of treated teeth.

(FYI: The typical source of data used for studies involving large populations is dental insurance company databases.)

Chen -

This study evaluated the 5-year outcome of over 1.5 million teeth that had received conventional root canal treatment.

(We're using the term "conventional" to refer to routine nonsurgical endodontic therapy, which is the standard procedure you can expect your dentist to perform for your tooth.)

This study determined that:

  • 90% of the teeth were retained (still in the patient's mouth and functioning) at a point 5 years after their original treatment. (This group of teeth had required no additional attention.)
  • 3% of the studied teeth did experience root canal failure but were salvaged via endodontic retreatment. (Meaning either performing their conventional root canal treatment again, or by performing some type of root surgery.)

    (By adding in this group of successfully retreated cases, 93% of all of the evaluated teeth were retained at a point 5 years out via the use of endodontic procedures.)

  • The remaining 7% of teeth experienced failure and were extracted.
An x-ray showing evidence of failed root canal treatment.

Raedel -

This study accessed a dental insurance database to determine the outcome of over 500,000 conventional root canal cases over their initial 3-year period.

Case failure was equated to the fact that following its treatment, the tooth was later documented in the database as either having non-surgical or surgical retreatment, or else it was extracted.

Using these parameters, the following survival rates were observed: 1 year - 93%, 2 years - 88% , 3 years - 84%.

 

Salehrabi -

This study evaluated the 8-year outcome of over 1.4 million conventional root canal cases performed by both general dentists and endodontists (root canal specialists).

Just like with the other studies above, the data evaluated came from a dental insurance database. And endodontic failure was defined as the tooth requiring some type of endodontic retreatment or extraction at a later date.

The findings of the study were that 97% of the treated teeth were still retained (still in the subjects' mouth and functioning) at a point 8 years after their original treatment.

Why did these studies only evaluate 3, 5 and 8-year periods?

We'd anticipate that most people who are considering root canal treatment for their tooth are more interested in how it will do over the course of their lifetime, as opposed to just 3, 5 or 8 year intervals, like those used in the studies above.

In response, we'll offer the following points:

  • One of the findings of the Salehrabi study above was that when further treatment was required (either retreatment or extraction), 88% of those procedures were performed within the first 3 years following their tooth's original root canal work.

    That suggests that even the shortest study discussed above completely encompassed the most important time frame to evaluate.

  • Another consideration is that with longer-term studies, additional pathologies (like gum disease) become an ever increasing factor in the survival of the tooth.

    And since insurance databases only document events (like tooth extraction) and not the reason for them, the ability to accurately estimate failure rates over a long duration seems questionable.


B) Success of treatment performed by general dentists vs. endodontists.

It seems logical to speculate that the extra training a root canal specialist (endodontist) receives positively influences the outcome of their work. Research seems to confirm this:

  • Background information included in a paper by Iqbal states that success rates for root canal work performed by general dentists runs on the order of 65% to 75%. Whereas for specialists, this number lies around 90%.
  • A small study involving just 350 teeth conducted by Alley found a success rate of 98% for therapy performed by endodontists vs. 90% for cases completed by general practitioners.

More evidence, a different spin.

A study by Lazarski evaluated the outcome of over 100,000 root canal cases (each tooth was followed over a minimum time frame of 2 years).

It reported a similar success rate for work completed by both specialists and general dentists.

But it also noted that the specialist group treated a substantially greater percentage of molars (multi-rooted teeth often having a very complex root canal system), whereas the generalist group more single-rooted, typically easier to treat, teeth. (See our "failure rate by tooth type" table below for a comparison.)

Possibly you could conclude from this study that:

  • The similar success rate achieved by specialists while treating more difficult cases suggests that the extra training and experience they have plays a valuable role in treatment outcome.
  • But this extra experience may not be needed for simple cases.

C) Incidence of root canal failure by tooth type.

We ran across three studies that included data about endodontic failure by tooth type.

Iqbal -

As a part of its evaluation of 90 failed root canal cases, this study reported the following failure rates:

Distribution of failed root canals by tooth type.
4.4% of cases ... Upper incisors
3.3% of cases ... Upper canines (eyeteeth)
15.5% of cases ... Upper premolars (bicuspids)
44.4% of cases ... Upper molars
5.5% of cases ... Lower incisors
1.1% of cases ... Lower canines
5.5% of cases ... Lower premolars
20.0% of cases ... Lower molars

 Reference: 

Iqbal A. - linked above.

Burry -

As a part of it's investigation of an insurance database, this study evaluated groups of teeth that had been treated by general dentists that had since experienced root canal failure (those that had developed problems at 1, 5 and 10 years after completion, over 338,000 teeth total). The failure rate per tooth type was similar for all three groups.

Distribution of failed root canals by tooth type.
19% to 20% of cases ... Incisors and Canines
32% to 34% of cases ... Premolars
46% to 47% of cases ... Molars

Hoen -

This study evaluated 337 teeth whose initial root canal treatment had failed.

Distribution of failed root canals by tooth type.
20% of cases ... Incisors and Canines
22% of cases ... Premolars
58% of cases ... Molars
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Discussion.

Together, these studies seem to suggest that:

  • Anterior teeth (incisors and canines) tend to experience failure less often than premolars and molars.
  • Teeth that most frequently have a single root canal (incisors, canines, lower premolars) tend to have the lowest failure rates.
  • Teeth frequently/typically having multiple canals (upper premolars, upper molars, lower molars) tend to have the highest percentage of failures.
  • Molars in general, and possibly upper molars in particular (the type of tooth typically having the greatest number of canals, which is 3 or more), have the highest failure rate by far.

    (Not only does a larger number of canals present greater challenges but many additional canals are small and curved, thus making them difficult to both identify and treat.)

This data makes it easy to understand why a general dentist might be more inclined to refer the treatment of teeth that have a relatively more complex anatomy (molars, especially upper molars) to a
root canal specialist.

 

Last revision/review: 11/29/2018 - Page created.

 
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