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

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 agreement 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 (2007) –

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 The steps., which is the standard procedure you can expect your dentist to perform for your tooth.)

• 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 performing some type of endodontic retreatment procedure. Possible options.

  (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.

Raedel (2015) –

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

Salehrabi (2004) –

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.

▲ Section references – Chen, Raedel, Salehrabi

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

• 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) The 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 run 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.)

• 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 outcomes.
• But this extra experience may not be needed for simple cases.

▲ Section references – Iqbal, Alley, Lazarski

C) Incidence of root canal failure by tooth type.

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

Iqbal (2007) –

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

Burry (2016) –

As a part of its 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.

Hoen (2002) –

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

Discussion.

• 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.)

▲ Section references – Iqbal, Burry, Hoen