Persistent (long-term) pain following root canal treatment. – (Persistent Dentoalveolar Pain disorder – PDAP) –

Persistent Dentoalveolar Pain Disorder (PDAP).

This page describes the syndrome where a dental patient experiences continued discomfort with their root canalled tooth but an underlying condition associated with the tooth or its work does not seem to lie at fault.

The current name that’s most frequently used in conjunction with this condition is “Persistent Dentoalveolar Pain Disorder” (PDAP disorder). This is, however, relatively new terminology.

(For example, Cohen’s Pathways of the pulp, likely the most used endodontic textbook in US dental schools, makes no reference to PDAP in it’s 2011 10th edition. In its 2016 11th edition, this term is mentioned extensively.)

▲ Section references – Hargreaves

• Describes the signs and symptoms typically associated with PDAP cases.
• Explains underlying events that have been suggested to be causes of this condition.
• Discusses treatments that may be used in the management of PDAP disorder.
• Explains issues and concerns that people who have this condition should be aware of.

What are the usual symptoms of Persistent Dentoalveolar Pain disorder?

The initial signs and symptoms.

The general scenario that occurs with this condition is one where:

• The patient notices discomfort with their tooth.
• Upon evaluation, their dentist determines that root canal treatment is indicated as a solution.
• Following the completion of the tooth’s treatment, its symptoms persist for months on end.
• When evaluated, no issues can be found with the quality of the tooth’s endodontic work.

That means that the initial signs and symptoms associated with what is eventually categorized as PDAP disorder start off as the same pain-related ones that typically signal a tooth’s need for root canal treatment. Example scenarios.

When is a case formally classified as persistent dentoalveolar pain disorder?

• The person’s discomfort is present on the order of at least 8 hours per day, at least 15 days per month, for at least 3 months (Warnsinck). (A criteria of 6 months is sometimes used.)
• The patient has no hesitation in identifying the tooth associated with their symptoms.
• In terms of description, the patient may state that what they feel seems to be a continuation of their original toothache. With other cases, the feeling is a new/different sensation. (Durham)
• Patients frequently describe the pain they feel as continuous, dull and/or pressing. With some cases, the terms itching, tingling and pricking also apply.

  The pain is typically described as coming from deep within the jawbone. Its level of intensity may fluctuate throughout the day and/or as days pass. (Warnsinck)

Incidence rates.

▲ Section references – Sobieh, Durham, Warnsinck

What is the cause of PDAP disorder?

The actual underlying cause of persistent dentoalveolar pain disorder isn’t known.

Neuropathic factors.

The general consensus among experts seems to be that the pain associated with PDAP disorder has an actual neuropathic origin, as opposed to a primarily psychosocial one (Warnsinck).

As such, it would be expected that some type of lesion or disease process could be identified with cases. However, this is the conundrum that exists:

• Some type of neurological process occurs that causes the patient’s painful toothache. A condition that’s expected to be resolved by performing a deafferentation dental procedure.

  (The term deafferentation means that the sensory input from the nerve is disrupted. In dentistry, this is accomplished by either removing the tooth’s nerve [via root canal treatment] or removing the entire tooth.)

• But even after the offending nerve tissue has been removed, painful sensory input still comes from the same area.
• One would anticipate that it would be a simple matter of identifying some type of condition or abnormal process in the tissues that remain. But as of yet, no type of causative pathology has been identified (Warnsick).

Psychosocial factors.

In light of the nature of the above conundrum, it’s been suggested that PDAP disorder may instead have a primarily psychosocial origin.

Some studies evaluating this issue have found no difference in these types of factors between test and control groups. However, one study did determine that PDAP disorder sufferers scored higher in the areas of depression and somatization (experiencing medical symptoms with no discernible organic cause) than the pain-free group. (Warnsinck)

▲ Section references – Warnsinck, Nixdorf

Treatment for PDAP disorder.

Treating persistent dentoalveolar pain disorder, in the sense of resolving or even just improving the patient’s discomfort level, is unpredictable. Success (total absence of pain) may not be possible.

Endodontic retreatment.

Since by definition PDAP cases involve the situation where no fault is found with the tooth’s current root canal work, conventional retreatment or other endodontic procedures (like root tip amputation) Explained. will provide no improvement.

Extraction.

Removing the tooth does not provide a solution. Since the source of the pain does not lie with the tooth itself, the discomfort will persist. (Warnsinck)

Medications.

The usual treatment approach used with PDAP cases involves a pharmacological one. Although, there is limited evidence for its effectiveness, nor is there a general consensus about which medications should be used.

• Based on the treatment of other neuropathic disorders, centrally acting oral medications (like tricyclic antidepressants and anticonvulsants [eg gabapentin]) are frequently used.
• Topical (surface) application of pain medication has been used with some success. (Capsaicin or a combination of carbamazepine, lidocaine, and ketoprofen or ketamine with gabapentin.)

Patient support.

▲ Section references – Warnsinck, Durham

Treatment outcomes.

The reality of treating PDAP patients is that success may not be possible. As an example of what might be expected, a study by Pigg followed 37 patients over a period of 7 years. It was found that:

• 13 of the participants stated that their pain status had significantly improved. 5 of these 13 reported that they were pain-free.
• 22 of the subjects (60%) considered their pain level to be unchanged or little improved.
• 2 patients felt that their situation had worsened.

▲ Section references – Pigg

Issues and considerations.

For the patient, there are several factors associated with persistent dentoalveolar pain disorder that makes experiencing it difficult.

Diagnosis.

With an incidence rate somewhere around 3% of cases or fewer, most general dentists will have little, if any, experience in diagnosing PDAP disorder.

• A worst-case scenario is one where through a failure to diagnose this condition, multiple teeth, each in turn, are suspected of being the source of the patient’s persistent pain and as a result, are subjected to root canal treatment or extraction to no avail (since neither provides a solution for this condition). This scenario is not all that uncommon.
• A complicating issue in diagnosing PDAP disorder is that a conclusion must be reached that the tooth’s current endodontic work does not lie at fault for the pain. There might be some debate as to the ability of most general dentists to arrive at this conclusion with a great degree of certainty.

Referral.

It seems easily debated that there might be benefits associated with referring the patient to a root canal specialist endodontist for evaluation fairly early in the diagnostic and/or treatment process.

• The underlying premise of PDAP disorder is that it does not stem from a deficiency with, or failure of, the tooth’s root canal work.

  Due to their higher level of training and clinical experience, and usually more sophisticated equipment (like 3D x-ray imaging), it would be expected that an endodontist would be in a better position to accurately make this determination.

  Either by way of identifying problems with the tooth’s current work that might be remedied. Or by knowing when to look for non-endodontic reasons to explain the tooth’s persistent pain.

• Since as a specialist their day only involves performing endodontic procedures, it would be expected that an endodontist would have much more previous experience with diagnosing and treating PDAP disorder than a general dentist.

Earlier diagnosis.

There are a number of reasons why the patient benefits if their PDAP condition is diagnosed comparatively sooner rather than later.

• Undergoing ineffectual treatment. – Typically those who suffer from PDAP disorder bounce around to a number of different practitioners (including different types of doctors) in search of resolution. Often with each one, in good faith, recommending a treatment that ultimately provides no solution at all.
• Emotional toll. – As mentioned above, experiencing this disorder can be a draining ordeal. At least with appropriate diagnosis, some the emotional drain associated with experiencing it might be alleviated.
• Pain centralization. – In theory, the complication of “pain centralization” may take place with longer-standing PDAP cases. (Hargreaves)

  This phenomenon involves a situation where the constant pain from an area leads the central nervous system (spinal cord and brain) to become a more efficient carrier of this information.

  As a result, even small inputs from the painful area are interpreted by the central nervous system as being large ones. As a worst-case scenario, treatment applied directly at the peripheral site (like numbing it up with anesthetic) might not prevent pain from being felt.

▲ Section references – Hargreaves