When our patients experience a “flare-up”, we wish they were experiencing a transcendental jazz trumpet experience, and not the other kind, the endodontic kind!

flare up

Fortunately, the reported incidence of flare-ups is relatively low, generally somewhere between 1-8%.  But when it happens, no one is happy, which is a negative experience for the patient, of course, but is hard on the clinician too, especially when we secretly congratulated ourselves only 12 hours earlier for getting through that tough and calcified access or for creating one of the most beautiful obturation radiographs known to man. It can happen to any of us, and we cannot predict who, exactly, will experience a flare-up.


Moderate to severe pain hours or days after initiation or completion of endodontic treatment, with or without swelling.

Etiology & Diagnosis

the main culprit is usually microbes, but can be due to mechanical or chemical reasons too.  Over-instrumentation, incomplete instrumentation, apical extrusion of infected debris, and the irrigants or sealers used can all contribute to the occurrence of a flare-up.  The diagnosis of a flare-up is often simple, but is important to rule out pain from adjacent teeth and pain of non-endodontic origin.  The local considerations for the tooth itself might include a crown or root fracture or an untreated canal (particularly if there is temperature sensitivity).  We also need to identify any signs of spreading infection, osteomyelitis, fever, swelling, etc., and treat that appropriately, with the appropriate antibiotics and very careful follow-up, or referral to an oral surgeon if there is potential for danger, which can develop extremely quickly.


1. Reassure your patient: patient does appreciate when we explain what is happening and why, and the steps we are going to take, including following up.
2. Definitive treatment:

  • opening the tooth up under a rubber dam again, to provide re-instrumentation to a proper working length with copious irrigation.  This also gives us a chance to search for any untreated canals, and allow for any suppurative drainage.  If there is drainage, allow the tooth to drain, which can take several minutes.  Avoid leaving the tooth “open” – that is, without a temporary filling in the access- and always place an intra-canal medicament, such as calcium hydroxide.  Occlusion can be reduced.
  • incise and drain (I&D) if there is vestibular swelling.  If the abscess is localized, generally antibiotics are not needed unless there are other signs of systemic infection, cellulitis, poor drainage, or immune compromise.
  • cortical trephination – the jury is out on this one.  While this is not indicated routinely, it should be considered in areas with dense and thick cortical plates (i.e. lower molars).

3. Drugs: NSAIDS such as ibuprofen address inflammation very well, but some patients may require stronger analgesics, or combinations of analgesics for adequate pain relief.  My “go-to” is generally ibuprofen, and I rarely find that I need to prescribe narcotic analgesics.  However, I will consider acetaminophen only (plus or minus an opioid), other NSAIDS, or combinations of analgesics, depending on the patient’s risk of GI bleeding.  Antibiotics will not reduce post-treatment pain or decrease the risk of developing a flare-up when used prophylactically, but are indicated when there is sign of systemic involvement, presenting as fever, malaise, cellulitis, lymph node involvement, trismus, rapid onset of severe infection, or a compromised immune system.


it is important to inform your patients that they may experience a flare-up!  Tell them what to expect, how to identify the symptoms, and how they may reach you if this should happen.  I discuss this possibility with every patient.  If your patient comes to you with significant pain before you even start treatment, now is the time to consider pre-operative dosing of analgesics, and possibly a single oral dose (some prefer supra-periosteal infiltration) of an appropriate steroid (a common dose is 4 mg of dexamethasone) if there is no know contraindications.  Finally, shaping techniques such as a “crown-down” method may help prevent us from pushing infected debris into the periapical area.

Dr. Ellen Park @ vanendo

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