Causes
- Phoenix abscesses are believed to be caused by changes in the internal environment of the root canal system during root canal treatment.
- These changes can lead to a sudden worsening of symptoms of chronic periradicular periodontitis.
- Instrumentation during root canal treatment can stimulate residual microbes in the root canal space, causing an inflammatory reaction.
- The microbes involved are predominantly facultative anaerobic gram-positive bacteria, such as Streptococcus, Enterococcus, and Actinomyces species.
- Another cause of a phoenix abscess is a decrease in a patient's resistance to these bacteria and their products.

Signs & Symptoms
- Exacerbated and exaggerated pain is a common clinical feature of a phoenix abscess.
- Pain may or may not be associated with pus and suppuration.
- The signs and symptoms are similar to those of an acute periradicular abscess, with the presence of a periradicular radiolucency.
- The affected tooth will have a non-vital pulp with no previous symptoms.
- The tooth is extremely tender to touch and may be extruded from the socket, leading to high occlusion.
- Mobility of the tooth may be observed.
- Radiographically, a periapical lesion associated with the tooth will be visible.
- This lesion is usually present prior to the onset of the phoenix abscess.
- A widened periodontal ligament (PDL) space can be seen on the radiograph.

Treatment
- Further root canal treatment is often the recommended option for treating a phoenix abscess.
- The tooth should be accessed and thoroughly irrigated using sodium hypochlorite.
- After irrigation, the canals should be dried using paper points.
- Debridement of the tooth should be performed, and drainage should be established.
- Antibiotics may be necessary in certain circumstances, such as the presence of diffuse swelling or cellulitis.
- Antibiotics may also be indicated when immediate drainage cannot be achieved or when the patient has systemic involvement.
- Analgesics may be advised to control pain associated with a phoenix abscess.
- If the tooth is unrestorable, extraction may be considered as a treatment option for a phoenix abscess.
- Adjusting the bite may provide temporary relief, but it is not a permanent solution to the problem.

References
- Classification of Pulpal and Periradicular Pathoses «UCLA School of Dentistry Clinic Guide.
- Sakko, Marjut; Tjäderhane, Leo; Rautemaa-Richardson, Riina (2016-05-01). Microbiology of Root Canal Infections.
- Carrotte, P (September 2004). Endodontics: Part 3 Treatment of endodontic emergencies (PDF).
- McClanahan, Scott B (2002). Pulpal and Periradicular Diagnostic Terminology (PDF).
- Shetty, Neeta. Mid Treatment Flareups in Endodontics (PDF).

Subtopics (not included in the previous groups)
- SUBTOPIC 2.1: Clinical Features
- SUBTOPIC 2.2: Radiographic Features
- SUBTOPIC 3.1: Further Endodontic Treatment
- SUBTOPIC 3.2: Medications
- SUBTOPIC 3.2.i: Antibiotics
- SUBTOPIC 3.2.ii: Analgesics
- SUBTOPIC 3.3: Extraction
- SUBTOPIC 3.4: Bite Adjustment