Acute apical periodontitis (AAP) is an inflammatory condition of the periapical tissues of the periodontium, usually resulting from irreversible pulpitis and pulpal necrosis. Although chemical and physical factors can cause pulpitis, most cases have a microbial cause, usually secondary to caries or trauma.1 Although the presence of some bacteria in the periapical region of an affected tooth has been demonstrated,2 AAP is predominantly an inflammatory, rather than an infectious, process.
Patients with AAP often have moderate to severe pain, which results in the need for emergency treatment.3 Because the transition from inflamed pulp to necrotic pulp to acute periapical disease occurs along a continuum, not all of the signs and symptoms, as described below, will be present in all patients. Patients with AAP usually present with dull, throbbing, constant pain; absence of swelling; a negative or delayed positive result on vitality testing; absence of thermal sensitivity of the tooth; and pain on biting or percussion.4 Radiographic changes such as widening of the periodontal ligament may be present, but frank radiolucency will not be observed.
Because of the progression from inflamed pulp to AAP, the diagnosis is not always straightforward. Vitality tests are affected by a number of factors, including the amount of residual pulp in the periapical area and the size of any restoration on the tooth.5 Sensitivity of the tooth to thermal changes may be due to recession,6 occlusal trauma, orthodontic movement or sinusitis.7 Tooth pain may also be referred from other orofacial structures or sites distant from the tooth.8 A misdiagnosis may lead to inappropriate treatment.