Tooth position
When an opposing tooth bites into the operculum, it can initiate or exacerbate pericoronitis resulting in a spiraling cycle  of inflammation and trauma. Over-eruption of the opposing tooth into the unoccupied space left by the stalled eruption of a tooth is a risk factor to operculum trauma from biting. Teeth that fail to erupt completely (commonly the lower mandibular third molars) are often the result of limited space for eruption, or a non-ideal angle of tooth eruption causing tooth impaction. The presence of supernumerary teeth (extra teeth) makes pericoronitis more likely. Diagnosis
The presence of dental plaque or infection beneath an inflamed operculum without other obvious causes of pain will often lead to a pericoronitis diagnosis; therefore, elimination of other pain and inflammation causes is essential. For pericoronal infection to occur, the affected tooth must be exposed to the oral cavity, which can be difficult to detect if the exposure is hidden beneath thick tissue or behind an adjacent tooth. Severe swelling and restricted mouth opening may limit examination of the area. Radiographs can be used to rule out other causes of pain and to properly assess the prognosis for further eruption of the affected tooth.Sometimes a "migratory abscess" of the buccal sulcus occurs with pericoronal infection, where pus from the lower third molar region tracks forwards in the submucosal plane, between the body of the mandible and the attachment of the buccinator muscle to the mandible.
Pericoronitis is inflammation of the soft tissues surrounding the crown of a partially erupted tooth, including the gingiva (gums) and the dental follicle. The soft tissue covering a partially erupted tooth is known as an operculum, an area which can be difficult to access with normal oral hygiene methods. The hyponym operculitis technically refers to inflammation of the operculum alone. Pericoronitis is caused by an accumulation of bacteria and debris beneath the operculum, or by mechanical trauma (e.g. biting the operculum with the opposing tooth). Pericoronitis is often associated with partially erupted and impacted mandibular third molars (lower wisdom teeth), often occurring at the age of wisdom tooth eruption (15-26). Other common causes of similar pain from the third molar region are food impaction causing periodontal pain, pulpitis from dental caries (tooth decay), and acute myofascial pain in temporomandibular joint disorder. Pericoronitis is classified into chronic and acute. Chronic pericoronitis can present with no or only mild symptoms and long remissions between any escalations to acute pericoronitis. Acute pericoronitis is associated with a wide range of symptoms including severe pain, swelling and fever. Sometimes there is an associated pericoronal abscess (an accumulation of pus). This infection can spread to the cheeks, orbits/periorbits, and other parts of the face or neck, and occasionally can lead to airway compromise (e.g. Ludwigs angina) requiring emergency hospital treatment. The treatment of pericoronitis is through pain management and by resolving the inflammation.