potential spaces (including the sublingual space, submandibular space, parapharyngeal space, pterygomandibular space, infratemporal space, submasseteric space and buccal space) to areas of the neck or face resulting in facial swelling, or even airway compromise (called Ludwig's angina). Bacteria Inadequate cleaning of the operculum space allows stagnation of bacteria and any accumulated debris. This can be a result of poor access due to limited room in the case of the 3rd molars. Pericoronal infection is normally caused by a mixture of bacterial species present in the mouth, such as Streptococci and particularly various anaerobic species. This can result in abscess formation. Left untreated, the abscess can spontaneously drain into the mouth from beneath the operculum. In chronic pericoronitis, drainage may happen through an approximal sinus tract. The chronically inflamed soft tissues around the tooth may give few if any symptoms. This can suddenly become symptomatic if new debris becomes trapped or if the host immune system becomes compromised and fails to keep the chronic infection in check (e.g. during influenza or upper respiratory tract infections, or a period of stress). 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