Following this procedure, the gingival cuff tightens around the tooth, which may be enough to trap the bacteria left in the pocket. A gingival retraction cord which is accidentally left in situ is an occasional cause of a periodontal abscess. Penetrating injury to the gingiva--for example, with a toothbrush bristle, fishbone, toothpick or periodontal instrument--may inoculate bacteria into the tissues. Trauma to the tissues, such as serious impact on a tooth or excessive pressure exerted on teeth during orthodontic treatment, can be a possible cause as well. Occlusal overload may also be involved in the development of a periodontal abscess, but this is rare and usually occurs in combination with other factors. Bruxism is a common cause of excessive occlusal forces. Systemic immune factors such as diabetes can predispose a person to the formation of periodontal abscesses. Perforation of a root canal during endodontic therapy can also lead to a periodontal abscess which if left untreated could become "prolonged" ultimately rupture then enter the blood stream and could lead to serious situations such as endocarditis. Diagnosis
Periodontal abscesses may be difficult to distinguish from periapical abscesses. Since the management of a periodontal abscess is different from a periapical abscess, this differentiation is important to make (see Dental abscess#Diagnostic approach) For example, root canal therapy is unnecessary and has no impact on pain in a periodontal abscess. Classification
There are four types of abscesses that can involve the periodontal tissues:
Gingival abscess—a localized, purulent infection involves only the soft gum tissue near the marginal gingiva or the interdental papilla.
Periodontal abscess—a localized, purulent infection involving a greater dimension of the gum tissue, extending apically and adjacent to a periodontal pocket. Pericoronal abscess—a localized, purulent infection within the gum tissue surrounding the crown of a partially or fully erupted tooth. Usually associated with an acute episode of pericoronitis around a partially erupted and impacted mandibular third molar (lower wisdom tooth). combined periodontal/endodontic abscess

Treatment
An important factor is whether the involved tooth is to be extracted or retained. Although the pulp is usually still vital, a history of recurrent periodontal abscesses and significantly compromised periodontal support indicate that the prognosis for the tooth is poor and it should be removed. The initial management of a periodontal abscess involves pain relief and control of the infection. The pus needs to be drained, which helps both of these aims. If the tooth is to be removed, drainage will occur via the socket. Otherwise, if pus is already discharging from the periodontal pocket, this can be encouraged by gentle irrigation and scaling of the pocket whilst massaging the soft tissues. If this does not work, incision and drainage is required, as described in Dental abscess#Treatment. Antibiotics are of secondary importance to drainage, which if satisfactory renders antibiotics unnecessary. Antibiotics are generally reserved for severe infections, in which there is facial swelling, systemic upset and elevated temperature.