Dental Abscess Workup

Updated: Jan 22, 2019
  • Author: Jane M Gould, MD, FAAP; Chief Editor: Jeff Burgess, DDS, MSD  more...
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Laboratory Studies

Uncomplicated (ie, simple) dental abscess: No laboratory studies are required.

Complicated abscess (accompanying cellulitis)

  • The CBC count may reveal leukocytosis with neutrophil predominance.

  • Obtain a blood culture (aerobic and anaerobic) before initiating parenteral antibiotics.

  • Needle aspirate is indicated for Gram stain and aerobic and anaerobic cultures.


Imaging Studies

Depending on severity of abscess based on clinical presentation the following is recommended:

  • Periapical radiography is the first level of investigation. It provides a localized view of the tooth and its supporting structures. Widening of the periodontal ligament space or a poorly defined radiolucency may be noted.

  • Panoramic radiography (pantomography) is most helpful in emergency situations because it provides the most information for all teeth and supporting structures.

If cellulitis swelling extends beyond local area then the following is indicated:

  • Lateral and anteroposterior neck views to rule out a soft tissue neck mass that impinges on the airway.

  • CT scanning with intravenous contrast is the most accurate method to determine the location, size, extent, and relationship of the inflammatory process to the surrounding vital structures.



Confirm presence of the abscess via needle aspiration.

  • If pus is obtained, do not aspirate more than 1-2 drops. Leave the abscess as large as possible to make the area easier to find for further management.

  • If pus cannot be aspirated, manage medically until a more localized infection develops.

Incision and drainage may be performed only if pus can be aspirated.

Packing a periapical abscess is generally not necessary.


Histologic Findings

The flora at different oral sites varies. The surface of the carious tooth usually contains acid producing aerobic and anaerobic bacteria including Streptococcus mutans, Lactobacillus acidophilus, and Actinomyces viscosus. S mutans is the only organism recovered from decaying dental fissures. Obligate anaerobes such as Propionibacterium, Eubacteria, Arachnia, Lactobacillus, Bifidobacterium, and Actinomyces constitute most organisms isolated from carious dentin. The bacteria isolated from inflamed pulp and root canals are aerobic, facultative anaerobic and strict anaerobic organisms, in addition to yeast.

  • Anaerobes usually outnumber aerobes and facultative anaerobes.

  • Most odontogenic infections involve plaque organisms.

  • Supragingival plaque mainly consists of gram-positive facultative anaerobes or microaerophilic cocci and rods.

  • Subgingival plaque consists of anaerobic gram-negative rods with motile form, including spirochetes.