Identifying Pus Collections (Abscesses) on Intraoral Radiographs (RVG)
Pus itself is not directly visible on intraoral radiographs; instead, you identify abscesses by detecting periapical radiolucency—a dark area around the tooth apex representing bone destruction from the infectious process. 1
Primary Radiographic Signs of Periapical Abscess
Periapical Radiolucency
- Look for a radiolucent (dark) area at or around the apex of the tooth, indicating inflammatory bone destruction from the infectious process 2, 3
- The radiolucency represents bone loss, not the pus itself—pus has similar radiodensity to soft tissue and is not distinguishable on plain radiographs 3
- Widening of the periodontal ligament space to more than twice the normal width around the apex is an early sign of periapical pathology 2
Optimal Imaging Technique
- Periapical intraoral X-ray using a dedicated film holder and beam aiming device is the first-line imaging modality for suspected periapical abscess 1, 4
- This paralleling technique provides the highest spatial resolution and most accurate assessment of periapical tissues 1
- Bitewing radiographs are insufficient for periapical assessment—always obtain a periapical view when infection involving the pulp or apex is suspected 1
Special Diagnostic Technique for Fistulas
If a fistula (draining tract) is present clinically, obtain the intraoral radiograph with a gutta-percha cone inserted inside the fistula tract to accurately trace its origin back to the source tooth 1, 4, 5. This technique has a Grade A strength of recommendation and provides definitive identification of which tooth is responsible for the abscess 4.
When Standard Radiographs Are Insufficient
- CBCT can detect periapical disease more accurately than standard intraoral X-rays, particularly when bony structures superimpose on the area of interest 1, 4
- However, CBCT is explicitly NOT indicated in the initial diagnostic phase of periapical tissue swelling 1, 4
- Reserve CBCT only for suspect or unclear cases after traditional intraoral examination remains inconclusive, following the ALARA principle for radiation exposure 1, 4
Common Pitfalls to Avoid
- Do not expect to see pus directly—you are identifying the bone destruction (radiolucency) caused by the abscess, not the purulent material itself 3
- Do not skip the film holder and beam aiming device—freehand technique produces suboptimal images that may miss periapical pathology 1, 4
- Do not order CBCT as first-line imaging—this exposes patients to unnecessary radiation when simpler imaging suffices 4, 6
- Do not confuse periodontal abscesses with periapical abscesses—periodontal disease can present with similar gingival swelling but originates from the gingival margin rather than the tooth apex 1, 6
- Do not overlook subtle widening of the periodontal ligament space—this may be the only early radiographic sign before frank radiolucency develops 2
Clinical Correlation Required
- Acute alveolar abscess is often impossible to identify definitively by clinical examination alone, making radiographic assessment essential 1
- Gray discoloration of a tooth with localized gingival swelling suggests pulpal necrosis and warrants immediate periapical radiography 6
- The presence of a vestibular mucosal fistula near a tooth apex should always raise suspicion of a septic pulpal lesion affecting periapical tissues 1, 6