OMFS-0211Odontogenic infectionsInfectionbeginnerRight mandibular first molar / buccal space

Acute facial swelling from a non-vital lower molar

34-year-old female

Draft — educational study aid, pending faculty review.

§Chief complaint

Severe throbbing toothache with cheek swelling for 3 days

§Medical & dental history

01No systemic disease
02No penicillin allergy
0346 root-filled 4 years ago, recurrent discomfort
04Irregular dental attendance

§Clinical examination

01Diffuse tender swelling of the right cheek with loss of the buccal sulcus
0246 tender to percussion, grade I mobile, non-responsive to pulp testing
03Temperature 37.9 C, mouth opening 35 mm
04No floor of mouth elevation, airway patent, no dysphagia

§ figuresFigures (4)

Periapical Abscess — clinical image: A root showing an abscess at the apex after extraction. — Fig. 1A root showing an abscess at the apex after extraction.
“Periapical abscess” · lacihobo · CC BY-SA 4.0 · Wikimedia Commons

Verified open-access images only, reproduced for education under their stated licences · no AI-generated or illustrative artwork · Periapical Abscess figures pending faculty review.

§Differential diagnosis

Acute periapical abscess with buccal space involvementNon-vital tooth, localised tender swelling

Periodontal abscessVital tooth, deep pocket, lateral swelling

Infected radicular cystRadiolucency with acute exacerbation

Buccal space infection from 47Check all teeth for the true source

§Final diagnosis

Acute periapical abscess of 46 with buccal space involvement

A non-vital, percussion-tender tooth with a periapical radiolucency and an adjacent fluctuant swelling that drains pus on incision localises the source; the absence of floor-of-mouth elevation or airway compromise keeps this a low-severity space infection.

§Investigations

01Pulp sensibility testing of 45-47 — 46 non-responsive
02Pus swab for culture and sensitivity
03Temperature, pulse and mouth opening recorded as severity markers

§Radiology

01IOPA 46 — short, under-filled distal canal with a 6 mm periapical radiolucency
02OPG — no other periapical pathology, no bony destruction beyond the apex

§Treatment plan

01Remove the source: incision and drainage plus pulpal drainage
02Empirical amoxicillin with metronidazole adjusted by culture
03Analgesia, fluids, review in 48 hours
04Definitive root canal retreatment or extraction

§Surgical procedure

01Intraoral incision at the point of maximal fluctuance, blunt dissection with sinus forceps, 15 mL pus drained
02Corrugated drain sutured for 48 hours; access cavity opened for pulpal drainage

§Follow-up & outcome

0148 hours — swelling halved, drain removed, apyrexial
021 week — sulcus re-formed, retreatment commenced
033 months — periapical healing on radiograph

Outcome: Infection resolved without hospital admission; tooth retained after retreatment.

§Discussion

01Source control outweighs antibiotics — drainage and pulpal or surgical removal of the focus is the definitive treatment.
02Red flags mandating admission: trismus under 20 mm, floor-of-mouth elevation, dysphagia, dyspnoea, rapid progression, systemic sepsis or immunocompromise.

§Clinical pearls / learning points

01Antibiotics never substitute for drainage.
02Always confirm the offending tooth with pulp testing before irreversible treatment.

§Viva questions

What organisms predominate in odontogenic abscesses?

Mixed aerobic-anaerobic flora: viridans streptococci, Prevotella, Porphyromonas, Fusobacterium and Peptostreptococcus.

When do you admit?

Airway threat, severe trismus, dysphagia, systemic sepsis, spread to multiple or deep spaces, or failure of outpatient treatment.

§MCQs

Q1The most important step in managing an odontogenic abscess is:

Q2Buccal space infection from a lower molar spreads when pus perforates:

§ evidenceReferences & Evidence

Current Classification

WHO Classification of Tumours Online — Head and Neck

IARC / WHO · 2022

Continuously updated online edition of the WHO head and neck tumour classification.

View official source

Evidence summary

Highest level of evidence linked to this page: WHO / Official Classification.

L1 · Classification — 1
L6 · Textbook — 3

1 linked source was published from 2024 onwards. Where guidance is limited or contested, rely on the higher-level sources above rather than this summary. Educational use only — not a substitute for clinical judgement.

Content last reviewed

September 2026

Evidence last reviewed

September 2026

Next scheduled review

September 2027

Review status

EVIDENCE REVIEWED

Search latest PubMed evidence

Last literature search: 7 September 2026

Open PubMed

Current Classification