Equis ISSN 2398-2977

Teeth: apical infection

Synonym(s): Peri-apical abscess

Contributor(s): Gordon Baker, Vetstream Ltd


  • Bacterial infection of the apex of an incisor or mandibular or maxillary cheek tooth.
  • Cause: vertical impaction/overcrowding, retained deciduous 'caps', hematogenous or lymphatic spread; secondary to other dental abnormalities.
  • Signs: mandibular/maxillary swelling, draining sinus tract, paranasal sinus infection; less commonly dysphagia.
  • Diagnosis: physical examination, radiography.
  • Treatment: antimicrobials, repulsion, oral extraction.
  • Prognosis: good-guarded (for initial resolution) depending on location of affected tooth and involvement of paranasal sinuses.



Mandibular cheek teeth
  • Rostral mandibular cheek teeth (especially 2nd and 3rd) most commonly affected.
  • Age of infection closely related to time of eruption of affected tooth.
  • 'Eruption cysts' may be associated with overcrowding and have a genetic predisposition   Mandible: alveolar pseudocyst - radiograph  .

Maxillary cheek teeth

  • Most infections involve the rostral three (1st, 2nd and 3rd), but a significant number involve the caudal three (4th, 5th and 6th).
  • More than one tooth may be involved.
  • Vertical impaction.
  • Breed susceptibility.
  • External trauma.
  • Pressure atrophy due to incongruous growth rates of tooth vs mandible.
  • Retained deciduous caps   Teeth: maleruption  .
  • Hematogenous or lymphatic spread of bacteria.
  • Extension of periodontal disease.
  • Some of these factors may combine to result in infection; or be associated with 'eruption cysts' that may predispose to infection.
  • Secondary to other causes, eg infundibular caries   Teeth: caries - infundibular cement  , dental trauma, deep periodontal infection   Teeth: periodontal disease  , diastemata, supernumerary and displaced cheek teeth.
  • Recent eruption of affected tooth.
  • Vertical impaction:
    • Incident angles of adjacent teeth, ie 1st and 3rd or 2nd and 4th cheek teeth, totalling close to 30° rather than approximately 14°.
    • Mechanical interference with eruption   →   pressure necrosis   →   susceptibility to bacterial infection.
  • External trauma:
    • Rupture of the thin ventral mandibular cortex beneath 'eruption cyst'.
  • Hematogenous spread:
    • Delayed eruption/eruption cysts   →   inflammation and devitalization of local apical tissues   →   susceptibility to bacterial infection via transient bacteremia or gingival lymphatics draining gingival sulcus.
  • The long reserve crowns and apices of the mandibular cheek teeth occupy most of the mandible   Maxilla: normal adult 02 - oblique radiograph    Mandible / maxilla: normal young adult - LM radiograph  .
  • The majority of infections (91.4%) affect adjacent alveolus and mandible; drainage usually occurs through the ventral mandibular cortex   →   external sinus tract (58.6% of cases).
  • Oral involvement is rare.
  • Occasionally inflammation and possible infection may result in ankylosis of the apex to the mandibular cortex   →   preventing tooth from erupting (maleruption   Teeth: maleruption  )   →   overgrowth   Teeth: abnormal wear  of opposing maxillary cheek teeth.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Tremaine H & Casey M (2012) A modern approach to equine dentistry 2. Identifying lesions. In Pract 34 (2), 78-89 VetMedResource.
  • Dixon P M et al (2000) Equine dental disease Part 4 - a long-term study of 400 cases - apical infections of cheek teeth. Equine Vet J 32, 182-194 PubMed.