Endodontic Disease in Small Animals

I. Definition, Pathogenesis, and Scope

• Definition: Endodontic disease (pulpitis) is inflammation or infection of the tooth pulp.

• Pulp Components: The dental pulp includes odontoblasts, fibroblasts, undifferentiated mesenchymal cells, blood vessels, and nerves in the center of the tooth.

• Disease Categories:

    ◦ Reversible: Inflamed pulp can potentially heal after a minor injury.

    ◦ Irreversible: Caused by more severe trauma, eventually leading to pulp necrosis. Most cases diagnosed in dogs and cats are irreversible.

• Healing Limitations: Dental pulp has no collateral circulation. Injuries are less likely to heal, and blood that has leaked out remains trapped in the dentinal tubules where it deteriorates.

• Consequences of Dead/Inflamed Pulp: Inflammatory mediators are released into the periradicular tissues via apical foramina, lateral canals, and furcation canals.

    ◦ This leads to the development of a periapical granuloma, cyst, or abscess around the apex of a tooth.

II. Etiology (Causes)

• Loss of Protection: The pulp is normally protected by the impervious enamel covering the dentin.

    ◦ Damage to enamel via trauma or a developmental abnormality allows bacteria to reach the pulp, resulting in pulpitis.

• Trauma/Fracture:

    ◦ Direct exposure of the pulp at a fracture site causes the tooth to die.

    ◦ Blunt trauma (concussive force) can injure the pulp beyond its ability to heal, even without crown structure loss.

    ◦ Sources of trauma: Catching rocks, automobile impacts, aggressive play, or biting inappropriate objects (e.g., real bones, hooves, antlers, hard nylon toys, rocks, fences, or cages).

• Other Routes of Infection:

    ◦ Secondary Endodontic Disease: Severe periodontitis may progress apically to reach the root apex.

    ◦ Deep Caries: In dogs, deep cavities may extend into the endodontic system.

III. Clinical Findings and Lesions

• General Signs: Reluctance to chew or hold toys, tooth sensitivity, hypersalivation, and signs of pain.

• Pain Progression:

    ◦ Teeth are painful as long as the neurovascular supply is alive (can take weeks, months, or longer).

    ◦ Once the nerve is nonvital, the tooth may enter a non-painful (quiescent) phase lasting months to years.

    ◦ Pain returns once the tooth exhibits evidence of endodontic infection.

• Discolored Teeth (Intrinsic Staining):

    ◦ Signifies endodontic disease and is evidence of previous trauma and hemorrhage into the dentinal tubules.

    ◦ Colors observed: Pink, purple, gray, or green, or a dull appearance.

    ◦ 87%–92% of intrinsically stained teeth are reported to be nonvital and require treatment.

• Fracture/Pulp Exposure (Most Obvious Sign):

    ◦ A complicated crown fracture (e.g., a "slab" fracture) exposes the pulp.

    ◦ The exposed site may appear as a red dot (vital pulp) or a black hole (necrotic pulp).

• Infection Drainage (Fistulas/Abscesses):

    ◦ Drainage usually occurs through the fracture site.

    ◦ A periapical abscess may occur if the fracture site becomes occluded.

    ◦ Parulis: An intraoral red draining fistula near the mucogingival junction adjacent to the tooth.

    ◦ Facial Swelling/Draining Tract:

        ▪ Maxillary fourth premolar: Common cause of swelling/drainage on the skin ventral to the medial canthus of the eye.

        ▪ Abscessed maxillary canine tooth (dogs): Swelling along the side of the nose.

        ▪ Abscessed canine tooth (cats): Swelling often immediately rostral to the eye.

IV. Diagnosis

• Methods: Thorough oral examination and diagnostic imaging of affected teeth.

• Radiographic Evidence:

    ◦ A tooth with a periapical granuloma or cyst typically shows a periapical lucency (an irregular circular lesion with decreased radiopacity around a root tip).

    ◦ A tooth with an acute periapical abscess may not show distinct radiographic signs.

    ◦ Pulp Cavity Width: A necrotic pulp discontinues dentin production, resulting in a wider cross-sectional pulp cavity compared to normal teeth. Conversely, an inflamed pulp may produce dentin at an accelerated rate, potentially leading to an abnormally narrow pulp chamber (apparent accelerated aging).

• Focus of Evaluation: Gross structural defects at the crown, radiographic appearance of the root apex, pulp cavity width, and periapical tissues.

V. Treatment Options

Treatment is required for a fractured tooth with pulp exposure. The goal is to remove the source of inflammation.