Radiographic Interpretation of Endodontic Disease - Small Animal

Interpreting Endodontic Disease

Radiographs may provide information about the presence, nature, and severity of periapical and root pathology. This information is essential for the diagnosis of endodontic disease as well as for the prognosis of its treatment. Radiographs do not provide direct information about pulp health; however, many of the effects of pulp pathology are radiographically visible.

Clinical findings that may indicate the presence of endodontic disease include a fractured tooth with exposure of the pulp chamber, a discolored tooth, or an intraoral or extraoral draining fistula. Except in the obvious case of a direct pulp exposure, a definitive diagnosis of endodontic pathology is difficult to make based only on clinical examination of veterinary patients due to the limitations of pulp testing and lack of patient input.

Radiographs should be made of teeth that are fractured, close to a draining fistula, intrinsically discolored, anomalous, or compromised from periodontal disease to determine the extent of the problem and to evaluate the endodontic and periradicular health.

Dental radiographs can be misleading and unreliable. Early endodontic disease may not show any radiographic abnormalities, while superimposed anatomy can mimic endodontic disease on a radiograph of a healthy tooth. Despite these limitations, dental radiographs continue to be the best tool available to evaluate endodontic health in veterinary patients. The site of exit does not always directly correlate to the problem tooth. Radiographs are needed to determine which tooth is involved.

Radiographic Signs of Endodontic Disease

Inflammation caused by endodontic disease affects the surrounding bone and teeth, resulting in changes that can be radiographically detected. Radiographs that are meant to evaluate the periapical tissues should include the entire root tip and surrounding bone, be well positioned to avoid elongation, foreshortening, angulation, or distortion of the image.

Radiographic signs of endodontic disease that are associated with the tissues around tooth roots include:

• Increased width of the apical radiolucent periodontal ligament space
• Loss of the radiopaque lamina dura at the apex or other portals of exit such as lateral canals
• Diffuse periapical radiolucency with indistinct borders that may indicate an acute abscess
• Clearly evident periapical radiolucency with distinct borders that is evidence of a more chronic lesion
• Diffuse area of radiopacity where low-grade chronic inflammation results in sclerosing osteitis
• Changes in the trabecular bone pattern around the root apex

Radiographic signs of endodontic disease that are associated with the tooth itself include:

• Root tip resorption
• Internal root or crown resorption. Inflammation of the pulp can cause internal resorption.
• External root resorption. Inflammation in the periodontal ligament can cause external root resorption.
• Arrested tooth maturation (pulp necrosis). Pulp necrosis causes the opposite effect, arresting any further dentin formation or tooth maturation. The result is a tooth that appears radiographically less mature (wider root canal space) than the adjacent teeth.
• Accelerated apparent tooth maturation (pulpitis). Pulpitis can also result in formation of tertiary, or reparative dentin on the walls of the pulp cavity. Pulpitis that is generalized over a section of a root canal creates the radiographic effect of a narrower canal in that section, giving the appearance of a more mature tooth. The extreme of this can manifest as “pulp cavity obliteration,” a radiographic term that describes an inability to identify sections of, or the entire, pulp space.

Endodontic lesions in cats appear radiographically similar to those in dogs.

Lucencies That Can Mimic Endodontic Lesions

Apical radiographs can be challenging to interpret due to the two-dimensional depiction of complicated anatomy that combines trabecular (spongy) bone, compact bone, soft tissue, and air spaces all projected at various angles and configurations. Other confusing lucencies and opacities can be created by the summation effect of superimposed structures, projecting overlying anatomy in a way that makes it appear to be associated with a tooth root or its supporting bone. These can include bony foraminae, bony fissures, bony canals, and trabeculae. Many nonpathological lucencies, opacities, and apparent deviations from normal can be distinguished from true lesions by comparison with a radiograph of the contralateral tooth.

Causes of Endodontic Disease

Two categories of insult that most commonly cause endodontic disease are bacterial infection and dental trauma.

Bacteria can also enter the endodontic system of a nontraumatized tooth through extension of periodontal disease. If the periodontal epithelial attachment migrates apically to an endodontic vascular entrance such as a lateral canal, furcation communication, or the apical foramen or delta, then the pulp could become infected. This is referred to as a primary periodontal lesion with secondary endodontic involvement (it has also been referred to as a “perio-endo lesion”). Apical and radicular LEOs can dissect coronally along the side of the root to exit in the sulcus, creating a primary endodontic lesion with secondary periodontal disease (has also been referred to as an “endo-perio lesion”). The bony defects around a tooth with primary endodontic disease and concurrent but unrelated periodontal disease can meet to form a combined periodontal and endodontic lesion.

Pulp inflammation and necrosis can also result from deep dental caries with extension of the bacterial infection to the pulp.

Blunt trauma can cause pulp haemorrhage and endodontic disease even when the tooth crown does not fracture. Although the pulp has some ability to heal after mild trauma, the most common result of pulp trauma is irreversible pulpitis even when there is no bacterial contamination of the pulp.

Radiographic signs depend on the pulp response:

• Arrested development of a tooth (wide pulp with thin dentin)
• Pulp calcification
• Internal resorption
• External resorption
• Wide periodontal ligament space
• Periradicular radiolucencies
• Discontinuous lamina dura
• Root fractures