Image 7B points to internal resorption, which decreases the chance of a successful root canal.
Crown pathology The determination of pulpal exposure is key to the treatment of endodontic disease. When the pulp is exposed to the oral environment,
bacteria have a direct entrance into the tooth causing pulpal necrosis and periapical lysis. Teeth that are fractured with
near pulp exposure without radiographic signs of periodontal disease, can often be treated with crown restoration compared
to those with chronic pulp exposure that must be extracted or have root-canal therapy erformed.
Image 8 notes the differences between both mandibular canals; enlarged canals indicate a "dead tooth" due to pulpal necrosis.
Root disease Internal resorptionaffects the pulp. The cause is unknown, but trauma and pulpal death from anachoresis (bacteria gaining access to the injured
pulp through vascular channels) is believed to be contributing factors. External resorption affects the root from the outside.
At times it is difficult to determine whether a lesion is due to internal or external resorption. When a normal-appearing
root canal is visualized radiographically, the lesion is considered external in origin.
Image 9 shows fractured maxillary second molar showing periapical lucency.
When examining the radiograph, the clinician should pay close attention to:
Radiographic apical closure necessary for conventional endodontic therapy;
Additional fractures (Image 6);
Abnormalities in the canal, such as obstruction or internal resorption (Images 7A and 7B).
Relative canal widths compared to adjacent or contralateral teeth. If a tooth shows an enlarged canal compared to adjacent
teeth, the tooth is termed non-vital due to arrested development from pulpal necrosis (Image 8).
Image 10 finds the first molar affected by dilacerated crown and roots.
Periapical diseaseis a pathologic process surrounding the apex of one or more roots that occurs as an extension of periodontal disease, or necrosis
of the dental pulp from trauma or infection. Radiographic appearance of periapical disease appears as:
Minimal to moderate alveolar bone resorption typical of a granulomatous lesion from pulpal necrosis (Image 9);
A large homogeneous radiolucency at theapexor a dark halo in the periapical tissues caused by lysis of the bone around the tooth's apex (Image 10);
Sharply outlined circumscribed radiolucent areas caused by a cyst (most apical cysts arise from preexisting granulomas) (see
Images 11A and 11B).
Osteomyelitissecondary to chronic endodontic disease appears as lysis of the surrounding bone (Image 8).
Image 11A shows feline mandibular molar with inflamed gingiva over the distal root.
Endodontic/periodontic lesions Sometimes endodontic and periodontic disease exist in the same tooth.
Image 11B shows a radicular (root) cyst of the distal root.
Class I endoperio lesionsare primary endodontic lesions that extend coronally from the root apex reaching the gingival sulcus, causing a secondary
periodontal lesion. The pattern of bone loss often resembles a "J" shape with a narrow periodontal pocket at the alveolar crest (Image 12).
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