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Diagnostics: Radiographic Features

The features of periapical inflammatory lesions vary depending on the time course of the lesion.

  1. Very early lesions may not show any changes in the image, diagnosis of these lesions relies solely on the clinical symptoms
  2.   Chronic lesions may show lytic (radiolucent) or sclerotic (radiopaque) changes, or both.

 Very early lesion involving the pulp of the second bicuspid without significant change in the periapical bone (arrow). In contrast, note the loss of the lamina dura and periapical bone at the apex of the mesial root of the second molar. Also note the subtle halo of sclerotic bone reaction around this apical radiolucency.

Location

The epicenter of periapical inflammatory lesions is found at the apex of the involved tooth

 The lesion usually starts within the apical portion of the periodontal ligament space. Less often, such lesions are centered about another region of the tooth root; this may occur because of accessory pulpal canals, perforation of the root structure from instrumentation of the pulp canal, and root fracture.

Periapical inflammatory lesions associated with a mandibular first molar (A) and a maxillary lateral incisor (B). In both cases, the epicenter of bone destruction is located at the apex of the root. Also, note gradual widening of the periodontal membrane space (arrow) characteristic of an inflammatory lesion. C, Periapical image of sclerosing osteitis related to the first molar shows a gradual transition from thick and numerous trabeculae (short arrow) to a normal trabecular pattern (long arrow).

Periphery

The periphery of periapical inflammatory lesions is ill defined, showing a gradual transition from the surrounding normal trabecular pattern into the abnormal bone pattern of the lesion. Rarely, the periphery may be well defined, with a sharp transition zone and an appearance suggesting a cortical boundary.

Internal Structure

Early periapical inflammatory lesions may show no apparent change in the normal bone pattern.

The earliest detectable change is loss of bone density, which usually results in widening of the periodontal ligament space at the apex of the tooth and later involves a larger diameter of surrounding bone.No evidence may be seen of a sclerotic bone reaction

 Later in the evolution of the disease, a mixture of sclerosis and rarefaction (loss of bone giving a radiolucent appearance) of normal bone occurs.  The percentage of these two bone reactions varies.

When most of the lesion consists of increased bone formation, the term periapical sclerosing osteitisRadiopaque

 When most of the lesion is undergoing bone resorption, the term periapical rarefying osteitis : Radiolucent.

Radiolucency :  The area of greatest bone resorption usually is centered on the apex of the tooth, with the sclerotic pattern located at the periphery. The radiolucent regions may be bereft of any bone structure or may have a faint outline of trabeculae.

Radiopaque, surrounding lucency: Close inspection of sclerotic regions reveals thicker than normal trabeculae and sometimes an increase in the number of trabeculae per unit area.

 In chronic cases, the new bone formation may result in a very dense sclerotic region of bone, obscuring individual trabeculae. Occasionally, the lesion may appear to be composed entirely of sclerotic bone (sclerosing osteitis), but usually some evidence exists of widening of the apical portion of the periodontal membrane space

Examples of a mixture of rarefying and sclerosing osteitis. Note the similarity of the pattern, comprising a radiolucent region at the apex of the tooth surrounded by a radiopaque reaction of sclerotic dense bone.

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