ROLE OF RADIOLOGY IN PERIODONTICS

Introduction

An overall assessment of the periodontal tissues is based on both the clinical examination and radiographic findings the two investigations complement one another. Unfortunately, like many other indicators of periodontal disease, radiographs only provide retrospective evidence of the disease process. However, they can be used to assess the morphology of the affected teeth and the pattern and degree of alveolar bone loss that has taken place.

Bone loss: the difference between the present septal bone height and the assumed normal bone height for any particular patient, taking age into account.

In fact radiographs actually show the amount of alveolar bone remaining in relation to the length of the root. But this information is still important in the overall assessment of the severity of the disease, the prognosis of the teeth and for treatment planning.

Use of Radiographs in Periodontology:

Assess the extent of bone loss and furcation involvement Determine the presence of any secondary local causative factors Assist in treatment planning Evaluate treatment measures particularly following guided tissue

regeneration (GTR)

The main radiographic projections used to show the periodontal tissues include:

Paralleling technique periapicals Bitewings — horizontal or vertical, normally for posterior teeth Dental panoramic toniographs, where there is pocketing greater

than 5 mm in depth Digital radiography — including subtraction radiography and

densitometric image analysis which may assist in showing and measuring subtle changes in fine alveolar and crestal bone pattern.

The quality of the radiographs should be assessed in relation to detailed interpretation:

Technique Exposure factors — remembering that these should be reduced

sufficiently to avoid burnout of the interdental crestal bone

Processing.

In the interpretation of the periodontal tissues, films of excellent quality are essential perhaps more so than in other dental specialit ies because of the fine detail that is required.

Radiographic features of healthy periodontium

A healthy periodontium can be regarded as periodontal tissue exhibiting no evidence of disease. Unfortunately, health cannot be ascertained from radiographs alone, clinical information is also required.

However, to be able to interpret radiographs successfully clinicians need to know the usual radiographic features of healthy tissues where there has been no bone loss. The only reliable radiographic feature is the relationship between the crestal bone margin and the cemento-enamel junction (CEJ). If this distance is within normal limits (2-3 mm) and there are no clinical signs of loss of attachment, then it can be said that there has been no periodontitis.

Illustrations of the radiographic appearances of a healthy periodontium.

A The upper incisor region. B The lower molar region.

The normal distance of 2-3 mm from the crestal margin to the cemento enamel junction is indicated.

Paralleling technique periapical radiograph of4567 (slightly reduced exposure) showing the radiographic features of a healthy periodontium (arrowed) before the onset of periodontitis.

The usual radiographic features of healthy alveolar bone include:

Thin, smooth, evenly corticated margins to the interdental crestal bone in the posterior

regions.

Thin, even, pointed margins to the interdental crestal bone in the anterior regions.

Cortication at the top of the crest is not always evident, owing mainly to the small amount

of bone between the teeth anteriorly.

The interdental crestal bone is continuous with the lamina dura of the adjacent teeth. The junction of the two forms a sharp angle.

Thin even width to the mesial and distal periodontal ligament spaces.