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 can be defined as 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.

Radiographs are therefore used to:

Selection criteria

Several radiographic projections can be used to show the periodontal tissues. Those recommended by the Faculty of General Dental Practice (UK) in 2013 are summarized in Table 22.1.

In addition, digital radiography and image manipulation including subtraction and densitometric image analysis (see Ch. 5), may assist in showing and measuring subtle changes in fine alveolar and crestal bone pattern. However, these techniques require the inclusion of a reference object of known density and a highly reproducible positioning technique to be helpful.

Important points to note

• In the interpretation of the periodontal tissues, images of excellent quality are essential – perhaps more so than in other dental specialties – because of the fine detail that is required.

• Exposure factors should be reduced when using film-based techniques to avoid burn-out of the interdental crestal bone.

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.

The usual radiographic features of healthy alveolar bone are shown in Figs 22.1 and 22.2 and include:

Important points to note

• Although these are the usual features of a healthy periodontium, they are not always evident.

• Their absence from radiographs does not necessarily mean that periodontal disease is present.

• Failure to see these features may be due to:

– Technique error

– Overexposure

– Normal anatomical variation in alveolar bone shape and density.

• Following successful treatment, the periodontal tissues may appear healthy clinically, but radiographs may show evidence of earlier bone loss when the disease was active. Bone loss observed on radiographs is therefore not an indicator of the presence of inflammation.

Classification of periodontal disease

Various classifications of periodontal disease have been put forward over the years. The most comprehensive, although not universally agreed, was produced by the International Workshop of the American Academy of Periodontology and the European Federation of Periodontology in 1999. A simplified version is shown in Table 22.2.

        3. Gingival diseases modified by medications, e.g. phenytoin, nifedipine     4. Gingival diseases modified by malnutrition, e.g. Vitamin C deficiency     B. Non-plaque-induced gingival lesions II Chronic periodontitis A. Localized     B. Generalized III Aggressive periodontitis A. Localized     B. Generalized IV