Recommendation	Evidence-based Grading*
Horizontal bitewings if a patient has generalised pocketing <6 mm (BPE scores of Code 3) and little or no recession.	C
Vertical bitewings if a patient has pocketing 6 mm or more (BPE scores of Code 4), supplemented by paralleling technique periapicals at sites where the alveolar bone is not shown on the bitewings.	C
Bitewings (horizontal or vertical depending on pocket depth), supplemented by paralleling technique periapicals if necessary if a patient has localised pocketing	C
A paralleling technique periapical if a periodontal/endodontic lesion is suspected	C
CBCT is not indicated as a routine method of imaging prriodontal bone support	C
Small volume, high resolution CBCT may be indicated in selected cases of infra-bony defects and furcation lesions, where clinical and conventional radiographic examination do not provide the information needed for patient management	C

^*Evidence-based grading C = based on evidence from expert committee reports or opinions and/or clinical experience of respected authorities and indicates an absence of directly applicable studies of good quality.

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:

Fig. 22.1 Diagrams illustrating 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.

Fig. 22.2 Paralleling technique periapical radiograph of (slightly reduced exposure) showing the radiographic features of a healthy periodontium (arrowed).

• 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.

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.

Table 22.2

Simplified classification of periodontal diseases and conditions based broadly on that produced by the International Workshop of the American Academy of Periodontology and the European Federation of Periodontology

I	Gingival diseases	A. Plaque-induced gingival diseases
		1. Gingivitis associated with dental plaque only (a) Without local factors (b) With local factors

2. Gingival diseases modified by systemic factors,

e.g. Smoking

Pregnancy

Uncontrolled diabetes

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

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