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 Periodontitis as a manifestation of systemic disease

A Associated with haematological disorders,

e.g. Leukaemia

Acquired neutropenia

B Associated with genetic disorders,

e.g. Down’s syndrome

Papillon–Lefevre syndrome

Langerhans cell disease (histiocytosis X)

C. Not otherwise specified, e.g. HIV V Necrotizing periodontal diseases A. Necrotizing ulcerative gingivitis (NUG) B. Necrotizing ulcerative periodontitis (NUP) VI Abscesses of the periodontium A. Gingival abscess B. Periodontal abscess C. Pericoronal abscess VII Periodontitis in association with endodontic lesions VIII Developmental or acquired deformities and conditions

Radiographic features of periodontal disease and the assessment of bone loss and furcation involvement

It is beyond the scope of this book to describe the features of all the periodontal diseases and conditions shown in the classification in Table 22.2. Discussion will be restricted to:

• Abscesses of the periodontium.

The terms horizontal and vertical have been used traditionally to describe the direction or pattern of bone loss using the line joining two adjacent teeth at their cemento–enamel junctions as a line of reference. The amount of bone loss is then assessed as mild, moderate or severe, as shown diagrammatically in Fig. 22.3.

Fig. 22.3 Diagrams illustrating the various radiographic appearances of *periodontitis*. A Mild loss of the corticated crestal bone, widening of the periodontal ligament and loss of the normally sharp angle between the crestal bone and the lamina dura. B Moderate horizontal bone loss. C Severe generalized horizontal bone loss with furcation involvement. D Localized vertical bone loss affecting . E Extensive localized bone loss involving the apex of – the so-called *perio-endo* lesion.

Severe vertical bone loss, extending from the alveolar crest and involving the tooth apex, in which necrosis of pulp tissue is also believed to be a contributory factor, is classified as periodontitis associated with an endodontic lesion, often abbreviated to a perio-endo lesion (see Figs 22.3E and 22.14).

The term furcation involvement describes the radiographic appearance of bone loss in the furcation area of the roots which is evidence of advanced disease in this zone, as shown diagrammatically in Fig. 22.4. Although central furcation involvements are seen more readily in mandibular molars, they can also be seen in maxillary molars despite the superimposed shadow of the overlying palatal root. In addition, early maxillary molar furcation involvement between the mesiobuccal or distobuccal roots and the palatal root produces a characteristic triangular-shaped radiolucency at the edge of the tooth (see Figs 22.8C and 22.10A).

Fig. 22.4 Diagrams illustrating the radiographic appearances of varying degrees of furcation involvement in lower molars (arrowed). A Very early involvement showing widening of the furcation periodontal ligament shadow. B Moderate involvement. C Severe involvement.

Chronic periodontitis (Figs 22.5–22.11)

This is the most common and important form of periodontal disease, affecting the majority of the dentate and partially dentate population. It is the main cause of loss of teeth in later adult life. The main pathological features of this disease are:

Fig. 22.5 Periapical radiographs showing the typical radiographic features of horizontal bone loss (arrowed) in periodontitis affecting maxillary incisors. A Moderate bone loss. B Severe bone loss.

Fig. 22.6 A RIGHT and B LEFT vertical bitewings showing severe bone loss (open arrows) typical of chronic periodontitis. The black arrows indicate calculus deposits.

Fig. 22.7 Periapical radiographs showing the typical radiographic features of horizontal bone loss in chronic periodontitis affecting posterior teeth. **A (i)** Early or mild and **(ii)** moderate bone loss (arrowed) affecting mandibular molars. **B (i)** Moderate and **(ii)** severe bone loss (open arrows) affecting maxillary molars. The black arrows indicate calculus deposits.

Fig. 22.8 Periapical radiographs showing examples of vertical bone loss in chronic periodontitis. A Mild/moderate. B Moderate. C Severe localized defect (arrowed).

Fig. 22.9 Periapical radiographs. A Moderate furcation involvement (black arrows) in maxillary molars. Note the characteristic mesial and distal cervical triangular radiolucent shadows indicating furcation involvement between the mesiobuccal and palatal roots and the distobuccal and palatal roots. B Severe degrees of furcation bone loss (arrowed) in maxillary molars. C Moderate and severe degrees of furcation bone loss (arrowed) in mandibular molars.

Fig. 22.10 Radiographic examples of some secondary local causative factors (arrowed) associated with periodontal disease. A Small calculus deposits. B Gross calculus deposits. C Defective contact point and root caries.

Fig. 22.11 Further radiographic examples of secondary local factors. A Overhanging filling ledge. B Defective contact point and overhanging filling ledge. C Pin perforated into the periodontal tissues. D Tilted tooth.

• Inflammation (usually a progression from chronic gingivitis)

• Destruction of periodontal ligament fibers

• Resorption of the alveolar bone

• Loss of epithelial attachment

• Formation of pockets around the teeth

• Gingival recession.

It is the resorption of the alveolar bone that provides the main radiographic features of chronic periodontitis. These include:

• Loss of the corticated interdental crestal margin, the bone edge becomes irregular or blunted

• Widening of the periodontal ligament space at the crestal margin

• Loss of the normally sharp angle between the crestal bone and the lamina dura – the bone angle becomes rounded and irregular

• Localized or generalized loss of the alveolar supporting bone

• Patterns of bone loss – horizontal and/or vertical – resulting in an even loss of bone or the formation of complex intra-bony defects

• Loss of bone in the furcation areas of multirooted teeth – this can vary from widening of the furcation periodontal ligament to large zones of bone destruction

• Widening of the interdental periodontal ligament spaces

• Associated complicating secondary local factors – although the primary cause of periodontal disease is bacterial plaque, many complicating secondary local factors may also be involved. Some of these factors can be detected on radiographs (see Fig. 22.11) and include:

– Calculus deposits

– Caries cavities

– Root resorption

– Overhanging filling ledges

– Poor restoration margins

– Lack of contact points

– Poor restoration contour, including pontic design

– Perforations by pins or posts

– Endodontic status in relation to perio-endo lesions

– Overerupted opposing teeth

– Tilted teeth

– Root approximation

– Gingivally fitting partial dentures

– Developmental grooves

– Dens-in-dente.

Aggressive periodontitis (Figs 22.12, 22.13)

As mentioned earlier, in aggressive periodontitis the progression of the disease and subsequent bone destruction is rapid and can be either generalized or localized. One example is early onset periodontitis which includes localized juvenile periodontitis and prepubertal periodontitis. Radiographic features include:

Fig. 22.12 Part of a panoramic radiograph showing the typical localized bone defects affecting the first molars (arrowed) of aggressive localized juvenile periodontitis.

Fig. 22.13 Periapicals showing the typical localized bone defects (arrowed) of aggressive localized juvenile periodontitis affecting A the mandibular molars and B the mandibular incisors in an 18-year-old.

• Severe vertical bone defects affecting the first molars and/or incisors

• Arch or saucer-shaped defects

• Sometimes the bone loss is more generalized

• Migration of the incisors with diastema formation

• Rapid rate of bone loss.

Abscesses of the periodontium

As was shown in the classification in Table 22.1, abscesses of the periodontium are divided into three groups. These include:

• Gingival abscess

• Periodontal abscess

– Lateral periodontal abscess

– Perio-endo lesion

• Pericoronal abscess.

Typically the patient presents with a localized acute exacerbation of underlying periodontal disease, usually originating in a deep soft tissue pocket that may have become occluded. The diagnosis of an abscess is made clinically where the signs of acute inflammation and infection are evident. Vitality testing helps to differentiate between the lateral periodontal abscess and the perio-endo lesion. The underlying radiographic bone changes may be indistinguishable from other forms of periodontal bone destruction, as shown in Fig. 22.14.