The information gained by interpretation of intraoral dental radiographs is essential to the practice of veterinary dentistry.
Figure 1: Periodontal anatomy: (A) alveolar margin (B) lamina dura; (C) periodontal ligament.
Dental radiographs, when correlated with clinical examination and case history, allow the practitioner to see where he cannot
feel or probe. In the May 2004 edition of DVM Newsmagazine , intraoral dental indications, equipment, positioning and processing were discussed. This will be the first installment
of a multipart series on dental film interpretation as it applies to clinical case management. The images in this series were
taken with the ImageVEt 70 Plus and the AFP Imaging EVA-Vet digital senor system.
Stages of periodontal disease
Periodontal disease can be classified from Stages 1 to 4 based on severity of radiographic and clinical signs. Normally, interdental
bone appears 1-2 mm apical (toward the root) to the cementoenamel junction (CEJ) (Figure 1). The bone level in periodontal
disease decreases as inflammation extends and bone is resorbed. The radiograph is used indirectly to determine the amount
of bone loss. Forty percent of the bone must be destroyed before bone loss can be radiographically visualized. Distribution
of bone loss is classified as either localized or generalized, depending on the number of areas affected. Localized bone loss
occurs in isolated areas. Generalized bone loss involves the majority of the crestal bone. Bone loss is a crude determination
of support level. The actual level of periodontal support can be less than the radiographic bone height.
Figure 2: Loss of the normally sharp angles between the lamina dura and the alveolar margins and vertical bone loss of a dog's
second mandibular molar typical of Stage 2 periodontal disease.
Gauging attachment loss
Stage1 , gingivitis, occurs when the gingiva appears inflamed. In Stage 1 disease, there is no periodontal support loss or radiographic
changes. Stage 2 , early periodontitis, occurs when attachment loss is less than 25 percent of the root, as measured from the CEJ to the apex.
Clinically, early periodontitis is typified by pocket formation or gingival recession. Radiographically, Stage 2 disease appears as blunting (rounding) of the alveolar margin. The continuity of the lamina dura at the level of the alveolar
margin might show a loss in Stage 2 (Figure 2).
Figure 3: Twenty-five to 40 percent horizontal bone loss around the second and third mandibular premolar tooth roots typical
of Stage 3 periodontal disease.
Stage 3 , established periodontitis, is diagnosed when 25-50 percent of attachment loss occurs (Figure 3). The direction of bone
loss can be horizontal or vertical (angular).
Figure 4: Horizontal bone loss around the mandibular fourth premolar and first molar.
- Horizontal bone loss radiographically appears as decreased alveolar marginal bone around adjacent teeth. Normally, the crestal
bone is located 1-2 mm apical to the cementoenamel junction. With horizontal bone loss, both the buccal and lingual plates
of bone, as well as interdental bone, have been resorbed. Clinically, horizontal bone loss is typified by suprabony pockets,
which occurs when the epithelial attachment is coronal to the bony defect (Figure 4).
- Vertical bone loss, resulting from infrabony (intrabony if three-walled) defects, occurs when the walls of the pocket are
within a bony housing. Periodontal disease can cause a vertical defect to extend apically from the alveolar margin. At first,
the defect is surrounded by three walls of bone: two marginal (lingual or palatal and facial) and a hemisepta (the bone of
the interdental septum that remains on the root of the uninvolved adjacent tooth).