Interpreting dental radiographs for periodontal disease

Interpreting dental radiographs for periodontal disease

Jul 01, 2004

Figure 1: Periodontal anatomy: (A) alveolar margin (B) lamina dura; (C) periodontal ligament.
The information gained by interpretation of intraoral dental radiographs is essential to the practice of veterinary dentistry.

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.

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.
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 3: Twenty-five to 40 percent horizontal bone loss around the second and third mandibular premolar tooth roots typical of Stage 3 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 4: Horizontal bone loss around the mandibular fourth premolar and first molar.
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).
  • 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).