Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

648 Small Animal Radiolo g y and Ultrasono graphy
periodontal disease. 146,147 Hypercementosis, or deposition of excessive amounts of secondary
cementum on the tooth roots, resulting in root thickening and bulbous apical
enlargement of the tooth roots is an uncommon but normal aging change. 17,148 Idiopathic
dental root replacement resorption has been reported in older dogs. 149 Radiographically
abnormal and or partially resorbed roots with replacement of root structures by radiographically
normal trabecular bone is noted. Histology reveals that the resorption is not
associated with inflammation of hypercementosis.
Periodontal Disease. The most common problems that affect teeth result from gingivitis,
or gum inflammation. Gingivitis is more common in smaller breed and older dogs as well
as cats. 150,151 Gingivitis may be primary and associated with accumulation of plaque and
calculus or occur secondary to the presence of tooth root fragments retained from inadequate
tooth extraction or fracturing of teeth below the gum line (Fig. 5-44). Gingivitis progresses
to inflammation of the periodontal ligaments, which causes resorption of the walls
of the alveolus, destruction of the periodontal ligament and adjacent bone, and ultimately
results in the loosening of the tooth (Fig. 5-45). Active efforts at periodontal care are usually
not successful in preventing periodontal disease, although they may lessen its severity.
152 Gingivitis and periodontal disease may cause focal or generalized loss of bone. In
most instances the radiographic findings lead one to underestimate the extent of the bony
lesion, because a loss of greater than 30% to 50% of bone mineral is required before radiographic
lucency can be appreciated. 144
Periodontal disease is classified in five stages based on the degree of clinical and radiographic
changes. Stages I and II have no radiographic changes. In stage III the alveolar
crest becomes indistinct and rounded. In stage IV there is loss of integrity of the lamina
dura, an increase in periodontal space, and destruction of bone between the tooth roots.
Further loss of bone is indicative of stage V disease. 4 In some instances of chronic infection,
there may be partial resorption of the tooth root and enlargement of the bony alveolus
(Fig. 5-46). Another manifestation is formation of a periapical lucency. This is seen
radiographically as a focal loss of bone density with variable degrees of sclerosis at the borders
of the lesion (Fig. 5-47). These may be due to formation of granulomas, cysts, or
abscesses. 4 In severe cases of periodontal disease there may be extension of the infection
into the nasal cavity or spread of infection diffusely into the supporting bone.
Caries and Acquired Lesions. Although uncommon in dogs and cats, dental cavities, or
caries, do occur. Radiographically they appear as focal lucencies within the tooth (Fig. 5-48).
Feline odontoclastic resorption lesions, previously referred to as cervical line erosions,
neck lesions, or feline cavities, start as defects in the tooth near the gum line. 153 These
Fig. 5-44 An 8-year-old male
Cocker Spaniel with halitosis.
Physical examination revealed active
gingivitis. The lateral oblique radiograph
isolated the left maxilla and
revealed resorption of alveolar bone
from the area around the first premolar
and the area of absence of the
second, third, and fourth premolars.
Close scrutiny revealed root tips
embedded in the bone where the
teeth were missing. There are indistinct
zones of lysis around these
roots (black arrows) indicating active
infection. Diagnosis: Gingivitis and
osteomyelitis.