Diagnostic Imaging in Veterinary Dental Practice

Robert D. Campbell Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853.

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Santiago Peralta Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853.

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History and Physical Examination

A 7-year-old 15.9-kg (35-lb) castrated male Cocker Spaniel was referred to the dentistry and oral surgery service of a veterinary teaching hospital for evaluation of a mass on the caudal aspect of the right mandible. The clients first noted the mass approximately 3 weeks prior to referral. Clinical manifestations associated with the mass included halitosis; the patient was reported to have no other clinical signs. The pertinent medical history was unremarkable except for mitral valve disease with no overt clinical signs. The pertinent dental history consisted of extraction of the right mandibular fourth premolar and second molar teeth because of a suspected odontogenic infection 2 months prior to referral. No intraoral radiographs had been obtained at that time. The patient developed substantial halitosis after the extractions were performed.

At the time of examination at the referral hospital, the patient was bright, alert, and responsive. Heart rate, respiratory rate, and body temperature were within the respective reference ranges. Thoracic auscultation revealed a grade II/VI systolic heart murmur consistent with previously diagnosed degenerative mitral valve disease and no signs of congestive heart failure. The patient appeared otherwise systemically healthy. Routine clinicopathologic testing was performed, including a CBC and serum biochemical analysis, and 3-view thoracic radiographs were obtained; no clinically important abnormalities were identified. Oral examination of the conscious patient revealed several missing teeth including those previously extracted, generalized calculus, and mild to moderate generalized gingivitis. A firm, approximately 10 × 30-mm expansile mass was palpable on the caudal ventral aspect of the right mandible. Palpation elicited signs of pain from the patient. Severe halitosis was appreciated during examination. Mild right mandibular lymphadenomegaly was noted on palpation.

The dog was anesthetized, and a complete oral examination including periodontal probing and charting was performed. Relevant clinical findings included moderate generalized plaque and calculus accumulation, moderate generalized gingivitis, and exposed alveolar bone at the distal aspect of the right mandibular first molar tooth. Full-mouth intraoral radiography was performed with a standard technique1 (Figure 1).

Figure 1—
Figure 1—

Images of a 7-year-old 15.9-kg (35-lb) castrated male Cocker Spaniel referred for evaluation of a caudal right mandibular mass. A—Clinical photograph of the right mandibular first molar tooth. B—Intraoral radiograph of the caudal aspect of the right mandible obtained by use of a standard parallel technique.

Citation: Journal of the American Veterinary Medical Association 247, 1; 10.2460/javma.247.1.51

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Diagnostic Imaging Findings and Interpretation

Examination of the radiograph revealed a 20 × 14-mm periapical lucency at the distal root of the right mandibular first molar tooth, extending to the root of the right mandibular third molar tooth (Figure 2). An osseous fragment with a mildly moth-eaten appearance was observed attached to the right mandibular first molar tooth. The first molar tooth appeared to be highlighted by surrounding radiolucency. An approximately 47 × 12-mm solid periosteal reaction with a smooth ventral margin was evident on the ventral border of the mandible and centered over the alveolus of the missing right mandibular second molar tooth. These radiographic findings were consistent with apical periodontitis at the distal root of the right mandibular first molar tooth, with bone sequestration and chronic osteomyelitis.2 The solid periosteal reaction on the ventral aspect of the mandible was considered likely secondary to infection or a benign neoplastic process.3

A CT scan of the head with and without contrast medium administration was performed during the same anesthetic episode. Computed tomographic images were consistent with radiographic findings and were helpful for further characterization of the nature, location, and extent of the lesions as well as for surgical planning. The CT images revealed a lytic osseous lesion that measured approximately 18 × 15 × 17 mm and involved the caudal quarter of the mandibular body and ventral fifth of the ramus. In the center of the lesion, the right mandibular first molar tooth had severe periapical lysis surrounding the caudal root (Figure 3). Within this lytic lesion there was a bone fragment corresponding to the sequestrum, with several gas lucencies surrounding it. The surrounding soft tissues were mildly thick and moderately contrast enhancing, suggestive of inflammation or vascular permeability.

Treatment and Outcome

On the basis of clinical and imaging findings, a clinical diagnosis of osteonecrosis of the jaws (ONJ) secondary to osteomyelitis with sequestration was established. The differential diagnosis included fungal osteomyelitis, neoplasia (primary vs metastatic disease), and traumatic injury. Complete periodontal treatment, including supra- and subgingival ultrasonic scaling, was performed. A full-thickness mucogingival flap was raised on the buccal aspect of the caudal right mandible extending from the mandibular third premolar tooth to past the third molar tooth. A bony defect was identified distal to the right mandibular first molar tooth; sterile swabs were used to obtain samples for aerobic and anaerobic microbial culture and fungal culture. The right mandibular first and third molar teeth were surgically extracted. The sequestrum was removed and submitted for histologic evaluation along with the right mandibular first molar tooth. The osseous defect was debrided and lavaged with sterile saline (0.9% NaCl) solution, and the mucogingival flap was closed with 5-0 poliglecaprone 25 in a simple interrupted suture pattern. The patient recovered uneventfully from surgery and was discharged; treatment included amoxicillin-clavulanic acid (13.75 mg/kg [6.25 mg/lb], PO, q 12 h, for 28 days), meloxicam (0.1 mg/kg [0.05 mg/lb], PO, q 24 h, for 5 days), and tramadol hydrochloride (2.0 mg/kg [0.91 mg/lb], PO, q 8 to 12 h, as needed for signs of pain).

Figure 2—
Figure 2—

Same radiographic image as in Figure 1. Notice the bony sequestrum (solid outline) delineated by a radiolucent rim (arrows) and ventral solid periosteal reaction (asterisk), consistent with chronic osteomyelitis.

Citation: Journal of the American Veterinary Medical Association 247, 1; 10.2460/javma.247.1.51

Figure 3—
Figure 3—

Transverse CT image of the head of the same dog as in Figure 1. The image was obtained with a bone algorithm at the level of the mass in the right mandible. The bony sequestrum (white arrow) is delineated by a radiolucent rim (dark arrows) and the periosteal reaction on the ventral aspect of the mandible.

Citation: Journal of the American Veterinary Medical Association 247, 1; 10.2460/javma.247.1.51

Histologic analysis of the bone sample confirmed the presence of bone necrosis (sequestrum) and osteomyelitis. Large numbers of bacteria of various morphologies (including cocci, filamentous bacteria, and spiral bacteria) were found within the medullary cavity. Bacterial culture results revealed a pleomorphic population of bacteria including Fusobacterium nucleatum, Bacteroides fragilis group, Peptostreptococcus spp, and Porphyromonas macacae. Fungal culture results were negative. Reevaluation of the patient 4 weeks after the surgery revealed that the surgical site had completely healed and the halitosis had resolved.

Comments

This case illustrates the importance of intraoral radiography combined with CT in assessing jaw lesions and planning a therapeutic approach. Importantly, differentiating between a neoplastic lesion versus a benign process by means of a biopsy and histologic evaluation of sampled tissues was instrumental in establishing a final treatment plan and prognosis. Osteonecrosis of the jaws is defined as exposed necrotic bone that fails to heal after 6 to 8 weeks in patients with no history of radiation therapy.4,5 Causes of ONJ not related to radiation therapy include maxillofacial injuries, tooth extraction, and chronic infection.4,5 Although the precise etiology of the ONJ in this patient could not be determined, the reported extraction of the right mandibular fourth premolar and second molar teeth prior to referral could have predisposed the dog to ONJ; dental extractions have been associated with ONJ in humans.6

The radiographic appearance of ONJ has not been described in dogs. In humans, only advanced cases can be detected radiographically.7 Computed tomography provides more detailed imaging of the targeted area and is especially useful when attempting to differentiate neoplastic disease from osteonecrosis.7 In cases of ONJ, CT imaging reveals extensive periosteal bone reaction with soft tissue edema; these findings are consistent with the CT findings of the patient described in this report.

In both radiographic and CT images, a sequestrum is usually seen as a fragment of mineralized tissue surrounded by a lucent rim, completely separated from the surrounding bone.7 In humans, conditions that can be associated with sequestrum formation include osteomyelitis, skeletal tuberculosis, osteoradionecrosis, Langerhans cell histiocytosis, metastatic carcinoma, primary lymphoma of bone, aggressive fibrous tumors, osteoid tumors, cartilaginous tumors, lipomatous tumors, and benign fibrous tumors.8 Osteomyelitis is considered the primary differential diagnosis in patients with a bony sequestrum.8 Although early in the disease process there may be no radiographic signs, chronic osteomyelitis usually manifests radiographically as normal-appearing trabecular bone that transitions to areas of bone with a dense granular pattern; sequestra can be detected within the affected area, and its density may contrast with the surrounding structures.2

Computed tomography is the imaging modality of choice for detecting sequestra because it reveals more bone surface, allows for detecting periosteal new bone, and is superior for revealing the internal bony structure, especially when very dense sclerotic bone is present, by removing superimposition of overlying structures.2 Although CT was used in evaluation of the dog of this report, the lucency in the caudal aspect of the affected mandible and the bony sequestrum within the lytic lesion were evident on conventional intraoral radiographs. This serves to emphasize that although CT is a routinely used tool in diagnosing lesions of the maxillofacial structures, conventional intraoral radiography remains instrumental in diagnosing dental pathosis.

References

  • 1. Tsugawa AJ, Verstraete FJM. How to obtain and interpret periodontal radiographs in dogs. Clin Tech Small Anim Pract 2000; 15: 204210.

  • 2. Lee L. Inflammatory lesions of the jaws. In: White S, Pharoah M, eds. Oral radiology principles and interpretation. 6th ed. St Louis: Mosby Elsevier; 2009; 331336.

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  • 3. Ragsdale BD, Madewell J, Sweet D. Radiologic and pathologic analysis of solitary bone lesions. Part II: periosteal reactions. Radiol Clin North Am 1981; 19: 749783.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4. Manfra Marretta S, Lommer MJ. Management of maxillofacial osteonecrosis. In: Verstraete FJ, Lommer MJ, eds. Oral and maxillofacial surgery in dogs and cats. Philadelphia: Saunders Elsevier, 2012; 51924.

    • Search Google Scholar
    • Export Citation
  • 5. Zacher AM, Manfra Maretta S. Oral and maxillofacial surgery in dogs and cats. Vet Clin North Am Small Anim Pract 2013; 43: 609649.

  • 6. Walter C, Sagheb K, Bitzer J, et al. Analysis of reasons for osteonecrosis of the jaws. Clin Oral Invest 2014; 18: 22212226.

  • 7. Vassiliou V, Tselis N, Kardamakis D. Osteonecrosis of the jaws: clinicopathologic and radiologic characteristics, preventive and therapeutic strategies. Strahlenther Onkol 2010; 186: 367373.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 8. Jennin F, Bousson V, Parlier C, et al. Bony sequestrum: a radiologic review. Skeletal Radiol 2011; 40: 963975.

  • Figure 1—

    Images of a 7-year-old 15.9-kg (35-lb) castrated male Cocker Spaniel referred for evaluation of a caudal right mandibular mass. A—Clinical photograph of the right mandibular first molar tooth. B—Intraoral radiograph of the caudal aspect of the right mandible obtained by use of a standard parallel technique.

  • Figure 2—

    Same radiographic image as in Figure 1. Notice the bony sequestrum (solid outline) delineated by a radiolucent rim (arrows) and ventral solid periosteal reaction (asterisk), consistent with chronic osteomyelitis.

  • Figure 3—

    Transverse CT image of the head of the same dog as in Figure 1. The image was obtained with a bone algorithm at the level of the mass in the right mandible. The bony sequestrum (white arrow) is delineated by a radiolucent rim (dark arrows) and the periosteal reaction on the ventral aspect of the mandible.

  • 1. Tsugawa AJ, Verstraete FJM. How to obtain and interpret periodontal radiographs in dogs. Clin Tech Small Anim Pract 2000; 15: 204210.

  • 2. Lee L. Inflammatory lesions of the jaws. In: White S, Pharoah M, eds. Oral radiology principles and interpretation. 6th ed. St Louis: Mosby Elsevier; 2009; 331336.

    • Search Google Scholar
    • Export Citation
  • 3. Ragsdale BD, Madewell J, Sweet D. Radiologic and pathologic analysis of solitary bone lesions. Part II: periosteal reactions. Radiol Clin North Am 1981; 19: 749783.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4. Manfra Marretta S, Lommer MJ. Management of maxillofacial osteonecrosis. In: Verstraete FJ, Lommer MJ, eds. Oral and maxillofacial surgery in dogs and cats. Philadelphia: Saunders Elsevier, 2012; 51924.

    • Search Google Scholar
    • Export Citation
  • 5. Zacher AM, Manfra Maretta S. Oral and maxillofacial surgery in dogs and cats. Vet Clin North Am Small Anim Pract 2013; 43: 609649.

  • 6. Walter C, Sagheb K, Bitzer J, et al. Analysis of reasons for osteonecrosis of the jaws. Clin Oral Invest 2014; 18: 22212226.

  • 7. Vassiliou V, Tselis N, Kardamakis D. Osteonecrosis of the jaws: clinicopathologic and radiologic characteristics, preventive and therapeutic strategies. Strahlenther Onkol 2010; 186: 367373.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 8. Jennin F, Bousson V, Parlier C, et al. Bony sequestrum: a radiologic review. Skeletal Radiol 2011; 40: 963975.

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