Diagnostic Imaging in Veterinary Dental Practice

Erin D. Vicari Dentistry and Oral Surgery Service, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108.

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Kevin Stepaniuk Dentistry and Oral Surgery Service, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108.

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Gary Goldstein Dentistry and Oral Surgery Service, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108.

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History and Physical Examination Findings

A 7-year-old castrated male American Staffordshire Terrier was evaluated because of an oral mass. The referring veterinarian reported a thickened area distal to the right mandibular canine tooth and a missing right mandibular first premolar tooth. Incisional biopsy was performed prior to referral, and the referring veterinarian noted discharge of dark brown fluid from the biopsy site. The histopathology report described normal to somewhat hyperplastic epithelium overlying dense collagen with moderate lymphoplasmacytic inflammation and an area of reactive bone.

The dog was referred to the University of Minnesota Veterinary Medical Center for additional diagnostic testing and treatment. A thorough oral examination could not be performed in the awake dog because of its temperament. Three-view (left lateral, right lateral, and ventrodorsal) thoracic radiography was performed with no abnormalities detected. Results of oral examination with the dog under general anesthesia revealed a 2.1 × 2.9 × 2.3-mm moderately firm, fluid-filled swelling, and pink to slightly pale purple mucosa along the rostral region of the right mandible from the distal aspect of the right mandibular canine tooth to the mesial aspect of the right mandibular third premolar tooth. A 6-mm periodontal pocket was identified by periodontal probing at the distolabial aspect of the right mandibular canine tooth. The right mandibular first premolar tooth was absent, and the right mandibular second premolar tooth was displaced lingually.

Intraoral dental radiographic images were obtained with a size 4 computer radiography platea (Figure 1). Transverse computed tomographic CTb images of the head were acquired after IV administration of ioversolc contrast medium (350 mg of iodine/mL; 2.0 mL/kg [0.91 mL/lb]) with 0.5-mm slice thickness and 0.3-mm slice interval and were reconstructed into transverse and reformatted dorsal plane images with 2-mm slice thickness and 2-mm slice interval (Figure 2).

Figure 1—
Figure 1—

Intraoral right lateral (A) and occlusal (B) radiographic views of the rostral aspect of the mandibles of a 7-year-old American Staffordshire Terrier evaluated

Citation: Journal of the American Veterinary Medical Association 245, 8; 10.2460/javma.245.8.889

Figure 2—
Figure 2—

Computed tomographic views of the mandibles of the same dog in Figure 1. A CT examination of the entire skull was performed, and images were created by use of a bone reconstruction algorithm and displayed in a bone window. A—Dorsal plane reformatted image (window width = 4,500 Hounsfield units [HU]; window level = 450 HU). B—Transverse plane image obtained at the level of the missing right mandibular first premolar tooth (window width = 2,000 HU; window level = 350 HU).

Citation: Journal of the American Veterinary Medical Association 245, 8; 10.2460/javma.245.8.889

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Diagnostic Imaging Findings and Interpretation

An expansile mass lesion with decreased bone density was identified between the distal aspect of the right mandibular canine tooth and the mesial aspect of the right mandibular third premolar tooth on radiographic images (Figure 3). Although the periodontal ligament space was visible on the distoapical aspect of the right mandibular canine tooth, geographic bone loss was detected around the lingually displaced mandibular second premolar tooth, and thinning of the ventral border of the mandible was evident. An irregularly shaped radiopacity with a surrounding relative radiolucency was observed at the coronal extent of the mass lesion on the lateral view and at the lateral margin of the mass lesion on the occlusal view.

Figure 3—
Figure 3—

Same intraoral radiographic views as in Figure 1. Notice the expansile mass lesion with decreased bone density between the distal aspect of the right mandibular canine tooth and the mesial aspect of the right mandibular third premolar tooth. There is geographic bone loss around the lingually displaced right mandibular second premolar tooth (asterisk) and thinning of the ventral border of the right mandible (black arrow). There is an irregularly shaped radiopacity (white arrowhead) surrounded by relatively radiolucent tissue at the coronal extent of the lesion on the lateral view and at the lateral margin of the lesion on the occlusal view.

Citation: Journal of the American Veterinary Medical Association 245, 8; 10.2460/javma.245.8.889

Evaluation of CT images (Figure 4) revealed an expansile, multiloculated, hypoattenuating, non–contrast enhancing lesion that involved the right mandibular incisor teeth, left mandibular first and second incisor teeth, right mandibular canine tooth, and right mandibular second and third premolar teeth. This extension of the lesion across midline to the level of the left mandibular third incisor tooth was not apparent on the intraoral radiographs. Absence of the right mandibular first premolar tooth and lingual displacement of the right mandibular second premolar tooth were confirmed. Expansion with thinning and disruption of the cortical mandibular bone was evident in the affected area, and some internal mineralization was present, possibly representing bone or remnants of the missing right mandibular first premolar tooth. Differential diagnoses included odontogenic cyst and odontogenic tumor.

Figure 4—
Figure 4—

Same CT views as in Figure 2. The right mandibular first premolar tooth is absent, and the right mandibular second premolar tooth is displaced lingually. A—Notice thinning of the ventral border of the right mandible (black arrow), and extension of the lesion across midline to the level of the left mandibular third incisor tooth, which was not detectable on intraoral radiographs. B—The expansile lesion (white arrows) has a multiloculated appearance.

Citation: Journal of the American Veterinary Medical Association 245, 8; 10.2460/javma.245.8.889

Treatment and Outcome

With the dog under general anesthesia, a mucoperiosteal flap was elevated, and an incision into the mass at the level of the alveolar margin revealed copious amounts of dark brown fluid. There was no grossly identifiable tooth structure within the multilobulated, soft tissue lined, cyst-like lesion. The involved teeth (right mandibular incisor teeth, left mandibular first and second incisor teeth, right mandibular canine tooth, and right mandibular second and third premolar teeth) were extracted. Marginal bone surrounding the lesion was resected, the cystic lining was enucleated, and the surgical flap was closed routinely. Carprofen (2.2 mg/kg [1.1 mg/lb], SC) was administered after surgery. The patient recovered without complications, and buccal and labial bone specimens with attached alveolar bone and cystic lining were submitted for histologic examination. Discharge instructions included continuation of NSAID medication (carprofen, 2.4 mg/kg [1.1 mg/lb], PO, q 12 h) for 7 days and a soft diet for 2 weeks. Continued monitoring was recommended, including oral examination and CT at 3 to 4 months after surgery for the following reasons: the absence of an unerupted tooth in the multiloculated lesion, the potential for recurrence, lack of definitive diagnosis, and the fact that oral examination in the awake patient was precluded by its temperament.

Histologic evaluation revealed a cystic lesion lined by stratified squamous epithelium extending into the surrounding fibrovascular tissue. Evidence of intense inflammation was present at the periphery of the lesion. Remodeling was noted in the alveolar bone as well as the buccal and lingual segments of mandibular bone submitted. No evidence of the cystic lesion was found within 5 mm of the bone margins. However, margins of the enucleated cystic lining curetted from the bone could not be determined. Morphological findings were consistent with an odontogenic cyst. A histologic diagnosis of the type of odontogenic cyst could not be determined and was complicated by intense inflammation of the lesion.

At the 3-month recheck examination, CT findings revealed no evidence of recurrence of the cystic lesion, and a moderate amount of sclerotic new bone formation was evident.

Comments

Imaging findings frequently play an important role in the differentiation of odontogenic cysts and tumors in addition to microscopic tissue evaluation and oral examination.1 In human cystic lesions, advanced imaging such as CT is superior to intraoral radiography for delineation of cyst margins, relationships with associated structures (tooth roots, cortical bone, mandibular canal, and sinuses), and presence of unerupted teeth.2

Odontogenic cysts and tumors in dogs are pathological, fluid-filled spaces derived from odontogenic epithelium.3,4 Dentigerous cysts arise from proliferation of remnants of reduced enamel associated with the crown of an unerupted tooth.4 Radiographically, the lesion appears as a well-defined, unilocular radiolucency.2,5 On CT images, a fluid-filled dentigerous cyst appears as a fluid-attenuating, expansile mass surrounding the crown of an unerupted tooth. Odontogenic keratocysts are derived from remnants of the rests of dental lamina. Radiographically, these are often interradicular, expansive, unilocular or multilocular radiolucent lesions that span multiple vital teeth and tend to show evidence of cortical bone thinning and displacement of adjacent teeth. Complete surgical excision should be curative; however, a 2% to 30% recurrence rate has been described in the human literature, with a higher recurrence rate seen in multiloculated lesions.1

Clinical and radiographic findings were initially suggestive of an odontogenic cyst or an odontogenic tumor in the dog of this report. Advanced imaging with CT played a useful role in the planning of surgical treatment by delineating the margins of the lesion, the extent of which was not appreciable on intraoral radiographs. Histopathologic findings were consistent with an odontogenic cyst but could not be used to definitively diagnose the type of cyst or to rule out an odontogenic tumor.

a.

Scan X Digital Radiography System, Air Techniques, Melville, NY.

b.

Toshiba Aquilion 64, Toshiba America Medical Systems Inc, Tustin, Calif.

c.

Optiray 350 (Ioversol), Mallinckrodt, Hazelwood, Wis.

References

  • 1. Chi AC & Neville B. Odontogenic cysts and tumors. Surg Pathol Clin 2011; 4: 10271091.

  • 2. Soukup J W. Computed tomography–assisted management of a mandibular dentigerous cyst in a dog with a nasal carcinoma. J Am Vet Med Assoc 2009; 235: 710714.

    • Crossref
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  • 3. Johnson NR, Gannon OM & Savage NW, et al. Frequency of odontogenic cysts and tumors: a systematic review. J Investig Clin Dent 2014; 5: 914.

  • 4. Regezi JA, Sciubba JJ, Jordan RC. Cysts of the jaws and neck. In: Regezi JA, Sciubba JJ, Jordan RC, eds. Oral pathology: clinical pathologic correlations. 6th ed. St Louis: Elsevier Saunders, 2012;246269.

    • Search Google Scholar
    • Export Citation
  • 5. Verstraete FJ, Zin BP & Kass PH, et al. Clinical signs and histologic findings in dogs with odontogenic cysts: 41 cases (1995–2010). J Am Vet Med Assoc 2011; 239: 14701476.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Figure 1—

    Intraoral right lateral (A) and occlusal (B) radiographic views of the rostral aspect of the mandibles of a 7-year-old American Staffordshire Terrier evaluated

  • Figure 2—

    Computed tomographic views of the mandibles of the same dog in Figure 1. A CT examination of the entire skull was performed, and images were created by use of a bone reconstruction algorithm and displayed in a bone window. A—Dorsal plane reformatted image (window width = 4,500 Hounsfield units [HU]; window level = 450 HU). B—Transverse plane image obtained at the level of the missing right mandibular first premolar tooth (window width = 2,000 HU; window level = 350 HU).

  • Figure 3—

    Same intraoral radiographic views as in Figure 1. Notice the expansile mass lesion with decreased bone density between the distal aspect of the right mandibular canine tooth and the mesial aspect of the right mandibular third premolar tooth. There is geographic bone loss around the lingually displaced right mandibular second premolar tooth (asterisk) and thinning of the ventral border of the right mandible (black arrow). There is an irregularly shaped radiopacity (white arrowhead) surrounded by relatively radiolucent tissue at the coronal extent of the lesion on the lateral view and at the lateral margin of the lesion on the occlusal view.

  • Figure 4—

    Same CT views as in Figure 2. The right mandibular first premolar tooth is absent, and the right mandibular second premolar tooth is displaced lingually. A—Notice thinning of the ventral border of the right mandible (black arrow), and extension of the lesion across midline to the level of the left mandibular third incisor tooth, which was not detectable on intraoral radiographs. B—The expansile lesion (white arrows) has a multiloculated appearance.

  • 1. Chi AC & Neville B. Odontogenic cysts and tumors. Surg Pathol Clin 2011; 4: 10271091.

  • 2. Soukup J W. Computed tomography–assisted management of a mandibular dentigerous cyst in a dog with a nasal carcinoma. J Am Vet Med Assoc 2009; 235: 710714.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 3. Johnson NR, Gannon OM & Savage NW, et al. Frequency of odontogenic cysts and tumors: a systematic review. J Investig Clin Dent 2014; 5: 914.

  • 4. Regezi JA, Sciubba JJ, Jordan RC. Cysts of the jaws and neck. In: Regezi JA, Sciubba JJ, Jordan RC, eds. Oral pathology: clinical pathologic correlations. 6th ed. St Louis: Elsevier Saunders, 2012;246269.

    • Search Google Scholar
    • Export Citation
  • 5. Verstraete FJ, Zin BP & Kass PH, et al. Clinical signs and histologic findings in dogs with odontogenic cysts: 41 cases (1995–2010). J Am Vet Med Assoc 2011; 239: 14701476.

    • Crossref
    • Search Google Scholar
    • Export Citation

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