Diagnostic Imaging in Veterinary Dental Practice

Ana Nemec William R. Pritchard Veterinary Medical Teaching Hospital, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616.

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Boaz Arzi William R. Pritchard Veterinary Medical Teaching Hospital, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616.

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History and Physical Examination Findings

An 8-year-old 23.5-kg (51.7-lb) spayed female Siberian Husky was evaluated because of a firm, 15-mm, right suborbital swelling that had not changed in size or appearance since it had first been noticed 7 weeks earlier. At the time of initial examination by the referring veterinarian, signs of pain were evident during manipulation of the mass, along with severe focal gingivitis and gingival recession at the right maxillary fourth premolar tooth. The dog was treated with meloxicam (0.2 mg/kg [0.09 mg/lb], SC, once), cefazolin (20 mg/kg [9.1 mg/lb], SC, once), and enrofloxacin (3.7 mg/kg [1.7 mg/lb], SC, once) and was anesthetized. An oral examination performed by the referring veterinarian after the dog was anesthetized revealed a possible draining tract on the buccal side of the right maxillary fourth premolar tooth apical to the gingival margin, but no tooth fracture or crown discoloration was evident. Radiographs were not obtained, and the tooth was extracted. No improvement was observed 2 weeks after tooth extraction, and enrofloxacin (5.8 mg/kg [2.6 mg/lb], PO, q 24 h) was administered for 2 weeks. Because gingival swelling had not resolved by 4.5 weeks after tooth extraction, the dog was referred to the Veterinary Medical Teaching Hospital at the University of California-Davis.

Results of a general physical examination performed at the time of initial examination at the veterinary teaching hospital were unremarkable, other than the firm, 15-mm, right suborbital swelling and a region of soft tissue swelling in the area of the extraction site of the right maxillary fourth premolar tooth. Results of a CBC and serum biochemical profile were unremarkable, other than a slightly high serum creatinine concentration (1.6 mg/dL; reference range, 0.3 to 1.2 mg/dL); urine specific gravity was normal.

The dog was anesthetized, and a detailed oral examination and full-mouth radiography were performed (with size 2 and 4 dental film). Mild localized periodontitis characterized by horizontal bone loss was seen to involve the right maxillary first molar tooth and left mandibular third premolar tooth, along with a 15-mm, friable, ulcerative soft tissue mass at the extraction site of the maxillary fourth premolar tooth (Figure 1). Intraoral radiographic views of the caudal portions of the right and left maxillae are provided (Figure 2).

Figure 1—
Figure 1—

Gross appearance of the extraction site in a dog that had undergone extraction of the right maxillary fourth premolar tooth 7 weeks earlier; the dog is positioned in dorsal recumbency.

Citation: Journal of the American Veterinary Medical Association 237, 9; 10.2460/javma.237.9.1037

Figure 2—
Figure 2—

Lateral radiographic views of the caudal portions of the right (A) and left (B) maxillae of the dog in Figure 1.

Citation: Journal of the American Veterinary Medical Association 237, 9; 10.2460/javma.237.9.1037

Determine whether additional studies are required, or make your diagnosis, then turn the page

Diagnostic Imaging Findings and Interpretation

A soft tissue mass was evident in the area of the vacated alveoli of the extracted right maxillary fourth premolar tooth (Figure 3). No obvious bone involvement was evident when radiographic views of the caudal portions of the left and right maxillae were compared. There was, however, a slightly increased periodontal ligament space at the mesial aspect of the palatal root of the right maxillary first molar tooth, and there were small bony spicules adjacent to this tooth. Although these findings were likely associated with trauma from extraction of the adjacent maxillary fourth premolar tooth, periodontal disease, endodontic disease, and neoplasia could not be ruled out. The line indicating the junction between the body and the palatine process of the maxilla seemed intact; however, a line was recognizable between the current alveolar margin and the junction between the body and the palatine process of the maxilla, which may have been indicative of bone destruction at the palatine process of the maxilla.

Figure 3—
Figure 3—

Same lateral radiographic view of the caudal portion of the right maxilla as in Figure 2. The vacated alveoli of the right maxillary fourth premolar tooth (arrows) is associated with an indistinctive soft tissue mass (arrowheads); there is no evidence of retained root tips or endodontic disease involving the adjacent teeth. There is an increased periodontal ligament space at the mesial aspect of the right maxillary first molar tooth, and bony spicules are evident adjacent to the right maxillary first molar tooth (open arrow). The line indicating the junction between the body and the palatine process of the maxilla seems intact; however, a line (dotted line) is recognizable between the current alveolar margin and the junction between the body and the palatine process of the maxilla. Notice also that the right maxillary third premolar tooth has 3 roots.

Citation: Journal of the American Veterinary Medical Association 237, 9; 10.2460/javma.237.9.1037

Retained root tips and endodontic disease of the adjacent teeth were ruled out.1,2 Although no radiographic signs of osteomyelitis were observed, acute osteomyelitis could not be ruled out because acute osteomyelitis may not be associated with any radiographic abnormalities.3

Treatment and Outcome

An incisional biopsy specimen was obtained with a 6-mm punch from the mass in the area of the vacated alveoli of the extracted right maxillary fourth premolar tooth. Histologic examination of the biopsy specimen revealed a well-differentiated carcinoma, and the dog was returned to the veterinary teaching hospital for clinical staging and possible surgery.

Abdominal ultrasonography and computed tomography (CT) of the thorax did not reveal any clinically important abnormalities. The dog was anesthetized, and contiguous pre- and postcontrast, 1.3-mm-thick, transverse CT images of the head processed with a bone algorithm (120 kV; 160 m A; window width, 2,900 Hounsfield units; window length, 600 Houn- sfield units; dual field of view, 162 × 162 mm in a 512 × 512-pixel matrix) were obtained. A destructive mass of the right maxilla was observed on CT images (Figure 4). There was a well-defined, expansile, hetero- geneously contrast-enhanced mass (processed with a standard algorithm [120 kV; 164 mA; window width, 2,964 Hounsfield units; window length, 898 Houn- sfield units; dual field of view, 163 × 163 mm in a 512 × 512-pixel matrix]) that measured 18 × 18 × 25 mm in the area of the extracted right maxillary fourth premolar tooth and the mesial aspect of the right maxillary first molar tooth. There was marked destruction of the right maxilla. Involvement of the ventral border of the infraorbital canal and endosteal scalloping of the alveolar process of the maxilla on the right side were visible. The mass did not extend into the retrobulbar space but approached within 10 mm of that region. No medial retropharyngeal or mandibular lymphadenopathy was identified.

Figure 4—
Figure 4—

Representative transverse computed tomographic image of the head of the dog in Figure 1. Notice the destructive mass involving the right maxilla (arrows). In the magnified view, involvement of the ventral border of the infraorbital canal (asterisk) and endosteal scalloping of the alveolar process of the maxilla (arrowhead) are evident. The right maxillary fourth premolar tooth is absent.

Citation: Journal of the American Veterinary Medical Association 237, 9; 10.2460/javma.237.9.1037

Clinical, radiographic, CT, and histologic findings were consistent with a diagnosis of locally invasive carcinoma without evidence of regional or distant metastasis, and right caudal maxillectomy was performed. Anattempt was made to remove the mass in its entirety with a 10-mm margin of grossly normal tissue while preserving the eye.4 The removed specimen was submitted for histologic examination of the surgical margins. No complications were encountered, and the dog was hospitalized overnight for supportive care, which included IV fluid administration and analgesic and antimicrobial treatment. The day after surgery, the dog appeared to be comfortable. A fentanyl patch (75 μg/h) was applied to provide analgesia, and the dog was discharged. The owner was instructed to administer amoxicillin-clavulanic acid (16 mg/kg [7.3 mg/lb], PO, q 12 h) for the next 2 weeks, carprofen (2.2 mg/kg [1 mg/lb], PO, q 12 h) for the next 1 week, and tramadol (2.1 mg/kg [0.95 mg/lb], PO, q 8 to 12 h) for 4 to 5 days after the fentanyl patch was removed and to rinse the dog's mouth with chlorhexidine gluconate. A follow-up examination 2 weeks after surgery revealed healing of the maxillectomy site without evidence of dehiscence and no gross local signs of recurrence.

Comments

Suborbital swelling in a dog can result from dental disease (eg, periapical lesions of any of the roots of the maxillary fourth premolar teeth, the mesial root of the maxillary first molar teeth, or the distal root of the maxillary third premolar teeth or a combined periodontal-endodontic lesion of any or all of these teeth) or can be of nondental origin (eg, penetrating wounds, foreign bodies, maxillary fracture with bone sequestration, or nasal or maxillary neoplasia).2

Radiography is an essential part of a comprehensive oral examination. Full-mouth dental radiography complements the clinical examination and is indicated in dogs with signs of oral pain.5,6

Dental radiography is essential in assessing the extent and severity of periodontitis if a periodontal-endodontic lesion is suspected.3 When an area of focal bone loss or tooth mobility is present in a dog without other evidence of periodontal disease, as was the case for the dog described in the present report, neoplasia should be considered and a biopsy should be performed.

Because the etiology of pulpitis and pulp necrosis varies,7 except in the obvious case of direct pulp exposure resulting from a complicated crown or crown-root fracture, a definitive diagnosis of endodontic disease is difficult to make on the basis of results of a clinical examination alone in veterinary patients, even when a suborbital facial swelling suggestive of long-standing endodontic disease is present.3,8 Dental radiography provides information about the presence, nature, and severity of periapical and root lesions in endodontic disease.3 Although many aspects of endodontic disease may be radiographically visible, radiography does not provide direct information about pulp health,3,4,6 and radiographic abnormalities can be absent in animals with early endodontic disease or can be subtle in animals with an acute apical abscess caused by severe inflammation secondary to pulp necrosis.3

Dental radiography should be performed prior to any tooth extractions to allow for appropriate treatment planning.5,8 Biopsy and CT should be considered in addition to radiography if radiography alone does not give a conclusive result or if suborbital swelling of nondental origin is suspected.9

In dogs, lack of healing of an extraction site ≥ 7 days after surgery is abnormal and is rarely a sequel of infection unless severe periodontitis causing localized osteomyelitis was present prior to extraction.1,10 A common cause for the lack of healing of an extraction site is the presence of retained root tips, for which the diagnosis can usually be obtained simply through dental radiography.1 If no root fragments are detected, the nonhealing area should be biopsied to rule out the possibility of neoplasia or osteomyelitis.1,5

In the dog described in the present report, dental radiography did not reveal any retained root tips or evidence of endodontic disease involving the adjacent teeth. The clinical appearance of the oral mass at the extraction site was suggestive of neoplasia, whereas radiographic findings were inconclusive, even when comparing radiographic views of the left and right maxillae. The pre-extraction radiographs and addition of occlusal views might be helpful to further assess any bone involvement. Computed tomography was used in this dog to help evaluate the extent of the lesion, as it provides better anatomic assessment than does dental radiography.9 Computed tomographic findings were helpful in planning the surgical margins, which is crucial when planning for curative surgery in animals with oral neoplasia.4

The present case demonstrates the need for comprehensive oral and maxillofacial examinations accompanied by appropriate diagnostic imaging to plan for and evaluate the treatment of dental and maxillofacial disease in dogs.

References

  • 1.

    Smith MM. Exodontics. Vet Clin North Am Small Anim Pract 1998; 28:12971319.

  • 2.

    Verstraete FJM. Self-assessment colour review of veterinary dentistry. London: Manson Publishing/The Veterinary Press, 1999; 145146.

  • 3.

    DuPont GA, DeBowes LJ. Atlas of dental radiography in dogs and cats. St Louis: Saunders Elsevier, 2009; 134-171, 221228.

  • 4.

    Kermer C, Poeschl PW & Wutzl A, et al. Surgical treatment of squamous cell carcinoma of the maxilla and nasal sinuses. J Oral Maxillofac Surg 2008; 66:24492453.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5.

    Gorrel C. Radiographic evaluation. Vet Clin North Am Small Anim Pract 1998; 28:10891110.

  • 6.

    Fiani N, Arzi B. Diagnostic imaging in veterinary dental practice. J Am Vet Med Assoc 2010; 236:4143.

  • 7.

    Niemiec BA. Fundamentals of endodontics. Vet Clin North Am Small Anim Pract 2005; 35:837868.

  • 8.

    Luskin IR, Kressin DJ. Endodontic decisions based on radiographic appearance. Clin Tech Small Anim Pract 2001; 16:173181.

  • 9.

    Bar-Am Y, Pollard RE & Kass PH, et al. The diagnostic yield of conventional radiographs and computed tomography in dogs and cats with maxillofacial trauma. Vet Surg 2008; 37:294299.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 10.

    Gottrup F, Storgard Jensen S, Andreasen JO. Wound healing subsequent to injury. 4th ed. Oxford, England: Blackwell Munks- gaard, 2007;144.

    • Search Google Scholar
    • Export Citation

Contributor Notes

Address correspondence to Dr. Nemec (anemec@ucdavis.edu).
  • Figure 1—

    Gross appearance of the extraction site in a dog that had undergone extraction of the right maxillary fourth premolar tooth 7 weeks earlier; the dog is positioned in dorsal recumbency.

  • Figure 2—

    Lateral radiographic views of the caudal portions of the right (A) and left (B) maxillae of the dog in Figure 1.

  • Figure 3—

    Same lateral radiographic view of the caudal portion of the right maxilla as in Figure 2. The vacated alveoli of the right maxillary fourth premolar tooth (arrows) is associated with an indistinctive soft tissue mass (arrowheads); there is no evidence of retained root tips or endodontic disease involving the adjacent teeth. There is an increased periodontal ligament space at the mesial aspect of the right maxillary first molar tooth, and bony spicules are evident adjacent to the right maxillary first molar tooth (open arrow). The line indicating the junction between the body and the palatine process of the maxilla seems intact; however, a line (dotted line) is recognizable between the current alveolar margin and the junction between the body and the palatine process of the maxilla. Notice also that the right maxillary third premolar tooth has 3 roots.

  • Figure 4—

    Representative transverse computed tomographic image of the head of the dog in Figure 1. Notice the destructive mass involving the right maxilla (arrows). In the magnified view, involvement of the ventral border of the infraorbital canal (asterisk) and endosteal scalloping of the alveolar process of the maxilla (arrowhead) are evident. The right maxillary fourth premolar tooth is absent.

  • 1.

    Smith MM. Exodontics. Vet Clin North Am Small Anim Pract 1998; 28:12971319.

  • 2.

    Verstraete FJM. Self-assessment colour review of veterinary dentistry. London: Manson Publishing/The Veterinary Press, 1999; 145146.

  • 3.

    DuPont GA, DeBowes LJ. Atlas of dental radiography in dogs and cats. St Louis: Saunders Elsevier, 2009; 134-171, 221228.

  • 4.

    Kermer C, Poeschl PW & Wutzl A, et al. Surgical treatment of squamous cell carcinoma of the maxilla and nasal sinuses. J Oral Maxillofac Surg 2008; 66:24492453.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5.

    Gorrel C. Radiographic evaluation. Vet Clin North Am Small Anim Pract 1998; 28:10891110.

  • 6.

    Fiani N, Arzi B. Diagnostic imaging in veterinary dental practice. J Am Vet Med Assoc 2010; 236:4143.

  • 7.

    Niemiec BA. Fundamentals of endodontics. Vet Clin North Am Small Anim Pract 2005; 35:837868.

  • 8.

    Luskin IR, Kressin DJ. Endodontic decisions based on radiographic appearance. Clin Tech Small Anim Pract 2001; 16:173181.

  • 9.

    Bar-Am Y, Pollard RE & Kass PH, et al. The diagnostic yield of conventional radiographs and computed tomography in dogs and cats with maxillofacial trauma. Vet Surg 2008; 37:294299.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 10.

    Gottrup F, Storgard Jensen S, Andreasen JO. Wound healing subsequent to injury. 4th ed. Oxford, England: Blackwell Munks- gaard, 2007;144.

    • Search Google Scholar
    • Export Citation

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