Diagnostic Imaging in Veterinary Dental Practice

Mercedes De Paolo Dentistry and Oral Surgery Service, William R. Pritchard Veterinary Medical Teaching Hospital, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616.

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Kevin Ng 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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Nadine Fiani Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853.

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History and Physical Examination Findings

An 11-year-old castrated male Labrador Retriever was referred to the oncology service at the Cornell University Hospital for Animals for evaluation and treatment of a nasal tumor. Three weeks earlier, the dog had a single episode of epistaxis and had been evaluated at a different referral facility. Computed tomography of the head was performed, revealing a right-sided nasal mass with possible invasion into the cribriform plate. Histopathologic findings from an incisional biopsy were consistent with nasal carcinoma. Carprofen (2 mg/kg [0.9 mg/lb], PO, q 12 h) was prescribed. Between the time of initial diagnosis and evaluation at the teaching hospital, the dog did not have any further nasal discharge and had no signs of neurologic disease. No other signs of systemic disease were observed.

On examination by the oncology service, physical examination findings were largely unremarkable except for unilateral sanguineous nasal discharge with absent airflow from the right nostril. Oral examination revealed generalized gingivitis and abundant dental calculus. The right and left mandibular fourth premolar teeth had uncomplicated (ie, enamel-dentin) crown fractures, and the left maxillary first incisor tooth was mesioverted. Examination of the oral cavity with the patient under general anesthesia revealed discolored cavitated defects on the occlusal surface of the right and left maxillary first molar teeth, with exposed dentin that lacked the hardness and consistency expected on exploration, consistent with advanced occlusal caries lesions. No other clinically relevant abnormalities were observed on oral examination.

The results of serum biochemical analysis, a CBC, and urinalysis were within the respective reference ranges. Three-view thoracic radiographic examination, abdominal ultrasonography, and cytologic evaluation of mandibular lymph node aspirates revealed no evidence of metastatic disease. The patient was anesthetized during the same visit, and a CT scan of the head was performed for palliative radiotherapy planning purposes. A transverse CT image obtained at the level of the maxillary first molar teeth is provided (Figure 1).

Figure 1—
Figure 1—

Transverse CT image of the skull of an 11-year-old Labrador Retriever referred to the oncology service of a veterinary teaching hospital for further evaluation and treatment of nasal carcinoma. The image (slice thickness, 2 mm) was obtained at the level of the right and left maxillary first molar teeth and viewed with bone window (window width, 4,500 Hounsfield units; window level, 1,100 Hounsfield units) settings.

Citation: Journal of the American Veterinary Medical Association 253, 3; 10.2460/javma.253.3.275

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Diagnostic Imaging Findings and Interpretation

Consistent with the history of nasal carcinoma, CT image examination revealed a soft tissue-attenuating mass in the right nasal cavity with associated lysis of the nasal turbinates and surrounding osseous structures. In addition, periapical bone lysis with some marginal sclerosis surrounding the roots of both maxillary first molar teeth was evident (Figure 2). Vertical bone loss affecting the mesiobuccal root of the right maxillary first molar tooth was also observed, and a retained root fragment of the right maxillary fourth premolar tooth was noted (corresponding CT images not shown).

Figure 2—
Figure 2—

The same transverse CT image as in Figure 1. Periapical alveolar bone lysis (asterisks) surrounds the apices of the right and left maxillary first molar teeth. Marginal sclerosis is present surrounding the periapical lucencies (arrows), increasing the index of suspicion for bilateral endodontal disease. There is a diffuse, soft tissue-attenuating opacity on the right side of the nasal cavity causing destruction of the nasal turbinates and several adjacent bony structures.

Citation: Journal of the American Veterinary Medical Association 253, 3; 10.2460/javma.253.3.275

Intraoral radiography performed under the same anesthetic episode revealed ill-defined periapical lucencies surrounding the palatal roots of the left and right maxillary first molar teeth, mild to moderate vertical bone loss at the mesial aspect of the right maxillary first molar tooth, and a retained root at the mesial area of the right maxillary fourth premolar tooth (Figure 3).

Figure 3—
Figure 3—

Lateral bisecting-angle intraoral radiographs of the caudal aspects of the right (A) and left (B) maxillae of the same dog as in Figure 1. Periapical lucencies are associated with the palatal roots of the right and left maxillary first molar teeth (arrowheads), consistent with apical periodontitis. Radiolucency consistent with vertical alveolar bone loss associated with the mesiobuccal root of the right maxillary first molar tooth, a caries lesion of the crown, or both are also present (asterisks). A retained root fragment of the right maxillary fourth premolar tooth is also visible (arrow).

Citation: Journal of the American Veterinary Medical Association 253, 3; 10.2460/javma.253.3.275

Given the bilateral nature of the periapical lesions and the unilateral position of the tumor, bone lysis secondary to neoplasia was considered unlikely to be the cause of the periapical lesions. Rather, the most probable diagnosis for these findings was primary endodontal disease secondary to caries in both teeth.

Treatment and Outcome

A complete periodontal treatment including supragingival and subgingival ultrasonic scaling was performed, followed by bilateral infraorbital nerve blocks with 0.5% bupivacaine solution. The right and left maxillary first molar teeth and the retained root fragment of the right maxillary fourth premolar tooth were surgically extracted. Postoperative intraoral radiographs confirmed that the alveoli of the extracted teeth and retained root were completely vacated. During extraction, purulent material was found associated with the roots of each of the maxillary first molar teeth. The corresponding alveoli were debrided with a Miller surgical curette and rinsed with sterile saline (0.9% NaCl) solution. No treatment of the uncomplicated crown fractures of the right and left mandibular fourth premolar teeth was performed. The extraction sites were routinely sutured closed. Antimicrobial and multimodal analgesic treatments were provided after surgery with amoxicillin-clavu-lanic potassium (14.8 mg/kg [6.73 mg/lb], PO, q 12 h) for 7 days, tramadol hydrochloride (3.9 mg/kg [1.8 mg/kg], PO, q 8 to 12 h) for 5 days, and carprofen (2 mg/kg, PO, q 12 h) indefinitely.

The dog was reexamined 2 weeks after surgery to evaluate healing of the extraction sites. Oral examination revealed gross healing of the extraction sites, and palliative radiotherapy was started 1 week later. Follow-up care was provided and overseen by the oncology service of the referral hospital. The client reported the patient died 12 months after the initial referral examination. The cause of death was not specified, and a necropsy was not performed.

Comments

Interpretation of the CT images obtained for radiotherapy planning purposes led to the recognition of intraoral disease in the dog of this report. There were no specific clinical signs that suggested periodontal or obvious endodontal disease, but evaluation of dentoalveolar structures on the CT images alerted clinicians to the abnormalities. On closer examination and probing while the patient was anesthetized, both of the maxillary first molar teeth were found to have cavitated occlusal lesions consistent with caries. Although caries are rare in dogs,1 they are an important cause of endodontal disease and were the likely cause of this patient's apical periodontitis. The development of caries depends on many patient-specific factors including the shape of a tooth, microflora present in the mouth, and proportion of carbohydrates in the diet. Maxillary first molar teeth are thought to be common sites for the development of caries in dogs owing to relatively broad occlusal surfaces with pits and fissures in which carbohydrates can become entrapped and subsequently fermented.1 If the integrity of the enamel and dentin become compromised during this process, endodontal disease and its sequelae can occur. In general, caries can be difficult to visualize on intraoral radiographs or CT images, but the subsequent signs of endodontal disease such as inflammatory root resorption, periapical lesions, and failure of the pulp cavity to narrow are more easily recognized.

In patients with nasal carcinoma, surgical resection alone has not been shown to increase survival time and often causes substantial adverse effects. If owners wish to pursue treatment, radiotherapy is generally recommended.2 Radiation treatment of the head and neck is associated with potential early and long-term complications, including dehiscence of surgical sites and osteoradionecrosis of the jaws.3,4 Osteoradionecrosis of the jaws is relatively rare but can be devastating for a patient. Preexisting periodontal or endodontal disease may increase the risk of developing osteoradionecrosis of the jaws, as can performing dental extractions in a previously irradiated field.3–7 Therefore, a patient's endodontal and periodontal status should be evaluated thoroughly so that any extractions can be performed 2 to 3 weeks prior to the start of radiotherapy.5,8

Given that intraoral radiography has historically been the diagnostic imaging modality of choice for periodontal and endodontal disease in companion animals,9 intraoral radiographs were obtained of the affected teeth in the dog of this report after CT had been performed. However, it is interesting to note that the radiographs did not provide any additional information over that obtained by CT and that the radiographic images were less striking in regard to the apical periodontitis. This is consistent with recent research indicating that advanced 3-D imaging modalities may be superior to intraoral radiography for evaluating dentoalveolar structures.10–12 This is especially relevant in the caudal maxillae, where superimposition of anatomic structures and foreshortening of the maxillary first molar teeth on standard bisecting-angle views complicate interpretation of intraoral radiographs. Therefore, it has been proposed that if a patient has received a CT scan with appropriate slice thickness, ideally < 0.5 to 1.0 mm, it may not be necessary to simultaneously perform intraoral radiography.12 The case described in the present report illustrated the utility of CT in diagnosis of oral disease as well as the importance of assessing CT images for dentoalveolar disease in patients that will be undergoing radiotherapy of the maxillofacial region.

References

  • 1. Hale FA. Dental caries in the dog. Can Vet J 2009;50:13011304.

  • 2. Turek MM, Lana SE. Nasosinal tumors. In: Vail DM, ed. Withrow and MacEwen's small animal clinical oncology. 5th ed. St Louis: Elsevier, 2012;435451.

    • Search Google Scholar
    • Export Citation
  • 3. Murray CG, Herson J, Daly TE, et al. Radiation necrosis of the mandible: a 10 year study. Part I. Factors influencing the onset of necrosis. Int J Radiat Oncol Biol Phys 1980;6:543548.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4. Oh HK, Chambers MS, Martin JW, et al. Osteoradionecrosis of the mandible: treatment outcomes and factors influencing the progress of osteoradionecrosis. J Oral Maxillofac Surg 2009;67:13781386.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5. Nemec A, Arzi B, Hansen K, et al. Osteonecrosis of the jaws in dogs in previously irradiated fields: 13 cases (1989–2014). Front Vet Sci 2015;2:5.

    • Search Google Scholar
    • Export Citation
  • 6. Nabil S & Samman N. Risk factors for osteoradionecrosis after head and neck radiation: a systematic review. Oral Surg Oral Med Oral Pathol Oral Radiol 2012;113:5469.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 7. Marx RE, Johnson RP. Studies in the radiobiology of osteoradionecrosis and their clinical significance. Oral Surg Oral Med Oral Pathol 1987;64:379390.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 8. Rustlander D. Radiation therapy. In: Slatter D, ed. Textbook of small animal surgery. 3rd ed. Philadelphia: Saunders, 2003;23292345.

    • Search Google Scholar
    • Export Citation
  • 9. Colmery B III. The gold standard of veterinary oral health care. Vet Clin North Small Anim Pract 2005;35:781787.

  • 10. de Paula-Silva FW, Wu MK, Leonardo MR, et al. Accuracy of periapical radiography and cone-beam computed tomography scans in diagnosing apical periodontitis using histopathological findings as a gold standard. J Endod 2009;35:10091012.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 11. Roza MR, Silva LA, Barriviera M, et al. Cone beam computed tomography and intraoral radiography for diagnosis of dental abnormalities in dogs and cats. J Vet Sci 2011;12:387392.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 12. Campbell RD, Peralta S, Fiani N, et al. Comparing intraoral radiography and computed tomography for detecting radiographic signs of periodontitis and endodontic disease in dogs: an agreement study. Front Vet Sci 2016;3:68.

    • Search Google Scholar
    • Export Citation

Contributor Notes

Address correspondence to Dr. De Paolo (mhdepaolo@ucdavis.edu).
  • Figure 1—

    Transverse CT image of the skull of an 11-year-old Labrador Retriever referred to the oncology service of a veterinary teaching hospital for further evaluation and treatment of nasal carcinoma. The image (slice thickness, 2 mm) was obtained at the level of the right and left maxillary first molar teeth and viewed with bone window (window width, 4,500 Hounsfield units; window level, 1,100 Hounsfield units) settings.

  • Figure 2—

    The same transverse CT image as in Figure 1. Periapical alveolar bone lysis (asterisks) surrounds the apices of the right and left maxillary first molar teeth. Marginal sclerosis is present surrounding the periapical lucencies (arrows), increasing the index of suspicion for bilateral endodontal disease. There is a diffuse, soft tissue-attenuating opacity on the right side of the nasal cavity causing destruction of the nasal turbinates and several adjacent bony structures.

  • Figure 3—

    Lateral bisecting-angle intraoral radiographs of the caudal aspects of the right (A) and left (B) maxillae of the same dog as in Figure 1. Periapical lucencies are associated with the palatal roots of the right and left maxillary first molar teeth (arrowheads), consistent with apical periodontitis. Radiolucency consistent with vertical alveolar bone loss associated with the mesiobuccal root of the right maxillary first molar tooth, a caries lesion of the crown, or both are also present (asterisks). A retained root fragment of the right maxillary fourth premolar tooth is also visible (arrow).

  • 1. Hale FA. Dental caries in the dog. Can Vet J 2009;50:13011304.

  • 2. Turek MM, Lana SE. Nasosinal tumors. In: Vail DM, ed. Withrow and MacEwen's small animal clinical oncology. 5th ed. St Louis: Elsevier, 2012;435451.

    • Search Google Scholar
    • Export Citation
  • 3. Murray CG, Herson J, Daly TE, et al. Radiation necrosis of the mandible: a 10 year study. Part I. Factors influencing the onset of necrosis. Int J Radiat Oncol Biol Phys 1980;6:543548.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4. Oh HK, Chambers MS, Martin JW, et al. Osteoradionecrosis of the mandible: treatment outcomes and factors influencing the progress of osteoradionecrosis. J Oral Maxillofac Surg 2009;67:13781386.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5. Nemec A, Arzi B, Hansen K, et al. Osteonecrosis of the jaws in dogs in previously irradiated fields: 13 cases (1989–2014). Front Vet Sci 2015;2:5.

    • Search Google Scholar
    • Export Citation
  • 6. Nabil S & Samman N. Risk factors for osteoradionecrosis after head and neck radiation: a systematic review. Oral Surg Oral Med Oral Pathol Oral Radiol 2012;113:5469.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 7. Marx RE, Johnson RP. Studies in the radiobiology of osteoradionecrosis and their clinical significance. Oral Surg Oral Med Oral Pathol 1987;64:379390.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 8. Rustlander D. Radiation therapy. In: Slatter D, ed. Textbook of small animal surgery. 3rd ed. Philadelphia: Saunders, 2003;23292345.

    • Search Google Scholar
    • Export Citation
  • 9. Colmery B III. The gold standard of veterinary oral health care. Vet Clin North Small Anim Pract 2005;35:781787.

  • 10. de Paula-Silva FW, Wu MK, Leonardo MR, et al. Accuracy of periapical radiography and cone-beam computed tomography scans in diagnosing apical periodontitis using histopathological findings as a gold standard. J Endod 2009;35:10091012.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 11. Roza MR, Silva LA, Barriviera M, et al. Cone beam computed tomography and intraoral radiography for diagnosis of dental abnormalities in dogs and cats. J Vet Sci 2011;12:387392.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 12. Campbell RD, Peralta S, Fiani N, et al. Comparing intraoral radiography and computed tomography for detecting radiographic signs of periodontitis and endodontic disease in dogs: an agreement study. Front Vet Sci 2016;3:68.

    • Search Google Scholar
    • Export Citation

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