Diagnostic Imaging in Veterinary Dental Practice

Milinda J. Lommer Aggie Animal Dental Service, 2343 Fillmore St, San Francisco, CA 94115.

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History and Physical Examination Findings

A 7-year-old 36.8-kg (81-lb) castrated male Labrador Retriever was examined because of a gingival mass near the left mandibular canine tooth. The mass had first been noticed approximately 8 weeks previously. The patient was reportedly healthy, other than having hypothyroidism, which was controlled with twice daily thyroxine administration.

Results of a general physical examination were unremarkable. Oral examination revealed moderate generalized plaque and calculus with mild gingivitis. An exophytic, nonulcerated gingival mass that was approximately 10 mm in diameter and had an irregular surface was identified at the mesial aspect of the left mandibular canine tooth. Moderate to severe generalized abrasion of the mass was noted. An apparent endodontic access site was identified on the right mandibular canine tooth; the coronal restoration was missing, and obturation material was exposed. The client was unaware of endodontic treatment of this tooth.

Sixteen days later, the dog was returned for general anesthesia, intraoral radiography, dental scaling and polishing, excisional biopsy of the gingival mass, and possible endodontic treatment of the right mandibular canine tooth. Following induction of general anesthesia, intraoral radiographic views of the rostral portions of the mandibles were obtained (Figure 1).

Figure 1—
Figure 1—

Lateral (A) and occlusal (B) intraoral radiographic views of the rostral portions of the mandibles in a dog with a gingival mass near the left mandibular canine tooth.

Citation: Journal of the American Veterinary Medical Association 230, 7; 10.2460/javma.230.7.997

Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page

Diagnostic Imaging Findings and Interpretation

Radiographic views reveal radiopaque material in the pulp cavity of the right mandibular canine tooth, consistent with previous endodontic treatment (Figure 2). The shaping and obturation of the canal appears suboptimal, as the canal lacks the desired uniform shape. In addition, an instrument fragment is lodged in the filling material in the apical portion of the canal. A large (approx 20 X 30 mm) lucency is identified surrounding the root apex of the right mandibular canine tooth. The right mandibular first premolar tooth is missing, and the roots of the right mandibular second premolar tooth have been resorbed. The mandibular cortex appears unaffected.

Figure 2—
Figure 2—

Same radiographic views as in Figure 1. Notice the large lucency surrounding the root apex of the right mandibular canine tooth (arrowheads). There is radiopaque material in the pulp cavity of this tooth, consistent with previous endodontic treatment, and an instrument fragment appears lodged in the filling material in the apical portion of the canal (black arrows). The roots of the right mandibular second premolar tooth have been resorbed (white arrow).

Citation: Journal of the American Veterinary Medical Association 230, 7; 10.2460/javma.230.7.997

Treatment and Outcome

Because of the severity of the periapical bone destruction, extraction of the right mandibular canine tooth was recommended. Placement of an autogenous cancellous bone graft was recommended but declined by the clients. Although the roots of the right mandibular second premolar tooth had been resorbed, no mobility was evident clinically and there were no periodontal pockets evident during probing. Therefore, extraction of this tooth was not deemed necessary.

Following ultrasonic scaling and air polishing of all teeth and excision of the gingival mass near the left mandibular canine tooth, a triangular mucogingival-periosteal flap was created at the buccal aspect of the right mandibular canine tooth. Partial buccal alveolectomy was performed with a round diamond bur on a high-speed dental handpiece with continuous irrigation. The right mandibular canine tooth was extracted with a combination of 3- and 5-mm luxators and a 4-mm wing-tipped elevator. Brown fluid was identified at the extraction site, and a soft tissue lining was identified within the osteolytic area. A clinical diagnosis of periapical cyst was made. The cyst lining was removed with a Miller bone curette and a periosteal elevator, and samples were submitted for histologic examination. The mucogingival flap was sutured with 5-0 poliglecaprone 25 in a simple interrupted pattern. Postoperative radiographs were obtained.

On histologic analysis, the soft tissue lining the cyst was composed of nonkeratinized, stratified squamous epithelium, with hemosiderin-laden macrophages and mild fibroplasia in the submucosa. Findings were consistent with the clinical diagnosis of a periapical cyst. Histologic examination of the gingival mass near the left mandibular canine tooth revealed ossifying fibromatous epulis, more correctly known as peripheral odontogenic fibroma.1

Nineteen days after treatment, the biopsy and extraction sites had healed. The dog was reexamined 8 months later. Follow-up radiography revealed new bone formation and elimination of the defect at the site of the right mandibular canine tooth (Figure 3). Despite resorption of its roots, the right mandibular second premolar tooth remained functional, without clinical evidence of mobility.

Figure 3—
Figure 3—

Eight-month follow-up occlusal intraoral radiographic view of the rostral portions of the mandibles of the dog in Figures 1 and 2. Notice that the defect at the site of the right mandibular canine tooth has been eliminated.

Citation: Journal of the American Veterinary Medical Association 230, 7; 10.2460/javma.230.7.997

Comments

The outcome of root canal treatment can only be determined radiographically.2 Failure of endodontic treatment is asymptomatic in more than 50% of human patients,3 and even if pain were present in association with failed root canal treatment, it is unlikely that signs of pain would be recognizable in dogs. Therefore, radiographic follow-up examination of endodontic treatment is imperative.2 Root canal treatment should be considered to have failed in patients in which a periapical radiolucency has not healed within 4 years.2

The most common finding associated with failed endodontic treatment in humans is a periapical granuloma.4 Periapical cysts are less common and typically develop from a preexisting granuloma as a result of stimulation of the epithelial rests of Malassez by inflammatory mediators. Proliferation of these epithelial cells helps to separate the inflammatory stimulus from the surrounding bone. Breakdown of cellular debris in the cyst lumen increases the protein concentration, which increases osmotic pressure and results in fluid ingress into the cyst lumen. The cyst expands with increasing fluid content and bone resorption.5 Radiographically, a cyst cannot be differentiated from a granuloma.5 However, with long-standing cysts, resorption of the affected tooth as well as adjacent teeth may occur, as was seen with the dog described in the present report. With a periapical granuloma, resorption of the affected tooth is occasionally seen but resorption of adjacent teeth would be unexpected.5

Treatment options for periapical cysts include apicoectomy and curettage or extraction. In either case, if the cyst lining is not completely removed, a residual cyst may develop.5 Although cancellous bone grafting had been recommended for this dog, follow-up radiography revealed elimination of the defect and evidence of new bone formation.

References

  • 1

    Gardner DG, Baker DC. Fibromatous epulis in dogs and peripheral odontogenic fibroma in human beings: two equivalent lesions. Oral Surg Oral Med Oral Pathol 1991;71:317321.

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  • 2

    Kuntsi-Vaattovaara H, Verstraete FJM, Kass PH. Results of root canal treatment in dogs: 127 cases (1995–2000). J Am Vet Med Assoc 2002;220:775780.

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  • 3

    Lin LM, Pascon EA, Skribner J, et al. Clinical, radiographic, and histologic study of endodontic treatment failures. Oral Surg Oral Med Oral Pathol 1991;71:603611.

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  • 4

    Nobuhara WK, del Rio CE. Incidence of periradicular pathoses in endodontic treatment failures. J Endod 1993;19:315318.

  • 5

    Regezi JA, Sciubba JJ, Jordan RCK. Cysts of the jaws and neck. In:Regezi JA, Sciubba JJ, Jordan RCK, ed.Oral pathology: clinical pathologic correlations. 4th ed. St Louis: Mosby Inc, 2003;241244.

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  • Figure 1—

    Lateral (A) and occlusal (B) intraoral radiographic views of the rostral portions of the mandibles in a dog with a gingival mass near the left mandibular canine tooth.

  • Figure 2—

    Same radiographic views as in Figure 1. Notice the large lucency surrounding the root apex of the right mandibular canine tooth (arrowheads). There is radiopaque material in the pulp cavity of this tooth, consistent with previous endodontic treatment, and an instrument fragment appears lodged in the filling material in the apical portion of the canal (black arrows). The roots of the right mandibular second premolar tooth have been resorbed (white arrow).

  • Figure 3—

    Eight-month follow-up occlusal intraoral radiographic view of the rostral portions of the mandibles of the dog in Figures 1 and 2. Notice that the defect at the site of the right mandibular canine tooth has been eliminated.

  • 1

    Gardner DG, Baker DC. Fibromatous epulis in dogs and peripheral odontogenic fibroma in human beings: two equivalent lesions. Oral Surg Oral Med Oral Pathol 1991;71:317321.

    • Search Google Scholar
    • Export Citation
  • 2

    Kuntsi-Vaattovaara H, Verstraete FJM, Kass PH. Results of root canal treatment in dogs: 127 cases (1995–2000). J Am Vet Med Assoc 2002;220:775780.

    • Search Google Scholar
    • Export Citation
  • 3

    Lin LM, Pascon EA, Skribner J, et al. Clinical, radiographic, and histologic study of endodontic treatment failures. Oral Surg Oral Med Oral Pathol 1991;71:603611.

    • Search Google Scholar
    • Export Citation
  • 4

    Nobuhara WK, del Rio CE. Incidence of periradicular pathoses in endodontic treatment failures. J Endod 1993;19:315318.

  • 5

    Regezi JA, Sciubba JJ, Jordan RCK. Cysts of the jaws and neck. In:Regezi JA, Sciubba JJ, Jordan RCK, ed.Oral pathology: clinical pathologic correlations. 4th ed. St Louis: Mosby Inc, 2003;241244.

    • Search Google Scholar
    • Export Citation

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