History and Physical Examination Findings
An 8-month-old 26.4-kg (58-lb) castrated male Standard Poodle was evaluated because of swelling of the right mandible in the area of a missing permanent fourth premolar tooth. The swelling had first been noticed 3 weeks earlier while the dog was undergoing routine castration. The dog was reported as being otherwise healthy, although the owner had noted delayed exfoliation of the deciduous right mandibular fourth premolar tooth.
General physical examination findings were unremarkable. Oral examination revealed a firm, intraoral swelling of the right mandible centered at the area of the missing permanent fourth premolar tooth. The swelling was most evident on the buccal aspect of the mandible with a slight enlargement lingually. There was an area of pink proliferative tissue in the gingiva measuring 7 × 5 × 2 mm (Figure 1). The dog was anesthetized to allow for a complete oral examination, dental radiography, and treatment of the mandibular swelling. Radiographs of the right mandibular body were obtained by use of a parallel technique and size 4 dental film.
Gross (A) and radiographic (B) appearance of the right mandible in a dog evaluated because of swelling in the area of a missing permanent fourth premolar tooth.
Citation: Journal of the American Veterinary Medical Association 235, 11; 10.2460/javma.235.11.1279
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Diagnostic Imaging Findings and Interpretation
The unerupted right mandibular fourth premolar is impacted and displaced and has dilacerated roots (Figure 2). There is a radiolucent, cyst-like area associated with the distal crown aspect of the unerupted tooth. Coronal to the unerupted tooth is a heterogeneous mass with radiographic density of dental hard tissue. Within the mass, tooth-like structures of various sizes are surrounded by a narrow radiolucent zone. Radiographic findings are suggestive of a compound odontoma.1
Same radiographic view as in Figure 1B. Notice the irregular radiopaque mass (white arrowheads) with a density similar to that of the hard tissue of the adjacent unaffected teeth. Surrounding the mass is a radiolucent space and sclerotic-appearing bone. There is a focal area of radiolucency (black arrows) associated with the impacted permanent fourth premolar tooth (asterisk).
Citation: Journal of the American Veterinary Medical Association 235, 11; 10.2460/javma.235.11.1279
Treatment and Outcome
A mucoperiosteal flap was created, and alveolar bone was removed on the buccal aspect of the right mandible. Tooth-like structures of variable size embedded in fibrous connective tissue were exposed. These structures were elevated and removed from the mandible, allowing the unerupted right mandibular fourth premolar to be exposed and extracted. The remaining defect was thoroughly débrided, and alveoloplasty was performed to smooth any sharp bone edges. The defect was flushed with an antiseptic solution prior to closure of the surgical site. Synthetic absorbable suture material was used to reposition the flap. Radiographs of the tooth-like structures and the surgical site were obtained post-operatively to confirm that the dental material had been completely removed and that no trauma had occurred to the adjacent teeth (Figure 3).
Radiographic views of tooth-like structures removed from the mass seen in Figure 2 (A) and postoperative appearance of the surgical site (B).
Citation: Journal of the American Veterinary Medical Association 235, 11; 10.2460/javma.235.11.1279
The tooth-like structures were submitted for histologic examination, which confirmed the diagnosis of compound odontoma. They consisted primarily of dentin with a central area resembling dental pulp lined by odontoblasts. Occasionally, ameloblasts lined the outer surface dentin, separated by a clear space which likely represented missing enamel secondary to demineralization of the hard tissue prior to sectioning. Most of the tooth-like structures were surrounded by fibrous connective tissue consistent with periodontal ligament. Reexamination 14 days later confirmed healing of the surgical site. Anesthesia and intraoral radiography 6 months after surgery was recommended to evaluate healing, check for any recurrence of the odontoma, and screen for development of periodontal or endodontic disease involving the adjacent teeth.
Comments
Odontomas are mixed odontogenic tumors arising from epithelial and mesenchymal tissues responsible for tooth formation and typically contain normal-appearing enamel, dentin, cementum, and pulp.2 There are 2 basic types—compound and complex. Compound odontomas consist of numerous rudimentary tooth structures; complex odontomas consist of a disorganized arrangement of dental tissue.2 Many authors believe that odontomas are more accurately described as hamartomas, rather than neoplasms, because they represent a proliferation of normal tissue with an abnormal organization.1–4 Odontomas may also occur in combination with other odontogenic tumors, as is the case with ameloblastic fibro-odontomas.4
Odontomas are the most common odontogenic tumors in humans1,5 but are considered rare in dogs and cats.4,6 They are benign tumors and often manifest as expansile lesions without other associated clinical abnormalities in young animals. Clinical signs suggestive of an odontoma may include a persistent deciduous tooth, an unerupted permanent tooth, and alveolar bone swelling.2 As in this case, most odontomas in dogs are associated with an unerupted or displaced tooth.3,7 Radiography should always be performed when a tooth is determined to be missing during a clinical examination. Although histologic examination was not performed on the cyst-like lining attached to the tooth and associated with the radiolucency mesial to the fourth premolar tooth on radiographs from the dog described in the present report, the cyst was most likely part of a developing dentigerous cyst or associated with the fibrous capsule of the odontoma.
In the present case, the unerupted permanent right mandibular fourth premolar was impacted, displaced, and malformed, perhaps because of the overlying odontoma. Differential diagnoses that were considered, given the clinical and radiographic findings, included a dentigerous cyst, epithelial odontogenic tumor, osteoma, focal sclerosing osteitis, and ossifying fibroma.2 Although histologic examination is always required for a definitive diagnosis, incisional biopsy was not indicated because radiographic findings were typical of those associated with compound odontoma in the present case. Marginal surgical excision or enucleation with thorough debridement is the treatment of choice, and the prognosis after surgery is good.2,3,5–7
References
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