Diagnostic Imaging in Veterinary Dental Practice

Florian F. Boutoille Clinique Vétérinaire Advetia, 5 rue Dubrunfaut, 75012 Paris, France.

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Philippe R. Hennet Clinique Vétérinaire Advetia, 5 rue Dubrunfaut, 75012 Paris, France.

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History and Physical Examination Findings

A 1-year-old 9-kg (19.8-lb) sexually intact male mixed-breed dog was evaluated because of generalized abnormally shaped teeth and several missing teeth. The dog had been adopted from a shelter at the age of 3 months. According to the client, all of the dogs in the litter had developed distemper during their first few months after birth, and all of the other littermates had died. The client reported that the dog had chronic diarrhea and avoided dry food, preferring a soft diet.

The dog was skinny (body condition score, 2/6), but physical examination findings were otherwise unremarkable. Oral examination revealed mild dental plaque and calculus accumulation associated with mild gingivitis; the right and left mandibular fourth premolar teeth were missing. Shallow brown enamel defects consistent with a clinical diagnosis of enamel hypoplasia were evident on all teeth.

Results of a CBC and serum biochemical profile were within reference limits. The dog was anesthetized, and intraoral radiography and periodontal charting were performed. Selected radiographic views are provided (Figure 1).

Figure 1—
Figure 1—

Lateral radiographic views of the right mandibular premolar (A) and molar (B) teeth in a dog examined because of abnormally shaped and missing teeth.

Citation: Journal of the American Veterinary Medical Association 238, 10; 10.2460/javma.238.10.1251

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Diagnostic Imaging Findings and Interpretation

Intraoral radiography confirmed that the left mandibular fourth premolar tooth was missing, but that the clinically inapparent right mandibular fourth premolar tooth was present but unerupted (Figure 2). There is a well-demarcated radiolucent area centered on the mesiocoronal aspect of the unerupted tooth, and this radiolucent area has corticated margins. These features were considered strongly suggestive of a dentigerous cyst. At the rostroventral aspect of the cyst, the margins are not well corticated, which may be explained by superimposition of the mandibular canal or may be secondary to an inflammatory process associated with cystic development. The cyst surrounds the mesial aspect of the crown of the right mandibular fourth premolar tooth and extends to the distal root of the right mandibular third premolar tooth. The distal root of the right mandibular third premolar tooth appears shorter than normal and the lamina dura is confluent with the corticated margin of the cyst, but the periodontal space appears intact.

Figure 2—
Figure 2—

Same radiographic views as in Figure 1. On the radiographic view of the premolar teeth (A), notice the fused roots of the right mandibular second premolar tooth (black arrowhead) and the convergent roots of the third premolar tooth (white arrow). A cyst surrounds the mesial part of the crown of the fourth premolar tooth; the cyst has well-corticated margins except on its rostroventral aspect (white arrowhead). Notice the irregularities of the alveolar margin between the mandibular right third premolar and first molar teeth (black arrow), which could correspond to the resorbing distal root of the right mandibular deciduous third premolar tooth. The tips of the crown of the right mandibular second and third premolar teeth appear less radiopaque than typical, consistent with enamel hypoplasia. On the radiographic view of the molar teeth (B), notice the abnormally narrow and small roots of the right mandibular first molar tooth (black arrows) and the convergent roots of the second molar tooth (white arrow). The irregular surface and decreased radiopacity of the crown of the first molar tooth are consistent with enamel hypoplasia.

Citation: Journal of the American Veterinary Medical Association 238, 10; 10.2460/javma.238.10.1251

The alveolar margin appears irregular between the right mandibular third premolar tooth and the right mandibular first molar tooth. Within the alveolar bone on the mesial aspect of the right mandibular first molar tooth, 2 discrete radiolucent lines delineate an elongated structure of the same density as bone, which could correspond to the resorbing distal root of the right mandibular deciduous third premolar tooth or could be an artifact.

The roots of the right mandibular premolar and molar teeth appear narrower and smaller than normal. Convergent roots are observed on the right mandibular third premolar and second molar teeth, and fused roots are seen on the right mandibular second premolar tooth. The tips of the crowns of the right mandibular second and third premolar teeth and first molar tooth are less radiopaque than expected, corresponding to clinically visible areas of enamel hypoplasia.

Treatment and Outcome

The crowns of all teeth were ultrasonically scaled supragingivally and subgingivally and air-polished. All teeth with signs of enamel hypoplasia were treated with a fluoride varnish. The crown of the unerupted right mandibular fourth premolar tooth was exposed by means of mucoperiosteal flap elevation and alveolectomy. The tooth was gently extracted with a luxator, and the cyst was entirely removed by means of enucleation (Figure 3). The cystic cavity was thoroughly curetted, and the surgery site was sutured with 5–0 poliglecaprone. On histologic examination, the cystic lining was found to consist of mature stratified squamous epithelium embedded in a fibrous matrix and surrounded by mild to moderate inflammation.

Figure 3—
Figure 3—

Photograph of the unerupted right mandibular fourth premolar tooth of the dog in Figure 1, after extraction and enucleation of the associated cyst lining. Notice the attachment of the cyst to the cementum-enamel junction of the tooth (white arrow).

Citation: Journal of the American Veterinary Medical Association 238, 10; 10.2460/javma.238.10.1251

During a follow-up examination 4 months after the surgery, intraoral radiography of the surgical site showed complete bony healing of the cystic cavity and resolution of the irregular pattern of the alveolar margin as well as complete resorption of what had been assumed to be a deciduous root. Following healing of the surgical site, a decrease of the bony height was observed, which could have been a result of the alveolectomy or a consequence of suppression of the bone trophic stimulus subsequent to tooth extraction (Figure 4).

Figure 4—
Figure 4—

Lateral radiographic view of the right mandibular second and third premolar teeth of the dog in Figure 1, 4 months after surgery. Notice the complete bony healing of the cystic cavity and disappearance of the irregular pattern of the alveolar margin.

Citation: Journal of the American Veterinary Medical Association 238, 10; 10.2460/javma.238.10.1251

Comments

Canine distemper virus has been reported to be associated with enamel hypoplasia in dogs, and histologic analysis has revealed viral inclusions in the stratum intermedium of developing teeth from infected dogs.1 In the dog described in the present report, abnormalities observed clinically and radiographically on the coronal surfaces of the permanent teeth were suggestive of enamel hypoplasia secondary to distemper virus infection. Radiographic examination of the mandibular premolar teeth showed abnormally narrow and short roots characteristic of root hypoplasia, which could be considered to be clinically not very important in the present case but which has been reported in dogs with severe enamel and dentin hypoplasia.2,3

Retention and partial eruption of teeth as a sequela of canine distemper virus infection has been reported in dogs.4 As a result of damage caused by the virus, the desmolytic action of the enamel epithelium may not be sufficient to cause resorption of the connective tissue between the crown and the oral epithelium, thus interfering with the process of eruption.4,5 Unerupted teeth can be associated with development of a cystic lesion resulting from proliferation of the enamel organ remnant or reduced enamel epithelium.6 In humans, dentigerous cysts are the second most common type of odontogenic cyst, and the most common developmental cysts of the jaws.6 In dogs, they are considered to be rare.7 The mandibular first premolar tooth seems to be the most common site for dentigerous cyst formation in dogs.7,8 No breed predilection has been documented, although several case reports7–10 describe brachycephalic dogs (Boxer, Shih Tzu, Pug, and Boston Terrier) being affected. By definition, a dentigerous cyst is attached to the cementum-enamel junction and encloses the crown of the unerupted tooth.6,7

Removal of the affected tooth in association with surgical enucleation of the cyst walls followed by curettage of the remaining alveolar bone is the treatment of choice for dentigerous cysts.6,7,11 If not removed completely, the cyst may recur.7

References

  • 1.

    Dubielzig RR. The effect of canine distemper virus on the ameloblastic layer of the developing tooth. Vet Pathol 1979; 16:268270.

  • 2.

    Arnbjerg J. Tooth enamel and root hypoplasia following distemper in dogs. Kleintierpraxis 1986; 31:323326.

  • 3.

    Fiani NArzi B. Diagnostic imaging in veterinary dental practice. J Am Vet Med Assoc 2009; 235:271273.

  • 4.

    Bodingbauer J. Retention of teeth in dogs as a sequel to distemper infection. Vet Rec 1960; 72:636638.

  • 5.

    Bittegeko SBArnbjerg JNkya R, et al. Multiple dental developmental abnormalities following canine distemper infection. J Am Anim Hosp Assoc 1995; 31:4245.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6.

    Regezi JASciubba JJJordan RC. Cysts of the jaws and neck. In: Regezi JASciubba JJJordan RC, eds. Oral pathology: clinical pathologic correlations. 5th ed. St Louis: Elsevier Saunders, 2008; 237259.

    • Search Google Scholar
    • Export Citation
  • 7.

    Baxter CJ. Bilateral mandibular dentigerous cysts in a dog. J Small Anim Pract 2004; 45:210212.

  • 8.

    Soukup JWLawrence JAPinkerton ME, et al. 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
  • 9.

    Doran IPearson GBarr F, et al. Extensive bilateral odontogenic cysts in the mandible of a dog. Vet Pathol 2008; 45:5860.

  • 10.

    Watanabe KKadosawa TIshiguro T, et al. Odontogenic cysts in three dogs: one odontogenic keratocyst and two dentigerous cysts. J Vet Med Sci 2004; 66:11671170.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 11.

    Kramek BAO'Brien TDSmith FO. Diagnosis and removal of a dentigerous cyst complicated by ameloblastic fibro-odontoma in a dog. J Vet Dent 1996; 13:911.

    • Crossref
    • Search Google Scholar
    • Export Citation

Contributor Notes

Address correspondence to Dr. Boutoille (flobnantes@aol.com).
  • Figure 1—

    Lateral radiographic views of the right mandibular premolar (A) and molar (B) teeth in a dog examined because of abnormally shaped and missing teeth.

  • Figure 2—

    Same radiographic views as in Figure 1. On the radiographic view of the premolar teeth (A), notice the fused roots of the right mandibular second premolar tooth (black arrowhead) and the convergent roots of the third premolar tooth (white arrow). A cyst surrounds the mesial part of the crown of the fourth premolar tooth; the cyst has well-corticated margins except on its rostroventral aspect (white arrowhead). Notice the irregularities of the alveolar margin between the mandibular right third premolar and first molar teeth (black arrow), which could correspond to the resorbing distal root of the right mandibular deciduous third premolar tooth. The tips of the crown of the right mandibular second and third premolar teeth appear less radiopaque than typical, consistent with enamel hypoplasia. On the radiographic view of the molar teeth (B), notice the abnormally narrow and small roots of the right mandibular first molar tooth (black arrows) and the convergent roots of the second molar tooth (white arrow). The irregular surface and decreased radiopacity of the crown of the first molar tooth are consistent with enamel hypoplasia.

  • Figure 3—

    Photograph of the unerupted right mandibular fourth premolar tooth of the dog in Figure 1, after extraction and enucleation of the associated cyst lining. Notice the attachment of the cyst to the cementum-enamel junction of the tooth (white arrow).

  • Figure 4—

    Lateral radiographic view of the right mandibular second and third premolar teeth of the dog in Figure 1, 4 months after surgery. Notice the complete bony healing of the cystic cavity and disappearance of the irregular pattern of the alveolar margin.

  • 1.

    Dubielzig RR. The effect of canine distemper virus on the ameloblastic layer of the developing tooth. Vet Pathol 1979; 16:268270.

  • 2.

    Arnbjerg J. Tooth enamel and root hypoplasia following distemper in dogs. Kleintierpraxis 1986; 31:323326.

  • 3.

    Fiani NArzi B. Diagnostic imaging in veterinary dental practice. J Am Vet Med Assoc 2009; 235:271273.

  • 4.

    Bodingbauer J. Retention of teeth in dogs as a sequel to distemper infection. Vet Rec 1960; 72:636638.

  • 5.

    Bittegeko SBArnbjerg JNkya R, et al. Multiple dental developmental abnormalities following canine distemper infection. J Am Anim Hosp Assoc 1995; 31:4245.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6.

    Regezi JASciubba JJJordan RC. Cysts of the jaws and neck. In: Regezi JASciubba JJJordan RC, eds. Oral pathology: clinical pathologic correlations. 5th ed. St Louis: Elsevier Saunders, 2008; 237259.

    • Search Google Scholar
    • Export Citation
  • 7.

    Baxter CJ. Bilateral mandibular dentigerous cysts in a dog. J Small Anim Pract 2004; 45:210212.

  • 8.

    Soukup JWLawrence JAPinkerton ME, et al. 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
  • 9.

    Doran IPearson GBarr F, et al. Extensive bilateral odontogenic cysts in the mandible of a dog. Vet Pathol 2008; 45:5860.

  • 10.

    Watanabe KKadosawa TIshiguro T, et al. Odontogenic cysts in three dogs: one odontogenic keratocyst and two dentigerous cysts. J Vet Med Sci 2004; 66:11671170.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 11.

    Kramek BAO'Brien TDSmith FO. Diagnosis and removal of a dentigerous cyst complicated by ameloblastic fibro-odontoma in a dog. J Vet Dent 1996; 13:911.

    • Crossref
    • Search Google Scholar
    • Export Citation

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