Diagnostic Imaging in Veterinary Dental Practice

Heather L. Duncan Animal Dental Center of Baltimore, 1209 Cromwell Bridge Rd, Baltimore, MD 21286.

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History and Physical Examination Findings

A 10-year-old 33.2-kg (73-lb) neutered male Standard Poodle was evaluated for treatment of chronic halitosis, decreased appetite of 2 weeks' duration, and signs of oral pain. The dog was fed a standard dry adult dog food with occasional table scraps. Oral examination revealed moderate gingivitis and calculus with irregularly shaped crowns of the right mandibular first molar tooth, the right maxillary fourth premolar tooth, and the right maxillary first molar tooth. On the areas of the irregular crowns, the teeth had a brown discoloration that appeared as a hard leathery surface. Use of a dental explorer to evaluate these areas revealed soft, adherent dentin. Results of the remainder of the physical examination were unremarkable. Results of a CBC and serum biochemical panel were unremarkable except for high alanine aminotransferase activity (223 U/L; reference range, 10 to 118 U/L) and hypercholesterolemia (343 mg/dL; reference range, 112 to 328 mg/dL).

The patient was anesthetized to allow for a complete oral examination, dental radiography, and treatment of the affected teeth. Intraoral radiographs of the right mandibular first molar tooth were obtained by means of the parallel technique and size 4 dental film, and intraoral radiographs of the right maxillary fourth premolar and first molar teeth were obtained by means of the bisecting angle technique and size 2 dental film (Figure 1).

Figure 1—
Figure 1—

Intraoral parallel view of the right mandibular first molar tooth (A) and intraoral bisecting angle view of the right maxillary fourth premolar and first molar teeth (B) in a 10-year-old dog examined because of chronic halitosis, decreased appetite of 2 weeks' duration, and signs of oral pain.

Citation: Journal of the American Veterinary Medical Association 237, 1; 10.2460/javma.237.1.41

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Diagnostic Imaging Findings and Interpretation

Crown defects of the right mandibular first molar tooth consisting of well-defined circular radiolucencies indicative of loss of tooth structure (enamel and dentin) are evident (Figure 2). Both defects appear to extend to the pulp chamber, exposing the pulp. There is also a well-defined periapical lucency and loss of the lamina dura at the mesial root of the right mandibular first molar tooth.

Figure 2—
Figure 2—

Same radiographic views as in Figure 1. On the view of the right mandibular first molar tooth (A), notice the well-defined circular radiolucencies involving the crown (white arrows) and the well-defined periapical lucency and loss of the lamina dura at the mesial root (black arrows). On the view of the right maxillary fourth premolar and first molar teeth (B), notice the circular radiolucencies in the distal aspect of the crown of the right maxillary fourth premolar tooth and the mesial aspect of the crown of the right maxillary first molar tooth (white arrows) and the periapical lucencies involving the distal root of the right maxillary fourth premolar tooth and the mesial root, palatal root, or both (black arrows).

Citation: Journal of the American Veterinary Medical Association 237, 1; 10.2460/javma.237.1.41

Circular radiolucencies are also present in the distal aspect of the crown of the right maxillary fourth premolar tooth and the mesial aspect of the crown of the right maxillary first molar tooth (Figure 2). The defect in the distal aspect of the right maxillary fourth premolar tooth appears to extend to the pulp chamber; however, the defect in the mesial aspect of the crown of the right maxillary first molar tooth does not appear to do so. There are periapical lucencies involving the distal root of the right maxillary fourth premolar tooth and the mesial root, palatal root, or both.

Radiographic findings of large well-defined circular radiolucencies of the crowns with loss of enamel and dentin supported a diagnosis of dental caries causing demineralization of the enamel and dentin.1,2 Dental caries lesions have distinctive radiographic characteristics depending on where they are found on the tooth surface. Early caries lesions involving the proximal surface of the tooth typically have a triangular shape with a broad base at the tooth surface. As the lesion deepens toward the pulp, a second radiolucent triangle with the base of the triangle toward the pulp cavity is often visible on radiographs.2 Dental caries lesions involving the buccal and lingual aspects of the tooth often develop as enamel pits and fissures. When small, these lesions are usually round; as they enlarge, they become elliptical or semilunar2 and typically have sharp, well-defined borders. Dental caries lesions involving the occlusal tooth surfaces, as seen in the dog described in the present report, commonly start on the sides of a fissure wall rather than at the base and tend to penetrate perpendicularly through the enamel and dentin. The classic radiographic appearance of a dental caries lesion extending into the dentin is a broad-based radiolucent zone, often beneath a fissure, with little to no apparent changes in the enamel. The deeper the occlusal lesion, the easier it is to detect on radiographs.2 In the dog described in the present report, the disease had progressed without the owner's knowledge and much of the enamel and dentin had been destroyed.

Treatment and Outcome

Treatment options considered for this patient were root canal treatment with restoration of the crown or surgical extraction. Because of the extent of hard tissue loss and endodontic disease, surgical extraction was elected.

A mucoperiosteal flap was raised. The buccal alveolar bone of the individual tooth roots was removed, and the teeth were sectioned to allow for elevation of the individual tooth roots. Synthetic absorbable suture material (5-0 poliglecaprone 25) was used to suture the repositioned flap. Postoperative dental radiographs were obtained to ensure complete extraction of the affected teeth. The patient was reevaluated 2 weeks after surgery. The surgical sites had completely healed, and the client stated that the halitosis and signs of oral pain had resolved.

Comments

Dental caries is a multifactoral disease involving interactions between 3 factors: the teeth, the microflora of the oral cavity, and the diet.2 It is caused by bacterial demineralization of the inorganic enamel layer and inorganic structures of the dentin. Plaque bacteria, which reside on the superficial surfaces of the teeth, use fermentable sugars (carbohydrates) from the diet as a source of energy,3 and changes in bacterial flora appear to be driven by changes in diet.4 Products of carbohydrate fermentation are acidic and can cause demineralization of enamel and dentin.5 Bacteria primarily involved in supragingival dental caries in people include Streptococcus mutans, Streptococcus sobrinus, and Lactobacillus spp.4 Dental caries lesions are most commonly found on the flat occlusal surfaces of the teeth, specifically the maxillary molar teeth and the distal aspect of the crown of the mandibular first molar tooth, in dogs.3

As was the case for the dog described in the present report, dental caries can be associated with signs of pain in dogs. Although the exact cause of pain in affected dogs is not known, 3 mechanisms have been proposed. The first is that dentin contains nerve endings that extend through tubules in the dentin from the pulp and that stimulation of these nerve endings results in pain. The second proposed mechanism for signs of pain in dogs with dental caries is that odontoblasts serve as receptors that are coupled to nerves in the pulp. The third proposed mechanism is that tubules in the dentin allow fluid to move through the dentin when a stimulus is applied and that this movement of fluid is registered by pulpal free nerve endings close to the odontoblasts.1

Progression of dental caries lesions causes demineralization of the enamel and dentin, allowing bacteria to enter the dentin tubules and, eventually, resulting in inflammation of the pulp. An important sequela of pulpitis is pulpal necrosis,6 which can result in periapical lesions.

Dental radiography should always be performed to confirm a tentative diagnosis of dental caries. In addition, dental radiography is crucial for assessing degree of endodontic involvement, which is important both for treatment planning and determining a prognosis.7 Dental radiographs should be of good quality and allow visualization of the entire tooth crown, at least 2 mm of alveolar bone surrounding each root apex, and if the tooth has multiple roots, all roots. Additional views may be necessary to evaluate the mesial and palatal roots of the right maxillary fourth premolar tooth, especially if endodontic treatment is being considered.

References

  • 1.

    Nanci A, Simmer JP & Smith AJ, et al. Dentin-pulp complex. In: Ten Cate's oral histology: development, structure, and function. 7th ed. St Louis: Mosby, 2008;232234.

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  • 2.

    White SC, Pharoah MJ. Dental caries. In: Oral radiology, principles and interpretation. 6th ed. St Louis: Mosby, 2009;270280.

  • 3.

    Hale FA. Dental caries in the dog. J Vet Dent 1998;15:7982.

  • 4.

    Ruby J, Goldner M. Nature of symbiosis in oral disease. J Dent Res 2007;86:811.

  • 5.

    Cawson RA, Binnie WH & Barrett AW, et al. Dental caries, its sequelae, and regressive changes to teeth. In: Oral disease. 3rd ed. St Louis: Mosby, 2001;3.23.11.

    • Search Google Scholar
    • Export Citation
  • 6.

    Gorrel C. Common oral conditions. In: Veterinary dentistry for the general practitioner. Philadelphia: Saunders, 2004;7778.

  • 7.

    Dupont GA, DeBowes LJ. Part three: radiographic evidence of pathology—miscellaneous conditions. In: Atlas of dental radiography in dogs & cats. St Louis: Saunders, 2009;226.

    • Search Google Scholar
    • Export Citation
  • Figure 1—

    Intraoral parallel view of the right mandibular first molar tooth (A) and intraoral bisecting angle view of the right maxillary fourth premolar and first molar teeth (B) in a 10-year-old dog examined because of chronic halitosis, decreased appetite of 2 weeks' duration, and signs of oral pain.

  • Figure 2—

    Same radiographic views as in Figure 1. On the view of the right mandibular first molar tooth (A), notice the well-defined circular radiolucencies involving the crown (white arrows) and the well-defined periapical lucency and loss of the lamina dura at the mesial root (black arrows). On the view of the right maxillary fourth premolar and first molar teeth (B), notice the circular radiolucencies in the distal aspect of the crown of the right maxillary fourth premolar tooth and the mesial aspect of the crown of the right maxillary first molar tooth (white arrows) and the periapical lucencies involving the distal root of the right maxillary fourth premolar tooth and the mesial root, palatal root, or both (black arrows).

  • 1.

    Nanci A, Simmer JP & Smith AJ, et al. Dentin-pulp complex. In: Ten Cate's oral histology: development, structure, and function. 7th ed. St Louis: Mosby, 2008;232234.

    • Search Google Scholar
    • Export Citation
  • 2.

    White SC, Pharoah MJ. Dental caries. In: Oral radiology, principles and interpretation. 6th ed. St Louis: Mosby, 2009;270280.

  • 3.

    Hale FA. Dental caries in the dog. J Vet Dent 1998;15:7982.

  • 4.

    Ruby J, Goldner M. Nature of symbiosis in oral disease. J Dent Res 2007;86:811.

  • 5.

    Cawson RA, Binnie WH & Barrett AW, et al. Dental caries, its sequelae, and regressive changes to teeth. In: Oral disease. 3rd ed. St Louis: Mosby, 2001;3.23.11.

    • Search Google Scholar
    • Export Citation
  • 6.

    Gorrel C. Common oral conditions. In: Veterinary dentistry for the general practitioner. Philadelphia: Saunders, 2004;7778.

  • 7.

    Dupont GA, DeBowes LJ. Part three: radiographic evidence of pathology—miscellaneous conditions. In: Atlas of dental radiography in dogs & cats. St Louis: Saunders, 2009;226.

    • Search Google Scholar
    • Export Citation

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