History and Physical Examination Findings
An 18-month-old 22.7-kg (50.0-lb) spayed female mixed-breed dog was evaluated because of halitosis and generalized abnormally shaped teeth. The dog had been adopted from a shelter 7 months earlier, and history prior to this time was unknown. The owner reported that the dog was otherwise healthy, did not have any signs of difficulty or pain related to prehension or mastication, and had been seen chewing on wooden sticks and rawhide bones without signs of discomfort.
Results of a general physical examination were unremarkable. Oral examination revealed mild to moderate plaque and calculus accumulation, mild gingivitis, and a missing right maxillary canine tooth. There was relative mandibular prognathism without trauma to soft tissues. Severe, shallow, brown enamel defects consistent with a clinical diagnosis of enamel hypoplasia were evident on all teeth (Figure 1).
Photograph of the maxillary incisor teeth in a dog examined because of halitosis and abnormally shaped teeth. Notice the discolored and irregular surface of the crowns consistent with enamel hypoplasia.
Citation: Journal of the American Veterinary Medical Association 235, 3; 10.2460/javma.235.3.271
Results of a CBC, serum biochemical profile, and urinalysis were within reference limits. The dog was anesthetized, and intraoral radiography and periodontal charting were performed. Selected radiographic views are provided (Figure 2).
Occlusal radiographic view of the rostral portion of the maxilla (A) and lateral radiographic views of the left maxillary canine tooth (B) and caudal portion of the left mandible (C) in the dog in Figure 1.
Citation: Journal of the American Veterinary Medical Association 235, 3; 10.2460/javma.235.3.271
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Diagnostic Imaging Findings and Interpretation
Oral radiography revealed generalized enamel and dentin defects and abnormally small roots (Figure 3) consistent with generalized enamel, dentin, and root hypoplasia. Diastemata (pathologic spaces) were evident between the right and left mandibular third and fourth premolar teeth and between the left mandibular first and second molar teeth. Periapical lucencies ranging from mild to severe were observed at the mandibular and maxillary incisor teeth and at the right mandibular third premolar tooth. Because the origin of these periapical lesions could not be determined, they were classified as type 3 periodontal-endodontic lesions1 and were considered to most likely have been a result of endodontal and periodontal diseases that may have developed independently. Affected incisor teeth had little to no remaining root structure, likely as a result of arrested root development causing root hypoplasia in combination with inflammatory root resorption associated with the type 3 periodontal-endodontic lesions. Several of the other teeth had evidence of early periodontitis with radiographic widening of the periodontal ligament space at the alveolar margin as well as interdental scalloping (ie, mild horizontal bone loss). Additionally, there was a complicated crown-root fracture of the right maxillary canine tooth with a missing coronal fragment but no evidence of a periapical lesion.
Same radiographic views as in Figure 2. On the occlusal radiographic view of the maxilla (A), notice the periapical lucency involving the left maxillary first incisor tooth (black arrow). Other lucencies are evident at the right maxillary first and second incisor teeth. The edge of the root of the left maxillary first incisor tooth is irregular (white arrow), consistent with inflammatory root resorption, and the pulp cavity is wider than normal, consistent with pulp necrosis. The roots of all the maxillary incisor teeth are abnormally small. The crown of the right maxillary canine tooth is missing. On the lateral radiographic view of the left maxillary canine tooth (B), there is abrupt narrowing at the cervical region of the left maxillary canine tooth (white arrows) and wedge-shaped widening of the periodontal ligament space, indicating early periodontitis. Notice the abnormally short and narrow appearance of the roots of the canine tooth and the first and second premolar teeth. On the radiographic view of the caudal portion of the left mandible (C), notice the irregular surfaces of the crowns of the left mandibular fourth premolar and first molar teeth, consistent with enamel hypoplasia (white arrows) and the abnormally small roots, consistent with root hypoplasia (black arrows). Periodontitis is evident as scalloping between the first and second molar teeth as well as widening of the periodontal ligament space at the mesial root of the second molar tooth.
Citation: Journal of the American Veterinary Medical Association 235, 3; 10.2460/javma.235.3.271
Treatment and Outcome
All teeth were ultrasonically scaled above and below the gingival margin and air-polished. Several teeth were extracted, along with the fractured root of the right maxillary canine tooth, either because of radiographic evidence of type 3 periodontal-endodontic lesions or because they were found to have excessive probing depths and mobility > 0.5 mm during periodontal charting. All remaining teeth with enamel hypoplasia lesions were treated with a light-cured flowable composite. The owner was advised to not allow the dog to chew hard toys or bones and to have the dog examined every 6 to 12 months by a veterinary dentist.
Comments
Enamel hypoplasia refers to a disturbance in the formation of a tooth leading to macroscopically visible defects in the enamel. Dentinal defects, or dentinal dysplasia, are characterized by abnormal dentin formation following the initial deposition of mantle dentin. This results in abnormally short or absent roots and a narrow pulp chamber (shell teeth).2 Root hypoplasia has rarely been reported in dogs with severe enamel hypoplasia.3 Clinical and radiographic findings for the dog described in the present report were consistent with descriptions of odontodysplasia in humans.2,4 Odontodysplasia refers to an imperfect development of the enamel and dentin of the teeth. A variety of genetic, infectious, and nutritional factors have been reported as possible causes for enamel and dentin disturbances,4–6 with distemper virus infection consistently reported as the most common cause of generalized enamel and dentin hypoplasia in dogs. Other etiologies, however, have also been suggested, including nonspecific bacterial or viral infection, nutritional factors, toxicoses, and trauma.7–10 It was not possible to identify the underlying cause in the dog described in the present report. However, given that the dog had been obtained from a shelter and that its medical history was unknown, it is plausible that distemper may have played a role in the disease process.
The extent of the abnormalities involving the crowns and roots of the teeth in the dog described in the present report indicated that the inciting cause occurred during the bell stage of tooth development. If distemper virus infection was indeed the underlying cause, then it is most likely that infection would have occurred at approximately 15 weeks of age.11,12
Several of the teeth in the dog described in the present report were mobile and had various degrees of periodontal disease. We believe that teeth with enamel, dentin, and root hypoplasia are predisposed to periodontitis because the crowns and the crevices that result from the abrupt narrowing at the cervical region are more likely to retain plaque. It was difficult to determine whether endodontic abnormalities in this dog developed secondary to the periodontal disease or because of dentin hypoplasia resulting in an external communication with the pulp. We opted to restore all lesions with a flowable composite to cover any exposed dentin, which may have been sensitive, and to establish smooth crown surfaces in an effort to reduce plaque retention.
References
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