History and Physical Examination Findings

An 8-year-old 6.5-kg (14.3-lb) spayed female Papillon was referred to a veterinary dental practice for evaluation and treatment of periodontal disease. Approximately 2 weeks prior to this examination, the patient was examined by its primary care veterinarian because of halitosis. A substantial amount of calculus and purulent discharge was noted at an unspecified caudal maxillary tooth at that time.

The dog was reported to have a regular activity level at home and was eating and drinking normally. The dog was bright, alert, and responsive; aside from the oral cavity, the general physical examination results were unremarkable. Results of a CBC and serum biochemical analysis were within the respective reference ranges. The dog was anesthetized, and full-mouth dental radiographs and periodontal charting were performed. Oral examination revealed a calculus index¹ of 3 of 3 for the caudal maxillary teeth and 1 to 2 of 3 for the remainder of the teeth. Teeth throughout the mouth were associated with a gingivitis index¹ of 1 to 2 of 3. Furcation involvement of the left mandibular second premolar tooth was stage 3.² No discolored teeth were observed. Selected photographs and radiographic views are provided (Figures 1 and 2).

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Photographs of the left maxillary second, third, and fourth premolar teeth (A) and left mandibular first, second, and third premolar teeth (B) of an 8-year-old spayed female Papillon that was referred to a veterinary dental practice for evaluation and treatment of periodontal disease.

Citation: Journal of the American Veterinary Medical Association 252, 1; 10.2460/javma.252.1.49

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Left lateral intraoral radiographic views of the left maxillary second, third, and fourth premolar teeth (A) and left mandibular first, second, and third premolar teeth (B) of the same dog as in Figure 1. The images were obtained with a bisecting angle technique.

Citation: Journal of the American Veterinary Medical Association 252, 1; 10.2460/javma.252.1.49

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Diagnostic Imaging Findings and Interpretation

Examination of dental radiographs revealed that the pulp cavity of the left maxillary third premolar tooth appeared larger than that of the adjacent teeth, consistent with nonvitality characterized by failure of physiologic dentin production³ (Figure 3). The apex of the mesial root of this tooth had evidence of external inflammatory resorption leading to a flattened apex and loss of the periodontal ligament space and lamina dura. A round, well-defined radiolucency was present in the bone, with the epicenter at the mesial root apex. These findings were suggestive of pulp necrosis and chronic apical periodontitis, consistent with a lesion of endodontic origin.⁴ A well-defined, rounded, radiolucent defect indicative of horizontal bone loss was detected overlying the distal root of the left maxillary third premolar tooth. Increased radiopacity of the bone between the left mandibular second premolar roots, consistent with sclerosis of trabecular bone secondary to chronic periodontitis, was evident. The pulp cavity of the left mandibular second premolar tooth appeared large relative to those of the adjacent teeth, suggesting nonvitality and failure of physiologic production of dentin in the pulp cavity owing to pulp necrosis.³

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Same radiographic views as in Figure 2. The pulp cavities of the left maxillary third premolar (A) and left mandibular second premolar (B) teeth (black arrows) appear larger than those of adjacent teeth, indicating a failure to narrow that was consistent with nonvitality. In panel A, a well-defined, round, periapical lucency (arrowheads) is present at the mesial root of the left maxillary third premolar tooth, and a well-defined, rounded radiolucent defect is present overlying the distal root (white arrows), indicating horizontal bone loss. In panel B, loss of bone (asterisk) is evident at the furcation of the left mandibular second premolar tooth.

Citation: Journal of the American Veterinary Medical Association 252, 1; 10.2460/javma.252.1.49

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Treatment and Outcome

All teeth were ultrasonically scaled above and below the gingival margin. As a result of semigeneralized, early to advanced periodontitis (stages 2 through 4)² diagnosed by clinical periodontal examination and evaluation of full-mouth radiographs, 10 teeth were extracted. The left maxillary third premolar and left mandibular second premolar teeth were among those extracted, largely because of nonvitality. Single-rooted teeth were extracted with a simple extraction technique.⁵ A surgical extraction technique was used for multirooted teeth.⁵ The patient had an uneventful recovery from anesthesia. The owners were instructed to feed soft food for 10 days at home. Meloxicam (an initial dose of 0.2 mg/kg [0.09 mg/lb], followed by 0.1 mg/kg [0.045 mg/lb], q 24 h, for a total of 7 days) was prescribed.

Oral examination of the conscious patient at a follow-up visit 2 weeks after surgery revealed appropriate healing of the extraction sites. At a 3-month follow-up (by telephone) with the clients, the dog was reported to be more playful than it had been prior to the dental procedure. The owners reported an in-home care routine of brushing the dog's teeth 3 to 4 times/wk.

Comments

Full-mouth radiography of dogs frequently reveals unexpected findings of clinical interest.⁶ The dog of this report was referred for evaluation of periodontal disease, and it had no clinical evidence of or known cause for nonvital teeth. The periodontal findings were only briefly described, as they were considered beyond the scope of this clinical report. Full-mouth radiography has been shown to be beneficial in veterinary patients with any clinical lesion,⁶ and this was exemplified by the unexpected finding of nonvital teeth in this Papillon. Minimal changes were evident on oral examination of the awake patient, compared with the radiographic findings, particularly in regard to the 2 nonvital teeth. These teeth did not appear overtly diseased or discolored from intrinsic staining on visual examination.

A relatively wider pulp cavity, compared with those of surrounding teeth, can be attributable to nonvitality of the tooth or internal inflammatory resorption. Internal inflammatory resorption results in distortion of the outline of the pulp cavity as the resorption process removes dentin from its walls.^3,7 The pulp cavities of the teeth in the dog of this report had a smooth, uniform appearance, consistent with pulp necrosis rather than internal resorption.

Necrosis of the pulp occurs secondary to irreversible pulpitis when damaged or diseased pulp is unable to heal itself.⁸ The pulp cavity fails to narrow as a result of death of the odontoblasts responsible for secondary dentinogenesis. Secondary dentin is formed after tooth eruption and is continually laid down within the pulp cavity throughout the life of a vital tooth, gradually reducing the size of the pulp cavity.^8,9 Pulp necrosis arrests tooth maturation, resulting in a pulp cavity inconsistent with the maturity of the animal. This is seen radiographically as a relatively wider pulp cavity, compared with those of the surrounding and contralateral teeth. Causes of pulp necrosis include infection, excessive forces from orthodontic movement, concussive forces from chewing hard objects, trauma, thermal injury, or long-term disruption of the blood supply.¹⁰

Whereas nonvital teeth are commonly discolored,¹⁰ the 2 teeth affected by pulp necrosis in this case were clinically normal in color, emphasizing the necessity of full-mouth dental radiography in combination with a thorough oral examination in veterinary patients. Treatment options for nonvital teeth with intact apices include endodontic therapy or exodontia, and treatment is determined on the basis of the periodontal health of the tooth, importance of the tooth, patient's overall health status, and client approval.⁵ The relative importance of the nonvital teeth in this patient was considered to be low, as the second and third premolar teeth in dogs are nonstrategic, nonesthetic teeth.¹¹ This, in combination with periodontitis, was indication for extraction of the nonvital left mandibular second premolar tooth. Extraction was also indicated for the left maxillary third premolar tooth, which was affected by chronic apical periodontitis and inflammatory root resorption in addition to pulp necrosis. Development of apical periodontitis follows total pulp necrosis, regardless of the cause of the necrosis.⁴ This persistent inflammation results in bone destruction surrounding the apex of the tooth and is seen radiographically as a periapical radiolucency (commonly) or a periapical radiopaque lesion (rarely).^4,12 Although microscopic examination is necessary to definitively identify chronic inflammation and granulation tissue, the radiographic findings of blunting of the tooth root and a well-defined periapical radiolucent lesion are supportive of chronic apical periodontitis and external inflammatory resorption.^4,13

External inflammatory resorption is among the most common types of tooth resorption in dogs, and its prevalence increases with age.¹³ This type of tooth resorption results in loss of dental structures and commonly occurs secondary to inflammation associated with endodontic disease, periodontal disease, or a combination of these conditions.¹³ In addition to inflammation, other causes of external inflammatory resorption include pressure (from erupting permanent teeth on primary teeth as well as intentional and unintentional orthodontic manipulation); chronic, low-grade infections; osteomyelitis; oral neoplasia (nonodontogenic tumors more so than odontogenic tumors); and certain systemic diseases.^14–17

The findings described for the left maxillary third premolar tooth in the dog of this report were consistent with endodontic disease. Lesions of endodontic origin involve inflammatory changes affecting the apex and apical periodontium of a nonvital tooth. In this dog, a pronounced endodontic lesion was appreciated on the mesial root of the left maxillary third premolar tooth and affected the root tip and surrounding structures. This tooth as well as the left mandibular second premolar tooth had evidence of arrested maturation, which is a sign of endodontic disease.

The endodontic changes identified radiographically were unexpected because the patient had no clinical evidence or known history to cause suspicion of nonvital teeth. The findings were clinically important and required appropriate treatment, illustrating the importance of full-mouth intraoral radiography in veterinary dental patients as a diagnostic tool complementary to comprehensive oral examination.