History and Physical Examination Findings
A 7-year-old 6.3-kg (13.8-lb) spayed female domestic shorthair cat was referred to our facility for dental examination and treatment. The client indicated that the cat had been adopted at 2 years of age and was anesthetized 3 weeks later for a dentistry procedure. No anesthetic complications during that procedure were noted in the medical record. Oral examination at that time had revealed a fractured left maxillary canine tooth without evidence of pulp exposure. Intraoral radiographs were not obtained.
Results of a general physical examination at the referral hospital were unremarkable. Oral examination revealed a fractured left maxillary canine tooth with approximately 1 mm of the most coronal extent of the crown missing on the basis of visual comparison with the contralateral tooth. The affected tooth was partially extruded, and approximately 3 mm of cementum was visible coronal to the gingival margin. The crown of the right maxillary third incisor tooth had stage 3 mobility1 and was easily detached from the root. The left maxillary third incisor tooth appeared to be missing.
Results of a CBC and serum biochemical analysis were within the respective reference limits. The cat was anesthetized, and intraoral occlusal and lateral radiographs of the right and left maxillary canine teeth were obtained by means of a bisecting angle technique with a size 2 digital sensor (Figure 1).
Intraoral occlusal radiographic view of the maxillary canine and incisor teeth (A) and lateral views of the left (B) and right (C) maxillary canine teeth of a 7-year-old 6.3-kg (13.8-lb) spayed female domestic shorthair cat. Images were obtained by means of a bisecting angle technique.
Citation: Journal of the American Veterinary Medical Association 242, 12; 10.2460/javma.242.12.1645
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Diagnostic Imaging Findings and Interpretation
Evaluation of radiographs revealed a normally developed right maxillary canine tooth, with sizes of the pulp cavity and dentin layer consistent with the age of the patient. The size of the pulp cavity of the left maxillary canine tooth was inconsistent with the age of the cat and was wider than the pulp cavity of the contralateral maxillary canine tooth (Figure 2), consistent with a nonvital tooth. The root apex of this tooth appeared blunted and irregular, with loss of the periodontal ligament space, consistent with apical external inflammatory root resorption. External inflammatory root resorption may occur as a result of endodontic disease, chronic periodontal disease, or a combination of both.2 The radiolucency noted in the apical alveolar bone was consistent with chronic periapical inflammation caused by endodontic disease. Evidence of external inflammatory resorption was also detected on the mesial aspect of the left maxillary canine tooth adjacent to an area of bone loss indicative of periodontitis. Severe vertical bone loss along the mesial and buccal aspects of the left maxillary canine tooth and mild vertical bone loss along the buccal aspect of the right maxillary canine tooth, consistent with periodontal disease, were observed. The right maxillary canine tooth was also found to have changes consistent with periodontitis.
Same occlusal radiographic view (A) and lateral radiographic view of the left maxillary canine tooth (B) as in Figure 1. In the occlusal view (A), the dentin layer of the left maxillary canine tooth appears thinner than the dentin layer of the right maxillary canine tooth and the pulp cavity of the left maxillary canine tooth (double arrow) appears wider than that of the right maxillary canine tooth. Evidence of external inflammatory root resorption with loss of periodontal ligament space is seen on the mesial aspect of the tooth root (black arrowhead). In the lateral view (B), the root apex has a blunted appearance (white arrow), consistent with apical external inflammatory root resorption. Notice the periapical radiolucency (black arrows) indicative of inflammatory bone resorption. Moderate vertical bone loss along the mesial, buccal, and palatal aspects of the left maxillary canine tooth evident in both views (white arrowheads) and vertical bone loss along the buccal aspect of the right maxillary canine tooth in the occlusal view (white arrowhead) are consistent with periodontal disease. In addition, most of the crown regions of the left and right maxillary third incisor teeth are absent (white asterisks). The roots of the left and right maxillary third incisor teeth and left maxillary second premolar tooth (black asterisk in panel B) have signs of advanced external replacement resorption.
Citation: Journal of the American Veterinary Medical Association 242, 12; 10.2460/javma.242.12.1645
Most of the crown of the left maxillary third incisor tooth and most of the root of the left maxillary second premolar tooth were absent. These lesions were considered unrelated to those affecting the left maxillary canine tooth. The crown of the right maxillary third incisor tooth was present on the lateral view but was not present on the occlusal view because it had been previously detached from the root. Loss of the periodontal ligament space associated with these 3 teeth and opacity of the tooth roots approaching the opacity of the surrounding bone was consistent with external replacement resorption.2,3
Treatment and Outcome
A detailed oral examination in the anesthetized cat revealed a complicated crown fracture of the left maxillary canine tooth in addition to the previously described findings. Pulp exposure was confirmed with a dental explorer. Periodontal probing depths of 3 mm on the palatal aspect of the left maxillary canine tooth and 2 mm on the buccal aspect of the right maxillary canine tooth were found. Left and right infraorbital nerve blocks were performed with 0.75 mg of bupivacainea at each site to provide regional anesthesia. Because of the severe external inflammatory resorption, root canal treatment was not indicated and the left maxillary canine tooth was surgically extracted via a standard technique.4
Odontoplasty and alveoplasty with intentional root retention were performed on the left and right maxillary third incisor teeth to prevent irritation of the overlying gingiva. Coronectomy of the left maxillary second premolar tooth was also completed.4 These 3 teeth had evidence of complete external replacement resorption,2 described as type 2 tooth resorption in the American Veterinary Dental College classification system, with an absence of the periodontal ligament space and root replacement by alveolar bone.1–3 Removal of the roots of affected teeth or adequate crown removal with intentional root retention was confirmed by evaluation of postoperative radiographs. Reexamination 14 days after treatment confirmed that the oral surgery sites had healed. The client reported the cat had a greatly improved appetite following oral surgery.
Comments
Occlusal radiographic views are useful to evaluate the maxillary incisor teeth, to compare the pulp cavity sizes of the maxillary canine teeth, and to examine the buccal aspects of the maxillary canine teeth for signs of periodontitis. Lateral views of the right and left maxillary canine teeth are required to accurately evaluate the periapical region without superimposition on the maxillary premolar teeth and to evaluate periodontal status at the mesial and distal aspects of the canine teeth.5
Bacteria can gain access to the pulp cavity of a tooth directly through the fracture site in the case of a complicated crown fracture or through the dentinal tubules in an uncomplicated crown fracture. This results in irreversible pulpitis and subsequent pulp necrosis. Bacterial toxins and inflammatory mediators that are produced exit the tooth through the apical delta and lateral canals, inducing an inflammatory reaction in the periapical bone.6 In the cat of the present report, the radiolucency around the apex of the left maxillary canine tooth was typical of chronic apical periodontitis.
A dental explorer held perpendicular to the tooth surface is used to detect pulp exposure. A fine dental explorer or magnification must be used for evaluation of feline teeth because the signs of pulp exposure are usually more subtle than in dogs. This is partially attributable to small tooth size in cats.7 In cats, the pulp cavity also extends to just beneath the crown tip, whereas mature dogs usually have several millimeters of enamel and dentin protecting the pulp cavity.8 In the cat of this report, it was possible that bacteria gained access to the pulp cavity through the dentinal tubules when the fracture first occurred if the initial lesion was an uncomplicated crown fracture as described in the medical records. It is also possible that pulp exposure was present, but not recognized, at the time of initial evaluation because of the small size of the pulp cavity at the coronal extent of the tooth.
Endodontic and periodontal disease may result in histologic changes to the tooth itself as well as to the tissues around the tooth. Inflammatory tooth resorption resulting from endodontic or periodontal disease,2 periapical bone resorption resulting from endodontic disease,9 and horizontal or vertical bone loss secondary to periodontal disease10 can be detected radiographically. Radiographic examination of the pattern of tooth resorption can be used to obtain a diagnosis and provide a treatment recommendation.2 In patients with endodontic disease, radiographic changes to the affected tooth may include external inflammatory resorption,2 accelerated apparent tooth development as occurs with pulpitis and internal inflammatory resorption,2,11 and signs of arrested development such as an open apex or relatively wide pulp cavity. Radiographic changes in adjacent tissues that may be associated with a lesion of endodontic origin include an increase in the periodontal ligament space, loss of lamina dura, periapical radiolucency in the immediate region, and changes in the trabecular bone pattern around the root apex.11 In addition to horizontal and vertical bone loss, radiographic patterns of periodontitis can include an increase in the width of the buccal alveolar bone, especially associated with the maxillary canine teeth in cats.10 With external inflammatory tooth resorption, there is loss of dental tissues adjacent to these areas of alveolar bone loss secondary to either endodontic or periodontal disease.11
Pulp necrosis in an immature tooth causes death of the odontoblasts, which are located in the periphery of the pulp tissue, with extensions into the inner portion of the dentin.12 Odontoblasts produce secondary dentin on the periphery of the pulp, resulting in a progressively smaller pulp cavity with age13; death of odontoblasts arrests the production of secondary dentin. Radiographically, this appears as a thinner dentin layer and a wider pulp cavity when compared with radiographs of the vital contralateral tooth. In the cat of the present report, the wider pulp cavity of the left maxillary canine tooth was consistent with a nonvital tooth in which development had ceased at an early age.
The cat of the present report had been evaluated for the fractured tooth under general anesthesia at a young age, and the potential clinical relevance of a crown fracture affecting the canine tooth of the cat was not recognized at the time. Clinicians should be aware that, in this species, a crown fracture of the most coronal extent of a maxillary or mandibular canine tooth often exposes the pulp cavity, resulting in a complicated fracture.7
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References
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8. Bellows J. Oral pathology. In: Feline dentistry. Singapore: Blackwell Publishing, 2010; 101–148.
9. Tanomaru-Filho M, Jorge EG, Duarte MAH, et al. Comparative radiographic and histological analysis of periapical lesion development. Oral Surg Oral Med Oral Pathol 2009; 107: 442–447.
10. Lommer MJ, Verstraete FJM. Radiographic patterns of periodontitis in cats: 147 cases (1998–1999). J Am Vet Med Assoc 2001; 218: 230–234.
11. DuPont GA, DeBowes LJ. Endodontic disease. In: DuPont GA, DeBowes LJ, eds. Atlas of dental radiography in dogs and cats. Philadelphia: WB Saunders Co, 2009; 142–171.
12. Lin L, Huang G. Pathobiology of the periapex. In: Hargreaves KM, Cohen S, eds. Pathways of the pulp. 10th ed. St Louis: Mosby Inc, 2011; 529–558.
13. DuPont GA, DeBowes LJ. Intraoral radiographic anatomy of the dog. In: DuPont GA, DeBowes LJ, eds. Atlas of dental radiography in dogs and cats. Philadelphia: WB Saunders Co, 2009; 5–80.
