Diagnostic Imaging in Veterinary Dental Practice

Robert A. Menzies Department of Clinical Studies-Philadelphia, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104

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Torbjörn S. Lundström Section of Large Animal Medicine and Surgery, Department of Clinical Sciences, Faculty of Veterinary Medicine, Swedish University of Agricultural Sciences, 75007 Uppsala, Sweden

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Alexander M. Reiter Department of Clinical Studies-Philadelphia, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104

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John R. Lewis Department of Clinical Studies-Philadelphia, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104

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History and Physical Examination Findings

A 2.5-year-old Standardbred gelding trotter was evaluated because of possible signs of oral discomfort during performance. The horse reportedly would shake its head during training and was not training to its usual standard. Signs of discomfort were also evident when the horse was eating. Previous dental treatments performed on the horse had been provided by a nonveterinary dental technician.

The horse was evaluated by the referring veterinarian for a problem with the right eye and a facial swelling overlying the right maxillary premolar teeth. Substantial resistance was felt when the right nasolacrimal duct was flushed by the referring veterinarian; however, the duct was patent. The horse was treated with antimicrobials and NSAIDs, but the facial swelling failed to resolve.

Abnormalities identified during a general physical examination included right-sided purulent nasal discharge, minor facial swelling overlying the right maxillary second premolar tooth, and mild irritation of the right eye with perilimbal hyperemia, conjunctivitis, and chemosis. No other clinically important abnormalities were noted. Oral examination revealed that the deciduous maxillary second premolar teeth had recently been exfoliated or extracted. A probe passed into the mesial and distal infundibula of the permanent right maxillary second premolar tooth failed to meet resistance within the length of the tooth. The horse responded to provocation tests (percussion and application of hot and cold stimuli) performed on the right maxillary second premolar tooth. Overly aggressive generalized odontoplasty had been performed on the molariform teeth, as evidenced by the amount of clinical crown removed. No other abnormalities were evident during the oral examination. Barium sulfate suspension (105% [wt/vol]; 58% [wt/wt]) was injected into the mesial infundibulum of the right maxillary second premolar tooth, and radiography was performed (Figure 1). At the time of radiography, the contrast solution was noted to discharge from the right eye.

Figure 1—
Figure 1—

Left dorsal–to–right ventral, oblique, extraoral radiographic view of the right maxilla of a 2.5-year-old horse evaluated because of possible signs of oral discomfort (A) and left rostrodorsal–to–right caudoventral, oblique, extraoral radiographic view of the right maxilla in the same horse following injection of contrast medium into the mesial infundibulum of the right maxillary second premolar tooth (B).

Citation: Journal of the American Veterinary Medical Association 240, 8; 10.2460/javma.240.8.949

Determine whether additional images are required, or make your diagnosis from Figure 1—then turn the page →

Diagnostic Imaging Findings and Interpretations

Examination of the left dorsal–to–right ventral, oblique, extraoral radiographic view (Figure 2) revealed a localized, focal, moderately sized intraosseous lesion of the right maxilla with its epicenter at the apex of the right maxillary second premolar tooth. An ill-defined, blending border with a subtle halo of sclerotic bone surrounded a predominantly radiolucent periapical lesion. There was widening of the periodontal space and loss of the lamina dura associated with the mesial aspect of the reserve crown of the second premolar tooth. No teeth appeared to be displaced. The deciduous right maxillary second premolar tooth was absent. The deciduous dentition of the right maxillary third and fourth premolar teeth and right mandibular second, third, and fourth premolar teeth was present.

Examination of the left rostrodorsal–to–right caudoventral oblique extraoral radiographic view obtained following administration of contrast material (Figure 2) revealed that the needle that had been used to deliver contrast material via the mesial infundibulum to the apex of the right maxillary second premolar tooth was bent dorsally. There was a moderately small, irregular accumulation of radiopaque material within the area that coincided with the periapical radiolucency seen on the survey radiographic view. A ribbon of contrast material extended caudally within the nasolacrimal duct from the caudal aspect of this area to the right orbit.

Figure 2—
Figure 2—

Same radiographic views as in Figure 1. On the left dorsal–to–right ventral, oblique, extraoral radiographic view obtained prior to injection of contrast medium (A), a periapical lucency of the right maxillary second premolar tooth is visible (black arrowheads). Notice the loss of lamina dura and surrounding osteosclerosis. The deciduous premolar dentition (black check marks) is identified. On the left rostrodorsal–to–right caudoventral, oblique, extraoral radiographic view obtained following injection of contrast medium into the mesial infundibulum of the right maxillary second premolar tooth (B), notice the deciduous premolar dentition (black check marks), orbit (white check mark), septum of the right maxillary sinus (short arrows), contrast medium within the right nasolacrimal duct (large arrows), periapical contrast medium deposition (small arrowheads), and needle hub of the syringe containing contrast medium (large arrowhead). Black P2 = Right maxillary second premolar tooth. Gray P2 = Right mandibular second premolar tooth. M1, M2, and M3 = Right maxillary first, second, and third molar teeth. P3 and P4 = Right maxillary third and fourth premolar teeth.

Citation: Journal of the American Veterinary Medical Association 240, 8; 10.2460/javma.240.8.949

Radiographic findings were most consistent with developmental and acquired abnormalities. The communication between the infundibulum and the common pulp chamber, as illustrated by the passage of contrast material via the infundibulum into the periapical region of the recently erupted, immature permanent right maxillary second premolar tooth, was most likely a developmental problem (but not a congenital one). The cause was most likely premature extraction of the deciduous dentition. The remaining radiographic abnormalities (ie, the periapical rarefaction and dacryocystogram) were most likely acquired. The ill-defined, mildly sclerotic border surrounding a moderately regular, predominantly radiolucent periapical intraosseous lesion with widening of the mesial periodontal space and loss of the lamina dura combined with the lack of displacement of the teeth and the minimal effect on tooth structure was suggestive of a chronic inflammatory process that was related to the common pulp chamber. The passage of contrast material from the periapical region of the second premolar tooth into the right nasolacrimal duct and caudally to the orbit demonstrated a communication between the periapical region and the nasolacrimal duct. Patency of the right nasolacrimal duct from the lacrimal sac to the nasal puncta could not be determined from these radiographic views. The cause of the right-sided nasal discharge was also not determined.

The most likely diagnosis was incomplete formation of the apical infundibula of the permanent right maxillary second premolar tooth (often referred to as patent infundibula), which resulted in a mixture of periapical rarefying and sclerosing osteitis, rupture of the nasolacrimal duct, dacryocystitis, and conjunctivitis. It is possible that the nasolacrimal duct was inadvertently ruptured as a result of being flushed, with the periapical inflammation causing functional stenosis and weakening of the duct. The radiographic appearance following injection of contrast material suggested that the periapical lesion was likely a periapical abscess or combined abscess and granuloma and was less likely to be a true periapical cyst or pseudocyst. Although differentiating between apical periodontitis and osteomyelitis by means of radiography can at times be difficult, the presence of osteomyelitis in the case described in the present report was less likely. A benign or malignant neoplastic process was considered to be unlikely.

Treatment and Outcome

With the horse sedated, the affected tooth was treated endodontically in a manner which has not yet been described in the literature. Penicillin G procaine (25,000 U/kg [11,400 U/lb], IM, q 24 h) was administered beginning the day before the procedure and continuing for 3 days after the procedure. The irritation of the right eye and right-sided nasal discharge resolved within 1 week after treatment. The performance problems were no longer evident when the horse returned to training, although follow-up radiographs were not obtained. Anecdotally, the horse remained free of clinical signs for at least 5 years following the procedure.

Comments

Development of the infundibular apex and deposition of infundibular cementum occur late in the development of the permanent maxillary premolar and molar teeth. Apical blood supply to the infundibular cementoblasts is believed to essentially cease with the formation of the infundibular apex. Once the infundibular apex has formed, the blood supply to the infundibular cementoblasts is predominantly maintained via the occlusal aspect of the tooth until it ceases with the loss of the deciduous dentition (in the case of the premolar teeth) or eruption into the oral cavity (in the case of the molar teeth). However, the apical blood supply may occasionally continue to support the infundibular cementoblasts for years after tooth eruption.1 The occlusal blood supply to the permanent maxillary premolar teeth is protected as long as the deciduous dentition is in place. Premature loss of the deciduous dentition, either through natural means or iatrogenic removal, results in disruption of the occlusal blood supply and allows ingress of oral bacteria and debris. Disruption of the cementoblast blood supply results in cemental hypoplasia, which may contribute to the apical movement of oral bacteria and debris. If disruption of the occlusal blood supply occurs early enough, ameloblastic and odontoblastic activity at the infundibular apex may also be compromised, resulting in an abnormal communication between the common pulp chamber and infundibulum, sometimes referred to as a patent infundibulum. It is important to note that the term patent infundibulum has also been used to describe infundibular cemental hypoplasia and infundibular caries, where there is no communication between the infundibulum and end-odontic system. It is suspected that premature extraction of the deciduous dentition results in iatrogenic damage. However, this is not the only process implicated in infundibular cemental hypoplasia because the maxillary molar teeth can be affected, despite not having deciduous dentition.1 It is possible for the molariform teeth in horses to develop apical periodontitis as a result of a communication between the infundibulum and periapical tissues without any involvement of the pulp horns or loss of their vitality.2

Owing to the close anatomic relationship between the apices of the maxillary premolar teeth and the nasolacrimal duct in young equids, secondary effects on the nasolacrimal and even ocular system have been reported with periapical disease.3–5 It is likely that periapical disease results in inflammation or compression of the nasolacrimal duct and subsequent stenosis.3 Rupture of the nasolacrimal duct and ascending infection to the eye are not common.

Barium sulfate was used as the contrast medium for the horse of the present report. Another option would have been to use a nonionic iodine-based contrast material, which may have had some potential advantages.6 Communication between the infundibula and periapical region of the maxillary second premolar tooth in a 2.5-year-old horse was likely to be due to premature deciduous tooth exfoliation and subsequent eruption of the permanent tooth and unlikely to be due to the presence of carious lesions.

Failure of endodontic treatment would result in persistent apical periodontitis and possibly osteomyelitis. Failure may be subclinical or result in relapse of clinical signs. Oral examination findings could include pulp exposure, communication between an infundibulum (or both infundibula) and the periapical region, or an intraoral draining sinus tract. Ideally, the treatment of end-odontic disease should be assessed long term by means of diagnostic imaging such as radiography or CT. The true status of endodontic and apical periodontal health can only be determined by use of histologic examination and microbiological studies. Ongoing monitoring of endodontically treated teeth with communications between the infundibula and periapical region is important and recommended at 1, 3, and 6 months, then every 12 to 18 months. Such monitoring should involve a detailed anamnesis, physical examination, thorough oral examination with the animal sedated, radiography, and any additional diagnostic procedures indicated.

References

  • 1.

    Fitzgibbon CM, Du Toit N, Dixon PM. Anatomical studies of maxillary cheek teeth infundibula in clinically normal horses. Equine Vet J 2010; 42:3743.

    • Search Google Scholar
    • Export Citation
  • 2.

    Dacre I, Kempson S, Dixon PM. Pathological studies of cheek teeth apical infections in the horse: 5. Aetiopathological findings in 57 apically infected maxillary cheek teeth and histological and ultrastructural findings. Vet J 2008; 178:352363.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 3.

    Dixon PM, Tremaine WH, Pickles K, et al. Equine dental disease part 4: a long-term study of 400 cases: apical infections of cheek teeth. Equine Vet J 2000; 32:182194.

    • Search Google Scholar
    • Export Citation
  • 4.

    Ramzan PH, Payne RJ. Periapical dental infection with nasolacrimal involvement in a horse. Vet Rec 2005; 156:184185.

  • 5.

    Cleary OB, Easley JT, Henrisen MdL, et al. Purulent dacryocystitis (nasolacrimal duct drainage) secondary to periapcial tooth root infection in a donkey. Equine Vet Educ 2011; 23:553558.

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

    Eggli KD. The newer radiographic contrast media. Clin Pediatr (Phila) 1992; 31:554558.

  • Figure 1—

    Left dorsal–to–right ventral, oblique, extraoral radiographic view of the right maxilla of a 2.5-year-old horse evaluated because of possible signs of oral discomfort (A) and left rostrodorsal–to–right caudoventral, oblique, extraoral radiographic view of the right maxilla in the same horse following injection of contrast medium into the mesial infundibulum of the right maxillary second premolar tooth (B).

  • Figure 2—

    Same radiographic views as in Figure 1. On the left dorsal–to–right ventral, oblique, extraoral radiographic view obtained prior to injection of contrast medium (A), a periapical lucency of the right maxillary second premolar tooth is visible (black arrowheads). Notice the loss of lamina dura and surrounding osteosclerosis. The deciduous premolar dentition (black check marks) is identified. On the left rostrodorsal–to–right caudoventral, oblique, extraoral radiographic view obtained following injection of contrast medium into the mesial infundibulum of the right maxillary second premolar tooth (B), notice the deciduous premolar dentition (black check marks), orbit (white check mark), septum of the right maxillary sinus (short arrows), contrast medium within the right nasolacrimal duct (large arrows), periapical contrast medium deposition (small arrowheads), and needle hub of the syringe containing contrast medium (large arrowhead). Black P2 = Right maxillary second premolar tooth. Gray P2 = Right mandibular second premolar tooth. M1, M2, and M3 = Right maxillary first, second, and third molar teeth. P3 and P4 = Right maxillary third and fourth premolar teeth.

  • 1.

    Fitzgibbon CM, Du Toit N, Dixon PM. Anatomical studies of maxillary cheek teeth infundibula in clinically normal horses. Equine Vet J 2010; 42:3743.

    • Search Google Scholar
    • Export Citation
  • 2.

    Dacre I, Kempson S, Dixon PM. Pathological studies of cheek teeth apical infections in the horse: 5. Aetiopathological findings in 57 apically infected maxillary cheek teeth and histological and ultrastructural findings. Vet J 2008; 178:352363.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 3.

    Dixon PM, Tremaine WH, Pickles K, et al. Equine dental disease part 4: a long-term study of 400 cases: apical infections of cheek teeth. Equine Vet J 2000; 32:182194.

    • Search Google Scholar
    • Export Citation
  • 4.

    Ramzan PH, Payne RJ. Periapical dental infection with nasolacrimal involvement in a horse. Vet Rec 2005; 156:184185.

  • 5.

    Cleary OB, Easley JT, Henrisen MdL, et al. Purulent dacryocystitis (nasolacrimal duct drainage) secondary to periapcial tooth root infection in a donkey. Equine Vet Educ 2011; 23:553558.

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

    Eggli KD. The newer radiographic contrast media. Clin Pediatr (Phila) 1992; 31:554558.

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