Diagnostic Imaging in Veterinary Dental Practice

Jennifer Tjepkema Pacific Coast Veterinary Dentistry, 511 Saxony Pl, Ste 100, Encinitas, CA 91941.

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History and Physical Examination Findings

An 8-month-old 2.3-kg (5.06-lb) neutered male Bolognese dog was evaluated because of a suspected unerupted right mandibular canine tooth. Apparent absence of the tooth was first observed when the patient was neutered 2 months prior to this evaluation. At that time, the left mandibular canine tooth had also failed to erupt. The referring veterinarian observed no other apparently missing teeth, but a class III malocclusion (relative mandibular prognathism) was present, and examination by a veterinary dental specialist was recommended.

On examination, the patient was bright, alert, and responsive. There was no history of systemic disease, and the patient was receiving no medications. Results of hematologic analysis at the time of neutering, including a CBC, serum biochemical analysis, prothrombin time, and partial thromboplastin time were within the respective reference ranges. Oral examination revealed a persistent deciduous right mandibular second premolar tooth with no permanent counterpart clinically apparent. Additionally, the right mandibular canine tooth, both mandibular first premolar teeth, the left mandibular first molar tooth, and both mandibular third molar teeth were nonapparent. The left mandibular canine tooth was partially erupted. There was a focal gingival bulge over the left mandibular first molar tooth (Figure 1). The crown of the left mandibular first molar tooth was palpable beneath the gingiva. All remaining permanent dentition had fully erupted. Class III malocclusion was confirmed.

Figure 1—
Figure 1—

Photograph depicting the partially erupted left mandibular first molar tooth of an 8-month-old Bolognese dog that was evaluated because of a suspected unerupted right mandibular canine tooth and had multiple missing or suspected unerupted teeth identified on oral examination. Notice the gingival bulge overlying the crown of the left mandibular first molar tooth (arrow).

Citation: Journal of the American Veterinary Medical Association 250, 8; 10.2460/javma.250.8.847

The patient was anesthetized for complete oral examination and full-mouth dental radiography. Intraoral dental radiographs were obtained with size 2 photostimulable phosphor plates and bisecting angle and parallel techniques. Selected radiographs are provided (Figure 2).

Figure 2—
Figure 2—

Intraoral radiographs showing regions of missing teeth in the same dog as in Figure 1. Views of the rostral aspects of the right (A) and left (B) mandibles were obtained with a bisecting angle technique. Views of the caudal aspects of the right (C) and left (D) mandibles were obtained with a parallel technique.

Citation: Journal of the American Veterinary Medical Association 250, 8; 10.2460/javma.250.8.847

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Diagnostic Imaging Findings and Interpretation

Examination of the radiographs revealed that the right mandibular canine tooth and both mandibular first premolar teeth were unerupted (Figure 3). Multiple teeth (the permanent right mandibular second premolar tooth and both mandibular third molar teeth) were missing. The deciduous right mandibular second premolar tooth was present.

Figure 3—
Figure 3—

Same radiographic images as in Figure 2. A—The right mandibular canine tooth (single arrow) and first premolar tooth (asterisk) are unerupted, and mesioversion of the crowns is evident. The deciduous right mandibular second premolar tooth (double arrows) is present. B—The left mandibular canine tooth is partially erupted and has mesioversion; notice alveolar bone coronal to the cementoenamel junction of the distal aspect of this tooth (double arrows). The left mandibular first premolar tooth is unerupted and has mesioversion (single arrow). C—The right mandibular first molar tooth is fully erupted, and the right mandibular third molar tooth is missing. The right mandibular fourth premolar tooth is present (arrow), but the diastema is wide between the right mandibular first molar and fourth premolar teeth. D—The left mandibular first molar tooth is partially erupted through the alveolar bone; a thin layer of alveolar bone is present coronal to the mesial and distal cusps of the tooth (single arrows), and dilaceration of the mesial root (double arrows) is evident. The left mandibular fourth premolar tooth is present, but the diastema between the right mandibular first molar and fourth premolar teeth is wide.

Citation: Journal of the American Veterinary Medical Association 250, 8; 10.2460/javma.250.8.847

The crowns of the mandibular canine and mandibular first premolar teeth were directed mesially toward the third incisor teeth. The left mandibular canine tooth was partially erupted, with alveolar bone evident on its distal aspect coronal to the cementoenamel junction. The left mandibular first molar tooth was partially erupted through the alveolar bone, and a thin layer of radiopaque alveolar bone was evident coronal to the mesial and distal cusps of this tooth (Figure 3).

Both mandibular canine teeth still had open apices (Figure 3). All remaining permanent dentition had normally developed root apices. The mesial root of the partially erupted left mandibular first molar tooth had abnormal curvature (ie, dilaceration). In contrast, both roots of the fully erupted right mandibular first molar tooth were radiographically normal.

Treatment and Outcome

Treatment options were discussed with the owners after oral examination and dental radiography were performed. Considering the potential for development of dentigerous cysts, options discussed with the owners included extraction of the unerupted teeth or yearly radiographic monitoring.1–3 The owners elected to have both mandibular first premolar teeth and the right mandibular canine tooth extracted. Because the left mandibular canine tooth was only partially erupted and apexogenesis was not complete, there was the concern that if its eruption did not continue, pericoronitis and periodontitis would develop.3 The owners elected monitoring of this tooth with plans for extraction if the aforementioned conditions developed.

Tooth-sparing treatment options for the left mandibular first molar tooth were discussed. Removal of the overlying gingiva with crown lengthening was proposed.3,4 On the basis of the patient's age and radiographic evidence of apexogenesis, there was a concern that this tooth might not continue to erupt, although some reports3,4 have indicated this can occur in young dogs after apical closure. The goal of the proposed treatment was to provide conditions that could enable continued eruption of the tooth and minimize the risk of pericoronitis and periodontitis. Radiographic monitoring of this tooth in lieu of prompt treatment was not advised owing to concerns about soft tissue trauma to the overlying gingiva from the left maxillary fourth premolar tooth or first maxillary molar tooth.3 Orthodontic extrusion of the left mandibular first molar tooth5 was also discussed but was declined by the owners, with crown lengthening and gingivectomy elected instead.

The procedure was performed with the patient under general anesthesia and placed in dorsal recumbency. Surgical extraction of the right mandibular canine tooth and both mandibular first premolar teeth was performed.6 The persistent deciduous right mandibular second premolar tooth was also extracted to allow surgical access to the right mandibular canine and first premolar teeth.

Periosteal elevators were used to remove the gingiva overlying the left mandibular first molar tooth after an oval incision with a No. 15c scalpel blade was made over the crown.3 A full-thickness mucoperiosteal flap was created to allow alveolar bone removal over the mesial and distal cusps of the left mandibular first molar tooth by use of a round, medium-coarse diamond bur.3 The left mandibular second molar tooth hindered bone removal overlying the distal aspect of the crown and flap closure, and the owners authorized extraction of this tooth as well. The flap was positioned apically and sutured closed with absorbable suture in a simple interrupted pattern. Histologic examination of the excised tissue was recommended but was declined by the owners.

The patient recovered uneventfully from anesthesia and was discharged from the hospital the same evening. Postoperative analgesic treatment included meloxicam (0.1 mg/kg [0.05 mg/lb], PO, q 24 h) and tramadol hydrochloride (3.0 mg/kg [1.4 mg/lb], PO, q 8 to 12 h) for 3 to 5 days. The owners were instructed to feed soft food and enforce strict mouth rest (eg, no access to chew toys) until the recommended postsurgical recheck examination 2 weeks later. Follow-up with dental radiographs in 6 months was also recommended; however, the patient was not returned for any of the recommended postsurgical evaluations.

Comments

The case described here exemplified the importance of obtaining full-mouth dental radiographs when multiple dental anomalies are present. Multiple teeth were not clinically apparent during oral examination. If it was assumed that the apparently missing permanent teeth had not developed, future complications such as dentigerous cyst formation or trauma to the soft tissue overlying the left mandibular first molar tooth could have resulted.1–3 Early detection and resolution of potential physical barriers that could hinder tooth eruption in puppies is important.

In dogs, replacement of deciduous teeth by permanent teeth typically occurs between 3 and 7 months of age.4,7,8 Each tooth develops and erupts independently of the others,2,8,9 but these changes occur simultaneously.9

The mechanisms that control tooth eruption are very complex and not fully understood. However, it is known that there must be a path or space available into which a tooth can erupt.3,4,9 When a physical barrier such as adjacent teeth, bone, or soft tissue prevents eruption, this is known as tooth impaction3,7,9; when there is no physical barrier, the tooth is in its normal position, and the tooth germ is intact but eruption does not take place, this is known as primary tooth retention.3,7,9 In dogs, tooth impaction is further described as soft tissue or bony impaction, according to the type of apparent barrier to eruption.3,7,9 It has been hypothesized that gingiva can act as a soft tissue barrier preventing tooth eruption in dogs.3,7,8 This tissue is typically thought to be tough and fibrous.3,7,9 However, despite this speculation, there is no evidence that this tissue actually impedes eruption, and the process may be impeded for other reasons, such as loss of eruption potential.3

Potential physical barriers that could have resulted in tooth impaction in the dog of this report included mesioversion of teeth, persistence of overlying bone, and presence of overlying gingiva. In this case, it was unknown whether the gingiva overlying the left mandibular first molar tooth was thickened or normal because histologic examination was not pursued.

Tooth eruption in young dogs typically continues until the apex is closed; although eruption can continue without the need of orthodontic extrusion after the apex has formed, this is less common.3,4 The referring veterinarian recommended immediate follow-up with a dental specialist when missing or unerupted teeth were first observed in the dog of this report (at the time of neutering). If surgery had been pursued at that time, the potential physical barriers hindering eruption could have been removed prior to apexogenesis, and this could have influenced the subsequent eruption of some teeth. However, there was a 2-month delay in pursuing treatment, and whether this may have affected the patient's outcome is unknown because the patient was lost to follow-up. It is critical to recognize and diagnose failure of permanent dentition to erupt when deciduous teeth are exfoliating and permanent dentition is erupting. Treatment planning is time sensitive and can be affected by the patient's age.

References

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