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DENTISTRY · August 20th, 2017

Dentigerous Cysts: More Common than You Think

Dentigerous cysts are a type of benign odontogenic cyst that are associated with impacted teeth. They are most commonly diagnosed in impacted mandibular 1st premolar teeth of brachycephalic breeds (Pugs, Boxers, Boston Terriers), although they can be seen in any impacted tooth of any breed (Figure 1). Significant bony destruction can occur secondary to expansion of the cyst, leading to disease of the neighboring teeth if they remain undiagnosed for a period of time. The pathogenesis is unknown, but they are thought to arise from proliferation of tissue remnants of the enamel organ.

How are dentigerous cysts diagnosed?

Clinically, dentigerous cysts can present as a large, fluctuant swelling, simply as a missing tooth, or as an incidental finding on whole mouth dental radiography. Radiographic features of dentigerous cysts are considered pathognomonic as the crown of the unerupted tooth will be enclosed by a radiolucent halo of variable size (Figure 1). Needle aspirate of the fluid, although not typically necessary for diagnosis, will reveal a brown tinged transudate.

FIGURE 1: An intraoral radiograph of the mandibular area of a 5-yr old MN Boston Terrier. The mandibular canine teeth are missing on the oral exam, but evident on the radiograph. The white arrows point out a widening of the periodontal ligament space surrounding the right and left mandibular 3rd incisors (303 and 403). There are impacted right and left mandibular canine teeth and left mandibular 1st molar tooth.
(Image courtesy of the Journal of Veterinary Dentistry, volume 29, NO 4; page 242)

Treatment

The treatment of a dentigerous cyst involves a surgical approach using a gingival flap to accomplish extraction of the impacted tooth, curettage of the cyst lining, and possibly a bone graft if the bony defect is extensive.

Step 1: Obtain pre-operative dental radiograph

Pre-operative radiograph of a missing. 1st premolar tooth in the left mandible of a 5 yr. old MN Boxer dog. The black circle outlines the cyst area. The 1st premolar is impacted and the second premolar affected by the expansion of the cyst.

Step 2: Make a wide gingival flap, allowing access to the affected area

Step 3: Extract the impacted tooth and any neighboring affected teeth with the use of appropriate burs on a water-cooled high-speed dental unit.

A wide gingival flap was created and the offending impacted first premolar tooth was extracted. The left mandibular second premolar (306) was also extracted, although not pictured here.

Step 4: Utilize bone graft material if indicated

An osteoallograft material (Periomix, Veterinary Transplant Services: vtsonline.com) was placed after curettage of the cyst lining to stimulate bone growth and to act as a scaffolding for bony remodeling.

Step 5: Obtain post-operative dental radiograph

A post-operative radiograph was taken to demonstrate complete extraction of the left 1st and second premolar teeth (305,306) and for medical records. The bone graft appears as radio-opaque material within the alveolus. Monitoring of the site, including the mandibular canine tooth is recommended in 6-12 months with dental radiography.

Step 6: Suture gingival flap

The gingival incision was sutured with 5-0 Monocryl in a simple interrupted pattern.

Significance

Untreated dentigerous cysts can lead to significant bone destruction with possible secondary pathologic fractures of the weakened bone, pulpitis of adjacent teeth, or malignant transformation of the cyst to a more aggressive disease…ameloblastoma or squamous cell carcinoma. Intraoral radiographs are therefore important to evaluate any missing teeth noted on oral examination. Early diagnosis is imperative and any impacted tooth should ideally be extracted to prevent the occurrence of this preventative destructive disorder.

Further Reading

Oral and Maxillofacial Surgery in Dogs and Cats: “Clinical Behavior and management of odontogenic cysts”; F Verstraete, M Lommer; Saunders Elsevier, 2012.

Journal of Veterinary Dentistry: “Endodontic Therapy of a Mandibular Canine Tooth with Irreversible Pulpits Secondary to
Dentigerous Cyst”; S MacGee; Vol 31, No 1, Spring 2014

This article was submitted by Dr. Laura Sasser, DVM. Questions? Please reach out to the Medical Advisory Board at MAB@nvanet.com.

The Medical Advisory Board

Special to NVA, our Medical Advisory Board functions as an expert board of veterinarians dedicated to improving the comfort and well being of patients by providing progressive veterinary care guidance.

Please reach out to them with questions or ideas on how they can help optimize your daily practice life. Email them at MAB@NVAnet.com.

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