A ten year old Maltese terrier cross was referred to North Coast Veterinary Specialists and Referral Centre with a 6 month history of bilateral jaw swelling caudal to his mandibular canine teeth.
A full COHAT (comprehensive oral health assessment and treatment) was performed which consists of a whole body examination including organ function tests in an elderly patient, extraoral, intraoral examination and radiographs under general anaesthetic. From this a comprehensive treatment plan can be formulated and presented to the owner.
An extraoral conscious examination revealed a sharp bony mass on the ventral cortex of the right mandible, caudal to the mandibular canine tooth on that side.There was a labial and crestal bony deficits palpable on both sides of the mandible caudal to the canine teeth. An intraoral examination revealed missing 1st premolar teeth (305/405) on both sides of the mandible. The unerupted 405 had been extracted previously by the referring veterinarian. However, even with the extraction of the unerupted tooth, jaw swelling continued in this area. There was obvious intraoral swelling of both rostral mandibles (worse on the left side) and there was a caseous and purulent discharge from the left side swelling which drained through a mucosal sinus opening at the level of and ventral to the third premolar tooth (307).
A diagnosis (based on the breed and clinical findings) of bilateral dentigerous cyst was made. This diagnosis had been made previously based on intraoral radiographs that the referring veterinarian had taken.
Dentigerous cysts are developmental cystic lesions (classified as odontogenic cysts) often which are epithelial lined of about 3-4 cell thickness. Often the cyst lining is difficult to remove completely due to its thinness. The cyst epithelium is attached to an unerupted tooth at the level of the cemento-enamel junction of that tooth. They are slow growing, fluid filled and in the case of this dog, most likely to have been present for many years. They often cause pressure necrosis of the surrounding bone as they expand in size.In humans, they are often associated with unerupted wisdom teeth, and the cyst expansion causes fracturing of the buccal cortical plate of bone (so called egg shell cracking). These cystsare reasonably common in small breeds, but also in Boxer and Boxer cross dogs.I have seen these cysts penetrate the lingual plate of bone in the rostral mandible leading to jaw fracture. They are often associated with unerupted 1st premolar teeth. It is prudent, as the primary clinician, to always radiograph young dogs with missing 1st premolar teeth, due to frequent incidence of dentigerous cysts in the dog population.
A treatment plan was formulated for this dog, based on the intraoral radiographic findings. (Image 1 – Impacted Dental Cyst).
The dog was scheduled to have both cysts removed as well as extraction of the unerupted tooth (305) and other premolar teeth (306/307/406) that had been periodontally undermined by the cyst expansion. More intraoral radiographs were taken to assess the vitality of the canine teeth. Extraction of these teeth would further weaken and compromise the fragile rostral mandible and make it prone to iatrogenic or a later pathological fracture. The owners were thoroughly warned of jaw fracture. Fortunately, because these cysts are slow growing, the blood and nerve supply to the canine teeth is often preserved. In this case, intraoral radiographs confirmed that there was no apical lysis (apical periodontitis) occurring around these teeth. If these teeth were non vital, then root canal treatment could be performed at the same time as the cyst removal.
After the cyst lining was removed by mainly curettage and debridement and the use of special slow speed burs, and because there was a significant loss of bone in the rostral mandible, a synthetic bone graft (Hydroxyapatite and Tricalcium phosphate mixture-Synergy made by Veterinary Transplant Services Inc.) combined with a platelet rich fibrin graft (using the patient’s own blood- plain tube spun at 2700 RPM for 12 minutes) was placed into the bony deficit. (Image 2 – Cyst Bone Grafting)
The overlying gingival tissues were sutured with simple interrupted absorbable 4/0 suture to contain the graft material. The dog was discharged that same day and the owners were advised on giving a soft diet (no bones or dry biscuits). The owners were also advised to attend regular follow ups to monitor his progress. Normally, 6 months post-surgery,the doghas themandible re X-rayed to look for new bone growth in the rostral mandible and to make certain there is no recurrence of the cyst and no loss of vitality in the mandibular canine teeth and no jaw instability.