Managing challenging oral cases in dogs: part II (Proceedings)
Unusual oral lesions that may require surgical treatment include: osteomyelitis and bone sequestra, dentigerous cyst, mucoceles, lip avulsions inability to open or close the mouth, management of electrical cord injuries and severe tongue lesions requiring partial glossectomy.
Osteomyelitis and bone sequestra occur infrequently in dogs and cats and may be a complication of advanced periodontal disease, extraction complications or maxillofacial fractures. Several cases of severe osteomyelitis with secondary necrosis of bone have occurred in Cocker Spaniels and less frequently in other breeds. These animals are usually presented for examination because of fetid breath, severe oral pain, facial swelling, reluctance or inability to eat and have severe purulent nasal discharge if the osteomyelitis or bone sequestra are located in the maxilla. Dental radiography is performed to assist in the diagnosis. All necrotic bone and teeth in necrotic bone must be removed and the surrounding bone must be curettaged to the level of healthy, bleeding bone. Intraoperative samples should be collected and submitted for bacterial culture and sensitivity testing. Samples of tissue should also be submitted for histopathologic examination to rule out the possibility of an underlying neoplasia. The surgical site should be liberally flushed with sterile saline and closed with a mucoperiosteal flap using 3-O PDS in a simple interrupted pattern.
Dentigerous cysts occur infrequently in dogs, however, the diagnosis of dentigerous cysts should be a primary consideration in young dogs presenting with fluid filled oral swellings. Additionally, the possibility of an iatrogenic dentigerous cyst must be considered in those dogs in which a deciduous tooth was extracted or a traumatic episode had occurred in a puppy and subsequently the permanent tooth fails to erupt. Definitive diagnosis of a dentigerous cyst is based on history, physical examination, radiography, and histopathologic examination. Dentigerous cysts arise from the cellular components of the developing dental follicle. The cyst contains one or more embedded teeth and usually surrounds the coronal aspect of the tooth. As the tooth bud continues to develop but fails to erupt, the cyst becomes filled with fluid. Fluid pressure within the cyst results in a smooth-bordered radiolucent cavity typically adjacent to the cementoenamel junction as viewed radiographically. The treatment of a dentigerous cyst usually involves surgical extraction of the affected tooth and thorough removal of the entire epithelial lining of the cyst wall which is submitted for histopathologic examination. Complete excision of the tooth and the cystic epithelium is curative.There are four pairs of major salivary glands in the dog and cat. The major salivary glands are: the parotid, mandibular, sublingual, and zygomatic salivary glands.
The parotid salivary gland is located at the base of the auricular cartilage. The parotid duct is formed by 2 or 3 short radicles and passes lateral to the masseter muscle. It enters the oral cavity opposite the maxillary fourth premolar. The mandibular salivary gland is located at the junction of the maxillary and linguofacial veins. It is covered by a dense capsule. The mandibular duct leaves the medial surface of the gland and courses between the masseter muscle and mandible laterally and the digastricus muscle medially and then passes over the digastricus muscle laterally. The mandibular duct enters the mouth on a papilla lateral to the rostral end of the frenulum. The sublingual salivary glands consist of a caudal portion located at the rostral pole of the mandibular gland and a rostral portion which lies directly below the oral mucosa lateral to the tongue. The sublingual salivary duct originates at the caudal portion of the gland and accompanies the mandibular duct to a common or separate opening on the papilla at the rostral end of the frenulum. The zygomatic salivary glands are located ventral to the zygomatic arch. They are found only in carnivores. The major zygomatic duct opens about one centimeter caudal to the parotid papilla on a ridge of mucosa and minor ducts open on this ridge caudal to the major duct. In addition to the major salivary glands, there are small clusters of seromucus secretory units in the submucosa of the oral cavity known as minor salivary glands. These minor salivary glands are named according to their location (lingual, labial, buccal, palatine).
Salivary mucoceles or sialoceles result from damage to the duct or gland with leakage of saliva into the surrounding tissues. Salivary mucoceles are lined by inflammatory connective tissue and do not have an epithelial lining that is present in cysts. The cause of salivary mucoceles is rarely identified, although blunt trauma (choke chains), foreign bodies, and sialoliths have been suggested. Saliva tends to take the path of least resistance, most commonly accumulating in the cranial cervical or intermandibular region and less frequently accumulating in the sublingual area, pharyngeal tissues, and retrobulbar space. The most common sites for mucoceles include: cervical mucoceles and ranulas, and less commonly pharyngeal and zygomatic mucoceles. Ranulas are located in the sublingual tissues on the floor of the mouth on one side of the tongue.