An overview of dentigerous cysts in dogs and cats.

M any dental diseases can be easily treated or even prevented if the diagnosis is made early. A simple example is the dentigerous cyst, although many veterinarians are not familiar with this condition. This article presents an overview of dentigerous cysts in dogs and cats, in the hope that more of these cysts will be prevented or diagnosed early. Dentigerous cysts (follicular cysts) are, in my experience, the most common odontogenic cysts in dogs and cats, and are similar to those described in humans (1–3). Dentigerous cysts are associated with the crown of an unerupted tooth, usually a permanent tooth. They arise from the epithelial remnants of the enamel organ or the reduced enamel epithelium that surrounds the crown during odontogenesis (1,3) (Figure 1). Dentigerous cysts enclose the crown of the unerupted tooth and are attached to the tooth at the cementoenamel junction. Unerupted teeth are usually a developmental problem due to a physical barrier (impacted tooth) or a lack of eruptive forces (embedded tooth) (4,5). An iatrogenic dentigerous cyst was also reported in a dog following the extraction of a deciduous tooth. The permanent tooth bud was damaged which resulted in a malformed impacted tooth (6). Dentigerous cysts are more common in dogs than in cats (7). Brachycephalic dogs are more frequently affected and the condition is sometimes bilateral (5,8–12). Although these cysts could be associated with any tooth, the mandibular first premolar of the dog is the most frequent (8,10,11,13). The maxillary and mandibular canine are also often implicated (5). They can be diagnosed at any age but late diagnosis is usually associated with larger lesions. Affected animals often have no clinical signs apart from the absence of 1 or more teeth (hypodontia). These cysts are capable of achieving significant size, and their slow growth causes a thinning and expansion of the adjacent cortical bone. Facial asymmetry and an oral mass may then be observed. This mass may be fluctuant or hard on palpation depending on the presence or absence of a thin layer of bone over the cyst cavity. The soft tissues overlying the cyst generally have a normal appearance but can sometimes have a bluish tint, mainly with larger lesions (Figure 2). It is usually not associated with pain