A 5-year-old male Rhodesian ridgeback presented to me for evaluation of proliferative gingival enlargement over the maxillary canine teeth. Historically, the owner noted a flap of partially detached gingiva over tooth 104, which had since become completely detached, resulting in the unique combination of gingival recession over most of the lateral portion of the tooth and gingival enlargement over the mesial, distal and palatal surfaces of the tooth (Figure 1). John Lewis, VMD, FAVD, Dipl. AVDC Figure 1: The right maxillary quadrant showing generalized gingival hyperplasia and gingival recession over the labial (vestibular) surface of the right maxillary canine tooth (tooth 104). Tooth 204 had a similar appearance, though more irregular, with a large circumscribed area of enlargement toward the distal portion of the crown (Figure 2). Nearly every tooth in the mouth was affected at least mildly by gingival enlargement, though the canines and incisors were affected most severely (Figure 3). The appearance of the gingiva over teeth 104 and 204 likely was due to the following events: Gingival enlargement results in pseudopockets. Pseudopockets allow for hair, plaque and debris to be trapped between the gingiva and the tooth. True pockets begin to form secondary to an inflammatory response to the accumulated plaque, calculus and hair. A draining tract (parulis) forms through the gingiva due to the inflammation and foreign body reaction to the accumulated hair. Blood supply of the gingiva coronal to the draining tract is compromised due to the enlarging draining tract. Gingiva eventually is shed, leading to the overall effect of gingival recession. Histopathology in this case confirmed the diagnosis of gingival hyperplasia at multiple sample sites, including teeth 204, 209 and 404. John Lewis, VMD, FAVD, Dipl. AVDC Figure 2: The left maxillary canine tooth (tooth 204) shows a combination of gingival enlargement and a focal area of gingival recession due to a prior parulis (gumboil) that affected survival of the gingiva coronal to the parulis. Etiology First, a note about terminology. When we see overgrown gingiva, we tend to call it gingival hyperplasia, but, in reality, we can’t call it hyperplasia until histopathology has been done. Hyperplasia is a histopathologic diagnosis, whereas gingival enlargement is a clinical diagnosis. Histopathology may reveal hyperplasia, but it also might reveal a benign gingival mass (peripheral odontogenic fibroma, previously called fibromatous or ossifying epulis) or a malignancy. You have seen gingival hyperplasia many times, and more times than not it probably was occurring in a boxer dog. Gingival enlargement can be so severe that the entire crowns of some teeth are not visible beneath the hyperplastic gingiva. Though boxers are perhaps the most commonly affected breed, great Danes, collies, Doberman pinschers and Dalmatians have shown familial tendencies. Though a genetic predisposition to gingival enlargement might be difficult to overcome, good dental hygiene can help minimize inflammation and gingival proliferation to some degree. Bernese mountain dogs, many brachycephalic dogs and even some small breed dogs and cats may be affected. John Lewis, VMD, FAVD, Dipl. AVDC Figure 3: The mandibular incisor teeth are nearly covered with enlarged gingiva, resulting in pseudopockets around each of the mandibular incisors. Note also the gingival enlargement on the lingual surface of the mandibular canine teeth. Brachycephalic dogs might be predisposed not only due to genetic causes but also because of the effects of mouth breathing and drying of the gingiva. The exact mechanism by which mouth breathing causes gingival changes is not known. It has been hypothesized that irritation from dehydration of the gingival surface might play a role. Because panting is a common practice of virtually all dogs, it is difficult to make conclusions regarding the role of mouth breathing in dogs. Human mouth breathers often suffer from malocclusion or high upper lips, leaving areas of gingiva exposed to air.1 When gingival hyperplasia occurs in cats, it often is associated with a condition called juvenile gingivitis, where the gingiva surrounding nearly every tooth is enlarged, inflamed and proliferative. Juvenile gingivitis sometimes responds to removal of excess gingiva, frequent professional dental cleanings and excellent home care. Systemic conditions also can cause gingival hyperplasia. Gingival enlargement occurs in humans when hormonal changes of the patient alter the usual gingival response to dental plaque. Increased levels of progesterone and estrogen are seen in pregnant women at levels 10 to 30 times that of normal menstrual cycles. These hormonal changes cause increased vascular permeability, resulting in gingival edema and increased inflammatory response to dental plaque. Gingival enlargement during puberty occurs in both male and female adolescents, usually only on facial and buccal (vestibular) surfaces. In these cases, extreme inflammatory overgrowth can be seen in the presence of mild plaque accumulation. Gingival enlargement secondary to vitamin C deficiency is a conditioned enlargement that modifies the defenses of the gingiva to plaque. Collagen degeneration results in edema, inflammation and massive gingival enlargement. Acromegaly has been documented to cause multiorgan enlargement, including gingival enlargement. Another possible etiology relates to chronic ingestion of certain medications. Administration of cyclosporine, calcium channel blockers and certain anti-seizure medications can cause gingival hyperplasia. Cyclosporine, phenytoin and calcium-channel blockers are calcium antagonists. Studies in rats have shown that calcium is an important factor in the biochemical cascade of apoptosis (programmed cell death), a process that plays a role in control of tissue overgrowth. Transglutaminase, a calcium- dependent enzyme involved in apoptosis, normally is found to have a higher activity in gingiva than any other tissues tested to date. Medications that prevent normal enzyme activity may thus allow for development of gingival enlargement. Another mechanism of gingival enlargement may be related to the upregulation of certain cytokines. Drugs that cause gingival enlargement in humans have been shown to upregulate various cytokines, including IL-6 and PGE2.1 Next month, we will discuss treatment and prevention of gingival enlargement. Until then, keep on drilling! References 1. Lewis JR, Reiter AM. Management of generalized gingival enlargement in a dog- case report and literature review. Journal of Veterinary Dentistry 2005; 22: 160-9. Originally published in the February 2016 issue of Veterinary Practice News. Did you enjoy this article? Then subscribe today!
