Periodontal Disease - The Merck Veterinary Manual

Periodontal Disease

Bacterial infection of the tissue surrounding the teeth causes inflammation of the gingivae, periodontal ligament, cementum, and alveolar bone. An early form of periodontal disease, gingivitis, progresses to periodontitis if left untreated. Ultimately, teeth are lost due to the loss of their supporting tissues. This is the major reason for tooth loss in dogs.

Etiology and Pathogenesis:

Periodontal disease is caused by gross accumulation of many different bacteria (bacterial plaque) at the gingival margin due in part to a lack of proper oral hygiene. Over time, the flora changes from nonmotile, gram-positive, coccoid, aerobic bacteria to more motile, gram-negative, rod-shaped, anaerobic bacteria. Important flora include Porphyromonas gingivalis , Bacteroides asaccharolyticus , Fusobacterium nucleatum , Actinomyces viscosus , and A odontolyticus as well as many others. Other contributing factors in disease development may include host response, species and breed, genetics, age, and diet.

As the level of subgingival bacteria increases to 10-20 times normal, gingivitis develops. The accumulation of bacterial metabolic products increases epithelial permeability in crevicular epithelial desmosomes and allows antigens to contact connective tissue. Metabolic products of bacterial metabolism include hydrogen sulfide, ammonia, endotoxin, hyaluronidase, chondroitin sulfatase, mucopeptides, lipoteichoic acids, acetate, butyrate, isovalerate, and propionate. These bacterial products and host defense mechanisms cause tissue necrosis. Polymorphonuclear leukocytes (PMN) migrate through the sulcular epithelium and form a barrier between the subgingival bacteria and the gingiva. With overwhelming bacterial challenge, PMN die in increasing numbers and release breakdown products. The immune system produces lymphokines that participate in tissue destruction, which follows the path of the local vascular supply. Accelerated tissue destruction and inappropriate repair cause loss of periodontal support. Two forms of disease are recognized: gingivitis and periodontitis.

In gingivitis, inflammation of the marginal gingival tissues is induced by bacterial plaque and does not affect the periodontal ligament or alveolar bone. There is a change from coral-pink to red or purple, swelling of the gingival margin, and a serous or purulent exudate in the sulcus. The gingivae tend to bleed on contact. Fetid breath is common. Gingivitis is reversible with proper tooth cleaning but, if untreated, may lead to periodontitis. A form of juvenile-onset gingivitis is seen in some cats at 6-8 mo of age; these cats often have gingival hyperemia and halitosis.

Gingivitis, dog

Gingivitis, cat

In periodontitis, the destructive inflammatory process of the periodontium is induced and driven by bacterial plaque that destroy the gingiva, periodontal ligament, alveolar bone, and root cementum. It usually is seen after years of development of plaque, calculus, and gingivitis. There is apical migration of the epithelial attachment and resorption of supporting alveolar bone. It is irreversible and results in permanent loss of tooth support. Affected teeth may show increased mobility, concurrent gingivitis, and subgingival calculus.

Periodontitis, dog

Periodontitis, cat

Periodontitis, radiograph, cat

Periodontitis is characterized by increased pocket depth, attachment loss, gingival recession, furcation exposure, and horizontal vs vertical patterns of bone loss. Small-breed dogs usually experience more problems than large-breed dogs. Dogs on a hard diet develop fewer problems due to the mechanical cleaning effect on the teeth as the food is chewed. Caudal teeth are affected more often than rostral teeth. The maxilla is affected more severely than the mandible, and buccal surfaces have more disease than lingual surfaces. Gingivitis often becomes evident at ~2 yr of age but resolves if treated. Periodontitis usually begins at 4-6 yr of age and, if untreated, progresses to tooth loss.

Treatment:

Gingivitis usually can be treated by thorough cleaning of the teeth, including below the gingival margin (subgingival scaling). If gingivitis does not resolve, further examinations should be performed for the presence of subgingival plaque and calculus, which should be removed in subsequent cleanings. When cleanings are completed, a barrier sealant can be applied to prevent bacterial recolonization and improve healing. Refractory cases should be evaluated for immunocompetence, cellular defects (eg, diminished neutrophil chemotaxis), and systemic disease (eg, diabetes mellitus). Gingivitis reestablishes if the teeth are not kept clean and free of bacteria. Therefore, at-home oral hygiene methods (eg, brushing, plaque prevention gel) and regular cleanings to prevent gingivitis and its progression to periodontitis should be encouraged.

Periodontitis needs to be treated with thorough cleaning above and below the gum line. In areas of increased subgingival depth (>6 mm), surgical means should be used to gain access to the root surface for cleaning, preserving all attached gingiva. Teeth can generally be salvaged until they have lost 75% of their bone support from one or more roots. This can be evaluated by radiography of the jaws, which should be performed if periodontal disease is advanced. Infrabony defects (defects below the crest of the alveolar bone) require flap surgery. Defects on the palatal surface of maxillary canine teeth, which are infrabony in character and invade or approximate the nasal cavity, should be treated with infrabony grafting procedures before a decision is made to extract the tooth. Improper extraction of such teeth frequently results in oronasal fistulas, which require surgical repair; however, the use of proper extraction technique can help avoid this complication. Advanced surgical therapies include guided tissue regeneration using osteoinductive and osteoconductive materials with or without epithelial barriers.

Animals with periodontitis should be maintained postoperatively on oral hygiene methods at home, including mechanical control (daily toothbrushing), dietary changes (providing diets designed to control plaque and calculus), plaque prevention gel, and chemoprophylaxis (such as rinsing with chlorhexidine [10 mL of a 0.2% solution, bid ]). Frequent (every 3 mo to 1 yr) prophylactic cleanings should be encouraged to avoid relapse and prevent further bone loss. Dogs with concurrent stomatitis benefit from doxycycline (2.5 mg/kg for 30-60 days).

Prevention:

Prevention or reduction of plaque deposition can be achieved with barrier sealants and plaque prevention gels, which use inert polymer sealants to prevent plaque formation on teeth in dogs and cats. The polymer forms a physical (electrostatic) bond to the enamel surface of the teeth, creating a hydrophobic barrier. This barrier effectively repels bacteria-laden saliva from the tooth surface, preventing colonization by oral bacteria and plaque formation.

Mechanical control, in the form of toothbrushing and diets designed to remove tartar and calculus from teeth, can be used proactively to prevent periodontal disease. Consistent use of such products, along with regular dental examinations, are required. The basic principle is that active periodontal disease will not develop around a clean tooth.