Dental Corner: A foundation for treating canine periodontal disease

Patients with periodontal disease, the most common disease in dogs, suffer from progressive inflammation and destruction of the tissues supporting the teeth. In addition to causing oral pain and tooth loss, periodontal infections can spread systemically and may adversely affect various organs, including the heart, kidneys, and liver.1

PERIODONTAL ANATOMY

Literally translated from Latin as "around the tooth," periodontium refers to the tissues that attach the teeth to the jaws. These structures include the gingiva, the alveolar bone, the cementum (connective tissue that covers the tooth root), and the periodontal ligament (collagen fibers that attach the tooth to the alveolar bone). The gingival sulcus is a shallow space around a tooth bounded by the tooth surface on one side and the marginal epithelium lining the free gingival margin on the other.2 In periodontal disease, these tissues become progressively diseased and are destroyed while the tooth remains unaffected. Therefore, we should not think of periodontal disease as tooth disease but rather as around-the-tooth disease.

ETIOLOGY

The inflammation and destruction associated with periodontal disease is initiated by bacterial plaque accumulating on the tooth surface. Hundreds of bacterial species inhabit the oral cavity, and probably many more have yet to be identified. However, in people as well as in animals, certain bacteria are implicated as the primary cause of the disease and have been labeled periodontopathogens. In people, Porphyromonas gingivalis, a black-pigmented, gram-negative anaerobe, has been identified as a periodontopathogen, and certain Porphyromonas species are also likely periodontopathogens in dogs.3,4 Additionally, it appears that complex interactions among the various microbe populations in the oral cavity influence the disease's progression, so to think of periodontal disease as an infection with a single bacterial species would be an oversimplification. However, when treating periodontal infection, specifically target the gram-negative anaerobes.

Many other factors, such as a patient's age, diet, chewing habits, occlusion, and size, can affect the severity of its periodontal disease. A major factor appears to be a host's reaction to bacterial plaque. Bacterial endotoxins and other bacterial byproducts primarily cause the tissue destruction, but the body's own inflammatory response—set into motion by the oral immune system—can also influence the degree of tissue inflammation and destruction (i.e. a greater immune response can cause more tissue damage).

PERFORMING AN ORAL EXAMINATION

Ideally, oral examinations should be done in anesthetized patients because the diagnosis and staging of periodontal disease require periodontal probing and radiographic examination. At least one problem is usually found in an awake patient that should be addressed in an anesthetized patient, so always inform clients that complete dental diagnostic evaluation and treatment require anesthesia.

DIAGNOSING PERIODONTAL DISEASE

The periodontal probe, an essential diagnostic tool, has calibrated markings for measuring the gingival sulcus depth (Figures 1A-1D). This depth, also known as pocket depth, is measured from the gingival margin to the apical extent of the pocket and should be checked on four sites around every tooth. Normal pocket depth is 1 to 3 mm in dogs, but it can increase because of periodontal tissue destruction from disease or because of pathologic overgrowth of the gingiva. Pockets caused solely by gingival overgrowth are termed pseudopockets. Exposure of the area where the roots join the crown in multirooted teeth is termed furcation exposure.

Figures 1A-1D

In addition to increased pocket depth, the oral examination may reveal gingival recession. Document gingival recession in millimeters. The sum total of gingival recession plus abnormal pocket depth is termed attachment loss. In cases of gingival recession, there can be marked attachment loss without pocket formation.

Dental radiography is another essential tool for diagnosing periodontal disease. The most common radiographic abnormality resulting from periodontitis is alveolar bone loss. Bone loss from periodontal disease is generally horizontal (suprabony) or vertical (infrabony) (Figures 2A & 2B). When describing bone loss in the patient record, include the percentage of bone loss, for example, "The mesial root of the mandibular left first molar shows 75% horizontal bone loss."

Figures 2A & 2B

STAGING PERIODONTAL DISEASE

Periodontal disease can range in severity from mild gingivitis (which resolves with proper treatment) to end-stage periodontitis (which is, for the most part, irreversible). It can be classified according to a four- or five-stage system. It is important to know each tooth's periodontal disease stage so appropriate therapy can be administered on a tooth-by-tooth basis. For this purpose, a convenient periodontal triage system would consist of three categories: gingivitis, treatable periodontitis, and end-stage periodontitis. Halitosis is a hallmark sign of periodontal disease, but its presence or absence does not indicate a specific disease stage.

GINGIVITIS

In patients with gingivitis, the initial stage of periodontal disease, only gingival tissues exhibit inflammation. Patients may have mild, moderate, or severe bacterial plaque or calculus accumulation and hyperemia and edema of the marginal gingiva. Gently probing the gingival sulcus with a periodontal probe may induce spontaneous bleeding, but the pocket depth remains normal (< 3 mm). No radiographic abnormalities are associated with this stage.

TREATABLE PERIODONTITIS

Clinical signs of early periodontitis are related to periodontal tissue destruction and may include increased pocket depth (up to 5 mm), gingival recession, and furcation exposure. In veterinary dentistry, our patients come in a variety of sizes, and there is variation in the clinical significance of a 5-mm pocket on a Mastiff's canine (minor problem) vs. a 5-mm pocket on the first maxillary premolar of a Yorkshire terrier (probably a candidate for extraction). Horizontal or vertical alveolar bone loss may be seen radiographically. In early periodontitis, 0% to 30% bone loss may occur.

The clinical signs of established periodontitis include deep periodontal pockets (> 5 mm), gingival recession and root exposure, alveolar bone loss (sometimes with furcation exposure), and mild tooth mobility. Bone loss ranges from 30% to 75%.

END-STAGE PERIODONTITIS

In patients with end-stage periodontitis, one or more tooth roots exhibit > 75% bone loss. Single-rooted teeth exhibit mobility, but multirooted teeth may not be loose if one or more roots retain some attachment to bone. Therefore, a tooth does not have to be loose to have end-stage periodontal disease.

TREATING PERIODONTITIS

After the complete oral examination, update your findings and treatment recommendations in the record and discuss them with the owner. Patients whose teeth exhibit gingivitis should undergo complete dental scaling (both supragingival and subgingival) and polishing. The proper techniques and steps for performing dental prophylaxis are well-documented. On the other end of the spectrum, treating patients whose teeth exhibit end-stage periodontitis is straightforward as well: dental extraction. Patients with treatable periodontitis have diverse pathologies, and a variety of treatments are available.

Diagnosing and treating periodontitis in people consumes an entire specialty in the field of dentistry, and many textbooks and journals are devoted to the subject. At the risk of oversimplifying the art and science of periodontology, presented below is a framework for treating treatable periodontitis in dogs.

BEFORE STARTING TREATMENT

The key diagnostic information required is periodontal pocket depth and intraoral radiographic examination results, including the percentage and type of bone loss. The absolute necessity of obtaining intraoral dental radiographs cannot be overemphasized.

TREATMENT OPTIONS

The most important treatment for all cases of advanced periodontitis is the complete removal of bacterial plaque and calculus from the tooth crown, gingival sulcus, and root surfaces. This allows healing and stops disease progression.

For periodontal pockets < 5 mm deep with mild to moderate (0% to 50%) radiographic evidence of bone loss (Figure 3), treatment consists of scaling (manual or ultrasonic débridement) the tooth surface (crown), gingival sulcus, and root surface and root planing. For 5-mm periodontal pockets with mild to moderate bone loss, treatment should include scaling, root planing, and administering a local doxycycline gel (Doxirobe—Pfizer Animal Health).

Figure 3

Before treating periodontal pockets > 5 mm deep, the client must agree to attempt home care and return for follow-up appointments. If the client cannot agree to these requirements, extraction should be considered or recommended.

To treat patients with deep pockets and horizontal bone loss, mucogingival surgery (flap exposure) and open curettage are required to access and clean the pockets (Figure 4). In cases of vertical bone loss, mucogingival surgery combined with open curettage and guided tissue regeneration can result in periodontal tissue (including alveolar bone) regeneration—contradicting the dogma "Periodontitis is irreversible."

Mucogingival surgery and guided tissue regeneration are advanced procedures that should be performed only after a clinician has received ample training and, ideally, hands-on experience. These procedures may be best referred to a board-certified veterinary dentist (a list is available at www.avdc.org.)

SCALING AND ROOT PLANING

Periodontal bacterial ultrasonic débridement involves using an ultrasonic scaler to remove plaque, calculus, and necrotic or diseased tissue from the tooth and root surface. The newer generations of ultrasonic equipment, including the piezoelectric ultrasonic scalers, are designed to operate both above and below the gum line. It is important to use a light touch and to keep the tip of the ultrasonic scaler constantly moving. However, even with the best and newest ultrasonic equipment, a thorough subgingival curettage and root planing performed with hand instruments (curettes) should always be included in periodontal treatment (Figure 5).

Curettes have many designs, but a key feature is a blunt tip to prevent injury to the delicate gingival tissues. The curette should always be sharp; sharpening stones are available. Insert the curette into the pocket, adapt the sharp edge of the blade to the root surface to engage the subgingival calculus and plaque, and pull the curette to scrape the root surface (Figure 6). Use many overlapping strokes to débride each root surface. The procedure is complete when the root surface is smooth and clean. Root planing can be a labor-intensive and technique-sensitive process and can require spending many minutes on each tooth. It is important to avoid excessive removal of normal cementum during this procedure.

Figure 4

LOCAL ANTIBIOTIC TREATMENT

Doxirobe, a polymer gel mixed with doxycycline, is a veterinary product used for nonsurgical treatment of periodontal pockets > 4 mm. The gel is injected through a bendable cannula into periodontal pockets. On contact with fluids, the gel hardens and remains in the pocket for several weeks, slowly releasing the doxycycline. In addition to its antimicrobial properties, doxycycline decreases the effect of collagenase, an enzyme released in the sulcus during active periodontal inflammation. This product is not a substitute for periodontal surgery when surgery is indicated (pockets > 6 mm).

The Doxirobe two-syringe system is easy to use but requires some practice. Gently place the tip of the cannula to the depth of the treated (scaled and root planed) pocket and move it across the length of the pocket as you slowly insert the material (Figure 7). Continue inserting the gel until a small amount extrudes from underneath the gingival edge. Don't overfill the pocket. By applying light digital pressure on the top of the gum and by gently scraping the cannula tip on the tooth surface, the cannula can be removed without taking the gel with it.

Figure 6

The gel stiffens within a minute or two. To speed up the process, place a drop of water on the material. Once firm, gently pack the visible material into the pocket with a plastic composite filling instrument (beaver tail). Instruct the owner not to brush the dog's teeth in the treated area for about a week (gels and solutions are recommended) and not to pick at the ridge of material that may become visible (light yellow-brown). The material is biodegradable and does not need to be removed.

MUCOGINGIVAL SURGERY

Mucogingival surgery includes a variety of procedures designed to gain access to deep periodontal defects and to recontour or reposition gingival tissue. Mucogingival flaps are created to gain exposure to diseased root surfaces. In pockets > 5 mm, it is impossible to adequately scale and root plane without surgical exposure.

The simplest flap design is the envelope flap, in which the incision is made through the gingival attachment at the sulcus (sulcular incision) and the gingiva and oral mucosa are reflected without releasing incisions. When greater exposure is needed, releasing incisions can be made. Both the periosteum and the mucosa should be included in the flap (full thickness). After root planing, the flap should be reapposed and sutured in place with fine, absorbable suture.

Gingivectomy is a surgical procedure in which certain areas of gingiva are excised to restore a healthier periodontal pocket depth. Gingivectomy should be reserved for cases of gingival hyperplasia in which gingival overgrowth creates deep pseudopockets. Not long ago, gingivectomy and other periodontal surgical procedures to reduce pocket depth (e.g. apical repositioned flaps) were recommended treatments. However, preserving gingival height is now considered a goal of treatment.

GUIDED TISSUE REGENERATION

After a periodontal pocket undergoes thorough root planing, the tissue heals and the pocket depth is reduced. The reduction in pocket depth results from soft tissue reattachment. Reattachment is good, but true regeneration of periodontal tissue, including alveolar bone and periodontal ligament, is ideal. The problem is that the rapid initial regrowth of epithelial attachment (granulation tissue) interferes with the slower regeneration of bone and periodontal ligament. So in order for bone to regenerate, the epithelial regrowth must be delayed or obstructed. The process of excluding epithelial regrowth to encourage regrowth of periodontal tissue is called guided tissue regeneration. The success of guided tissue regeneration depends on many factors, a major one being defect morphology. Narrow, vertical pockets are more amenable to treatment than are broad, wide defects.

Various types of barriers have been developed to exclude epithelial regrowth. Consil (Nutramax Laboratories) is a bioactive, osteoconductive bone graft material that functions as a barrier to exclude epithelial attachment and promote bone regeneration. Because Consil is incorporated into the new bone, there is no need to remove Consil after its use.

Infrabony pockets often occur on the palatal and lingual aspects of canine teeth in dogs (especially small, dolichocephalic breeds). Left untreated, periodontal defects on the palatal aspect of the maxillary canine teeth often progress to oronasal fistulas, necessitating extraction. If caught early, these defects may be successfully treated with open curettage and guided tissue regeneration.

PREVENTING PERIODONTITIS

Educating clients about providing good oral hygiene at home is essential in preventing periodontitis.

TOOTH BRUSHING AND DENTAL DIETS

Daily tooth brushing is the best preventive measure you can recommend pet owners do at home. A daily tooth brushing is necessary because plaque bacteria can colonize on teeth 24 to 36 hours after scaling and polishing. In addition, several commercial diets significantly reduce plaque and tartar compared with regular dry food diets (Harvey C, Veterinary Oral Health Council, Philadelphia, Pa: Unpublished data). Specifically these foods are Iams Daily Dental Care (Iams), Prescription Diet Canine t/d (Hill's), Science Diet Oral Care (Hill's), Dental DD (Royal Canin), and Purina Dental Diet (Néstle Purina). With such a high prevalence of periodontal disease in dogs, there are few reasons not to provide a diet that promotes good oral health.

CHEW TREATS AND TOYS

Rawhide treats for dogs are readily available to pet owners and are effective in the control and removal of plaque and tartar from dogs' teeth. Rawhide is highly digestible; in the numerous scientific studies documenting its effectiveness, it has not been observed to cause the digestive problems that conventional wisdom ascribes to it.5,6 It has also been shown that coating rawhide treats with calcium-sequestering substances such as sodium hexametaphosphate can further enhance plaque and tartar reduction.7

However, there are chew toys on the market that should not be given to dogs because of their tendency to cause tooth fracture. Nylon bones, cow hooves, and real bones should also be avoided because they are too hard and often are associated with slab fractures of the carnassial teeth. Tennis balls cause attrition (mechanical wearing of the tooth surface) and are also not recommended.

PLAQUE PREVENTIVE SEALANT AND GEL

OraVet Barrier Sealant (Merial) is a biologically inert polymer that bonds to the surface of teeth and inhibits plaque and calculus adherence. The product is easy to apply in the office after a prophylaxis, and OraVet Plaque Prevention Gel (Merial) is applied weekly at home to maintain the protective barrier. OraVet Barrier Sealant can be used after a dental or periodontal surgery in which postoperative tooth brushing is contraindicated. Although there are no studies published to document its effectiveness, the preliminary scientific data look promising (Merial Limited: Unpublished data).

ORAL RINSES

Chlorhexidine gluconate, formulated as an oral rinse or a gel, is an excellent oral disinfectant. The chlorhexidine binds to gingival tissue and then exerts its antibacterial effects for 24 to 48 hours. Chlorhexidine kills the bacterial pathogens that contribute to periodontal disease and halitosis. Patients with chronic periodontitis should receive chlorhexidine rinses twice a week and regular tooth brushing on the other days. Other oral rinses, containing substances such as zinc ascorbate or chlorine dioxide, combat halitosis by neutralizing malodorous sulfur compounds. It is important to realize that masking halitosis may not be addressing the primary source of oral pathology.

BACTERIN

A novel approach to preventing periodontitis in dogs is on the horizon. Recent studies have shown that the most commonly isolated periopathogens from the oral cavity of dogs with periodontitis are three species of the black-pigmented anaerobic bacteria Porphyromonas: Porphyromonas gulae, Porphyromonassalivosa, and Porphyromonasdenticanis.8 A bacterin (Porphyromonas Denticanis-Gulae-Salivosa Bacterin—Pfizer Animal Health) has been shown to be safe in field studies (Pfizer Animal Health: Unpublished data) and effective in an experimental model.9 This soon-to-be-available periodontal disease vaccine will provide veterinarians with an innovative weapon to add to our arsenals in the fight to prevent this common canine disease.

Editors' note: Dr. Carmichael has consulted for Pfizer and Nutramax and has been sponsored by these companies to provide educational lectures.

The information and photographs for "Dental Corner" were provided by Daniel T. Carmichael, DVM, DAVDC, Veterinary Medical Center, 75 Sunrise Highway, West Islip, NY 11795.

Dr. Daniel Carmichael

REFERENCES

1. DeBowes LJ, Mosier D, Logan E, et al. Association of periodontal disease and histologic lesions in multiple organs from 45 dogs. J Vet Dent 1996;13:57-60.

2. Harvey CE, Emily PP. Small animal dentistry. St. Louis, Mo: Mosby, 1993;90-91.

3. Harvey CE. Management of periodontal disease: understanding the options. Vet Clin North Am Small Anim Pract 2005;35:819-836.

4. Holmstrom SE, Frost-Fitch P, Eisner ER. Veterinary dental techniques. 3rd ed. Philadelphia, Pa: WB Saunders Co, 2004.

5. Hennet P. Effectiveness of an enzymatic rawhide dental chew to reduce plaque in beagle dogs. J Vet Dent 2001;18:61-64.

6. Lage A, Lausen N, Tracy R, et al. Effect of chewing rawhide and cereal biscuit on removal of dental calculus in dogs. J Am Vet Med Assoc 1990;197:213-219.

7. Warwick JM, et al. Reducing calculus accumulation in dogs using an innovative rawhide treat system coated with hexametaphosphate, in Proceedings. Vet Dent Forum 2001;379-382.

8. Hardham J, Dreier K, Wong J, et al. Pigmented-anaerobic bacteria associated with canine periodontitis. Vet Microbiol 2005;106:119-128.

9. Hardham J, Reed M, Wong J, et al. Evaluation of a monovalent companion animal periodontal disease vaccine in an experimental mouse periodontitis model. Vaccine 2005;23:3148-3156.