Evidence Based Veterinary Dentistry

[malernee]

Evidence Based Veterinary Dentistry (S6A)
Western Veterinary Conference 2006
Fraser A. Hale, DVM, FAVD, DAVDC
Hale Veterinary Clinic
Guelph, ON, Canada

Objectives of the Presentation

To discuss the pros and cons of dental home care programs and some of the dental home care products currently on the market in light of available scientific evidence.

General Key Points

Prevention and control of periodontal disease requires both daily home care and regular professional care.

Many products are available to pet owners that claim to aid in the maintenance of good oral health. For some of these products there is little or no scientific evidence that they are of any value at all.

Some products have the potential to do harm.

Choosing which home care products to recommend in each particular situation depends on an understanding of how each product works, its benefits, risks and limitations.

Overview of the Issue

For animals predisposed to or afflicted with periodontal disease, professional treatment is only part of the plan. What the owner does at home on a daily basis for plaque control has as much or more impact on the long-term prognosis. To understand why homecare is so important, it is important to understand some things about plaque and calculus and the progression of periodontal disease. Unfortunately space restrictions preclude a review here, so the reader is directed to http://www.toothvet.ca/ for the unabridged version of this paper.

Homecare refers to anything the owners are doing at home on a regular basis to control plaque and maintain periodontal health. In numerous studies, daily brushing of the teeth with a soft-bristled toothbrush has been shown to be the most effective means of plaque control. It is the mechanical action of the bristles against the tooth surface that removes the plaque. The toothbrush also massages the gingiva to milk fluid and debris from the gingival sulcus and also directly stimulates the production of collagen within the gingiva to make it firmer and healthier.

Though it may seem heresy to say this, I have found that not all dogs and cats require homecare. I have seen mature, even geriatric dogs and cats that have never had any home care, never had any professional dental treatment and yet still have no significant gingivitis or periodontitis. Therefore, I suggest you pick you battles and put your energy where it will do the most good--concentrate on those animals with a predisposition to periodontal disease.

The Dangers of Home Care

Homecare can be harmful to the pet and the owner and can be counterproductive if not approached in the proper manner.

Homecare can cause pain to the animal. If an owner tries to brush the teeth of a cat that has resorptive lesions, it will cause pain. If an owner tries to brush a tooth that has a crown fracture and exposed pulp, it will cause pain. If an owner brushes too vigorously or roughly, it will cause pain. If the animal's early experience with homecare involves pain, it will be very difficult to ever get this animal to accept and enjoy daily homecare.

Homecare can lead to a false sense of security. If an owner is brushing the crowns of the teeth daily, the crowns will remain nice and clean. Therefore, at annual examination, you will see clean teeth and will be inclined to say that no further dental examination or treatment is required. However, there may well be problems brewing in an area that is not only hard for the owners to brush, but hard for you to examine with the animal awake.

What Home Care IS NOT

Home care is NOT a treatment for established disease.

Home care is NOT a substitute for regular professional examinations and treatment.

Home care is NOT an Over-the-Counter concept.

What Homecare Is

Home care is daily plaque control designed to maintain oral hygiene and prevent the development of gingivitis and periodontal disease. It does not remove calculus and it cannot reach into periodontal pockets. Therefore, home care should only be instituted AFTER appropriate professional treatment has established a clean and healthy mouth. Home care is then used in an attempt to maintain this healthy situation or to prevent the situation from deteriorating.

Since home care only cleans the crowns of the teeth and maybe 1 to 2 millimeters subgingivally, it will have little or no effect on established periodontal pockets. Home care is also only effective for those teeth (or tooth surfaces) the owner is able to reach. Therefore, even with home care, the animal should have regular professional examinations and treatments. I brush my own teeth 2-3 times a day and floss daily and I still see my hygienist and dentist every nine months.

There is a dizzying array of home care products and aids available for your client to choose from. It can be confusing to veterinarians which products to use when. Do not leave it up to your clients to decide for themselves which products to use or how to use them.

For those animals that need home care, take the time to discuss the situation with the owner and explain what they need to be doing. Listen to their thoughts and concerns, consider the animal involved and then customize a program based on the situation.

The remainder of this paper will discuss some home care products and how they work (according to manufacturer's claims or as confirmed by independent research). Inclusion here does not imply an endorsement and exclusion does not imply an indictment. There are far too many to cover them all in these pages, so you will have to apply the principles discussed to critically evaluate the claims of each product to see how it might fit into your dental program. Above all, remember that daily brushing is the most important part of the home care program.

Chemical Plaque Control

Chemical plaque control agents come in many forms including toothpastes, gels, rinses and water treatments. No chemical agent has been shown to be effective in plaque control by itself. Most will reduce or retard plaque accumulation to a degree, but they cannot stop it from forming. Once a plaque film has formed, it will be very resistant to chemical agents that are applied passively.

Pastes are meant to be used on the toothbrush and may have a number of functions. Most veterinary pastes are flavored for the peculiar taste preferences of dogs and cats and so can improve compliance by acting as a positive reinforcer.

Pastes also often have some abrasive material such as ground walnut shells, to improve the mechanical cleaning action of the brush.

VirbacTM markets a line of veterinary toothpastes under the brand C. E. TTM. These pastes contain a "dual-enzyme system" consisting of glucose oxidase, lactoperoxidase and a substrate (not specified). These ingredients combine with water (from saliva) and oxygen to form hypothiocyanite (OSCN). This ion is produced naturally in human and canine saliva (possibly in cat saliva as well), where it has been shown to have an antibacterial effect.

I have never disputed the value of the endogenous salivary lactoperoxidase enzyme system as part of the host defense system. What I have asked on several occasions over the years is, "Is there any research to show that adding more of this enzyme system in a toothpaste has any beneficial effect?" I know that brushing with C. E. T.TM will be beneficial, but would we get the same benefit from brushing with a placebo paste? To date, this research has not been done. For now, I tell clients that many pets like the taste of C.E.T.TM and so it can be useful in boosting compliance. If it also does have some antibacterial effect, I look on that as a bonus.

There are also a variety of gels and rinses available which act as oral antiseptics. The most common active ingredient in these products is chlorhexidine. Chlorhexidine is a non-specific antibacterial agent as well as having some effect on fungus and viruses. There is a large body of research on the efficacy of chlorhexidine as an antimicrobial agent. It acts by causing precipitation of the cytoplasmic contents of the bacterium--a mechanism against which resistance cannot develop. While chlorhexidine has been shown to reduce plaque and gingivitis, it paradoxically can increase the rate of mineralization of plaque (calculus formation). Chlorhexidine also causes a brown staining on the teeth when used as a rinse and can cause a decrease in the sense of taste. Chlorhexidine is likely best used as a pre-operative oral rinse and at home for the healing period following professional treatment.

Chlorhexidine comes in two forms; acetate and gluconate. Of the two, gluconate is more soluble and has been studied more. Either form bonds ionically with oral hard and soft tissues to give a prolonged effect (12 hours) from a single rinse.

Maxi/GuardTM is available as a gel and as a rinse. Both contain zinc and ascorbic acid (vitamin C) and taurine. Zinc is antibacterial and important for healthy epithelium. Vitamin C is important in the production of collagen, which is the main structural protein in gingiva. The taurine chelates volatile sulphur compounds produced by oral pathogens, which has an obvious effect of reducing halitosis and may reduce the damage to oral tissues that may be caused by these volatile sulphur compounds. The gel is tasteless and alcohol free and makes a nice oral anti-septic for the post-operative period. It has also found a use as a plaque retardant in cats that will tolerate no other forms of home-care. Maxi/GuardTM has a relatively low pH (4.6) and this may cause some cats to hypersalivate a bit.

Sodium Hexametaphosphate (HMP) is a sequestrant that binds salivary calcium, making it unavailable for precipitation as calculus. It has no direct effect on oral bacteria or plaque, but by reducing calculus accumulation, it would make plaque control easier. HMP is delivered as a coating on various treats and diets and may also be found in some toothpastes.

Chew Toys

There are a variety of items on the market upon which dogs are meant to chew. Most of them will claim some dental benefit such as "Cleans Dog Teeth". While many of these toys can legitimately claim to help keep a dog's teeth clean, many are also a major cause of dental fracture. Examples would include natural bone and dried cow hooves. Hard-pressed rawhide bones and nylon bones are also sufficiently resilient to cause dental fracture.

The criterion I use in practice is as follows. If you do not want me to hit you in the knee with a toy, then you should not give it to your dog to chew. If it is hard enough to hurt your knee, then it is hard enough to be a potential cause of dental fracture.

Tennis balls are a favorite toy for dogs, however, they can be quite damaging. The nylon fuzz itself is quite abrasive. Also, the fuzz will retain grit picked up from the ground. So chewing on a tennis ball will be like chewing in emery cloth.

Chew Aids

This category would include consumable items that are not considered to be a significant source of calories such as rawhide strips and bones, pig's ears. Any item that you give to a dog with the understanding that it is to be chewed into little bits and possibly swallowed, bears some risk of gastrointestinal upset or blockage. Consider each item and its relative risk and choose the safest one going.

Pig's ears are available at many pet stores and flea markets. They are basically just pigskin and cartilage, often dried and smoked to prevent decay. The skin-cartilage parfait has a mild abrasive effect on the tooth surfaces without great risk of being too abrasive. The thin and flexible nature of pig's ears makes them very unlikely to cause dental fractures. Some dogs tolerate these aids very well, while others may experience digestive upset. As the ears are sold from bulk bins generically, there is no assurance of quality control and there have been reports that they may harbor bacterial pathogens such as salmonella. If a large chunk of an ear is swallowed, it will likely be broken down by gastric juices and pass without incident. However, choking and esophageal blockage are possible. To my knowledge, no research has been published to determine the efficacy of pig's ears in the prevention of dental disease.

Rawhide strips are a consumable treat that many dogs really love, but as they provide non-digestible protein, they do not add greatly to the caloric intake. PurinaTM markets rawhide strips under the brand Chew-eezTM. Each strip is approximately 3-4 cm wide, 10 cm long and 1-2 millimeter thick. I consider these to be among the safest chew aids you can recommend. There is still a risk of choking, but this is a rare event. A brand name offers some quality assurance and the thinness of the strips makes it very unlikely that any teeth will be damaged. The abrasive action of chewing the rawhide does help reduce plaque, calculus and gingivitis.

VirbacTM markets raw hide strips similar to Chew-eezTM, but they impregnate theirs with the C. E. TTM. enzymes. Again, there is currently no research to support the notion that raw hide with C. E. T.TM is any more beneficial that raw hide without but the C.E.T. chews are much more expensive.

Treats

Treats would include any consumable item that adds to the total calorie intake. No treat has ever been shown to be able to maintain clinically healthy gingiva, no matter how much of it is fed. Treats are only a part of the plaque control program and should be used as well as, not instead of brushing.

DentaBoneTM is a compressed tapioca-based treat that has been shown in numerous short-term and mid-term studies to reduce plaque, calculus and stain while improving gingival health when given daily. Unfortunately, these treats fail the "knee-cap" test and have been known to fracture teeth.

C.E.T. Forte ChewsTM are designed for cats as a mildly abrasive treat, intended to improve oral hygiene. These chews contain the same dual-enzyme system found in other C.E.T.TM products. Whether it is the course texture of the chew mechanically helping to remove plaque, the enzyme system or a combination, is not clear from the research. In any event a controlled study in client owned cats found a statistically significant reduction in gingivitis when the cats received one chew a day compared to eating the same diet without the daily chew.

Diets

No diet has ever been shown to be able to maintain clinically healthy gingiva, no matter how much of it is fed. Diets are only a part of the plaque control program and should be used as well as, not instead of brushing.

It has long been felt that feeding a cat or a dog a dry kibble diet is better for the teeth than feeding them a processed, canned diet. The logic goes that dry food leaves less residue in the mouth for oral bacteria to feed on and so plaque would accumulate at a slower rate. Despite that, many animals fed on commercial dry diets still have heavy plaque and calculus accumulations and periodontal disease. This is because most dry pet foods are hard but brittle so that the kibble shatters without much resistance and so there is little or no abrasive effect from chewing.

There are currently seven commercially available pet foods that have received recognition by the Veterinary Oral Health Council as having a significant effect on plaque, calculus. These are Prescription Diet® Canine t/d Original Bites and Small Bites, New and Improved Prescription Diet® Feline t/d, Friskies® Feline Dental Diet, Science Diet ® Oral Care Diet for Dogs and Science Diet® Oral Care Diet for cats.

The mechanism of action for these diets is based on the physical properties of the kibble. Each nugget is quite large and so must be chewed before swallowing. The nuggets are hard, but not brittle, and so the teeth sink deep into the nugget before it splits. As the tooth is penetrating the nugget, the fibers in the food gently abrade the tooth surface, thereby removing plaque.

These diets are high-fiber maintenance diets for average mature animals but would not be appropriate to support growth, gestation/lactation or a very athletic life-style. Each of them is intended to be fed as the main calorie source. Research by Hill's found that the best results were obtained in this manner, but that there was still a measurable (but declining) benefit when the t/d diets were fed as 75%, 50% and even 25% of the total calorie intake. Using t/d simply as a treat will not meet expectations for the product.

Iams® has a line of diets under the name Dental DefenseTM and Innovative Veterinary Diets has a Dental FormulaTM. These diets have been coated with HMP to reduce calculus accumulation. Keep in mind that calculus does not cause gingivitis or periodontal disease, bacterial plaque does. Calculus just makes it easier for the plaque to adhere to the tooth surfaces. Reducing calculus accumulation alone will not prevent gingivitis and periodontal disease, but it may make the job easier. The Iams® Dental Defense diets have the VOHC Seal of Acceptance for calculus.

Conclusion

By the time you read this, there will likely be a few more products on the veterinary dental home care shelf. Whenever you are presented with a new (or old) product for consideration, consider this.

Look for the Veterinary Oral Health Councils Seal of Acceptance.

Look carefully at the claims and demand to see the research.

Does the research show:

High compliance

Safety

Efficacy

Reduced plaque, calculus and gingivitis scores (i.e., actual therapeutic benefit).

Also keep in mind that any product, no matter how good, will only work if it is used properly. Make sure you understand how to use the product and then make sure your clients understand.

References

1. Roudebush P, Logan E, Hale FA. Evidence-Based Veterinary Dentistry: A Systematic Review of Homecare for Prevention of Periodontal Disease in Dogs and Cats. J Vet Dent 22 (1); 6-15, 2005.


Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker)
Fraser A. Hale, DVM, FAVD, AVDC (Dentistry/Oral Surgery)
Hale Veterinary Clinic
Guelph, ON, Canada