Introduction

Periodontal disease has been recognized for over 100 years as a condition of high incidence in the dog. In 1899, Talbot reported that 75% of dogs 4 to 8 years of age were impacted by periodontal disease.¹ This disease incidence was recently confirmed in a review describing that 53 to 95% of dogs older than one year of age had some degree of periodontitis.¹ To better understand the progression of this disease we must first look at the cause.

Overview of Dental Disease

Dental disease is the result of a multi-step process that occurs within the oral cavity. In the first step, the tooth is coated with a thin layer of glycoproteins commonly known as the acquired pellicle. This layer adheres tightly to the tooth surface and cannot be removed with routine oral care measures such as brushing. Within hours, this layer will thicken as debris and normal oral bacteria accumulate along the gingival margin and begin to adhere and multiply. At this point, the plaque biofilm is quite soft and can be removed by simple abrasion from devices such as brushing or chewing. However, with time, the bacterial population will increase and the plaque will become more secured to the tooth surface through the production of glucans².

The presence of a mature plaque biofilm on the tooth surface creates a condition in which mineralization can occur within the bacteria. This process involves the precipitation of salivary components into a deposit commonly known as calculus, or tartar. Calculus is formed when soluble minerals, such as calcium carbonate and calcium phosphate, become supersaturated within the interstitial spaces between the bacteria during conditions of alkaline pH. Mucopolysaccharides, formed by the microorganisms in the plaque, are thought to play a role in this crystallization³. Unlike plaque, once formed, calculus can only be removed via a professional scaling procedure. Further, if left to accumulate, the porous surface of the calculus can serve as a nidus for new plaque bacteria. The accumulation of such bacteria along the gum line can create irritation of the soft tissues and eventually lead to gingival recession or loss of ligament integrity.

Preventative Care

Up until recently, the most common means to help prevent dental disease was with routine brushing and prophylaxis. Brushing is of particular interest because although Veterinary health professionals agree that it is the single most effective means of removing plaque, owner compliance is extremely low. This has led to an explosion of products (e.g., dental diets, chews, and toys) over the past several years with special abrasive textures designed to clean the chewing surfaces of the teeth. However, since abrasive products only work on contact surfaces, some companies have tried to offset this limitation by offering antimicrobial compounds incorporated into pet toothpastes (glucose oxidase and lactoperoxidase) and into topical gels and rinses (Chlorhexidine).

A Dietary Approach for Daily Preventive Dental Care

The latest approach to help prevent the formation of calculus in companion animals is to utilize nutritional mineral sources in a way that they can provide dental benefits. Nutritional sources of phosphates can be manipulated to enhance the dental properties of the kibble without altering the base formula, or kibble size. This is accomplished by a unique manufacturing procedure that coats the outer surface of the food with polyphosphates in a microcrystalline form. The polyphosphate crystals help to prevent the mineralization of plaque into calculus by forming a physical barrier on the plaque surface.

The benefit of the barrier approach is that polyphosphates can provide whole mouth benefits as they release from the diet during mastication and carry throughout the oral cavity. This allows the dental benefit to have an effect across the whole mouth as opposed to the contact chewing surfaces. Additionally, this nutritional approach offers a prolonged dental benefit as the polyphosphates remain within the plaque until the body absorbs them as phosphorus nutrients.

Studies with Polyphosphates

Studies were conducted on both canines and felines to test if nutritional sources of phosphate could be utilized to improve dental health.^4,5 The studies were of a crossover design, and utilized the guidelines set forth by the Veterinary Oral Health Council (VOHC) for determining dental benefits. In all studies, comparison diets were prepared on the same manufacturing date to ensure that no base ingredient differences existed in the formulations other than the polyphosphate coating. To ensure no product had a mechanical advantage, each dental diet was prepared with the same shape and thickness as the corresponding control.

Results demonstrated that the polyphosphate coating did not affect animal body weight or diet consumption. Nor was any difference detected in calcium or phosphorus absorption or blood chemistry. With regards to calculus growth rates, the results were similar for both canines and felines. The amount of calculus was assessed based on a 5-point classification where 0- no observable calculus; 1- less than 24% coverage on the buccal surface; 24-49% coverage on the buccal surface; 3calculus 50-74% coverage on the buccal surface; 4- more than 74% coverage on the buccal surface. Average dental calculus score in dogs fed diets with polyphosphate was 0.72 whereas those animals fed diet without polyphosphate was 1.60 per tooth. The average dental calculus score in cats fed diets with polyphosphate was 0.44 compared to cats fed diets without was 0.80.

Clinical Studies with Polyphosphates

These findings supported the need to perform a clinical study with dogs of different breeds. The study was conducted to evaluate the effectiveness of the polyphosphate technology (Dental Defense System; DDS) on calculus accumulation when incorporated into Eukanuba® Veterinary Diets (EVD) Senior Plus. Thirty-three senior dogs (6 to 11 years of age) representing multiple breeds (3.6kg to 60kg) were recruited and studied in a three period (35days each), double-blind crossover design. The health status of all dogs was confirmed prior to study initiation by complete physical examinations. During the initial visit the dogs underwent a dental prophylaxis while anesthetized with isoflurane then randomly assigned to a treatment group. The three diet treatment groups were EVD Senior Plus with DDS, EVD Senior Plus without DDS and Hill's® Prescription Diet® Canine t/d ®. The diets were fed for 35 days then the dogs underwent dental scoring, ultraviolet dental imaging and prophylaxis under the direction of the attending veterinarian. Calculus coverage was evaluated on maxillary I3, C, P3, P4 and M1 and mandibular C, P3, P4 and M1. The protocol was repeated for the final two periods of the study thereby allowing all dogs to be evaluated on each of the three study diets. No other dental treatments were used during the study. Data were evaluated by the General Linear Models procedure for treatment, period, animal and tooth effects. Tooth effect analysis included both a whole mouth average calculus score, and a tooth group score. The tooth group analysis was conducted to determine if polyphosphates provided a whole mouth dental benefit across the categories of canines(C), premolars (P2,P3,P4), and molars (M1). Means were compared by the least square method when significant differences (P<.05) were detected.

Table 1. Whole mouth mean tooth calculus score in senior dogs fed with or without polyphosphate compared to a typical dental diet (n=33)

* Eukanuba® Veterinary Diets Senior Plus

** Statistically significant at P<.05

Table 2. Mean calculus score by tooth group in senior dogs fed polyphosphate or a typical diet (n=33)

*Statistically significant at P<.05

Results of the clinical study demonstrated that:

1.  calculus accumulation in dogs fed Eukanuba® Veterinary Diets Senior Plus with Dental Defense System® was reduced by 37% (P<.05) compared with dogs fed Hill's® Prescription Diet Canine t/d® (table 1),

2.  calculus accumulation in dogs fed Eukanuba® Veterinary Diets Senior Plus with Dental Defense System® was reduced by 43% (P<.05) compared to dogs fed Eukanuba Veterinary Diet Senior Plus without Dental Defense Systems® (table 1), and

3.  calculus accumulation in dogs fed Hill's® Prescription Diet® Canine t/d® was reduced by 10% compared with dogs fed Eukanuba Veterinary Diet Senior Plus without Dental Defense Systems® (table 1).

These data clearly document that improved dental calculus control can be achieved in the senior dog by the provision of polyphosphate technology (i.e., DDS) in the EVD Senior Plus formula, compared to a dental diet relying solely on abrasive technology. Analysis of the tooth group data showed that polyphosphates have the ability to effect calculus growth on non-chewing teeth (canines, pre-molars) better than an abrasive action diet. A further advantage to the DDS technology is the ability to provide this dental benefit in association with a dietary matrix specifically designed to meet the unique nutritional needs of the senior animal.

References

1.  Watson A. Diet and periodontal disease in dogs and cats. Aust Vet J 1994;71:313-318.

2.  Gibbons RJ, Van Haute J. On the formation of dental plaque. J Periodontal 1973;44:347.

3.  Burke S. Oral physiology and physiotherapy. In: Dimensions of Dental Hygiene, 3^rd ed. 1982;91-141.

4.  Johnson RB. Recent dental advances for companion animals through dietary means, in Proceedings. TNAVC January 2002. Orlando, FL;179-180.

5.  Cox ER, Lepine AJ. Use of polyphosphates in canine diets to control tartar. J Dent Res 2002; 81:A349 (Abstr.)

Portions of this article were adapted from

1.  Cox ER, Lepine AJ. New Technologies for Investigating Dental Issues. Recent Advances in Dental Health Management (2003).