Introduction

Because virtually every pet encounters dental issues at some point in its life, there is great importance in understanding the evaluation techniques for dental problems. With more advanced diagnostic tools, preventative care strategies can be better defined. The key to developing these methods will be to ensure that they are both reliable and reproducible. The following discussion addresses methods to improve the current calculus evaluation processes that relate to scoring techniques and prophylaxis effort. Through better research tools, advancements in nutritional dental technologies can be more fully assessed.

Current Methods for Assessing Calculus

Over the past 50 years, a number of investigators have employed some type of grading system to quantify the amount of calculus deposition on the tooth surface. Two of the most common methods cited are the Greene-Vermillion index and the Volpe-Manhold index. Prior to this standardization, most observations of calculus were classified as either present or absent. Today, the technique of assessing calculus coverage via applying a numerical classification scheme is broadly accepted and the most common means of assessing oral care products. These techniques are based on visualization of the buccal surfaces on both sides of the mouth from canine tooth to first molar in white light. Some grading techniques also include a measure of calculus thickness that is multiplied by the area to produce a calculus score. The Veterinary Oral Health Council (VOHC) recommends the use of a 4 or 5 point scale to classify calculus coverage.

A New Technology for Assessing Calculus Severity

As an alternative to human examiners, a new method has been developed to measure the amount of calculus that deposits on the surface of a tooth. Recall that human examiners conduct visual/tactile grading of calculus severity as most deposits are easy to detect as they appear as a rough, yellow to brown mineral on the tooth surface. For veneer calculus, identification requires a tactile assessment of the tooth surface, as color and thickness are not as pronounced. Earlier attempts to replace tactile assessment of calculus area have relied on white light photography, but analysis was complicated when limited contrast existed between the calculus and the inherent tooth color, or when the teeth were heavily stained. To overcome these issues, a new technique has been developed that involves the use of ultraviolet light and digital photography.

Ultraviolet light enhances the photographic technique as both the teeth and calculus possesses different fluorescent properties.^1,2 Specifically, the tooth emits a blue color while the calculus emits a pink to red color. This differentiation in calculus fluorescence is due to the presence of Porphyromonas circumdentaria in the cat, and Porphyromonas gingivalis in the canine³. These bacteria accumulate within a mature biofilm and utilize hemin as a source of iron. The removal of iron leaves the hemin with a metal-free fluorescent porphyrin that accumulates within the mineral deposits of the calculus. By applying the principles of illumination and color separation, a new technique has been developed that allows for the precise quantification of calculus area.

The method employs a digital camera synchronized to two flash heads equipped with wavelength filters to optimize lighting. Analysis involves the use of a computer processor to decipher specific pixel information concerning the red, green and blue color space. Tooth shade is discerned from calculus shade through a discriminate rule created to identify specific color ranges associated with each target category. The result of this process is an assessment of calculus coverage based on specific pixel information.

UV Calculus Imagery Technique Validation

Four canines were recruited to compare a traditional calculus scoring methodology to the UV calculus imaging system. The goal of the study was to assess each technique for the ability to quantify the amount of calculus deposition. The two diets compared were Eukanuba® Reduced Fat with and without the Dental Defense System. Prior to feeding, all canines were anesthetized and a dental prophylaxis was performed to remove supra and sub-gingival calculus and plaque. After 28 days, the canines were anesthetized and calculus indices were evaluated on the following teeth: maxilla:I3, C, P3, P4 and M1; mandible: C, P3, P4, and M1. The calculus indices were based on a 5-point classification where 0- no observable calculus; 1-less than 24% coverage on the buccal surface; 2-24-49% coverage on the buccal surface; 3-calculus 50-74% coverage on the buccal surface; 4-more than 74% coverage of the buccal surface. The sum of the teeth scores was averaged to obtain a whole mouth mean calculus score for each animal. For UV photography, two photographs were taken per animal which included a right and left mouth profile. Digital analysis was conducted separately for each picture and compared to the corresponding human examiner score (Table 1).

Table 1. Methodology comparison of calculus coverage

The overall results show that both methods predicted similar calculus coverage for each animal tested. Results showed that both methods were able to detect less calculus for the diet containing the Eukanuba Dental Defense System, but the product efficacy evaluation was less sensitive with the traditional 5-point method. The traditional white light method was limited to 25% accuracy while the UV imaging technique was able to determine a precise coverage value. This experiment shows that through the use of mathematical modeling and computer analysis, it is now possible to determine true calculus coverage as opposed to broad range estimates.

Prophylaxis Effort and Calculus Area

Currently, the standard of care for removal of plaque and calculus deposits is routine prophylaxis performed under the supervision of a veterinarian. This procedure requires the aid of such equipment as power scalers, hand scalers, curettes and polishing equipment. If the calculus is sufficiently thick, then forceps can also be employed to fracture the deposits into smaller pieces. Regardless of the instrument, significant effort is required to render a tooth calculus free. To address this issue, several pet products currently market products that claim to reduce calculus accumulation; however, few publish technical support data. When product data is available, the typical focus is on the benefits of reducing calculus area alone. While this measurement is useful, it does not account for variations in the calculus hardness or adhesive tenacity. As a result, the true benefit of a dental product to the practitioner or animal has never been fully investigated.

A New Technique for Assessing Calculus Removal

One method to examine prophylaxis benefits is through the use of a specially designed Quanticalc scaling handpiece. This device utilizes a handheld scaler coupled with a force transducer to measure the work effort involved in removing calculus. The device is used like a hand scaler, but the number of strokes and the maximum scaling force is recorded. The maximum scaling force is defined as the amount of force required for cohesive and/or adhesive failure of the calculus sample during debridement. The benefits of this technique as applied to human prophylaxis were previously published in the Journal of Clinical Dentistry.⁴ With the aid of the Quanticalc device designed for animals, an exploratory clinical was run to measure the true prophylaxis-related benefits of a diet enhanced with Eukanuba® Dental Defense System.

Effects of a Dental Diet on Prophylaxis Scaling Effort

To test prophylaxis benefits, 28 adult Beagles were recruited for a comparative crossover feeding study. A traditional dental prophylaxis was performed prior to assigning the animals to two diet test groups. The animals were fed either Eukanuba® Reduced Fat diet or Eukanuba® Reduced Fat diet enhanced with the Dental Defense System for 28 days. The canines were then evaluated for the presence of calculus followed by QC scaling. Data collected via the QC scaling included the maximum force associated with a scaling stroke, and the number of strokes required for the manual debridement of the calculus. After prophylaxis the canines were crossed over to the second diet and fed for another 28 days followed by another evaluation for the presence of calculus and QC scaling.

Table 2. Quanticalc data for group one (n=14); 28 day interval

The results show that the QC scaler quantified the impact diet on prophylaxis effort. For group one, when canines underwent prophylaxis and switched to a dental diet, there was a reduction in the amount of scaling strokes and total prophylaxis force required for cleaning the teeth at the next scheduled visit (Table 2). Conversely, for group two, when canines were prophied and removed from the dental diet there was an increase in the amount of scaling strokes and total prophylaxis force required to clean the teeth at the next scheduled visit (Table 3). These data support that a diet can impact not only calculus area, but also reduce the work effort required during a dental prophylaxis.

Table 3. Quanticalc data for group two (n=14); 28 day interval

References

1.  Benedict H. A note on the fluorescence of teeth in the ultra-violet rays. Science 1928;67:442.

2.  Hartless R, Leaver A. Fluorescence of teeth under ultraviolet irradiation. Biochem J 1953;54:632-638.

3.  Dolowry WC, Brandes ML, Gouterman M, Parker JD, Lind J. Fluorescence of dental calculus from cats, dogs, and humans and of bacteria cultured from dental calculus. J Vet Dent 1995;2:105-109.

4.  White DJ, Cox ER, Arends J, Nieborg JH, Leydsman H, Wieringa DW, Dijkman AG, Ruben JR. Instruments and methods for the quantitative measurement of factors affecting hygienist/dentist efforts during scaling and root planing of the teeth. J Clin Dent 1996;7:32-40.

Portions of this article were adapted from

1.  Cox ER, Lepine AJ. New Technologies for Investigating Dental Issues. Current Perspectives in Canine and Feline Dental Health Management (2000).

2.  Johnson RB, Cox ER, Lepine AJ. Dietary Technology for Inhibition of Calculus Formation in Companion Animals. Recent Advances in Dental Health Management (2003).