Eric Servet, processing engineer - Royal Canin, Research Center, Aimargues, France
Dr. Hendriks Wouters and Dr. David Clarke - Massey University, New Zealand
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Introduction
Periodontal disease has been identified as the most frequently occurring clinical condition in domestic cats (1). It is known that 70% of cats, in the age range of 20-27 months, demonstrate signs of periodontal disease such as plaque, calculus and gingivitis (2).
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The disease begins with the accumulation of bacterial plaque on the tooth surfaces. This is gradually initiates an inflammatory response that affects the supporting tissues of the tooth: this is called gingivitis. This remains a reversible phenomenon if the plaque is removed. If left undisturbed, plaque is gradually calcified into calculus. Calculus is inert so it does not cause gingivitis but it provides a wonderfully rough surface onto which further plaque can accumulate. Gingivitis results eventually in the loss of attachment due to the destruction of the tooth socket tissues; this is periodontal disease and this is an irreversible phenomenon (3).
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The best way to prevent periodontal disease is to remove plaque build up, or better still, prevent it building up. Toothbrushing, with an adequate toothpaste, on a regular basis, has been found to be the most effective method of preventing periodontal disease in cats. But, the fact is that few pet owners are willing to comply with this toothbrushing, especially with cats (4).
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Control of dental deposit accumulation in cats by dietary means offers a more realistic approach. Much of the research, in the recent years, has focused on the development of specially formulated, designed and textured dry diets. These dry diets aim to reduce the incidence of periodontal disease in cats by preventing the build up of dental deposits (plaque and calculus) following dental clean up.
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The goal of this research was to evaluate the impact of dry dietary regimens specially designed for an oral care purpose on cat dental deposits, relative to a control diet, on a short-term basis. The impact was determined by measuring the extent of the accumulation of dental plaque and calculus (two markers of periodontal disease) in cats fed the different dry dietary regimens.
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This research included two studies that were carried out sequentially:
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- The goal of the first study was to evaluate the impact on plaque deposit of kibbles designed (size and shape) to induce better crunching and textured to induce greater tooth penetration;
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- The goal of the second study was to evaluate the impact on calculus accumulation of kibbles formulated with oral active ingredients that are known to chelate salivary calcium.
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Material & Methods
The two feline trials were conducted at a Feline Unit in New Zealand. Fifty cats (30 males and 20 females), aged between 4 to 9 years, were selected. Inclusion criteria were: normal dentition, scissor-configuration occlusion, no periodontal disease, dental plaque accumulation associated with no or mild gingivitis. The latter was assessed in a separate preliminary study involving plaque scoring 14 days after scaling. In the first study cats were randomly allocated based on gender and plaque forming ability to one of 5 diets. In the second study 40 out of these 50 cats (25 males and 15 females), were used. Exclusion criteria were failure to comform to one or more of the inclusion criteria, attachment loss characteristic of a periodontitis. Cats were housed in groups of 10 and provided their respective diet ad libitum. Fresh water was available ad libitum.
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Diets
Cats were fed only dry extruded diets throughout the studies.
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In order to evaluate what effect the kibble format and texture has on the measured parameters (dental deposit), a larger rectangle kibble was manufactured which was expected to induce sufficient difference in format to the smaller triangular control diet (Figure 1).
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In addition, the test kibbles had an improved texture with an increased distance of penetration of the tooth into the kibble before it breaks, compared to the control kibbles (Figure 2).
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The texture analyses were performed at the Royal Canin central lab using an internally developed texturometer (Figure 3).
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Figure 1 Picture of the study 1 dry diets; triangular control kibbles on the left and rectangular test kibbles on the right
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Figure 2 Comparison of penetration distance of the tooth into the kibble before breakage
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Figure 3 Texturometer (Royal Canin Research Centre)
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In order to evaluate the effect of a calcium chelator on the measured parameters (dental deposit), rectangle kibbles were formulated with polyphosphate salts and compared to similar kibbles with no calcium chelator.
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Procedure
Each trial consisted of two successive periods. The first period was a 1-week pre-feeding period used to customize the cats to their respective diets. This was directly followed by the second test period. The first study consisted of a 4-week test period while the second study ran over a 8-week test period (Figure 4).
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The measured parameter for study 1 was plaque index, which was evaluated according to the Logan & Boyce procedure (5). The measured parameter for study 2 was calculus index, which was evaluated according to the Warrick & Gorrel procedure (6). Plaque and tartar evaluations according to the Logan & Boyce and Warrick & Gorrel procedure were performed by the same person, in a blinded procedure to the different feeding regimens and the scoring order of the cats. The scored teeth were C, PM3, and PM4 for the upper jaw and C, PM3, PM4 and M1 for the lower jaw (Figure 5).
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The values for each parameters measured were expressed as a whole mouth score for each cat which was obtained from the mean value of the scores for each tooth examined. Data were expressed as the mean ± standard deviation. Analysis of variance tests were used to derive F-tests for significant differences between treatments. F-values with p less than 0.05 were considered significant. Analyses were performed using the ANOVA, GLM procedures in Statgraphics V5 statistical software.
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Results
Whatever the diet, dental plaque accumulated over time. But, plaque deposit rate differed according to the diets. And, feeding larger-rectangle kibbles to cats resulted in significantly less plaque build up (-41%, p=0.0089), compared to smaller-triangle control kibbles, 7 days after initial scaling/polishing (7 days is the Veterinary Oral Health Council reference period for plaque). The difference was still significant after 21 days (-20%, p=0.036) and after 28 days the difference reached –20% (p=0.062). This was correlated with observations on cats: test kibbles were crunched with a higher rate by cats compared to control kibble that tended to be swallowed whole with a higher rate (Figure 6).
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28 days after the initial scaling/polishing, there was no detected significant difference (p=0.836) between the diets, for calculus accumulation. However, 56 days after scaling/polishing, calculus deposit scores differed significantly according to the diet (p=0.0057). The polyphosphate salts-coated kibbles resulted in significantly less calculus build up with -45%, compared to the chelator free control kibbles (Figure 7).
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Figure 7 Calculus results
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Discussion
The objective of this research was to evaluate the impact of dry dietary regimens, specially designed for an oral care purpose, on limiting plaque deposit and calculus accumulation, on a short-term basis following scaling/polishing, on adult cats.
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It was shown that cats fed a diet composed of specially designed and textured kibbles were associated with significantly less plaque deposit within 7 days, compared to cats fed regular kibbles. This lower plaque deposit rate obtained with the test regimen was attributed to the fact that the test kibbles conveyed an enhanced mechanical action, attributable to increased friction, induced by first, a higher crunching rate and second, by an optimized crunching with a greater teeth penetration into the kibbles. This test regimen is mimicking tooth brushing in a better way than the control diet.
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It was also shown that cats fed a diet composed of kibbles coated with calcium-chelator were associated with significantly less calculus accumulation within 56 days, compared to cats fed regular kibbles. This lower calculus deposit rate obtained with the test regimen was attributed to the addition of polyphosphate salts onto the kibbles. This ingredient is expected to be first, released in the cat oral cavity and second, chelated with salivary calcium preventing it to be involved in the dental plaque calcification. The results are in agreement with other available feline calculus data showing that the incorporation of calcium chelators into a dry regimen was associated with less calculus formation (7, 8).
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It is reasonable to conclude that a dry diet combining both, increased mechanical impact and calcium-chelator coating, could lead to even greater beneficial impact on cat dental deposits.
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A home care dietary management can complete regular professional dental services and lead to a reduction of the risk of periodontal disease for your cat.
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Authors
 Eric Servet graduated from a French engineering school, specializing in food ingredients and food technology, in 1999. He was an engineer for dairy industries working on pilot development and product formulation from 1999 to 2001. After a year spent in the USA working for Royal Canin, USA on product stability and palatability, he joined the Royal Canin Research and Development department in France as a research engineer in 2002.
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 Dr. Wouter Hendriks graduated from Wageningen University in the Netherlands in 1992 with an Ingenieur degree in Animal Nutrition. He was awarded his PhD for studying protein metabolism in adult cats in 1996 by Massey University in New Zealand. In 1997 he became the director of the Centre for Feline Nutrition at Massey University and has since developed an active research programme into aspects of feline nutrition including nutritional requirements, palatability, functional foods and protein metabolism. Currently Dr. Hendriks is also a senior lecturer in companion animal nutrition and an executive member of the Institute of Food, Nutrition and Human Health at Massey University.
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 After graduating from the University of Queensland in Veterinary Science in 1989, David worked in general practice for six years. Dr. Clarke is a Diplomate of the American Veterinary Dental College, a Fellow of the American Academy of Veterinary Dentistry and a Member of the Australian College of Veterinary Scientists (Veterinary Dentistry), as well as, a registered specialist in veterinary dentistry in Victoria, Australia. He runs a specialist referral veterinary dental practice in Melbourne, and is Adjunct Associate Lecturer, Department of Veterinary Clinical Sciences, Massey University, New Zealand and Consultant, Veterinary Dentist at The University of Sydney, Taronga and Western Plains Zoo, NSW, Australia. David is currently President of the Australian Veterinary Dental Society.
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References
1. Lund, E. M., Armstrong, P. J., Kirk, C. A., Kolar, L. M.et al. Health status and population characteristics of dogs and cats examined at private veterinary practices in the United States. Journal of the American veterinary Medical Association 1999; 214: 1336-1341.
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2. Johnson, R. B. Recent dental advances for companion animals through dietary means. In: Proceedings. 2002 North American Veterinary Conference, Orlando. pp. 37-39.
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3. Hennet, P. Periodontal disease and oral microbiology. In: Manual of Small Animal Dentistry, British Small Animal Veterinary Association. Crossley, D. A., Penman, S. (eds) UK, 1995: 105-113.
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4. Flax, B. M. Compliance with oral hygiene following periodontal treatment. In: Academy of Veterinary Dentistry Meeting. Auburn: American Veterinary Dental College, 1993.
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5. Logan, E. I., Boyce, E. N. Oral health assessment in dogs: parameters and methods. Veterinary Dental Journal 1994; 11(2): 58-63.
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6. Warrick, J. and Gorrel, C.. A more objective method of scoring calculus. Proceedings of the 5th World Veterinary Dental Congress. Birmingham, UK, 1997: 40-42.
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7. Johnson, R.B., Cox, E.R. Recent dental advances for companion animals through dietary means. In: Current Perspectives in Canine and Feline Dental Health Management, Dental health issue, Iams, Dayton, Ohio. January 2002: 26-28.
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8. Stooke, G.R. Methods for preventing dental calculus in domestic animals. US patent Stookey, patent number 5, 296, 217; Indiana University Foundation, Bloomington, Indiana, June 1995.
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