dry food and teeth
Tiggs, yes I do...I summarized a few abstracts on the tartar/diet issue for my alternative vet list, and I'm happy to share them with you!
Logan, et al., Dental Disease, in: Hand et al., eds., Small Animal Clinical Nutrition, Fourth Edition, Topeka, KS: Mark Morris Institute, 2000, p. 487. "Although consumption of soft foods may promote plaque accumulation, the general belief that dry foods provide significant oral cleansing should be regarded with skepticism. A moist food may perform similarly to a typical dry food in affecting plaque, stain and calculus accumulation...Typical dry dog and cat foods contribute little dental cleansing. As a tooth penetrates a kibble or treat the initial contact causes the food to shatter and crumble with contact only at the coronal tip of the tooth surface...The kibble crumbles...providing little or no mechanical cleansing...." She also reviews two studies on cat "dental" treats which showed "no significant difference in plaque or calculus accumulation with the addition of dental treats to either a dry or a moist cat food." Of course, this book was produced by Hill's, and is very pro t/d. BTW, although t/d provided a statistically significant improvement, when you look at the actual graphs, the difference between Dog Chow and t/d is not all that impressive.
"...when comparing dry food only and non-dry food only fed dogs...there is no pattern to the trends (some teeth show an apparent protective effect from feeding dry food only, and others show the opposite -- for calculus index, the trend is protective for all five teeth in dogs feed dry food only, whereas for gingival index it is the opposite, and it is mixed for attachment loss). All maxillary teeth are significantly less likely to be mobile in the dry food only group, yet the mandibular first molar tooth showed the opposite effect." Harvey et al., Correlation of diet, other chewing activities and periodontal disease in North American client-owned dogs, J Vet Dent 1996 Sept;13(3):101-105. Logan (above) assesses this study as follows: "In a large epidemiologic survey, dogs consuming dry food alone did not consistently demonstrate improved periodontal health when compared with dogs eating moist foods."
There is an excellent review of the literature by Watson ADJ, Diet and periodontal disease in dogs and cats, Aust Vet J 1994;71:313-318. This study is fully of interesting historical items. For instance, one study of cat skulls found evidence of severe periodontal disease in 25% of 80 cats; 75 of the skulls were dated from 1841 to 1958, and two were from Pharaonic Egypt!
According to the review, many of the early studies showed less tartar formation with hard dry food vs the same food mixed with water, and similar results were reported in a study with canned vs dry cat foods. In 1965 a study compared feeding raw whole bovine trachea, esophagus, and attached muscle and fat, vs the same food minced. Plaque and gingival inflammation were increased with the minced diet. Even more fascinating, they tube-fed the minced food and found that plaque and gingivitis did not decrease, "showing food did not need to be present in the mouth to induce these changes." In fact, gingivitis tended to *increase* when dogs were tube-fed, "suggesting that even the minimal chewing required with minced food had some cleansing or protective effect."
A couple of studies showed that *large* dry food biscuits (not kibble) actually removed tartar, which is probably the theory underlying t/d's oversized chunks. Feeding of half an oxtail accomplished the same thing when fed weekly in another study. (I can just see it now, "Brand X's Half Oxtail Tartar Control Bones."
[BTW, "No harmful effects were observed from feeding oxtails to > 200 dogs for > 6 years.]
Gorrel and Rawlings (The role of tooth-brushing and diet in the maintenance of periodontal health in dogs, J Vet Dent 1996 Dec;13(4):139-143) state that: "In a previous study, we showed that the daily addition of an appropriately designed chew to a dry food diet is effective in reducing accumulation of dental deposits...the addition of the chew to the dry food diet also reduced the severity of gingivitis that developed, compared with the regimen of dry food diet alone." This points out that dry food does not prevent tartar/gingivitis.
Interestingly, Gorrel states in another article that "The consensus is that supragingival calculus per se is not directly involved in the etiology or pathogenesis of [periodontal] disease, and is mainly of cosmetic significance if plaque removal is adequate." (Periodontal disease and diet; J Nutr. 1998;128:2712S-2714S.)
Another more recent review (DuPont G. Prevention of periodontal disease. Vet Clin N Amer 1998 Sept;28(5):1129-1145) says, "In some dogs, dry kibble or fibrous diet helps slow plaque accumulation more than does soft or canned food...Other chewing behaviors may be even more important for reducing plaque than is feeding dry food." Not exactly a ringing endorsement of dry food! He cites 2 studies showing t/d to be effective for "decreasing plaque and calculus accumulation." There is no indication in this paper of any funding from or affiliation with Hill's; the author is with a veterinary dental clinic in Seattle.
A review of feline neck lesions found no significant influence of diet. (Johnson N, Acquired feline oral cavity disease, Part 2: feline odontoclastic resorptive lesions. In Practice. 2000 Apr:188-197).
Hope this helps!
Cheers,
Dr. Jean
