Page 949 - Small Animal Clinical Nutrition 5th Edition

Periodontal Disease 983

impaired taste. Saliva initiates film formation on all oral sur- Box 47-3. Do Commercial Cat Foods
VetBooks.ir faces (Scannapieco and Levine, 1990; Navazesh, 2002). Cause Tooth Resorption?

ENAMEL PELLICLE
Enamel pellicle is a thin film or cuticle. Early enamel pellicle Although the etiology of tooth resorption in cats is unknown,
examination of skulls that pre-date the 1960s revealed a lower
is composed of proteins and glycoproteins deposited from sali-
prevalence of tooth resorption than current estimates, which
va and gingival crevicular fluid. Early enamel pellicle protects
suggests a relatively recent increase. Commercial foods have
and lubricates. However, as pellicle ages, existing constituents
been implicated as a causative factor in the increased detection
are modified and additional salivary, crevicular and bacterial of tooth resorption in cats based on several physical and chem-
components are incorporated. Enamel pellicle and its compo- ical properties of these foods.
nents provide a framework for initial bacterial colonization and Questions have been raised that relate to the common prac-
also function in the maturation of dental plaque (Scannapieco tice of applying an acidic coating to dry cat foods (i.e., feline
and Levine, 1990; Rolla, 1983). digest) to enhance palatability. Human studies have demonstrat-
ed that consumption of a food or beverage with an acidic pH
DENTAL PLAQUE contributes to erosive lesions. Additionally, chronic vom-
iting/regurgitation have been associated with these lesions
Pellicle deposition and subsequent bacterial colonization
because vomitus is acidic. To address this issue, Zetner and
occur almost immediately after a dental prophylaxis. Studies
Steurer investigated the tooth surface pH of cats with 1) tooth
have demonstrated that within minutes after polishing, ap- resorption, 2) chronic oral inflammatory disease and 3) cats with
2
proximately one million organisms are deposited per mm of
no oral lesions. These researchers also measured tooth surface
enamel surface (Lindhe, 1989). Aggregates of bacteria com- pH after cats consumed either a commercial moist food or a
bine with salivary glycoproteins, extracellular polysaccharides commercial acid-coated dry food. Results from this study
and occasionally epithelial and inflammatory cells to form a demonstrated that cats with tooth resorption had lower tooth-
soft adherent plaque that covers tooth surfaces. Dental plaque surface pH values than healthy cats, but that consumption of the
is not easily removed by normal tongue actions, water drink- dry food was not associated with the pathogenesis of odonto-
ing or forced water spray, but can be affected by mechanical clastic resorptive lesions.
and chemical means. It has also been suggested that hard dry cat foods cause
microfractures that predispose teeth to infection and initiate the
Dental plaque has a specific composition and structure that
inflammatory cascade leading to odontoclastic activation.
changes with time (DuPont, 1997). Supragingival dental
However, it must also be noted that teeth that are not normally
plaque forms above and along the free gingival margin; subgin-
associated with mechanical forces related to consuming dry
gival dental plaque is formed entirely within the gingival sulcus.
foods are also susceptible to tooth resorption.
Growth and maturation of supragingival plaque are necessary Finally, recent work has implicated dietary vitamin D in the eti-
for subsequent colonization of subgingival surfaces by dental ology of tooth resorption. Evidence in support of this theory
plaque (Kornman, 1986). Supragingival and subgingival plaque includes the correlation between cats with tooth resorption and
are distinct compositional masses that influence the inflamma- increased blood levels of 25-hydroxyvitamin D, and histologic
tory reaction of gingival tissues. Studies in people have demon- comparisons of the effects of excessive intake of vitamin D to
strated an organized progression of microbial colonization and the effects of tooth resorption. Because cats cannot synthesize
growth that leads to the development of mature pathogenic vitamin D, they must rely on their diet to supply the nutritional
requirement.
dental plaque (Lindhe, 1989).
Definitive studies that document a cause-and-effect relation-
Canine and feline studies characterizing the microbial com-
ship implicating a single etiologic factor have not yet been done,
position of supragingival and subgingival plaque have been
and care must be taken to maintain distinctions between casu-
reported. Supragingival plaque in dogs with clinically healthy
al and causal relationships when evaluating current information.
gingivae is primarily composed of gram-positive aerobic organ- In addition, it is possible that tooth resorption has a multifactor-
isms. As plaque matures, the bacterial composition shifts to a ial etiology, highlighting the complexity of the problem and
predominately gram-negative anaerobic flora (Courant et al, emphasizing the need for additional research.
1968; Soames and Davis, 1974; Wunder et al, 1976; Syed et al,
1980, 1981; Svanberg et al, 1982; Isogai et al, 1988; Mallonee The Bibliography for Box 47-3 can be found at
et al, 1988; Hennet and Harvey, 1991, 1991a, 1991b; Boyce et www.markmorris.org.
al, 1995; Harvey et al, 1995). Several sources have detailed lists
of specific bacteria associated with periodontal diseases of dogs
(Hardham et al, 2005; Syed et al, 1980; Wunder et al, 1976; rial plaque is the most important substrate in the development
Hennet and Harvey, 1991, 1991a, 1991b; Allaker et al, 1997; of periodontal disease.
Isogai et al, 1989; Svanbert et al, 1982) and cats (Mallonee et
al, 1988). The inflammation and destruction that accompanies MATERIA ALBA AND OTHER ORAL DEBRIS
periodontal disease results from the direct action of bacteria and Materia alba is a soft mixture of salivary proteins, bacteria,
their by-products on periodontal tissues and the indirect activa- desquamated epithelial cells and leukocyte fragments. Materia
tion of the host immune response (Genco, 1990). Thus, bacte- alba and dental plaque are two distinct materials. Materia alba