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The incorporation of 1 or 3% sodium phytate in confectioners sugar produced minimal changes in the physical,chemical, and microbial composition of dental plaque in tube-fed monkeys during a two-week period. Only a reduction in yeasts and lactobacilli could be ascribed to the presence of phytate. Other changes were attributable to the transition from conventional feeding to tube-feeding, irrespective of the presence of absence of phytate.

Irradiation of the major salivary glands of monkeys (Macaca mulatta) fed cariogenic diets leads to caries clinically indistinguishable from radiation caries in man. This study compares the organic composition of individual samples of plaque fluid and saliva from irradiated and control monkeys receiving the same cariogenic diet. Plaque and saliva were collected from fasting, tranquillised animals. Four irradiated animals were sampled repeatedly as were non-irradiated controls. Total protein, albumin, immunoglobulins A, G, and M, and the third component of complement (C'3) were quantitated in plaque fluid and whole saliva. Salivary amylase and peroxidase activities were also determined. Plaque fluid and saliva samples were also subjected to polyacrylamide gel electrophoresis. The total viable anaerobic count and numbers of Streptococcus mutans were determined in samples of plaque. The results suggest that the major effect of irradiation leading to increased numbers of S. mutans and caries susceptibility is in the amount, and not the composition, of the saliva produced by the residual gland tissue. The scanty flow of saliva may reduce the effectiveness of cleansing, buffering and lubrication mechanisms as well as resulting in a marked reduction in the total amount of specific and non-specific immune factors entering the mouth.

Co-60 gamma irradiation of the salivary glands of Macaca mulata monkeys fed a cariogenic diet led to the rapid onset of dental caries resembling that in irradiated human patients. Plaque fluid and saliva were sampled from irradiated monkeys, nonirradiated controls and a group of animals fed a noncariogenic diet in order to look for changes which might occur in inorganic composition related to the caries development and to dietary differences. Salivary calcium and phosphate levels were not markedly changed after irradiation: iodide levels were raised, while thiocyanate levels fell. In plaque fluid, calcium concentrations were not affected by irradiation, but were higher in animals fed a noncariogenic diet. Phosphate levels were higher with a cariogenic diet and further increased in irradiated animals. Magnesium levels were occasionally higher than those of calcium. Other differences in plaque fluid composition may be related to secondary effects of the concomitant gingival disease. The results do not point clearly at a specific change in the quality of the saliva produced by the residual gland tissue after irradiation which precipitates the rampant caries. It is more likely that the great reduction in the quantity of saliva with its protective constituents is responsible.

Separate samples of supragingival dental plaque overtly free of blood were centrifuged to obtain the free fluid phase (plaque fluid). Bound protein was eluted from the plaque bacteria and matrix by washing the plaque with a low-pH buffer. The plaque fluid, low pH eluate, and whole saliva were assayed for immunoglobulins A, G, and M, the third component of complement, lysozyme, lactoferrin, and lactoperoxidase. Concentrations of total protein and albumin were also determined. Antibody reactive with specific plaque bacteria was detected by indirect immunofluorescent microscopy. Specific and nonspecific immune proteins were present in plaque fluid from adult subjects at significantly greater concentrations than in their saliva, which suggests that these proteins are concentrated in dental plaque. The results indicate that both saliva and gingival exudate contribute to the immunological proteins found in the free fluid phase of dental plaque. The observation that immunoglobulin A antibody reactive with plaque bacteria could be detected in plaque fluid suggests that a wide variety of immunological reactions may occur in the dental plaque. These potential interactions between host, plaque bacteria, and their products could serve to influence the plaque flora and its ability to induce disease.

The structural integrity of immunoglobulin A (IgA), IgG, and IgM and lactoferrin in dental plaque fluid samples from two populations of Colombian children with contrasting levels of dental caries was examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by electrophoretic transfer to nitrocellulose. The immune factors or their fragments or both were detected with monospecific antibody conjugated with horseradish peroxidase. All the immune factors examined were extensively degraded, although there appeared to be small amounts of intact IgA and IgG in some samples. Analysis of the samples with antibody to secretory component showed that secretory IgA as well as serum IgA was degraded. IgG appeared to be cleaved into two major fragments, one fragment having a relative mobility similar to the F(ab')2 fragment of IgG and the other a relative mobility slightly greater than Fc. IgM and lactoferrin were virtually completely degraded. There was no apparent relationship between the fragmentation patterns of IgA and IgG in the plaque fluid samples from the two communities and their susceptibility to dental caries.