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Introduction
The most popularly accepted theory on bad breath (Tonzetich) is that volatile sulphur compounds (VSCs) hydrogen sulfide and methyl mercaptan are the main components of oral malodor originating from the mouth. Dr. Yaegaki and colleagues have found that hydrogen sulfide is produced from the dorsum of the tongue, while methyl mercaptan and dimethyl disulfide are produced in periodontal disease sites.iv Tongue coating is a major source of VSC. This coating consists of epithelial cells from the oral mucosa, microorganisms, and leukocytes from periodontal pockets.
Studies by Drs. Kleinberg and Codipilly of New York showed gram-negative bacteria holding a significant role in oral malodor formation. Gram-positive bacteria are not involved. Sulfur-containing amino acids, cysteine, cystine and methionine also contribute to bad breath. Other gram-negatives: Fusobacteria, the black pigmented anaerobes, Haemophilus, and Veillonella as well as amino acids other than VSC are participants in malodor production.
When the main odoriferous volatiles are applied to an epithelial surface, hydrogen sulfide and methyl mercaptan are lost rapidly and indole/skatole, putrescine, cadaverine, and organic acids are lost more slowly, indicating the substances have an ability to adhere to the surface and prolong the malodor.v
Studies on whole saliva have yielded information about oral malodor and theories of dental caries etiology. The whole saliva contains a sample of the microbial population from the hard and soft tissues of the mouth and salivary components. Once centrifuged, sediment of bacteria and epithelial cell elements can be sampled (called salivary sediment). The bacteria are freely floating and attached to the epithelial components. The fluid from the centrifugation is saliva from the oral glands and some gingival crevicular fluid; found especially if the subject had significant inflammation. Studies have shown salivary sediment is metabolically and microbiologically similar to pooled dental plaque. (Denepitiya and Kleinberg, 1982; Singer and Kleinberg, 1983.)v
One hundred years ago, Miller added teeth to a mixture of whole saliva and glucose incubated 4 to 24 hours at 37°C. He found that the enamel on the teeth was demineralized and the caries process began (The Miller Acid Decalcification Theory). However, no malodor is produced. Whole saliva with glucose becomes acidic, whole saliva by itself does not. Further studies show that the acidity inhibits bacterial putrefication. The incubated saliva without the glucose is quite odoriferous. Early studies (Sulser, 1939, Berg and Fosdick, 1946; Berg 1947) showed the odor was a result of the bacteria acting on salivary proteins and peptides to yield compounds producing the odor. Tonzetich (1977) confirmed the findings and also showed the air around the incubated saliva is very similar to human breath air.v Malodor is produced in saliva that has a neutral or alkaline pH but is inhibited by an acidic pH. Fermentation of sugars inhibit malodor generation but is the basis of caries formation.
Not only are H2S (hydrogen sulfide) and Ch3SH (methyl mercaptan) major components of malodor, they are destructive to the oral tissues. They can penetrate and react with the mucosa, making it more permeable to some ions and molecules. Researchers have shown that mucosa treated with H2S can be restored to a normal state much more readily than mucosa treated with CH3SH after the compound is removed.ii
H2S and CH3SH damage the cell structure, the integrity of collagen, and the metabolism of cells. Studies demonstrated a 70% lower collagen content in tissues treated with the H2S and CH3SH as compared to the control tissues. Tests involving periodontal disease show collagen components in crevicular fluid in the diseased sites, and collagen loss of the same amount in surrounding tissues.ii
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the Tongue
