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Cariogenicity of lactobacilli
29-03-2010
Cariogenicity of lactobacilli According to the specific plaque hypothesis, some strains of lactobacilli are considered to be major caries pathogens along with S mutans and S sobrinus. Lactobacilli are acidogenic and even more aciduric than MS. Mutans streptococci are strongly correlated to the etiology of initial enamel and root surface lesions, because they can adhere to and colonize the tooth surfaces. Lactobacilli are more dependent on retentive sites for heavy colonization: Mutans streptococci are regarded as the pioneers, followed by lactobacilli in the succession toward more cariogenic plaque. This has been shown in a study on the development of so-called nursing caries (Milnes and Bowden, 1985) and by Mac Pherson et al (1990) in another study on plaque flora associated with early enamel demineralization. Lactobacilli are most often found in the deepest part of the lesion (dentin), an environment with prolonged periods of very low pH. Lactobacilli are highly influenced by the dietary carbohydrate content and intake frequency, in addition to reflecting an acidogenic environment by their very presence, because they are so aciduric. They also indicate the presence of substrate for other bacteria, such as mutans streptococci. Persistently high levels of lactobacilli after elimination of retention sites such as cavitated carious lesions indicate a diet rich in carbohydrates.
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Comments
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Articles for theme “caries”:
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29-03-2010
Methods of samplingAs mentioned earlier, the correlation between salivary MS counts and the number of MS-colonized tooth surfaces is relatively good (Lindquist et al, 1989), and simple salivary sampling methods are a more convenient and realistic means of assessing the severity of MS infection than sampling from individual tooth surfaces. Laboratory methods. Saliva is collected, mixed with a proper transport medium, and forwarded to a microbiologic laboratory. After incubation using a selective medium, mutans colonies are counted and the results are expressed as the number of colonyforming units per milliliter of saliva.
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29-03-2010
Cariogenicity of mutans streptococciMutans streptococci are acidogenic as well as aciduric and can adhere to tooth surfaces (Gibbons et al, 1986). Mutans streptococci can produce extracellular and intracellular polysaccharides from sucrose. Intracellular polysaccharides in particular can be degraded during periods of low nutrient supply, indicating that these polysaccharides increase the virulence of some MS species (S mutans and S sobrinus). Because the microbial ecology of the mouth is highly complex, strains of the same species could vary considerably in virulence (Bowden and Edwardsson, 1994).
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29-03-2010
Role of Specific Cariogenic MicrofloraIntroductionMicroorganisms implicated in the etiology of dental caries must be acidogenic as well as aciduric. To initiate carious lesions in enamel, the microorganisms must also be able to colonize the tooth surface and survive in competition with less harmful species, forming biofilms¾the so-called dental plaque. As early as 1960, Fitzgerald and Keyes showed that certain microorganisms isolated from human dental plaque, when inoculated in germ-free rodents on a high-sucrose diet, resulted in the spread of rampant caries.
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29-03-2010
Strategies for prevention and control of caries based on plaque ecology hypothesis According to the plaque ecology hypothesis, low pH (less than 5) will promote overgrowth of aciduric microorganisms, such as the cariogenic mutans streptococci and lactobacilli, at the expense of less acid-tolerant plaque microorganisms, such as S oralis, which are associated with healthy tooth surfaces. Therefore the treatment strategy would be to increase plaque pH and thereby promote reestablishment of the harmless normal microflora of the tooth surfaces.
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29-03-2010
Effect of plaque ecologyOwing to differences in local environmental conditions, the microflora of mucosal surfaces differs in composition from that of dental plaque. Similarly, the plaque microflora varies in composition at distinct anatomic sites on the tooth ¾ for example, in fissures, on approximal surfaces, and in the gingival crevice. The resident microflora of a site acts as part of the host defenses by preventing colonization by exogenous (and often pathogenic) microorganisms.
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