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Cariogenicity of other bacteria
29-03-2010
Cariogenicity of other bacteria There are overwhelming data from experimental and clinical studies in humans showing that S mutans and S sobrinus and lactobacilli are strongly correlated to caries etiology. However, the use of selective substrates in most of these studies may have introduced some bias. For example, Sansone et al (1993) found that plaque samples with and without MS and lactobacilli were equally acidogenic when cultured at low pH and in the presence of excess glucose. Borgstrom et al (1997) evaluated the pHlowering effect of plaque from carious lesions in enamel as a virulent variable and found a relatively weak correlation among lactobacilli, MS, and dental caries. Root caries is considered to develop at higher pH than enamel caries. Normally, demineralization precedes the breakdown of the organic part (about 40% by volume) of the root surface. Schupbach et al (1995), using a new sampling technique and unselective, anaerobic culturing methods, evaluated the composition of the plaque microbiota covering sound root surfaces, actively carious root surfaces, or arrested lesions. On all surfaces Actinomyces spp predominated, and streptococci and lactobacilli formed a minor part (less than 1%) of the microbiota. With respect to the detected proportions of anaerobes, microaerophiles, Actinomyces naeslundii, Prevotella buccae, and Selenomonas dianae, significant differences were observed among the three categories of root surfaces. The total numbers of CFUs were significantly higher on both caries-free and caries-active surfaces than on arrested lesions. In general, the results supported a polymicrobial etiology for caries initiation on root surfaces, during which A naeslundii, Capnocytophaga spp, and Prevotella spp make specific contributions to the processes of cementum and dentin breakdown. In other words, the roles of bacteria-producing proteolytic enzymes and of acidogenic bacteria other than MS and lactobacilli in the development of root surface caries warrant further investigation (for reviews on specific microflora related to the etiology of dental caries, see Bowden, 1997; Bowden and Edwardsson, 1994; Bratthall and Ericsson, 1994; Emilsson and Krasse, 1985; Loesche, 1986).
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Articles for theme "caries":
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29-03-2010
EvidenceLactobacillus counts have been used to predict the incidence of new carious lesions. Crossner (1981) studied a group of children, who had been given dental treatment at baseline so that no open lesions were present at the bacterial sampling. Two subgroups in this material are of special interest: those with very low or very high lactobacillus counts. Very few individuals in the low lactobacillus group developed new carious lesions over a 64-week period. In the high lactobacillus group, many, but not all, developed new lesions.
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29-03-2010
Cariogenicity of lactobacilliAccording 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.
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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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