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Molecular Analysis of the Caries Biofilm in Young Permanent Teeth

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Master's thesis

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Dental caries is the most common infectious disease in childhood. Only a small percentage of children will go through adolescence and not develop caries, and the disease typically is concentrated in children from poor socioeconomic backgrounds with limited access to routine dental care. 16S DNA based bacterial sequencing technology is beginning to make it possible to more accurately identify the pathogens responsible. Most of the previous research has only focused on cultivatable bacteria. This has created a bias in the reported diversity of the bacterial communities in the oral cavity. The purpose of this study is to define the bacterial plaque diversity on permanent teeth in school age children by replacing the traditional culture techniques with new non-culture open-ended methods for identification. Nine caries-free subjects and 9 subjects with caries 8 to 16 years of age were selected for identification of bacteria by cloning and sequencing 16S ribosomal DNA. A total of 43 plaque samples 34 samples collected from caries subjects and 9 samples from caries-free subjects were analyzed. A total of 2,151 clones were identified, and 112 species were detected. There was a large representation of known cariogenic taxa present. Streptococcus spp., Veillonella spp. Lactobacillus spp., and Selenomonas spp. were the most predominant genera found in samples. The bacterial flora on the tooth surfaces is quite heterogenous with a small number of taxa represented in the caries biofllm. The findings show that S. mutans and Lactobacillus spp are the prominent bacteria in caries of young permanent teeth. While S. mutans is higher in white spot lesions, Lactobacillus spp clearly out number S. mutans in the advanced lesions past the initial demineralization of tooth structure.

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  • Genetic Engineering and Molecular Biology
  • Medicine and Medical Research
  • Microbiology

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