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Micro Lesson 8 stu notes - Oral Microbiology Caries...

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Oral Microbiology: Caries, periodontal disease and other oral infections DEA 1135 Introduction to Microbiology Development of Oral Microflora Oral cavity usually sterile at birth Number of organisms increases 8 hours after birth At 12 months most children have several types of oral microorganisms By preschool age, oral flora resembles flora of adult Plaque Plaque is a group of microbes that stick to the tooth surface. It's defined as the soft deposits that form the biofilm adhering to the tooth surface or other hard surfaces in the oral cavity. Plaque is composed mostly of microorganisms, approximately 325 different bacterial species, as well as fungus, viruses, yeasts and protozoa In order for plaque to form it must have a form of energy. The energy used are sugars which are known to be metabolized to lactic acid, which acts as the demineralizing agent in dental caries. As the glucose is metabolized to the lactic acid, the cell transforms the glucose to adenosine triphosphate (ATP), heat and lactic acid. It is these materials in the plaque that cause decalcification and cavitation of tooth structure. It is formed readily on tooth surfaces after 1-2 days with no oral hygiene measures. It typically forms on the gingival 1/3 of the tooth surface and in cracks, pits and fissures. Early forming microorganisms are gram + aerobes but as the film develops, there is a transition to a gram - anaerobic environment. Initial colonizers are Actinomyces viscous and Streptococcus sanguis . Dental plaque plays a major role in dental caries. 1
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As the plaque continues to build, it begins to harden in response to minerals in the saliva. This is termed calculus. Calculus Calculus is non-living, it has no viable cells within it, and it’s usually hard and crusty. Because it forms near the gingival margin, it tends to harbor more plaque and act like a ledge under which food and microorganisms can hide. It is a calcifying mass that forms on the surface of natural teeth and dental prostheses consisting of mineralized bacterial plaque. It can be classified as either supragingival (salivary) or subgingival (serum). Caries is a bacterial infection of the teeth versus Periodontal disease is a bacterial infection of the supporting structures around the teeth. Dental caries is composed of three basic types of microorganisms: Streptococcus mutans - Streptococcus sanguis Actinomyces - A. Naeslundii - A. Viscosus Lactobacilli Each has its own anatomical site on the tooth and particular disease- causing microorganisms. All cause pit and fissure caries which are bacteria that are forced into the bony structures of the tooth. 2
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Caries Prerequisites for caries development: 1. Cariogenic bacteria 2. Supply of substrate for acid production 3. Susceptible host Acid production in plaque 1. Decalcification of teeth occurs by acids produced thru bacterial fermentation 2. Cariogenic plaque, when exposed to sugar, show a decrease in pH
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