Bacterial Flora in Human Oral Cavity

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Bacterial Flora in Human Oral Cavity

• Made by
• Luan Yijun, Zhang Yanhui, Liu Junying, Li Na,
  Xuxia, Liu Song, Wang Ge, Zhang Tianqi, Ying
  Wanggui,
• Li Shengfeng

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• 1.Normal flora in human oral cavity
• 2.Several dental diseases caused by bacteria
• 3.What can we do to prevent dental disease

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• The human mouth is home to more than 500 species
  of bacteria.
• Oral bacteria include streptococci, lactobacilli,
  staphylococci and corynebacteria(????), with a
  great number of anaerobes, especially
  bacteroides(???).

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Normal flora changes with age

• At birth the oral cavity is sterile
• It rapidly becomes colonized from the environment
  

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• Streptococcus salivarius is dominant and may make
  up 98 of the total oral flora until the
  appearance of the teeth (6 - 9 months in humans)
• The eruption of the teeth during the first year
  leads to colonization by S. mutans(?????) and S.
  sanguis ,they will persist as long as teeth
  remain

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• Other strains of streptococci adhere strongly to
  the gums(??) and cheeks but not to the teeth
• The creation of the gingival crevice(????) area
  increases the habitat for the variety of
  anaerobic species found

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• Bacteroides and spirochetes colonize around
  puberty

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Functions of normal flora

• occupy available colonization sites
• contribute to host nutrition
• contribute to immunity
• exert microbial antagonism against heterogenous
  species

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• Since some of these bacteria are parasites or
  opportunistic pathogens, if they invade tissues
  not normally accessible to them, characteristic
  diseases result
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• Dental Plaque (???)
• Dental Caries (??)
• Periodontal Disease (???)

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Dental Plaque

• material adhering to the teeth, consists of
  bacterial cells (60-70 the volume of the
  plaque), salivary polymers, and bacterial
  extracellular products
• Streptococcus sanguis and Streptococcus mutans

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Mechanism
a weak attachment of the streptococcal cells to
salivary glycoproteins ?a pellicle on the
surface of the teeth ? a stronger attachment ? (
glycosyl transferase, an enzyme on the cell
surface of Streptococcus mutans, is apparently
involved in initial attachment of the bacterial
cells to the tooth surface and ) ? conversion of
Sucrose (??)to dextran(????) and levan(????)
polymers ? form the extracellular matrix of plaque
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Dental Caries

• the destruction of the enamel(??), dentin(??)or
  cementum(???)
• of teeth due to bacterial activities
• Streptococcus mutans, Lactobacilli,
  Actinomyces(???), and various proteolytic
  bacteria

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Physiological and Biochemical Properties of
Streptococcus mutans

• a regular component of the normal oral flora of
  humans
• contains the enzyme glycosyl transferase
• produces lactic acid, produces more lactic acid
  and is more acid-tolerant than most other
  streptococci
• stores polysaccharides made from dietary sugars,
  can be utilized as reserve carbon and energy
  sources for production of lactic acid

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Periodontal Disease

• bacterial infections that affect the supporting
  structures of the teeth (gingiva, cementum(???),
  periodontal membrane and alveolar bone)
• Actinomyces, streptococci, spirochetes and
  Bacteroides

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• The mechanisms of tissue destruction in
  periodontal disease are not clearly defined but
  hydrolytic enzymes, endotoxins, and other toxic
  bacterial metabolites seem to be involved

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How to prevent dental diseases

• Brush your teeth two times everyday, after
  arousing and before sleeping
• Use toothpastes which contains fluoride
• Use dental floss to clean your teeth-gaps everyday

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Thank you!