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Oral Biology > Aetiology of Caries > Flashcards

Aetiology of Caries Flashcards

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1
Q

What are dental caries?

A

bacterial disease of calcified tissues of the teeth characterised by the demineralisation of the inorganic and destruction of the organic substance of the tooth

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2
Q

What’s the Acidogenic theory?

A
  • Caries is the result from a shift in metabolic activity accompanied by a gradual change in ecology of the dental biofilm
  • Acid production by oral bacteria as a result of carbohydrate fermentation leads to decalcification of the hard tissue tooth substance and disintegration of the organic matrix
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3
Q

What are Primary modifying factors for Dental Caries?

A
  • Tooth Anatomy
  • Saliva
  • Biofilm pH
  • Use of Fluoride
  • Oral hygiene
  • Immune System
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4
Q

What are the Secondary modifying factors for Dental Caries?

A
  • Socioeconomic status
  • Education
  • Life-style
  • Environment
  • Occupation
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5
Q

What’s the development of dental biofilms?

A
  1. Pellicle formation
  2. Attachment of eary bacterial colonisers (0-14hrs)
  3. Co-adhesion and growth of attached bacteria leading to the formation of microcoloconies (4-24hrs)
    4 Microbial succession leading to increased species diversity concomitant with continued co-adhesion and growth of microcolonies (1-7 days)
  4. Climax community/mature biofilm (1 week +)
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6
Q

What are examples of the Initial colonisers?

A

Streptococci: Sangius, Oralis, Mitis

  • 95% of the Streptococci
  • Actinomyces spp

Nutrients: from endogenous molecules from saliva

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7
Q

What are the next colonisers of biofilm?

A
  • Actinomyces dominate

- Bacteria produce polysaccharodes and these contribute to the biofilm matrix

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8
Q

What’s the composition of a mature biofilm?

A
  • Diverse composition
  • Majority are facultative or obligately anaerobic
  • Acid producing gram+ cocci
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9
Q

What are the cariogenic features of dental biofilm bacteria?

A
  • Rapidly transport fermentable sugars when in competition with other plaque bacteria - conversion of such sugars to ACID
  • Maintain sugar metabolism under extreme environmental conditions (low pH)
  • Production of extracellular and intracellular polysaccharides
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10
Q

Microbiology of Dental Caries: Does Streptococci Mutans play a role?

A
  • It plays an important role in caries initiation, while other bacteria such as lactobacilli may be important in lesion progression
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11
Q

Are Lactobacilli important in dentine caries?

A

YES

  • Contributes to demineralisation of teeth once lesions are established
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12
Q

What’s special about Oral Actinomyces?

A
  • Gram + , non-spore, rods and filaments
  • Goof plaque former
  • ALL SPECIES FERMENT GLUCOSE AND MOSTLY PRODUCE LACTIC ACID
  • A. Ciccosus + naeslundii have the ability to INDUCE ROOT CARIES
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13
Q

What are some of the Intrinsic factors for caries susceptibility?

A
  • Enamel composition
  • Enamel structure
  • Tooth morphology
  • Tooth position
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14
Q

What are some of the extrinsic factors for caries susceptibility?

A
  • Saliva
  • Diet
  • Use of fluoride
  • Immunity
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15
Q

What’s the resting plaque pH?

A
  • 6.5-7
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16
Q

What happens to the pH in the mouth after an oral rinse of sucrose?

A
  • Drops to 5 within 2-3 minutes

- Takes 20 minutes for the pH to go back to normal

17
Q

The speed with which pH drops is an indicator of?

A
  • The speed of sugar metabolism in the plaque
18
Q

What happens to dietary sugars when they interact with plaque?

A
  • They diffuse through the plaque

- Convert into lactic acid (mainly), acetic and propionic acids by bacteria

19
Q

What’s the critical pH?

A

5.5 - below this enamel begins to dissolve

20
Q

Can bacteria store Carbohydrates?

A
  • YES

- They can store them and use them at a later date

21
Q

What’s the role of Polysaccharides in plaque formation and cariogenesis?

A
  • Plaque store glucose as glycogen
  • S.mutans synthesise other polymers given access to sucrose
  • Increases the bulk of the plaque and are more cariogenic
  • Glucans & Fructans are deposited extracellularly thus providing a voluminous sticky environment for the plaque organisms
22
Q

The ability of microorganisms to form plaque on teeth is directly related to…

A
  • Their ability to synthesis glucans and fructans

- Plaque control methods have targeted Glucosyltransferases

23
Q

Is plaque composition influenced by diet?

A
  • YES
  • S.mutans are more prevalent with sucrose rich diets
  • Lactobacilli is acid tolerant and gound in greater proportions in carious cavities
24
Q

Why is sucrose important in caries development?

A
  • Sucrose intake affects the composition of early plaque leading to higher numbers of bacterial species capable of synthesising glucan from sucrose
25
Q

How does Sucrose alter the composition of plaque?

A
  • Makes it bulkier due to increased Glucan and Fructan secretions
26
Q

Are non-sugar sweeteners cariogenic?

A
  • NO

- Some have caries preventative features (xylitol)

27
Q

How might sugarfree chewing gum prevent caries?

A
  • Increases salivary flow rate and doesn’t contain sugar to feed the plaque
28
Q

What are the preventative qualities of Xylitol?

A
  • Affects bacterial growth and metabolism
  • Reduced biofilm formation
  • Decreases the number of S.mutans
29
Q

What effect do Fluoride ion have on plaque?

A
  • Inhibit bacterial metabolism
30
Q

What happens to Hydroxyapatite crystals with Carbonate incorporation?

A
  • Promotes the carious attack

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