Caries microbiology Flashcards
What is the pathogenesis of infection
• When microbes find a new host and start to multiply its called colonisation
• A balance can develop between colonised microbes and humans which is the normal flora
• If microbes cause disease it is an infection, caries is an infection
• If the source of microbe is a patient’s own flora it is called an endogenous infection
If the source of the microbe is flora from outside the patient’s own flora - called an exogenous infection
What is dental plaque
• A diverse microbial community (predominantly bacteria) found on the tooth surface, embedded in a matrix of polymers of bacteria and salivary origin
Plaque is the main aetiological agent associated with caries
Describe the oral microbiome
- At least 700 bacterial species
- Predominantly on hard tissues
- Also found on the dorsum of the tongue and on soft tissues (shedding)
- We are sterile at birth and we acquire bugs through food, milk, water, mother’s saliva etc
Outline plaque formation
- Pellicle formation
- Colonisation by pioneer bacteria (streptococcus species)
- Outgrowth
- Secondary colonisation by other organisms
- Climax community
What are the basic concepts of oral microbiology
- A wide variety of microbes regularly enter the oral cavity
- Host factors effect their growth and prevent many species from surviving
- Brushing and flossing clears some built up biofilm
- Oral antibiotics inhibit growth
- Symbiosis of the oral microbes that are able to survive these conditions form an elaborate scaffold that lives on the tooth enamel and at the interface with the gums
- It forms a barrier for incoming bacteria
What are the host factors
○ Saliva
○ pH
○ Temperature
Immune system
What is caries
• Loss of mineralized surfaces of the tooth
• Surfaces are permanently damaged
• Underlying dentine is at risk or damaged
• Multi-factorial disease
○ Microbial biofilms
○ Acidity, sugar metabolism
What makes someone low risk
○ Alkaline producing bacteria such as S. sanguinis
○ Unstimulated saliva flow >1ml/min
○ Infrequent sucrose consumption
Fluoride intake to levels allowing production of fluorapatite
What makes someone high risk
○ Acid producing bacteria such as mutans streptococci and lactobacilli
○ Unstimulated saliva flow of <0.7ml/min
○ Frequent consumption of high levels of sucrose and other fermentable carbohydrates
○ Little or no fluoride intake
Outline caries progression
- Adhesion
- Survival & growth
- Biofilm formation
- Complex plaque which is difficult to remove
- Acid
Caries and possibly irreversible damage
What are the key cariogenic pathogens
○ Streptococcus mutans ○ Lactobacillus acidophilus ○ Actinomyces viscosus ○ Candida albicans Nocardia spp.
What are the virulence factors of a prokaryotic cell
○ Pili for attachment
○ Capsule which is sticky and protects host immunity
○ Flagellum - swim through bacteria
Endotoxins - released from gram cell walls
Describe caries association with s. mutans
- Produces water soluble and insoluble extracellular polysaccharides from sucrose which help in colonization of the tooth surfaces by consolidating microbial attachment
- Ability to initiate and maintain microbial growth and to continue acid production in sites with a low pH
- Rapid metabolism of sugars to lactic and other organic acids
Can attain the critical pH for enamel demineralisation more rapidly than other common plaque bacteria
What is koch’s postulate
- The microbe must be present in every case of the disease
- The microbe must be isolated from the diseased host and grown in pure culture
- The disease must be reproduced when a pure culture is introduced into a susceptible host
- The microbe must be recovered from an experimentally infected host
Describe s. mutans
- Gram-positive coccus
- 8 serotypes
- Adhesion and biofilm formation
- Metabolizes dietary sucrose to form insoluble polymers of glucose – stick to surfaces
Survive in low pH environments – enamel dissolution
