pathogenesis of infection
When microbes find a new host and start to multiply – called colonisation
A balance can develop between colonised microbes and humans – will lead to ‘so called’ normal flora
If microbe causes disease – called an infection
If source of microbe is patient’s own flora – called an endogenous infection
If source of microbe is flora from outside the patient’s body – called exogenous infection
when microbes find a new host and start to multiple
colonisation
a balance can develop between colonised microbes and humans
so called ‘normal flora’
if microbe causes disease
infection
if source of microbe is patient’s own flora
endogeneous infection
if source of microbe is flora from outside the patient’ body
exogeneous infection
primary pathogens
alwyas cause disease in new susceptible humans
microbes that cause disease only in immunosuppressed individuals
oppurtunistic pathogens
opportunistic pathogens found in
normal flora
‘carrier state’
microbes can remain in the human body for some time after infection
The continued presence of an organism (bacteria, virus, or parasite) in the body that does not cause symptoms, but is able to be transmitted and infect other persons.
colonisation =
the presence of bacteria on a body surface (like skin, mouth, intestines, airway) without causeing disease in person
normal flora =
presence of bacteria normally found at specific body sites
infection =
invasion and multiplication of microorganisms in body tissues, especially that causing local cellular injury to competition
dental plaque
- ‘a diverse microbial community (predominantly bacteria) found on the tooth surface, embedded in a matrix of polymers of bacterial and salivary origin’
- Main aetiological agent associated with caries
main aetiological agent associated with caries
plaque
plaque develops
develops naturally on teeth, and forms part of the defence systems of the
host by helping to prevent colonisation of enamel by exogenous (and often pathogenic) microorganisms (colonisation resistance).
plaque beneficial role
colonisation resistance - forms part of host defence systems by helping prevent colonisation of enamel by exogenous microoganisms
plaque is a ….
biofilm
plaque preferentially found
at protected and stagnant surfaces on teeth
- greatst risk of disease
mechanisms of plaque formation
attachment, growth, removal and reattachment of bacteria to the tooth surface is a continuous and dynamic process.
However, several distinct processes can be recognised:
- Absorption of salivary proteins and glycoproteins, together with some bacterial molecules, to the tooth surface to form a conditioning film (the acquired pellicle).
- Long-range (>5Onm), non-specific interaction of microbial cell surfaces with the acquired pellicle via van der Waals attractive forces.
- Shorter-range (10-20nm) interactions, in which the interplay of van der Waals attraction forces and electrostatic repulsion produces a weak area of attraction that can result in reversible adhesion to the surface.
- Irreversible adhesion can occur if specific inter-molecular interactions take place between adhesins on the cell surface and receptors in the acquired pellicle.
- Secondary or late-colonisers attach to primary colonisers (coaggregation), also by specific inter-molecular interactions.
Cell division of the attached cells to produce confluent growth, and a bioflim.
oral microbiome
at least 700 bacterial species
predominately on hard tissues
- also found on dorsum of tongue
- can be found on soft tissues (shedding)
sterile at birth
- via food, milk, water, mothers’ saliva
plaque composition and variation
Environmental conditions on a tooth are not uniform.
Differences exist in the degree of protection from oral removal forces and in the gradients of many biological and chemical factors that influence the growth of the resident microfiora.
These differences will be reflected in variations in the composition of the microbial community, particularly at sites so obviously distinct as the gingival crevice, approximal regions, smooth surfaces, and pits and fissures.
- fissure plaque will be influenced more by saliva than other sites, whereas gingival crevicular fluid (GCF) has a greater impact on plaque in the gingival crevice.
- gingival crevice also has a lower redox potential (Eh) and is colonised by higher numbers of anaerobes, especially proteolytic species which obtain key growth factors from the catabolism of host proteins and glycoproteins in GCF.
plaque structure
studied mainly by electron microscopy.
A heterogeneous and a colonial type of sub-structure have been observed in sections of smooth surface plaque.
- heterogeneous type is associated with pallisaded regions where filaments and cocci appear to be aligned in parallel at right angles to the enamel surface.
- Micro-colonies, presumably of single populations, have also been observed.
- In addition, horizontal stratification has been described.
The early stages of development results in a condensed layer of apparently a limited number of bacterial types.
From 7 to 14 days, the bulk layer forms which shows less orientation but a higher morphological diversity.
This layering has been attributed directly to bacterial succession
In mature plaque, organisms have been seen in direct contact with the enamel due to enzymic attack on the pellicle. Electron microscopy has confirmed the presence of an inter-bacterial matrix of polysaccharide.
barriers to wide variety of microbes that enter the oral cavity regularly
- saliva
- pH
- temperature
- immune system
initally prevent many species from surviving
then brushing and flossing teeth clears up some built up biofilm
oral antibiotics inhibit growth
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Role of F42
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Caries Microbiology - The basics62
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methods of caries management67
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General Anaesthesia for Dental Treatment for Children76
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Caries Pattern and Diagnosis55
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introduction to radiographic interpretation and caries on radiographs21
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Caries management for children and young people- strategies at the tooth level49
