Endodontics
Course Review
Enoch Ng, DDS 2014
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Virulence – degree of pathogenicity of a microorganism
o
Capsules – protects against phagocytosis
o
LPS/endotoxin
– stimulates overproduction of inflammatory response
Fat and sugar chain, binds to blood proteins which bind to macrophages who release
inflammatory mediators
o
Enzymes – degrade host tissue
o
Ammonia, hydrogen sulfide – tissue toxins
o
Fimbriae – promotes adherence to tissues
o
Extracellular vesicles – stimulate immune response from host
o
Antibiotic resistance – through gene transfer
IDing Bacteria
Culturing
Advantages
Disadvantages
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Assess viability of microbes
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Low cost
-
Unable to grow many bacteria
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False negatives
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Low specificity and sensitivity
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Technique sensitive
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Contamination can occur
PCR – enzymatic method for repeat copying of specific DNA sequences, amplifies minute quantities of biologic
material (genetic Xeroxing)
Advantages
Disadvantages
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Excellent sensitivity
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IDs microbes that cannot be cultured
-
Recent use of 16s ribosome (much shorter t
½
than
DNA) is able to overcome difficulties detecting
viable organisms
-
IDs nonviable microbes (DNA can persist for up to
a year after death)
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Cost/availability
-
Contamination can occur
-
Technique sensitive
Microscopy
Dark field – illuminates organism against dark background
Bright field – specimens visualized by transillumination
Phase contrast – parallel beams of light pass through objects of different density – phase shifts in beams enable differing
contrast of image
Flourescnece – microorganism stained with fluorescent dye and visualized against dark background
Electron – beams of electrons directed through specimen onto a screen
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Obligate Anaerobes
o
Cocci – veillonella
o
Rods
Capnocytophaga
Eikenella
Bacteroides
Saccharolytic
Modified saccharolytic (prevotella)
Assaccharolytic (porpyromonas)
o
Spindle – Fusobacterium
o
Spirochetes – Treponema