L13 Microbiology of Endodontic Infection Flashcards
(18 cards)
What are the causes of endododontic infection?
- Caries progression (most common)
- Pulp exposure due to trauma or fracture
- Bacteria in circulation settling in pulpal circulation = anachoresis
- Severe periodontal disease, exposure of root and exposure of accessory canals
What is an apicetomy and when is it likely to be performed?
May be indicated after RCT when bacteria remains in apex or secondary canals, causes secondary infection,
Apicetomy: removal of the apical third of the tooth and its associated accessory canals to remove the bacterial population and prevent further infection.
How can we select the causative bacteria of a disease in a polymicrobial environment?
- Numerical predominance of microorganism + its presence in disease (association)
- E.g. streptococcus and sore throat
What are Koch’s postulates for endogenous infection?
- Numerical predominance
- Immune response
- Microbe produces relevant factors
- Virulence proven in vivo and in vitro
- Elimination studies
What are the various sampling sites of the endodontic environment?
- Periapical lesions
- Primary endodontic lesions
- Secondary endodontic lesions (after RCT)
- Deep carious lesions (advancing edge)
How can samples of the endodontic environment be acquired?
- Use paper points
- Discarded filling material of primary RCT when performing secondary RCT
- Pus
- Washings from canal (inject with saline)
- Extracted teeth
- Apicetomy
What considerations should be made when sampling the endodontic environment?
- Prevent contamination from surrounding environemnt, use rubber dam, antiseptics etc
- Transportation time to lab should be minimised
- Laboratory processing must be appropriate
How can bacteria be identified in culture?
- Agar plates
- Traditional biochemical and staining methods
Which bacteria are commonly identified in deep carious lesions?
- Gram positive organisms
- Lactobacillus sp
- Streptococci sp
- A few obligate anaerobes
- Mostly non-motile bacteria
Which bacteria are commonly identified in primary endodontic infection?
- Mostly strictly anaerobic species
- Prevotella sp
- Porphyromonas sp
- Tanerella forsythus
- Dialister species
Which bacteria are commonly identified in secondary endodontic infection?
- Fusobacterium nucleatum
- Prevotella sp
- Campylobacter rectus
- Streptococcus sp
- Enterococcus
Describe bacterial succession of caries lesions into the pulp.
- Acid producing organisms at advancing edge inavde dentinal tubules and demineralise tubule walls
- Followed by proteolytic bacteria which degrade the organic matrox
- Bacterial interdependence/synergy: in models, combinations of bacteria seem to be capable of inducing bacteria, rather than one species alone
What are virulence factors? Provide examples.
Assist bacteria in colonisation.
Survive well in nutrient depleted areas ie. after endodontic treatment.
E.g. LPS, PG, LTA
What are the 2 main methods of molecular analysis of oral bacteria?
- PCR
- Robust bacterial classification system
What is PCR?
Polymerase chain reaction:
- Amplifies short sequences of nucleic acids exponentially
What is the robust bacterial classification system?
Classifying bacteria based on evolution, compares variable sequences in 16S ribosomal RNA to construct a phylogenetic tree.
What is community profiling?
A form of metagenomics.
Advanced sequencing techniques to form a large profile of the species present, and how the profile in a patient changes over time.
Which bacterial species is highly prevalent in secondary endodontic infection?
Enterococci species
- Thrives in nutrient depleted areas
- Naturally resistant to many antimicrobials
- Can colonise areas that other bacteria cannot
- Good at forming biofilms
- Unknown origin, not present in deep carious lesions
- Fingerpriniting methods suggest they do not originate from oral cavity or elsewhere in the body
