Endodontic Microbiology Flashcards
What is the main causes of pulp disease?
Bacteria (When pulps were exposed to bacteria in rats the pulp degenerated and necrosed, when pulps were germ-free the pulps healed)
How do bacteria get into the pulp?
Possible pathways:
Caries
Cracks
Restorations breaking down
Fractures of teeth or restorations
Trauma
Periodontal disease
(Most common pathways are the first 3 methods)
Are cracks in the teeth the same thing as fractures in the teeth?
No
What is the role of bacteria in periapical diseases
Periapical inflammation is directly related to invasion of the canal (korzen et al 1974)
If bacteria are present all around the canal then periapical inflammation is more severe (Korzen et al 1974)
Periapical inflammation was found with necrotic pulps. (Moller et al 1981)
Inflammation was only found when the canals were infected. (Moller et al 1981)
Periapical inflammation was found only incases with infected canals (Sundqvist 1976)
Periapical inflammation and the size of it was directly correlated with the number of strains of bacteria present.
What did sundqvist 1976 find ?
Periapical inflammation was only found in cases with infected canals.
Infected canals always had >1 strain, up to 12 strains isolated.
Size of the radiolucency was directly related to the number of strains that were isolated.
Patients with pain had >6 strains
Acute inflammation means more strains are present
How does periapical inflammation correlate with the state if the pulp?
No periapical inflammation with necrotic pulps
Inflammation is only found when the root canal is infected
Apical periodontitis is a direct result of bacteria being in the root canal system
What happens to tooth if the apical blood supply is comprimised?
If there is damage to the apical blood supply there usually is damage to the tooth (crack)
What is the most common cause of root canal inflammation usually?
Possibly cracks in the tooth
What happens to the type of infecting microbes with time?
The longer the tooth has been infected the greater the proportion of anaerobic bacteria.
What are the conditions favourable for bacterial colonisation of root canals?
Space (Bacteria have to have space to colonize in the same way a finger needs to be cut for infection to take place. Avenue for bacterial entry is essential.)
Co-colonizing organisms (Bacteria co-colonizing organisms are essential for certain functions.)
Low oxygen tension (anaerobic bacteria)
Nutrients such as pulp tissue remnants, necrotic debris, saliva, foods, inflammatory exudate. (If bacteria can get in so can nutrients, and tooth anatomy protects bacteria from the immune system))
What are the biological aims of endodontic treatment?
To remove from the root canal system all organic material that is capable of decomposing into tissue destructive by-products or that can support bacterial growth.
To remove or destroy all the micro-organisms present in the root canal system.
Make environment of the tooth unsuitable for bacteria which makes it unlikely they will live in the tooth.
What are the mechanical aims of endodontic treatment?
To prepare root canal space to a form which allows complete filling
To fill the prepared canal space with a biocompatible filling material in order to completely seal the coronal and apical ends of the canal
(Don’t want anything in and of itself causing inflammation periapically. We want to also disinfect the root canal system)
Where should the apical end of the root filling be placed in the tooth?
Should be placed as close as possible to the cemento-dentinal junction.
Why can periapical healing take place in an incomplete endodontic treatment?
Endodontic treatment must have done a good job in cleaning and disinfecting the canals prior to adding root filling.
How can the presenting problem that requires root canal treatment be solved?
Diagnosis
Remove cause (cracks, caries, etc)
Remove pulp and disinfect canal
Medical (antiinflammatory and antibacterial)
Interim restortation
How can endodontic microbial flora be reduced?
Identify and remove the cause
Aseptic procedures (Rubber dam)
Mechanical instrumentation
Anti-bacterial irrigants
Intracanal medicaments
Interim and temporary restorations
Root canal filling
Coronal restoration
How important is using medicaments for bacterial colonization?
Did a bunch of studies on different steps of Root canal treatment and checked progression of disease
No irrigant or medicaments used to see purely the effect of filing and instrumentation on the canals.
Initially 88% of the bacteria were anaerboes and 10^4 - 10^6 bacterial cells were isolated
After instrumentation this number decreased 10^2 - 10^3.
After 5 visits 50% of the canals still had the bacteria
How important is instrumentation for eliminating bacteria from root canals?
Instrumentation will reduce number of bacteria but won’t totally eliminate bacteria.
Root canal system is incredibly complicated.
Supporting action of disinfectants is necessary
What is the purpose of irrigation of root canals?
Antimicrobial action
Dissolution of organic and inorganic matter
Flushing action
Lubrication
Help clean areas inaccessible to files
Which solutions are used for irrigation?
Sodium hypochlorite (1%)
EDTA (17%) or EDTA (17%) with cetrimide known as EDTAC
Which irrigant dissolves organic tissue?
NaOCl (sodium hypochlorite)
- Baumgartner and Cuenin - JoE 1992 *
What is left behind after treatment of root canals with sodium hypochlorite?
Removes all pulp remnants and predentin leaving behind smear layer when canal walls were instrumented.
Why is 1% sodium hypochlorite chosen?
It has effective anti-bacterial action
Good tissue dissolving ability
Lower toxicity
When 0.5% is used there is poor tissue dissolving action
Higher concentrations like 2.5% and 5.25% were found to be very toxic
What is the smear layer?
A layer of moistened debris compacted against the canal walls during instrumentation due to the filing/rasping action of files.
It is porous and weakly adherent and breaks down with time.
What does the smear layer consist of?
Mainly inorganic matter but also has come organic matter and tissue remnants and can contain bacteria.
Why must the smear layer be removed?
It reduces the permeability of dentine.
It is porous and weakly adherent and breaks down with time.
Reduces adhesion of sealers to the canal walls
How is the smear layer removed?
Can be removed with chelating agents such as EDTAC
What happens if the smear layer isn’t removed?
If smear layer isnt removed prior to the filling of an endodontic restoration gaps will form when the smear layer disappears.
What is the benefit of using EDTA ?
When irrigated with EDTA the inorganic material is removed from the smear layer.
Why is EDTA used in combination with NaOCl?
In the case of both organic and inorganic material being present in the smear layer it is important to use both EDTA and NaOCl.
When both are used together there is a better anti-microbial action compared to NaOCl being used alone.
How is EDTA and NaOCl administered to a root canal?
File -> Irrigate -> File -> Irrigate
Flush out canal as much as possible following filing.
A study by Baumgartner showed this is very effective compared to not following this sequence and had much better antibacterial action compared with NaOCl alone.
Which is easier to remove; organic or inorganic smear layer?
The organic smear layer is much easier to remove than the inorganic
Which irrigation sequence was found to be the best?
EDTAC / NaOCl / EDTAC
However, cleanest canal walls were seen to have the more NaOCl.
Other sequences that were tried were:
NaOCl / EDTAC / NaOCl
Savlon - control
- Abbott et al*
What is ledermix?
A combination of an antibiotic and a steroid used in endodontics.
What additional benefits were seen in using the EDTAC/NaOCl/EDTAC sequence?
The permeability of dentine was maintained.
Increased diffusive capacity of ledermix through the dentinal tubules.
More efficient anti-bacterial action.
Leaves dentinal tubules open which maintains permeability of dentine as well as increasing access for medicaments.
What steroid and what antibiotic is used in ledermix?
Triamcinolone
Demeclocycline
How can extraradicular infection and foreign body reactions be reduced in endodontic treatment?
Extraradicular infection or foreign body reaction can occur if the debris goes out through the apex of the tooth. Likewise if the file enters the gingiva through the apex. For this reason it is important to flush the canal out for prevention of formation of false canals.
More irrigation is always better
What is the purpose of irrigation?
Anti-microbial action
Dissolution of tissue and debris (organic and inorganic)
Flushing action
Lubrication
Help clean areas inaccessible to files
How is endodontic microbial flora reduced?
Identify and remove the cause
Aseptic procedures
Mechanical instrumentation
Anti-bacterial irrigants
Intracanal medicaments
Interim and temporary restorations
Root canal filling
Coronal restoration
