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1. CLINICAL IMPLICATIONS &
MICROBIOLOGY OF BACTERIAL
PERSISTENCE AFTER
TREATMENT PROCEDURES
Authors
Jose F. Siqueira Jr, Ph.D,
&
Isabels N. Rocas, PhD
JOE Vol 34, No 11, Nov 2008
PRESENTED BY
Dr. Kishore Kumar .S

2. Contents
Introduction
Aim
Discussion
1.Understanding bacterial Persistance
2.Microbiology goal of endodontic treatment
3.Persistent versus secondary infection
4.Bacterial persistence as a risk factor for
posttreatment disease
5.Strategies to persist
6.When residual bacteria influence treatment
outcome
7.Bacterial Taxa – persisting intracanal procedure
Conclusion
References

3. Introduction
Microorganisms cause virtually all pathoses of the
pulp and the periradicular tissues.
The control of microorganisms and possible
substrate must be an objective in every endodontic
case.
When root canal treatment fails, the cause is
generally believed to be intracanal infection resisting
treatment or microorganisms invading the canal via
coronal leakage of root –filling.
Non surgical retreatment of such cases has a modest
prognosis which may indicate difficulties in the
elimination of the microflora.
o I.E.J.(1998) 31, 1-7
Enterococcus Faecalis is commonly found organism
in failed endodontic cases.
 (JOE 2004)

4. Studies have revealed that the outcome of the
endodontic treatment is significantly influenced by
the presence of bacteria in the root canals at the
time of filling.
The concept of bacteria from the root canal system
should be ultimate goal of treatment of apical
periodontitis.
Successful treatment of both primary and secondary
endodontic infection involve effective eradication of
the causative microorganisms during root canal
treatment procedures
o OOO Vol 103, No 4, April 2007.

5. AIM
This review article focuses on the microbiology and
clinical implications of bacterial persistence after
treatment procedures.

6. Discussion
Understanding bacterial persistence
Studies of bacteria occurring in the root canal after
treatment involves 3 basic conditions
Post instrumentation samples
Post medication samples
Post Obturation samples
Studies investigation bacteria remaining in the root
canals after chemomechanical procedures or
intracanal medication serves the purpose to disclose
the species that has the potential influence the
treatment out come.
Bacteria detected in postmedication samples
survived both chemomechanical procedures or
gained entry into the canal via leakage through the
temporary restoration.
Bacteria found in the post obturation samples of
teeth indicated for retreatment

7. Microbial goals of the endodontic
treatment
Apical periodontitis is an infectious disease caused
by microorganisms colonizing the root canal system.
The endodontic treatment of the teeth containing
irreversibly inflamed pulps is essentially a
prophylactic treatment.
On the other hand, endodontic treatment should
focus not only on prevention of the introduction of
new microorganisms in to the root canal system but
also on the elimination of those located there in.
The success rate of the endodontic treatment will
depend on how effective the clinician is in
accomplishing these goals .

8. Microbiological goal of endodontic treatment of teeth
with apical periodontitis

11. Tissue damage caused either by the bacterial
themselves or by the host defense mechanisms in
response to infection.
The higher the bacterial virulence the lower the
number of cells necessary to cause the disease.
The reachable goal is to reduce bacterial populations
to a level below that necessary to induce or sustain
disease.

12. Endodontic infections usually treated by using a
broad spectrum non specific antimicrobial strategy.
The endodontic infections can only treated by means
of professional intervention using both chemical &
mechanical procedures.
The main step of endodontic treatment involved
with control of infection represented by
chemomechanical preparation & intracanal
medication.
Bacterial elimination from the root canal is
performed by means of mechanical instruments and
irrigation as well as antibacterial effects of the
irrigants.
Sodium hypochlorite is most widely used irrigant.
Chlorhexidine has been proposed as a alternative
irrigant but clinical studies showed that it is not
superior to NaoCl with regards to antibacterial
effectiveness.

13. Because residual bacteria can adversely effect the
treatment out come , the use of inter appointment
medication has been recommended to eliminate the
persisting bacteria.
Studies have shown that intra canal medication with
a calcium hydroxide paste may be necessary to
supplement the antibacterial effects
chemomechanical procedures and preferably render
root canals free of cultivable bacteria before filling.
Entombment of bacteria in the canals by the root
canal filling is one of the goals of Obturation phase.

14. Persistent versus secondary infection as the
cause of failure
It has not been well established whether bacteria
present in the root canal – treated teeth with post-
treatment disease remain from previous treatment
or a consequence of reinfection.
Last two decades have witnessed a marked interest
on the role of secondary infection resulting of
coronal leakage in treated root canals as an
important cause of posttreatment apical
periodontitis.
However, indirect evidence seems to point to
persistent infections as the most common cause of
treatment failure.
Should secondary infections caused by coronal
leakage be the most significant cause of
posttreatment disease, the failure rate for the
treatment of vital teeth, necrotic teeth, n even
would be similar, but they are not.

15. The bacteria present in the root canal at the time of
filling procedures & materials, surviving in the
changed environment, & maintaining periradicular
inflammation.
Bacterial persistence as a risk factor for post
treatment disease
Most intracanal bacteria are sensitive to standard
treatment procedures.
Nevertheless, some bacteria may survive treatment
procedures, & their presence at the time of filling as
detected by culture approaches has been recognized
as a risk factor for posttreatment apical
periodontitis.
In a cases of treatment failure, longitudinal studies
evaluating bacteria at the filling stage & retreatment

16. Microbial taxa found in the root canals filling
stage and the retreatment cases
o Gram positive bacteria
Actinomyces naeslundi
Actinomyces odontolyticus
Anaerococcus prevotii
Eggerthela lenta
Enterococcus faecalis
Gemelia morllorum
Parvimonas micra
Propionibacterium acnes
Propionibacterium propionicum
Pseudoramibacter alactolyticus
Streptococcus anginosus group
Streptococcus mitis

17. o Gram- negative bacteria
Fuso- bacterium nucleatum
Prevotella intermedia
o Fungi
Candida albicans
Studies have shown that Enterococcus faecalis is the
most commonly found species in the root canal
treated teeth exhibiting emergent or persistent
disease.
Theoritically taxa detected at the filling stage but not
at the time of retreatment may not be able to
endure the conditions with in obturated canals
Likewise, Taxa detected at the time of retreatment
but not at the time of filling may represent
secondary infection that developed by lack of a
bacteria tight coronal seal.

18. Stratagies to persist
For bacteria to endure treatment & be detected in
post treatment samples, they must
o 1.resist intracanal treatment procedures
o 2. Adapt to the drastically changed environment

19. o

20. Several strategies may help bacteria to resist the
treatment.
Bacteria can adhere to the root canal walls,
accumulate, & form communities organized in
biofilms, which may be important for the bacterial
resistance to & persistance after intra canal
antimicrobial procedure.
Antimicrobial medicaments used in endodontics can
be inactivated dentin, tissue fluids, & organic matter.

21. Some micro organisms , such as E Faecalis & Candida
albicans, can show resistance to calcium hydroxide, a
commonly used medicament.
Even though most necrotic tissue is removed during
chemo mechanical procedures , remaining bacteria
can also use necrotic tissue remnants as a nutrient
source.
Figdor et. al. reported that E.Faecalis has a ability
survive in environment with scarcity of nutrients &
to flourish when nutrient source is reestablished.
Sedgley. et.al. showed that E.Faecalis has a capacity
to recover from prolonged stravation state in root
canal- treated tooth; when inoculated in to the
canals, this bacterium maintained viability for 12
months without additional nutrients.
Thus viable E.Faecalis entombed at the time of root
canal filling may provide a long term nidus for
subsequent infection.

22. When recidual bacteria influence
treatment out come
Bacteria that resisted intracanal procedures & are
present in the canal at the filling stage can influence
the outcome of the endodontic treatment provided
that..
o they have the ability to withstand period of
nutrient scarcity.
o They resist to treatment induced disturbances
in the ecology of bacterial community.
o They reach relax population density.
o They have unrestrained access to the
periradicular tissues through perforation.
o They possess virulence.

23. BACTERIAL TAXA PERSISTING IN
INTRACANAL PROCEDURES
Studies of effective intracanal procedures, it is
advisable to identify bacterial species at the baseline
and after treatment so as to rule out
possible contamination during treatment,
samplingor laboratory handling of sample.

24. Studies that identified bacteria persisting after
intracanal disinfection procedures

25. Persistent infection ( filling stage)
Single mixed infection
1-5 species per canal
100 to 100000 bacterial cells per canal
Most bacteria
o Streptococcus mitis
o Other steptococci

26. o Fusobacterium nucleatum
o provotella spp.
o Pseuramibacter alactolyticus
o Parvimonas micra
lactobacilli
Oslenllle
Actinomyces spp.
Persistent/ secondary infection (Retreatment
cases)

27. Single mixed infection
Adequate treatment: 1 to 5 species
1000 to 10000000 bacterial cells per canal
55% uncultivated bacteria
Most frequent microorganisms :
o Enterococcus faecalis
o Candida albicans
o Straptococcus species
o Pseudoramibacter alactolyticus
o Filifactor alocis
o Diaster spp.
o Actinomyces spp.
o Pseudomonas aeruginosa
o Enteric rods

28. Conclusion
Bacteria participating in persistent infections can be
identified as those present in the root canal at the
time of filling, it must be recognized that many of
the species found still had no sufficient time to
establish a real infection and will die after filling.
However those that manage to survive in the new
drastically modified environment can establish a
persistent infection that put the treatment outcome
at risk.

29. References
Endodontics : Ingle, Barkland, 5th
edition
Pathways of pulp : Cohen, 9th
edition
Endodontics : Franklin Weine, 5th
edition
IEJ 1998,31,1-7.
IEJ 34, 399-405, 2001.
OOO ,Vol103, No 4, Aprial2007.
OOO Vol 1998; 85: 86-93.
JOE vol33, No 7, July 2007
JOE Vol 33, No 8, Aug 2007.