After reading this chapter, the student should be able to: 1. Understand the microbial etiology of apical periodontitis. 2. Describe the routes of entry of microorganisms to the pulp and periradicular tissues. 3. Recognize the different types of endodontic infections and the main microbial species involved in each one. 4. Understand the bacterial diversity within infected root canals. 5. Describe the factors involved with symptomatic endodontic infections. 6. Understand the ecology of the endodontic microbiota and the features of the endodontic ecosystem. 7. Discuss the role of microorganisms in the outcome of endodontic treatment. 8. Understand the development and implications of extraradicular infections.

1. ENDODONTIC
MICROBIOLOGY
SARANG SURESH HOTCHANDANI

2. ▪ The PURPOSE OF ENDODONTIC TREATMENT is to;
Eradicate the occurring infection
Prevent the microbes from infecting the root canal or peri
radicular tissue.
▪ Endodontic infections usually develop after pulpal necrosis or in
those cases in which pulp was removed for treatment.

3. ▪ Apical periodontitis is inflammatory disease of microbial origin caused
by infection of root canal.
▪ Bacteria are major microorganisms involved in etiology of apical
periodontitis.
▪ APICAL PERIODONTITIS DEVELOPS WHEN FIGHT B/W HOST DEFENSE
AND ROOT CANAL BACTERIA OCCURS WHICH RESULT IN
INFLAMMATION OF PERIAPICAL AREA.
▪ After death of pulp, host defense is lost, then after this, bacteria in root canal form biofilms
(similar to dental caries) which in result damage the periapical area.

4. ROUTES OF ROOT CANAL INFECTION
▪ Normally, dentine & pulp
are sterile and is covered by
enamel & cementum which
prevent the entry of
microorganisms.
▪ Microorganisms can reach
the pulp when these
protective coverings
(enamel & cementum) are
lost due to following
reasons.
▪ Microbes which can damage the pulp and
can lead to apical periodontitis comes from
following sources;
▪ Oral cavity
▪ Periodontium
▪ Systemic root
▪ Bacteria reach at pulp through following
routes;
▪ Dentinal tubules
▪ Lateral or apical foramina
▪ Systemic roots

5. ▪ Bacterial invasion of dentinal
tubules occurs more rapidly in non
– vital teeth than in vital teeth.
▪ But if the dentine thickness is very
small, permeability to microbes is
increased because of larger
diameter of tubules near the pulp.
▪ In non-vital pulp above mentioned
things does not occur & necrotic
pulp is best environment for
bacteria.
▪ EFFECTS OF VITALITY OF PULP;
▪ Outward movement of fluid in exposed
dentinal fluid prevent the diffusion of
microbes.
▪ Tubular contents also decrease the dentinal
permeability to microbes;
▪ Collage
▪ Crystals
▪ Host defense molecules
▪ Antibodies
▪ Dentinal sclerosis, reparative or reactionary,
smear layer also prevents the diffusion of
microbes.
▪ These effects are produced only when the pulp is
vital.

6. DIRECT PULP EXPOSURES
It is most
noticeable route of
endodontic
infection.
Caries (most common)
Trauma
Restorative procedures
Scaling & root planning
Attrition or abrasion
Naturally absent
Congenital anomalies
• Dens invaginates
• Dens evaginatus
• Palatal groove defects

7. PERIODONTAL DISEASE
▪ Microbes in subgingival biofilms reach the pulp thorough
▪ Dentinal tubules
▪ Lateral, apical or furcation canals.
▪ Pulp necrosis due to periodontal disease develop only when
periodontal pocket reaches the apical foramina which
damages the vessels penetrating through apical foramina.

8. ANACHORESIS
▪It is a process by which microorganisms
are transmitted in the blood or lymph to
an area of tissue damage.
▪There is no clear evidence that this
process cause root canal infection.

9. MICROBIOTA OF ENDODONTIC INFECTION
CLASSIFICATION OF
ENDODONTIC INFECTION
▪ Extra radicular infection
▪ Intra radicular infection
▪ Primary infection
▪ Secondary infection
▪ Persistent infection
• Asymptomatic apical
periodontitis
• Dialister invisnus
• Bacteroids.
• Symptomatic Apical
Periodontitis
• Treponema Denticola
• Acute Apical Abscess
• Porphyromonas
Endodonticalis,
• Treponema Denticola
The
different
types of
endodontic
diseases
contain
different
types of
microbes.

10. PRIMARY INTRA RADICULAR INFECTION
(VIRGIN INFECTION)
▪These are those microorganisms which
initially invade & colonize the necrotic pulp
tissue.
▪ These organisms may be those which initially infected
the pulp and resulted in inflammation & then
necrosis. OR these organisms may be late comers
which arrive as soon as pulp necrosis.

11. PRIMARY INTRA RADICULAR INFECTION
(VIRGIN INFECTION)
▪ Primary infection is caused by mixed group of bacteria;
gram +ve, gram -ve & others.
▪ Composed of 10 – 30 bacterial species & 103 – 108 bacterial cells
per canal.

14. PERSISTENT & SECONDARY ENDODONTIC
INFECTIONS.
▪ Persistent endodontic
infections; these are those
microbes which survive in
root canal after intra
canal antimicrobial
procedures.
▪ Secondary Endodontic
Infection; these are those
microbes which occupy the
root canal during or after
professional intervention of
root canal (RCT).
▪ They can be oral or non-oral
bacteria depending on source.

16. •Loss or leakage of
restorative material.
•Tooth fracture.
•Opened teeth for
drainage of
abscess.
SOURCE OF
MICROBES
BETWEEN
APPOINTMENTS

18. Gram Positive
Bacteria are Most
Common Persistent
Bacteria.

19. E. faecalis facultative
anaerobic gram positive
coccus (30 – 90% cases) &
Candida infections (3 – 18%
cases) are found more
commonly in root canal
treated teeth in post
treatment apical
periodontitis (Secondary
Intra Radicular)

20. EXTRA RADICULAR INFECTIONS
▪Extra radicular infections are
characterized by, microbial invasion &
proliferation in the inflamed peri radicular
tissue as a result of intra radicular
infections.
▪The most common form of extra radicular
infection is acute apical abscess.

21. EXTRA RADICULAR INFECTION CAN BE CAUSED BY INTRA
RADICULAR BACTERIA OR BACTERIA FROM OUTER SIDE.
▪ Those extra radicular infections which are caused
by intra radicular bacteria are treated easily by RCT.
▪Example; Sinus Tract
▪ If the extra radicular infection which are caused by
outer side are treated only by Endodontic Surgery.
▪Example; Actinomycosis

23. SYMPTOMATIC INFECTIONS
▪ Occurrence and intensity of symptoms is due to interaction
of following factors with each other;
▪ Difference in virulence ability among strains of same species
▪ The number of occurring species & interaction among them
▪ The number of bacterial cells (load)
▪ Environmental factors which regulate the expression of virulence
factor of microbes

24. ECOLOGY OF ENDODONTIC MICROBIOTA
▪ Necrotic root canal is a fertile
environment for bacterial growth.
▪ It gives bacteria a moist, warm,
nutritious & anaerobic environment
which is protected from host defense
due to absence of microcirculation in
necrotic pulp.
▪ The ecologic factors which affect
the composition of microbes in
necrotic root canal include;
▪ Oxygen tension & redox potential
▪ Type & amount of available nutrients
▪ Bacterial interactions

25. OXYGEN TENSION & REDOX POTENTIAL
▪ Different bacterial species dominate at different
stages of the infectious process.
▪ In initial phases of pulpal infectious process;
▪ Facultative bacteria predominate
▪ During pulp necrosis & consumption by facultative
bacteria, oxygen is reduced in root canal so;
▪ Obligate anaerobes predominate here

26. AVAILABLE NUTRIENTS UTILIZED BY
BACTERIA IN ROOT CANAL
The necrotic pulp tissue
Proteins & glycol proteins from tissue fluid
Components of saliva
Products of metabolism of other bacteria

27. INTERACTION WITH OTHER SPECIES IN
ROOT CANAL
▪Positive interaction enhances the survival
capacity & quantity of interacting bacteria;
▪ Mutualism, Commensalism
▪Negative interaction decreases the quantity
of bacteria;
▪ Example; Competition & Antagonism

28. APICAL PERIODONTITIS AS A BIOFILM
RELATED DISEASE
▪ Bacteria in root canal may exist in one of two
patterns;
▪Planktonic cells (unattached free floating cells)
▪ Easily eliminated with instrumentation & irrigation.
▪ Formation of biofilm that adheres to walls of root canal.
(DOMINANT PATTERN IN APICAL PERIODONTITIS)
▪ More difficult to eradicate & require special therapeutic
approaches.

29. APICAL PERIODONTITIS AS A BIOFILM
RELATED DISEASE
▪ So, it means apical periodontitis is also
biofilm induced oral disease like caries
& marginal periodontitis.
▪ Definition of Biofilm: sessile,
multicellular microbial community
characterized by cells that are firmly
attached to a surface and trapped in
self – produce matrix.
▪ Advantages of Biofilm:
▪ Good communication
among species
▪ Metabolic cooperation
▪ Protection against
exogenous threats
▪ Pathogenic effect on the
host