Normal microflora

NORMALORALMICROFLORA
AND
PLAQUE
Dr. Amitha G
Oral Pathology And
Microbiology

Contents :
◦ Introduction
◦ Terminologies
◦ Oral ecosystem
◦ Normal oral flora of the oral cavity development, factors
effecting it.
◦ Plaque
◦ Brief outline on oral microflora in diseases

INTRODUCTION
 The mouth is continually exposed to organisms from the external
environment, beginning with the passage through the birth canal.
 In time, ecological balance is reached that serves to establish a
resident microbial flora that remains fairly stable throughout life.

Introduction
◦ It has been estimated that the human body
is made up of over 1014 cells of which only
around 10% are mammalian. The
remainder are the micro-organisms that
comprise the resident micro flora of the
host.
(Sanders & Sanders, 1984)
◦ Microorganisms in mouth were first
described by Anton von Leeuwenhoek in
1683.

Terminologies
Habitat: Site where a microorganism grows
Ecology: Study of relationship between organisms
and their environment.
Ecological niche: The functional position of an
organism in its environment
comprising the living space,
periods of time during which it
is active there and resources it
obtains there.

Terminologies
Aerobes: Organisms require oxygen for aerobic cellular respiration to
obtain energy.
Obligate aerobe: Organism that can survive and grow only in an
oxygenated environment
Facultative anaerobes: Oraganism that use oxygen, but also have
anaerobic methods of energy production.

Terminologies:
Capnophiles: Organism which thrive in the presence of high
concentrations of carbon dioxide.
An Oligotroph: Organism that can live in an environment that offers very
low levels of nutrients.
Microaerophiles: Organisms that may use oxygen, but only at low
concentrations.

Terminologies:
◦ Indigenous Flora(Resident):
It comprises those indigenous species that are
almost always present in high numbers, greater
than 1 % of the total viable count.
◦ Supplemental Flora:
The supplemental flora are those bacterial
species that are nearly always present, but in
low numbers, less than 1 % of total viable count
◦ Transient Flora:
Transient flora comprise organisms "just
passing through" a host. At any given time a
particular species may or may not be
represented in the flora.

Terminologies:
◦ Pathogens
Microorganisms that have the
potential to cause disease are
termed pathogens.
◦ Opportunistic Pathogens
Micro-organisms that cause
disease only under exceptional
circumstances.
◦ True Pathogens
Micro-organisms that are
consistently associated with a
particular disease.

The Oral Ecosystems
Four major ecosystems are present in the oral
cavity
- Buccal epithelium
- Dorsum of the tongue
- Supragingival tooth surface
- Subgingival tooth and crevicular epithelial
surfaces

11
Tooth surface
• mitis group
• mutans group
• anginosus group
Saliva
• S. salivarius
• S. mitis
• S. oralis
• mitis group
• anginosus group
Tongue
• S. salivarius
• S. mitis
Pharynx
• S. mitis
• S. oralis
• mitis group
• anginosus group
Nasopharynx
• S. pneumoniae
Vestibular mucosa
• S. vestibularis
Buccal mucosa
• S. mitis
• mitis group
• anginosus group
Tonsils
• S. sanguis
• S. mitis
• S. mutans
• mitis group
• anginosus group
MicroFlora

◦ The buccal epithelium has gram positive
streptococci in contrast to tongue which has
more of gram positive filaments.
◦ The subgingival region is anaerobic as
compared to the supragingival region.

◦ Mutans streptococci (S. mutans, S. sorbinus, S.
cricetus, S. rattus) and S. Sanguis are found in
large number on teeth.
◦ S. Salivarius is isolated mainly from the tongue.
◦ S. mutans and S. sanguis appear only after
eruption of teeth.

◦ Buccal mucosa
The predominant bacterias is
Streptococcus mitior with
Streptococcus sanguis and
salivarius.
◦ Hard palate flora also resembles that of buccal
mucosa,
With predominance of streptococci.
◦ Soft palate
Harbours respiratory tract bacteria
Corynebacterium, Neisseria,
Haemophilus.

◦ Tongue
Is an ideal site for retention of
microorganisms to its keratinized
dorsal surface.
◦ Streptococcus salivarius
Is the predominant flora
accounting for upto 50% of the
total.
◦ Streptococcus mitior
Is also common here.

Gingival Crevice:
◦ Gingival crevice has the most numerous bacterial
population among all sites in mouth.
◦ As many as 1010-1011 organisms are recovered
per gram wet weight of gingival debris.
◦ It is considered to be due to absence of
dislodging forces and crevicular fluid acting as a
rich nutrient medium.

Normal Flora of the Human oral Cavity :
The presence of nutrients, epithelial debris, and
secretions makes the mouth a favorable habitat for
a great variety of bacteria.
Oral bacteria include streptococci, lactobacilli,
staphylococci and corynebacteria, with a great
number of anaerobes, especially bacteroides.
The mouth presents a succession of different
ecological situations with age, and this corresponds
with changes in the composition of the normal flora

Development of oral flora◦ The process begins with the colonization of habitat by pioneer microbial
populations.
◦ In oral cavity of newborns, streptococci are the pioneer organisms.
◦ They fill the niche of the new environment and modify the habitat and new
population develops.
◦ When no additional niche is available for new population, a stable
assemblage of bacterial population is achieved called as climax community.

At birth:
◦ The mouth of full term foetus is usually sterile, transient flora from the
birth canal may be acquired.
◦ Mouth then rapidly acquires organisms from mother and from the
environment.
◦ It consists of several streptococcal and staphylococcal species with
Lactobacilli, Bacillus, Neisseria and Yeasts.
◦ Streptococcus salivarius is the most common and forms the pioneer
community with Staphylococcus albus.

Infancy & Early Childhood:
◦ The infant comes into contact with an ever-increasing range of
microorganisms and some become established as part of commensal
flora.
◦ The eruption of deciduous teeth provides a new attachment surface
and turns Streptococcus sanguis and mutans as regular inhabitants of
oral cavity.
◦ Anaerobes are few in number due to absence of deep gingival crevice.
◦ Actinomyces , Lactobacilli are found regularly.

Adolescence:
◦ The greatest number of organisms in mouth occur when
permanent teeth erupt.
◦ These teeth have deep fissures, larger inter proximal spaces and
deeper gingival crevice, allowing a great increase in
anaerobes.

Adulthood:
◦ Its chief characteristic is its complexity of oral flora.
◦ There is an increase in Bacteroides and Spirochetes with maturity of
dental plaque.
◦ As the teeth are lost the available sites for microbial colonisation
decreases and several species diminish disproportionately in numbers.
◦ Edentulous persons harbour few Spirochetes or Bacteroides but
carriage of Yeast increases.
◦ S.sanguis & mutans disappear.

HUMAN ORAL FLORA
Gram-positive facultative
cocci
Gram-negative facultative
rods
Staphylococcus
epidermidis
Staph. aureus
Streptococcus mutans
Strep. sanguis
Strep. Mitis
Strep. Salivarius
Strep. Faecalis
Beta-hemolytic
streptococci
Enterobacteriaceae
Hemophilus influenzae
Eikenella corrodens
Actinobacillus
Actinomycetemcomitans

Gram-positive
anaerobic cocci
Gram-positive anaerobic
rods
Peptostreptococcus sp Actinomyces israelii
A. odonotolyticus
A. Viscosus
Lactobacillus
Gram-negative
anaerobic cocci
Gram-negative aerobic
or facultative cocci
Diphtheroids
Corynebacterium
Eubacterium
Neisseria sicca
N. Flavescens

Spirochetes Yeasts
Treponema denticola
T. Microdentium
Candida albicans
Geotrichum sp.
Protozoa Mycoplasma
Entamoeba gingivalis
Tirchomonas tenax
Mycoplasma orale
M. pneumoniae

Factors determining bacterial distribution
1. Physicochemical factors
a. - Temperature
b. - Oxygen tension
c. - Hydrogen ion concentration
2. Host factors
3. Nutrient sources

a. Temperature:
◦ Average temperature in the oral cavity is approx
37' C, temperatures can vary considerably,
especially on the mucosal surfaces and on the
clinical crowns of teeth.
Periodontal pockets with active disease have a
higher temperature – up to 39 C compared
with healthy sites (mean value 36.80 C).
Such changes in temperature affect gene
expression in periodontal pathogens, such as
Porphyromonas gingivalis.

b. Oxygen tension :
◦ The oxygen concentrations at different locations
in the oral cavity varies.
◦ Dorsum of the tongue, buccal and palatal
mucosa are aerobic.
◦ In periodontal pocket: Oxygen tension inside is
very low, with the species having a tendency to
become reduced rather than oxidised,
explaining the survival of obligate anaerobe.
◦ Therefore obligate aerobic organisms (which
require oxygen) cannot survive, whereas
obligate anaerobic organisms (which cannot
tolerate the presence of oxygen) are able to
thrive.

c. Hydrogen ion concentration:
 The term pH refers to the negative logarithm of hydrogen ion concentration
 Lower the pH value, the higher is the hydrogen ion concentration.
 The buffering capacity of plaque and saliva maintain the pH in oral cavity at
about 7.

pH can vary due to:
1) Exogenous materials placed in the mouth
2) Production of hydrogen ion by bacteria as a
result of carbohydrate fermentation
3) Buffering system in saliva (bicarbonates)
 The second reason is responsible for dramatic
drop in pH leading to Dental Caries.
 Most oral bacteria grow best at a pH of about 7
(essentially neutral).
 Most of the time the pH in the oral cavity is
maintained at about 7 by the buffering systems
in plaque and saliva.

Host factors :
1) Saliva
2) Crevicular fluid
1. Saliva :
◦ When Salivary components interact with oral flora
it either enhance or inhibit ability of these
organisms to survive.
◦ IgG is seen in gingival inflammation contributed
by GCF.
◦ These make it more difficult for bacteria to bind to
oral epithelium or hard tissue surfaces.

Non-specific factors:
These are lysozyme, lactoferrin and
lactoperoxidase.
◦ Lysozyme degrades bacterial peptidoglycan i.e
the cell wall, rendering bacteria susceptible to
osmotic disruption and death.
◦ Lactoferrin binds to iron which is a growth limiting
substance in bacteria. Making iron unavailable to
bacteria lactoferrin limits bacterial growth.
◦ Lactoperoxidase catalyses the formation of
hypothiocyanate ion ,inactivating bacterial
enzymes and finally death.

2. Crevicular fluid :
◦ It is an inflammatory exudate derived from plasma
with large amount of antibody and complement
proteins.
◦ The predominant immunoglobulin is IgG, derived
from plasma cells located in periodontal tissues as
well as from circulating plasma.
◦ These antibodies keep the subgingival flora in
check by inhibiting colonization or activating
complement system.

Nutrient sources in the oral cavity :

MICROBIOLOGY OF DENTAL PLAQUE
According to WHO :
Plaque is a highly specific and
selective but structurally variable
clinical entity characterized by
sequential colonization of
microorganisms on the surface
of teeth, restoration and other
parts of the oral cavity.
It is made up of
◦ Mucins
◦ Desquamative epithelial cells
◦ Microorganisms embedded in
an extracellular matrix.

MICROFLORA IN DISEASE
Interrelationship that leads to dental disease

DEFENITION
Dental plaque can be defined as the soft
deposits that form the biofilm adhering to the
tooth surfaces or other hard surfaces in the oral
cavity, including removable and fixed
prosthesis.
The term Biofilm is used to describe
communities of micro-organisms attached to a
Plaque:

CLASSIFICATION OF PLAQUE
Dental Plaque
Sub gingival
Tooth
associated
Tissue
associated
Supra gingival
38

39
• Gram +ve cocci and short rods
predominant at tooth surfaces.
• Gram –ve rods, filaments, spirochetes,
at outer surfaces.Supra gingival
• Filamentus microorganisms dominate.
• Cocci and rods also present .
• Gram +ve rods and cocci:
• St. mitis, St. sangius
• A. Viscosus , naeslundii
• Eubacterium.
Sub gingival Tooth
associated
Subgingival Tissue
associated
St. oralis, St. intermedius
Peptostreptcoccus micros
P. gingivalis, P. intermedia
T. Forsythis, F. Nucleatum

Development of dental plaque:
◦ Pellicle formation
◦ Attachment of single bacterial cell (0-4h)
◦ Growth of attached bacteria leading to formation
of distinct micro colonies.
(4-24h)
◦ Microbial succession and co-aggregation .(1-14
days)
◦ Climax community plaque.(2 weeks or older)

Pellicle formation:
◦ Microrganisms don’t colonize on the mineralised tooth surface.
◦ The teeth are always covered by an acellular proteinaceous film ,the pellicle
that forms on the naked tooth surface within mins to hours.
◦ The bacteria colonize the tooth surface only when pellicle is in place for
hours.

Function of pellicle
◦ Protect enamel.
◦ Reduces friction.
◦ Provide matrix for re-mineralization.
Pellicle contains-lysozyme,albumin,IgA,IgG.
Early colonisation :
◦ Plaque builds up first in small defects or pits on the
enamel surface and then spreads over the tooth
surface.
Early succession evolves adhesion between pellicle and
pioneer organism.
S.sanguis, A.viscosus, A.naeslundii and pepto streptoccous
attaches within 1 hr.

◦ The first organism to attach include Streptococcus
sanguis, Streptococci and gram-negative cocci
(Neisseria and Branhamella).
◦ After 24 hours,
plaque consists largely of Streptococci and
Veillonella, Corynebacterium, Actinomyces,
Lactobacillus and Rothia.
Veillonella is first anaerobe to appear followed by
facultative Actinomycetes and anaerobic
Actinomyces israelli.
◦ As plaque ages,
number of anaerobes increases and after 7
days Fusobacteria and Bacterioides can be
detected.

Late stage of plaque succession
◦ Responsible of causing specific disease.
◦ Early stage lack pathogenicity-aerobic, lack
sufficient production of damaging metabolites.
◦ Change of aerobic to anaerobic environment.
◦ Secondary colonizers are the microorganisms
that do not initially colonize clean tooth surfaces,
including P. intermedia, P. loescheii,
Capnocytophaga spp., F.nucleatum, and
Porphyromonas gingivalis.

◦ These microorganisms adhere to cells of bacteria
already in the plaque mass.
◦ Extensive laboratory studies have documented
the ability of different species and genera of
plaque microorganisms to adhere to one another,
a process known as coaggregation.

◦ Coaggregation is based on the specific interaction of
a proteinaceous adhesion procedure by one
bacterium and a respective carbohydrate or protein
receptor found on the surface of another bacterium.
◦ F. nucleatum with S. sanguis,
◦ P. loescheii with A. viscosus,

Tooth Habitats For Pathogenic Plaque
Tooth surface is stable and covered with pellicle ,
so it is an ideal surface for the attachment of many
oral streptococci .
Tooth habitats favorable for harboring pathogenic
plaque includes :
Pits and fissures- Community is dominated by
S.sanguis and other streptococci.
Smooth surface- Proximal areas of very young
patient are less favorable habitat for MS.

Root surface
Gingival recession favors the formation of plaque
in this area.
Sub gingival areas
◦Initial occupants of sulcus are merely extension of
immediate tooth surface
◦Plaque community changes from masses of cocci to
a community dominated by filamentous bacteria
and spirochetes in sub gingival area .
◦B. melaninogenicous can explore this habitat,
because protein and heme is available.

Differences between early and mature supra gingival plaque
Characteristic Early
Mature
Gram reaction + +/-
Morphotypes Cocci, branching rods cocci, rod,
spirochetes
Energy metabolism Facultative F- anaerobic
Tolerated by host Well Can cause
caries and
gingivitis

CHRONIC GINGIVITIS
Gram positive:
Actinomyces viscosus
Actinomyces naeslundii
Streptococcus sanguis
Streptococcus mitis
Peptosreptococcus micros
Gram negative:
Fusobactecterium nucleatum
P. intermedia
Veillonella parvula
Wolinella
Haemophilus species
51

Acute necrotising ulcerative gingivitis
Fusobacterium (fusobacterium
nucleatum)
Oral spirochaetes (treponema
species)
Fusospirochaetal complex
Others – Provetella intermedia
Veillonella
spirochaetes 52

CHRONIC PERIODONTITIS:
Caused by
P. gingivalis
P. intermedia
A. actinomycetemcomitans
53

P. gingivalis
◦ Gram negative ,non motile pleomorphic short rods
◦ Gram negative obligate anaerobe.
◦ P. gingivalis is a member of "black-pigmented Bacteroides" group
◦ Size – 0.5 * 1 microns
◦ Doesn’t ferment carbohydrate.
◦Major site of colonization – gingival
sulcus of human oral cavity
◦ Aggressive periodontal pathogen.
54

Localized aggressive periodontitis
◦ Microbiota is predominantly composed of gram –ve
anaerobic, capnophilic rods.
◦ Microbiological studies indicate- All disease sites
harbor A.comitans which may compose as much as
90 % of total cultivable microbiota.
◦ Other organisms found include
P. Gingivalis
C. Rectus
F. Nucleatum. 55

A. actinomycetemcomitansThis is a small, non-motile, Gram-negative saccharolytic, capnophilic, round-
ended rod that forms small, convex colonies with a "star-shaped" center when
grown on blood agar plates.
56

Actinomycetemcomitans
◦ May be isolated on non selective blood agar incubated anaerobically.
◦ Its growth is stimulated by addition of carbon dioxide
◦ Ferments glucose and fructose
◦ Site – subgingival sites in oral cavity
◦ Virulence factors – LPS, leukotoxin,
57

PRE-PUBERTAL PERIODONTITIS
P. Intermedia
A. Actinomycetemcomitans
Fusobacterium species
P. Gingivalis
JUVENILE PERIODONTITIS
58

REFRACTORY PERIODONTITIS A.
actinomycetecomitans
P. gingivalis
P.intermedia
B.forsythus
PAPILLON-LEFEVRE SYNDROME
P. intermedia
P.gingivalis
F.nucleatum
E.corredens
59

PERIODONTAL ABSCESS
60
• The micro flora contains mainly gram
–ve anaerobic rods
• There is high prevalence of putative
pathogens F.nucleatum , P. intermedia
, P. gingivalis & T. forsythia.

OSTEOMYELITIS
Caused by Staphylococcal aureus or enterobacteria
61

MICROBIOLOGY OF DENTAL CARIES
◦ Dental caries is a specific and treatable bacterial
infection due to mutans streptococcus (MS) and
in the later stages to lactobacillus.”
(Oral Sci Rev. 1976).
◦ “ Caries is a dynamic process of demineralization
of the dental hard tissues by the products of bacterial
metabolism alternating with periods of
remineralization. ”
Larsen and Bruun (Clinical Cariology, 1994)

◦ In 1976 Loesch (Oral Sci Rev, 1976) postulated
that dental caries is a specific and treatable
bacterial infection due primarily to MS and in the
later stages to lactobacillus
◦ There is evidence that some bacteria – S.
mutans, Lactobacilli and actinomyces- are more
important than others.

S. Mutans:
◦ The feature that supports its role as cariogenic
organisms are its:
◦ Rapid generation time
◦ Acidogenic nature
◦ Production of extra cellular polysaccharides from
sucrose which aids on adherence and acts as a
nutrient
◦ Isolated in high numbers in caries active mouth in
incipient lesions
64

S. Mutans:
◦ Capacity to attain critical pH for enamel demineralization more rapidly than
other plaque bacteria.
◦ S. mutans can produce glucan by using glucosyl transferase enzyme.It is this
glucans which help in the attachment of the bacteria to the tooth.
65

Mutans Streptococci
◦ Gram positive cocci forming chains
◦ Non motile, facultative anaerobes.
◦ Size – 0.5-0.75 microns in diameter
◦ Usually alpha hemolytic
◦ Selectively cultured in Mitis salivarius
(20% sucrose + 0.2% unit/ml of bacitracin)
Culture
◦ blood agar– grey to white
◦ sucrose-containing media –produce
extracellular polysachharides
66

Collection of seven different species
1. S. mutans
2. S. sobrinus
3. S. cricetus
4. S. ferus
5. S. rattus
6. S. macacae
7. S. downei
Primary habitat – human oral cavity to
colonize smooth surface of teeth.
Doesn’t appear prior to eruption of teeth
and disappear after eruption
67

Lactobacilli
◦ Gram negative ,non spore forming rods
◦ Grow under micro-aerophillic conditions
◦ They are both acidogenic and aciduric
◦ They are secondary invaders
◦ Lactobacilli for many years was believed to be the
causative agent of dental caries as
◦ High numbers were obtained in most enamel
caries
◦ Able to synthesis extra cellular and intra cellular
polysaccharides form glucose.
68

◦ They produces lactic acid at pH < 5
◦ Although these properties seemed valuable to
a cariogenic organism, it was also seen that
their affinity for the tooth surface and their
number prior to development of caries was
low.
◦ They were, in fact, absent from incipient
lesions while present is significant numbers in
developed caries.
◦ Thus, they were categorized as secondary
invaders which caused progression of caries
due to their acidogenic and aciduric properties.
69

Actinomyces
◦ Gram positive non acid fast non
motile non spore.
◦ Strict anaerobic or facultative
anaerobes.
Main species –
◦ [A. naesulundi + A. viscosus] :
facultative anaerobes
◦ [A.israelli +A.odontolyticus] :
strict anaerobes
70

Actinomysis:
◦ Found in increase numbers in plaque overlying
root surface and sound root surface.
Actinomyces species:
A.viscous, some other Gram +ve bacilli are
involved in the initiation of lesions on root
surface.
◦ Role played by a large number of other bacteria
isolated from caries such as Arachnia,
Eubacterium, Rothia etc are not yet clearly
known.
71

Fluoride and Cariogenic bacteria
◦ Antibacterial effects of fluoride are attributable to the weak acid nature of
hydrofluoric acid allowing its permeation at low pH into bacterial cells.
◦ The unionised hydrofluoric acid here dissociates due to alkaline intracellular
pH, which positions fluoride to affect a variety of vital enzymatic cell functions.
72

Fluoride and Cariogenic bacteria
◦ The significant ones are inhibition of enolase, potassium and inorganic
phosphate transport.
◦ The mutans streptococci are considerably more sensitive to fluoride inhibition
than A. viscosus or Lactobacilli.
73

Fungi In The Oral Cavity
◦ Most commonly found:- candida species (C.albicans,
C. tropicalis, C. stellatoidea, C. parapsilosis, C.
guilliermondi)
◦ Other rhodotorula & torulopsis ( denture wearer)
◦ Conditions – thrush ,erythematous
candidiasis,hyperplastic candiasis,angular chelitis
◦ Oral sampling – imprint culture
◦ Medium used – sabouraand’s agar(peptone-glucose)
◦ Indentification – psuedohyphae, septate hyphae and
germ tubes
74

Parasites In The Oral Caity
Entamoeba gingivalis Trichomonas tenax
◦ E. gingivalis –
◦ found in soft calculus,periodontal pockets and
infection of tonsils
◦ Can become opportunistic
◦ pathogen
◦ T.tenax – only parasitic flagellate in
◦ oral cavity
◦ --number increases in periodontitis
75

Role of oral flora in systemic disease
◦ Recently it has been recognized that plaque related oral
diseases, especially periodontitis, may alter the course
and pathogenesis of a number of systemic diseases.
◦ These includes:
Cardiovascular diseases:
◦ Infective endocarditis
• Coronary heart disease (atherosclerosis, MI)
• stroke
Bacterial pneumonia
Diabetic mellitus
AIDS
76

Diabetes Mellitus:
◦ capnocytophaga species
◦ P. intermedia
◦ A. actinomycetemcomitans
◦ P. gingivalis
AIDS
◦ fusobacterium species
◦ A. actinomycetemcomitas
◦ P. micros
◦ P. intermedia
77

Brief Outline Of Oralmicroflora In Disease
INFECTIONS OF THE MOUTH
Infection Organism
Dental caries Streptococcus mutans
Periodontal diseases Bacteroides, Actinomyces
Surgical infection
a) Dry socket
b) Dental abscess
c) Osteomyelitis
d) Ludwig’s angina
e) Pericoronitis
Actinomyces
Oral streptococci
Staphylococcus aureus
β -haemolytic streptococci
Bacteroides

Infection Organism
Soft tissue infections
a) Diphtheria
b) ANUG
c) Cancrum oris
d) Tuberculosis
e) Leprosy
C. Diphtheriae
Fuso-spirochaetes
Fuso-spirochaetes
M. Tuberculosis
M. Leprae
Viral infections
a) Herpetic stomatitis
b) Herpes Zoster
c) Mumps
d) Measles
Herpes simplex
Varicella-zoster
Mumps virus
Measles virus

Infection Organism
Fungal infections
a) Candidosis
b) Histoplasmosis
Candida albicans
H. Capsulatum
Miscellaneous
a) Erythema multiforme
b) StevensJohnson
syndrome

Conclusion
There are wide variety of organisms present, each with a
distinctive property. This determines the ways in which they
will react with their hosts therefore contribute to the
characteristics of the disease they cause.The normal flora
play a very important role in protection against these
established pathogenic microbes.

References
1. Textbook of Microbiology- Anantnarayan
2. Carranza’s clinical periodontology. 9th edition
3. Textbook of cariology – Ernest Newburn

Normal microflora

More Related Content

What's hot (20)

Similar to Normal microflora (20)

More from oral and maxillofacial pathology (20)

Recently uploaded (20)

Normal microflora

Editor's Notes