The document discusses the oral microbiome. It begins by introducing key terms and describing the oral ecosystem and habitats that support diverse microbial communities. It then details the development of the normal oral flora from birth through adulthood and how factors like teeth eruption influence community composition over time. Major groups of bacteria, fungi and other microbes that comprise the oral microbiome are also outlined. Physicochemical factors like temperature, oxygen levels, and pH that shape microbial colonization are explained.

3. 










Introduction
Terminologies
Oral ecosystem
Normal microbial oral flora and its
development
Factors determining bacterial oral flora
Dental implications of oral microbiology:
1.periodontal diseases
2. dental caries
Fungi and parasite in oral cavity
Role of oral flora in systemic diseases.
Preventive approach to oral infection
Conclusion
References

4. 
Microbes are the part of our lives in more
ways than most understand. They have
shaped the present environment and their
activities will greatly influence our future.

The oral cavity is a border area between
the environment and the human organism,
a gateway for food, an outpost of the
immune system and above all a
multilayered habitat inhabited by countless
microorganisms.

5. 
The mouth is continually exposed to organisms
from the external environment ,beginning with
the passage through the birth canal.

In time a ecological balance is reached that
serves to establish a resident microbial flora
that remains fairly stable throughout life.

6. 
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.

7. 
Habitat: the 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.

8. Aerobes: These organisms require
oxygen for aerobic cellular respiration to
obtain energy.
 Obligate aerobe: is an organism that
can survive and grow only in an
oxygenated environment
 Facultative anaerobes: can use oxygen,
but also have anaerobic methods of
energy production.


9. Capnophiles: are which thrive in the
presence of high concentrations of
carbon dioxide.
 An oligotroph: is an organism that can
live in an environment that offers very
low levels of nutrients.
 Microaerophiles: are organisms that
may use oxygen, but only at low
concentrations


10. 


Indigenous Flora(Resident):
It comprises those indigenous species that
are almost always present in high numbers,
greater than 1 percent 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 percent 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.

11. Pathogens
Micro-organisms 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 .

12. 
Four major ecosystems are present in the oral cavity
-Buccal epithelium
-Dorsum of the tongue
-Supragingival tooth surface
-Subgingival tooth and crevicular epithelial surfaces

13. 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
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
13

14. 
The buccal epithelium has more of gram
positive streptococci in contrast to
tongue which has more of gram positive
filaments.

The subgingival region is essentially
anaerobic as compared to the
supragingival region.

15. 
Mutans streptococci (S. mutans, S.
sorbinus, S. cricetus, S. rattus) and S.
Sanguis are found in large number on
teeth, whereas S. Salivarius is isolated
mainly from the tongue.

S. mutans and S. sanguis appear only
after eruption of teeth.

16. 

In the buccal mucosa the predominant
bacterium is Streptococcus mitior with
Streptococcus sanguis and salivarius.
Hard palate flora also resembles that of
buccal mucosa, with predominance of
streptococci. The soft palate harbours
respiratory tract bacteria
Corynebacterium, Neisseria,
Haemophilus.

17. 


Tongue is an ideal site for retention of
microorganisms owing to its keratinized
dorsal surface.
Streptococcus salivarius is the
predominant flora accounting for upto
50% of the total.
Streptococcus mitior is also common
here.

18. 


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.

19. 
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

20. 



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.

21. 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.

22. 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.

23. 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.

24. 
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.


25. 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

26. 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

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

28. 
Physicochemical factors
- Temperature
- Oxygen tension

- Hydrogen ion concentration
Host factors

Nutrient sources

29. Temperature:
 Although the average temperature in the oral
cavity is approximately 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.

30. Oxygen tension :
 The oxygen concentrations at different
locations in the oral cavity vary widely.
 As may be expected, the dorsum of the tongue
and the buccal and palatal mucosa are in an
essentially aerobic environment.
 The oxygen tension inside a periodontal pocket
is very low, with the species having a tendency
to become reduced rather than oxidised,
explaining the survival of obligate anaerobe.

31. 
Therefore obligate aerobic organisms (which
require oxygen) cannot survive, whereas obligate
anaerobic organisms (which cannot tolerate the
presence of oxygen) are able to thrive.
Hydrogen ion concentration:
 The term pH refers to the negative logarithm of
hydrogen ion concentration; thus, the 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.

32. 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.


33. 1)
2)
1.



Saliva
Crevicular fluid
Saliva :
Various salivary components interact with
oral flora in ways that can 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.

34. 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.

35. 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.

37. 1.Periodontaldiseases
2. Dental caries

38. 

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
and microorganisms
embedded in an extracellular
matrix.

39. 39

40. Subgingival Tissue
associated
St. oralis, St. intermedius
Peptostreptcoccus micros
P. gingivalis, P.
intermedia
T. Forsythis, F.
Nucleatum
40

41. 




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 coaggregation .(1-14 days)
Climax community plaque.(2 weeks or
older)

43. 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.


44. 



Function of pellicleProtect 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 peptostreptoccous
attaches within 1 hr.

45. The first organism to attach include
Streptococcus sanguis, other Streptococci and
gram-negative cocci (Neisseria and
Branhamella). After developing for about 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.


46. 
Responsible of causing specific disease.

Early stage lack pathogenicity-aerobic, lack sufficient
production of damaging metabolites.

Change of aerobic to anaerobic environment.

47. 
Secondary colonizers are the microorganisms that
do not initially colonize clean tooth surfaces,
including P. intermedia, P. loescheii,
Capnocytophaga spp., F.nucleatum, and P.
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.

48. 
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,

49. 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.

50.  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.

51. Characteristic
Early
Mature

Gram reaction
+
+/-

Morphotypes
Cocci, branching rods

Energy metabolism Facultative

Tolerated by host
Well
cocci, rod,
spirochetes
F- anaerobic
Can cause
caries and
gingivitis

52. Gram positive:
 Actinomyces viscosus
 Actinomyces naeslundii
 Streptococcus sanguis
 Streptococcus mitis
 Peptosreptococcus micros
Gram negative:
 Fusobactecterium nucleatum
 P. intermedia
 Veillonella parvula
 Wolinella
 Haemophilus species
52

53. Fusobacterium (fusobacterium
nucleatum)
Oral spirochaetes (treponema
species)
Fusospirochaetal complex
Others – provetella
intermedia,veillonella and
spirochaetes
53

54. CHRONIC PERIODONTITIS:
P. gingivalis
P. intermedia
A. actinomycetemcomitans
54

55. 






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.
55

56. 
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 in significant levels
include P. gingivalis, C.rectus & F. nucleatum.
56

57. This 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.
57

58. 




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,
58

59. PRE-PUBERTAL PERIODONTITIS
P. Intermedia
A. Actinomycetemcomitans
Fusobacterium species
P. Gingivalis
JUVENILE PERIODONTITIS
A. actinomycetemcomitans
59

60. REFRACTORY PERIODONTITIS
A. actinomycetecomitans
P. gingivalis
P.intermedia
B.forsythus
PAPILLON-LEFEVRE SYNDROME
A. actinomycetemcomitans
P. intermedia
P.gingivalis
F.nucleatum
E.corredens
60

61. The micro flora contains mainly gram –ve
anaerobic rods
There is high prevalence of putative pathogens
F.nucleatum , P. intermedia , P. gingivalis & T.
forsythia.
61

62. MOST COMMONLY BY Staphylococcal
aureus or enterobacteria
62

63. 

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)

64. 

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
T here is evidence that some bacteria – S.
mutans, Lactobacilli and actinomyces- are
more important than others.

65.  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
65

66. 
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.
66

67. 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

67

68. 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
68

69. 






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.
69

70. 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.

70

71. 


•
•
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
71

72. 
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.

72

73. 

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.
73

74. 
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.
74

75. 





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(peptoneglucose)
Indentification – psuedohyphae, septate
hyphae and germ tubes
75

76. 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

76

77. 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

77

78. DIABETES MELLITUS:
 capnocytophaga species
 P. intermedia
 A. actinomycetemcomitans
 P. gingivalis
AIDS
 fusobacterium species
 A. actinomycetemcomitas
 P. micros
 P. intermedia
78

79. 
Oral health is an integral element of
general health and well-being.

Oral diseases are highly prevalent and
their impact on both individual and
society is significant.

80. 
There are many ways to prevent or
reduce the risk of infection or diseases.
Brushing and Flossing are most basic
ways to reduce these risks. These two
help to get rid of bacteria which stick to
surfaces in our mouth to form plaque.
80

81. Caries:
Frequent mechanical removal of plaque
Use of fluorides
Diet modifications
Stimulation of saliva after meals
Caries vaccine
81

82. Periodontal diseases:
Mechanical removal of plaque
Mouthwash and Antibiotics
Anti-inflammatory agents to reduce flow
of GCF
Refractory - Antibiotics
82

83. 
Current dental therapy is focussed on
removing whole dental plaque. There
are new approaches towards selective
inhibition of pathogens and modulations
of microbial composition of dental
plaque to control community-based oral
microbial pathogenesis.
83

84. Brief outline of ORALMICROFLORA IN
DISEASE
INFECTIONS OF THE MOUTH
Infection
Dental caries
Periodontal diseases
Surgical infection
a) Dry socket
b) Dental abscess
c) Osteomyelitis
d) Ludwig’s angina
e) Pericoronitis
Organism
Streptococcus mutans
Bacteroides, Actinomyces
Actinomyces
Oral streptococci
Staphylococcus aureus
β -haemolytic streptococci
Bacteroides

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

86. INFECTIONS OF THE MOUTH
Infection
Organism
Fungal infections
a) Candidosis
Candida albicans
b) Histoplasmosis
H. Capsulatum
Miscellaneous
a) Erythema multiforme
b) StevensJohnson
syndrome

87. 

As a public health dentist it is very important
to in detail about the oral microflora, as we
commonly come across these micro
organisms while treating the diseases like
dental caries ,periodontitis etc.
We also should know about the various
types of microflora in oral cavity, the
mechanism by which they cause various
diseases so that we can effectively prevent
the disease.

88. 
Especially at the camp sites we come
across many diseases like lichen planus
,herpes , candidiasis etc. some of which
can be potentially infectious. Thus a deeper
understanding about the microflora can be
beneficial for us.

Also, there are microoraganisms which are
beneficial for the body thus treatment
planning of any disease should not interfere
with these microorganisms

89. 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.

90. Identification of the microorganisms found
during the different phases of the disease
process is technically challenging. The
interpretation of microbiologic data is greatly
influenced by the clinical classification of
disease status, that promise to provide much
information about the basic mechanisms
involved in the disease process.
Technologic advances in molecular
microbiology have improved the ability to
detect specific bacteria and their products,
which may serve as markers of ongoing
disease or predictors of future disease.

91. References
1.
2.
3.
4.
5.
6.
Textbook of Microbiology- Anantnarayan
Carranza’s clinical periodontology. 9th edition
Dental caries –disease and its clinical managenent –
Ole Fejerskov and Edwina A.M Kidd
Textbook of cariology– Ernest Newburn
An introduction to risk prediction and preventive
dentistry – Per Axelsson and Karlstad
Prevention of oral diseases – John J. Murray,June H
Nunn and James G. Steele