Dental plaque is a biofilm that forms on teeth and is composed of bacteria, salivary components, food debris and other materials. It develops in stages - first the acquired pellicle forms on the tooth surface within seconds of cleaning and provides binding sites for early colonizers like streptococci and actinomyces. These primary colonizers adhere reversibly at first, then irreversibly through adhesins. They promote the growth of secondary colonizers and the plaque matures into a complex biofilm. Mature plaque contains a variety of anaerobic bacteria embedded in a matrix. Dental plaque can be classified as supragingival above the gumline or subgingival below. Calculus forms through mineralization of dental

1. PREVENTIVE DENTISTRY
DENTAL PLAQUE

2. OBJECTIVE
S
¡ Explain why dental plaque is not unique among naturally occurring
microbial layers.
¡ Discuss some of the mechanisms proposed to explain bacterial
adhesion to the acquired pellicle.
¡ Distinguish between primary and secondary bacterial colonizers in
dental plaque, and cite examples of each.
¡ Identify the prime sites of calculus formation, explain how calculus
forms, and detail the differences between supragingival and subgingival
calculus.
¡ Explain the basis for the involvement of the acquired pellicle,
bacterial dental plaque, and dental calculus in caries and the
inflammatory periodontal diseases.

3. INTRODUCTIO
N
¡ Dental caries and periodontal diseases are to known
have a bacterial etiology.
¡ Dental caries and inflammatory periodontal diseases result
from the accumulation of many different bacteria that form
dental plaque,a naturally acquired bacterial biofilm that
develops on the teeth.
¡ Some bacterial species in dental plaque may be of greater
relevance to caries and periodontal diseases than others.

4. INTRODUCTIO
N
} Once a tooth erupts, various materials gather
on its surfaces, these substances are
frequently called tooth – accumulated
materials/deposits:
SOFT
DEPOSITS
• Acquired
pellicle
• Microbial
plaque
• Materia alba
• Food debris
• Calculus
• Stains
HARD
DEPOSITS

5. Microbial habitats within the
mouth
On the basis of physical & morphologic criteria, oral
cavity can be divided into 5 major ecosystems:
1. Supragingival, hard surfaces (teeth, implants,
restorations & prosthesis)
2. Periodontal/periimplant pocket (with its crevicular
fluid, root cementum or implant surface, & the pocket
epithelium)
3. Buccal epithelium, palatal epithelium & epithelium of floor
of mouth.
4. Dorsum of tongue
5. Tonsils

6. Distribution of Resident Oral Micro
flora
Teeth
•Non shedding surfaces
•Stagnant sites; food
impaction possible
• Influenced by GCF &
saliva
•Streptococcus,
Actinomyces, Veillonella,
Fusobacteria, Prevotella,
Treponema, unculturable
organisms
Tongue
•Highly papillated surfaces
•Some anaerobic sites.
•Facultative & obligate anaerobes
•Diverse microflora Streptococcus,
Actinomyces, Rothia, Neisseria
Cheeks, Lips, Palate
• Microflora has low
diversity
•Streptococcus spp.
predominate

7. Bacterial Composition of Dental
Plaque From Different Sites
TOOTH’S SURFACE
Approximal
Gram positive &
gram negative;
facultative &
obligate
anaerobes:
• Neisseria
• Streptococcus
• Prevotella
• Actinomyces
• veillonella
Gingival crevice
Gram positive & gram
negative & obligate
anaerobes:
• Streptococcus
• Prevotella
• Actinomyces
• Treponema
• Eubacterium
Fissure
Gram positive;
Facultative
anaerobes
• Streptococcus
• Actinomyces

8. Microorganisms commonly present in dental
plaque
Gram-positive Gram-negative
cocci rods and
filaments
cocci rods and filaments
Streptococcus Actinomyces Neisseria Bacteroids
Peptococcus Lactobacillus Branhamella Fusobacterium
Peptostreptoccus Bacterionema Veillonella Haemophilus
Staphyloccus Rothia Vibrio
(Campylobacter)
Micrococcus Arachnia Leptotrichia
Bifidobacterium Capnocytophaga
Eubacterium Selenomonas
Propionibacterium Spirochaetes

9. DEFINITION
S

10. What is dental plaque?

11. Definitions
¡ Dental plaque is defined clinically as a structured, resilient,yellow-
grayish substance that adheres tenaciously to intraoral hard surfaces,
including removable or fixed restorations. “Bowen WH: Nature of
plaque, Oral science
review 1976”
¡ Dental plaque is a general term for complex microbial community that
develops on the tooth surface, embedded in a matrix of polymers of
bacterial & salivary origin. “Philip D Marsh, Michael V Martin, Oral
Microbiology,
5th Edition.”

12. Definitions
¡ Dental plaque can be defined as the soft deposits thatform the
biofilm adhering to the tooth surface or other hard surfaces in the
oral cavity, including removable and fixed restorations.
Carranza 9th edition

13. DEFINITIONS
¡ Plaque can be defined as a complex microbial community,
with greater than 1010 bacteria per milligram.
¡ Socransky SS et al “The micro biota of gingival crevice area of
m a n ” JCP 25:134, 1998
¡ In addition to the bacterial cells, plaque contains a small number
of epithelial cells, leukocytes, and macrophages. The cells are
contained within a matrix, which is formed from bacterial
products and saliva.
¡ The matrix contains protein, polysaccharide, lipids and
glycoproteins.

14. ¡ Dental plaque must be differentiated from
other tooth deposits, like materia alba and
calculus.
¡ Materia Alba refers to soft accumulations of
bacteria and tissue cells that lack the organized
structure of dental plaque.
¡ Calculus is hard deposits that form by
mineralization of dental plaque and is generally
covered by a layer of unmineralized plaque.

15. ¡ Materia alba ¡ Calculus

16. Carranza 11th edition

17. Chemical composition of
dental plaque
 80% water
 Dry weight : Bacterial products 20-30% , Bacteria 70 to 80%
 Other than bacteria, non bacterial organisms include:
• Mycoplasma
• Yeast
• Protozoa
• Viruses
 Host cells in Dental plaque.
Epithelial cells
Macrophages
Leukocytes

18. COMPOSITION OF DENTAL
PLAQUE
Organic constituents
Inorganic constituents
Bacteria

19. ORGANIC
CONSTITUENTS
 Polysaccharides
 Proteins
 Glycoproteins
 Lipid materials
- Dextran 95% (adhesion), levan
5%, Sialic acid and fructose
- Albumin
- Saliva
- Membrane remnants of bacteria
and host cells.

20. INORGANIC
CONSTITUENTS
Primarily
Traces
Fluoride
- Calcium & Phosphate
- Sodium, Potassium and Fluoride
- From external sources like
tooth paste, mouth washes

21. FORMATIO
N

22. DEVELOPMENT OF
DENTAL PLAQUE
The formation of the
pellicle on the tooth
surface
Initial adhesion and
attachment of
bacteria
Colonization and
plaque maturation

23. Formation of the pellicle
¡ Within nanoseconds after a vigorously polishing the
teeth, a thin, saliva derived layer called the acquired
pellicle, covers the tooth surface.
¡ The pellicle is derived from components of saliva and
crevicular fluid.
¡ Consists of more than 180 peptides, proteins,
glycoproteins, including keratins, mucins, proline –
rich proteins, and other molecules.
¡ Functions as adhesion sites( receptors) for bacteria.

24. Formation of the pellicle
¡ Pellicles function as a protective barrier,
providing lubrication for the surfaces and
preventing tissue desiccation.
¡ The pellicle components serve as nutrients.
For example, proline-rich salivary proteins may be
degraded by bacterial collagenases, releasing
peptides, free amino acids, and salivary mucins that
may enhance the growth of dental plaque organisms,
such as actinomycetes and spirochetes

25. Ultra structure of dental pellicle
2 hr pellicle: Granular structures which form globules,
that connect to the Hydroxyapatite surface via stalk like
structures.
24 hrs Later: Globular structures get covered up by
fibrillar particles : 500 - 900 nm thick
36 hrs Later: The pellicle becomes smooth, globular

26. Primary colonizers
¡ Within a few hours, bacteria are found on the
dental pellicle.
¡ The initial bacteria colonizing the pellicle-
coated tooth surface are predominantly
gram- positive oxygen tolerant
microorganisms such as Actinomyces
viscosus and Streptococcus sanguis.

27. Primary colonizers

28. Initial adhesion
¡ Reversible adhesion of the bacterium
and the surface
¡ The proteins and carbohydrates that are
exposed on the bacterial cell surface
become important once the bacterial are in
loose contact with the acquired enamel
pellicle.

29. Attachment
¡ A firm anchorage between bacteriumand
surface will be established by specific
interactions ( ionic, covalent, or hydrogen
bonding)

30. Adhesins
¡ Adhesins can be subdivided into two major classes:
¡ Fimbrial adhesins
¡ fimbriae pili
¡ curli
¡ type IV pili
¡ Nonfimbrial adhesins
¡ autotransporter
¡ outer membrane
¡ secreted adhesins
Periodontology 2000, Vol. 52, 2010, 12–37

31. Fimbriae
• Are proteinaceous hair like
appendages
• Composed of protein subunits
called fimbrillin
• Fimbriae also carry adhesins
¡ Fimbriae of oral strain arethin,
flexible and 2-3nm in diameter,
thus differing from larger more
rigid filmbriae found on other
bacteria such as eschericia coli

32. Primary colonizers
¡ They provide new binding sites for adhesion by other
oral bacteria.
¡ The early colonizers (e.g., streptococci and
Actinomyces species) use oxygen and lower the
reduction-oxidation potential of the environment, which
then favors the growth of anaerobic species.
¡ Gram-positive species use sugars as an energy
source and saliva as a carbon source.

33. Secondary colonizers
¡ They do not initially colonize the clean tooth surface but
adhere to bacteria already in the plaque mass.
¡ Coaggregation- This process occurs primarily through:
¡ the highly specific stereochemical interaction of protein and
carbohydrate molecules located on the bacterial cell
surfaces,
¡ less specific interactions resulting from hydrophobic,
electrostatic, and van der Waals forces.

34. Secondary colonizers

36. Maturation
¡ Bacterial cells continue to divide until a three- dimensional
mixed-culture biofilm forms that is spatially and functionally
organized.
¡ There is a transition from the early aerobic environment
characterized by gram-positive facultative species to a
highly oxygen-deprived environment in which gram-
negative anaerobic microorganisms predominate.
¡ The bacteria that predominate in mature plaque are anaerobic
and asaccharolytic, and use amino acids and small peptides
as energy sources.

37. Plaque as a BioFilm
¡ The term biofilm describes the relatively
undefinable microbial community associated with
a tooth surface or any other hard, non- shedding
material (Wilderer & Charaklis 1989).
¡ Biofilm is a well-organized, co-operating
community of microorganisms which form
under fluid conditions.

38. In a pipe
Plaque on the teeth
In a Creek
In a membrane

41. Dental biofilm
¡ Biofilms have an organized structure.
¡ They are composed of micro colonies of bacterial cells
non randomly distributed in a shaped matrix or
glycocalyx.
¡ In lower plaque layers microbes are bound together in
polysaccharide matrix with other organic & inorganic
materials.
¡ On top of lower layer, a loose layer appears that is
often irregular in appearance; it can extend into
surrounding medium

42. Dental biofilm
¡ Bacteria in the biofilms produce compounds
that the same bacteria do not produce in
cultures, also the matrix surrounding the
colonies acts as a protective barrier.
¡ Substances produced by bacteria within the
biofilm are retained and concentrated which
fosters metabolic interactions among the
different bacteria.

43. Properties of a biofilm
¡ Cooperating community of various types of
microorganisms
¡ Microrganisms are arranged in microcolonies
¡ Microrganisms are surrounded by protective matrix
¡ Within the microcolonies are differing environments
¡ Microrganisms have a primitive communication
system and metabolic cooperativity
¡ Microrganisms in biofilms are resistant to antibiotics,
antimicrobials and host response.

44. Bacteria in biofilms
¡ Resistance of bacteria to antimicrobial agents is
increased in the biofilm.
¡ Almost 1000 to 1500 times more resistant to antibiotics
than in their planktonic stage

45. Biofilm
¡ Has certain properties that resists diffusion like strongly
charged or chemically highly reactive agents fail to reach
the deeper part of biofilm because biofilm acts as an ion-
exchange resin, removing such molecules from solution.
¡ Recently “super resistant” bacteria were identified; the
cells have multidrug resistant pumps that can extrude
antimicrobial agents from the cell.

46. Classification of dental
plaque
DENTA
L
PLAQU
E
SUPRAGINGIVAL - is found
at or above the
gingival margin
SUBGINGIVAL- found
below the gingival
margin, between the
tooth and the gingival
sulcular tissue.

47. Supragingival plaque
¡ It is made up of mostly aerobic bacteria,
meaning these bacteria need oxygen to survive.
If plaque remains on the tooth for a longer period
of time, anaerobic bacteria begin to grow in this
plaque.

48. Supragingival Plaque
Formation: Clinical Aspects
¡ During the 1st 24 hrs, starting from a clean tooth surface, plaque
growth is negligible from clinical view point.
¡ Following 3 days, plaque growth increases at a rapid rate, then
slows down.
¡ After 4 days, on average 30% of total tooth crown area will be
covered with plaque. Plaque does not seem to increase
substantially after 4th day.
¡ There will be a shift towards anaerobic & gram negative flora,
including an influx of Fusobacteria, filaments, spiral forms &
spirochetes.

49. Topography of supragingival
plaque
¡ Initial plaque formation takes place along the
gingival margin & from interdental space, later
further extension in coronal direction can be
observed.
¡ Plaque formation can also start from grooves,
cracks, perikymata, or pits
¡ Scanning electron microscopy reveals that early
colonization of enamel surface starts from surface
irregularities, where bacteria escape shear forces
allowing time needed to change from reversible to
irreversible binding.

50. Surface microroughness
¡ Rough intraoral surfaces accumulate & retain
more plaque & calculus in terms of thickness,
area & colony forming unit.
¡ Smoothing intraoral surfaces decreases rate of
plaque formation.
¡ There seems to be threshold for surface
roughness {Ra 0.2 micrometers}, above which
bacterial adhesion is facilitated.

51. Variation within dentition
Early plaque formation occurs faster:
¡ In lower jaw, compared to upper
jaw.
¡ In molars areas.
¡ On buccal tooth surfaces,
compared to oral sites.
¡ In interdental regions compared to
strict buccal or oral surface.

52. Impact of gingival inflammation
¡Plaque formation is more rapid on tooth
surfaces facing inflamed gingival margins,
than those facing healthy gingivae.
¡Studies suggest that increase in
crevicular fluid production enhances
plaque formation, it favors initial
adhesion & colonization of bacteria.

53. Subgingival Plaque Formation
¡ The gingival crevice or pocket is bathed by the
flow of crevicular fluid, which contains many
substances that the bacteria may use as
nutrients.
¡ Anaerobic gram negative bacteria

54. Diagram depicting the plaque- bacteria association with tooth
surface and periodontal tissues.

56. METHODS OF PLAQUE
DETECTION

57. Plaque disclosing agent

58. Use of plaque disclosing agent

59. Calculus
¡Dental calculus can be considered as an ectopic
mineralized structure.
¡Dental Calculus consists of mineralized
bacterial plaque that forms on the surfaces of
natural teeth and dental prosthesis.

60. }A deposit of inorganic salts composed primarily of calcium
carbonate and phosphate mixed with food debris bacteria and
desquamated epithelial cells. (Greene 1967)
} Mineralized dental plaque that is permeated with crystals of
various calcium phosphates (Schroeder,1969)
} Calculus is also known as odontolithiasis or tartar. It is also
called fossilized plaque.

61. Classification

62. ¡ Dental calculus is classified by its location on a tooth surface as related
to the adjacent free gingival margin:
DENTAL
CALCULUS
SUBGINGIV
A
L CALCULUS
SUPRAGINGIV
A
L CALCULUS

63. Supragingival Calculus

64. ¡ In extreme cases calculus may form a bridge-like
structure along adjacent teeth or cover the occlusal
surface of teeth without functional antagonist.
¡ Found nearly 100% in mandibular anterior teeth,
decreasing posteriorly to 20% of the third molars. In
maxilla, 10% of the anterior teeth and 60% of first
molars had supragingival calculus.

65. Subgingival calculus
¡ Located on the clinical crown apical to the margin of the
gingiva, usually in periodontal pockets, not visible upon
oral examination.
¡ Extends to bottom of the pocket and follows contour of
soft tissue attachment.

66. Subgingival Calculus

67. ATTACHMENT TO
TOOTH SURFACE
¡ Differences in the manner in which calculus is attached to the tooth
surface affect the relative ease or difficulty encountered in its removal.
¡ Several modes of attachment has been observed by
conventional histological techniques and by electron
microscopy.
¡ On any one tooth and in any one area, more than one mode of
attachment may be found.

68. Attachment
¡ Calculus attachment is superficial because no
interlocking or penetration occurs.
¡ Pellicle attachment occur most frequently on enamel
and newly scaled and planed root surfaces
¡ Calculus can be readily removed because of smooth
attachment

69. Mechanical locking into
surface irregularities
¡ Enamel irregularities include cracks, lamellae,
and carious defects.
¡ Cemental irregularities
lacunae, cemental tears.
include resorption
¡ Close adaptation of calculus undersurface
depressions to the gentle sloping moulds of the
unaltered cementum surface.

70. ¡ Attachment of organic matrix of calculus into minute
irregularities that were previously insertion locations
of sharpey’s fibres.
¡ Calculus embedded deeply in cementum may appear
morphologically similar to cementum and thus has
been termed calculocementum

71. Conclusion
¡ Despite tremendous increases in our understanding of the
pathogenic properties of specific plaque microorganisms and the
role of specific microorganisms in the disease process, current
therapy is largely non-specific.
¡ The treatments that we utilize (e.g., oral hygiene measures,
debridement by scaling and root planning, or even the currently
available mouthwashes) are oriented towards reducing the
accumulation of plaque on the teeth.
¡ Future developments in prevention will involve the development
of therapies which prevent the colonization or growth of specific
microorganisms that are known to function as pathogens in this
environment.

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References