Dental plaque - part 1

1. DENTAL PLAQUE
GUIDED BY:
DR. RUPINDER KAUR
DR. DIVYA JAGGI
PRESENTED BY:
DR.MALVIKA THAKUR
PG II YEAR

2. Page  2
CONTENTS
1. Introduction
2. Classification of soft deposits
3. Definitions of dental plaque
4. History of dental plaque
5. Classification of dental
plaque
6. Composition & Structure of
dental plaque
7. Formation of dental plaque
8. Dental plaque as a biofilm
9. Physiological properties
10. Microbial specificity of
periodontal disease
11. Detection of dental plaque
12. Conclusion
13. References
PART - I PART - II

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INTRODUCTION
Human fetus is sterile.
Colonization starts at birth.
Within hours – facultative & aerobic bacteria.
2nd day – anaerobic bacteria.
Within 2 weeks – mature microbiota estd in gut.
After weaning - 1014 microorganisms with 400 different type
of bacteria.
There are 10 times more bacteria than human
cells.

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Establishing microbiota - harmony with the host.
Constant renewal - prevents the accumulation of
microorganisms.
Teeth provide hard, non-shedding surfaces - accumulation &
metabolism of bacteria on hard oral surfaces is considered the
primary cause of dental caries, gingivitis, periodontitis and peri-
implant infections.
 In the oral cavity, the bacterial deposits have been termed dental
plaque or bacterial plaque.
 In 1 mm3 of dental plaque weighing approximately 1mg, approx
1011 bacteria are present. [Socransky et al ,1953]

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Classification of soft deposits
MATERIAL
ALBA
FOOD DEBRIS
A non-cellular thin film
An organized transparent deposit which is
primarily composed of bacteria and their
products
Soft, whitish deposit with no specific
architecture, which can be removed by
water spray.
Retained food which is usually removed by
saliva and oral muscular action.
Schwartz et al 1969
ACQUIRED
PELLICLE
DENTAL
PLAQUE

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Bowen W.H. (1976) defined dental plaque clinically as a structured,
resilient,yellow-grayish substance that adheres tenaciously to the
intraoral hard surfaces, including removable and fixed restorations.
According to Schwartz & Massler (1969) – Plaque is a dense microbial
Layer consisting of coherent mass of filamentous, rod like and coccoidal
microorganisms embedded in an inter microbial matrix which accumulates
on tooth surface.
Davies et al (1963) defined plaque as a soft concentrated mass containing
mainly of large variety of bacteria together with certain amount of cellular
debris which develops within a short time after tooth brushing.
DEFINITIONS

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According to WHO (1978) Plaque is a specific but highly variable
structural entity resulting from colonization and growth of
microorganisms on surfaces of teeth and consisting of numerous
microbial species and stains embedded in a extracellular matrix.
According to the GPT, 4th Edition An organized mass, consisting
mainly of microorganisms, that adheres to teeth, prostheses, and oral
surfaces and is found in the gingival crevice and periodontal pockets.
Other components include an organic, polysaccharide-protein matrix
consisting of bacterial by-products such as enzymes, food debris,
desquamated cells, and inorganic components such as calcium and
phosphate
According to Carranza, 11th Edition Dental plaque is defined
clinically as a structured, resilient yellow-grayish substance that
adheres tenaciously to the intraoral hard surfaces, including
removable and fixed restorations.

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HISTORY
 J Leon Williams (1897) – Described dental plaque
 GV Black (1899) – Coined term “gelatinous dental plaque”
 W D Miller (1902) - Bacterial plaque
 Wild (1941) - Shortened Black’s terminology to the term ‘Plaque’
 Waerhaug (1950) Described the importance of bacterial plaque in the
etiology of periodontal disease
 Loe et al (1965), Landmark study on plaque , saying that plaque is main
etiological agent in periodontal disease.

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 Schei (1959), Russel (1967) - Epidemiological studies-
Positive correlation between the amount of bacterial plaque and the severity
of gingivitis
 W.Loesche (1976) - Modern theories of specificity – “Specific plaque
hypothesis”
 Socransky 1979 - Modern Version of Specific Plaque Hypothesis
 Thelaide 1986 - Unified Theory
 PD Marsh & Martin (1999) - Ecological plaque hypothesis
 Costerton (1999) - Evolved Biofilm
 Hajishengallis et al 2012 - Keystone Pathogenic Hpothesis

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I.GRANTS CLASSIFICATION- ACCORDING TO LOCATION
A. Coronal plaque- Coronal to the gingival margin
B. Gingival plaque- forms on the external surface of the oral
epithelium and attached gingiva
C. Sub gingival plaque- located between the periodontal
attachment and the gingival margin, within the sulcus or
pocket.
D. Fissure plaque- develops in pits and fissures
E. Peri-implant plaque.
CLASSIFICATION

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II. GLICKMAN’S CLASSIFICATION- ACCORDING TO
LOCATION
11

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SUPRAGINGIVAL PLAQUE SUBGINGIVAL PLAQUE

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TOOTH
ATTACHED
UNATTACHED TISSUE
ATTACHED
Gram +ve,
Few Gram –ve
rods and cocci,
Gram negative
rods, filaments,
spirochetes
Gram negative
rods, filaments,
spirochetes
Does not
extend to JE
Extend to JE Extend to JE
Calculus
formation, root
caries
Gingivitis Gingivitis,
periodontitis
May penetrate
cementum
- May penetrate
epithelium and
connective
tissue

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 Pavel Godoroja and Olga Dulghieru 2004
The dental plaque is differentiated into two categories by
Supra-gingival
plaque
Gingival third of the
crown of the tooth
Inter-proximal areas
Pits and fissures and also on
other such surface with
irregularities.
Sub-gingival plaque
Tooth adherent
zone
Epithelial adherent
zone
Non adherent zone

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Composition of dental plaque
• Bacterial
• Non-bacterial
Micro-
organisms
70%
• Organic material
• Inorganic materials
Intercellular
Matrix
20%-30%
15
MICROORGANISM
INTERCELLULAR MATRIX
PLAQUE
SOLIDS 20-30% WATER 70-80%

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BACTERIAL PORTION
 70 to 80 % of total solid plaque volume.
 1 gm of plaque contains approximately 2 X 1011 bacteria.
(Socransky SS,1953), (Schroeder, De Boever-1970)
Bacteria Facultative Anaerobic
Gram +ve Strep.mutans
Strep.sanguis
A.viscosus
Gram -ve A.actinomycetemcomitans
Capnocytophypa sp.
Ekinella corrodens
P.Gingivalis
F.nucleatum
P.intermedia
B.forsythus
C.rectus
Spirochetes  T.denticola

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VIRUSES
YEAST
PROTOZOA MYCOPLASMA
NON
BACTERIAL
NON BACTERIAL PORTION

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ORGANIC
CONTENT
CARBOHYDRATES
30%
PROTEINS
30%
LIPIDS
15%
INTERCELLULAR MATRIX
 Accounts for 20% to 30% of the plaque mass
 Organic and inorganic material..
 Derived from – Saliva , Gingival crevicular fluid and Bacterial products.

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CALCIUM
PHOSPHORUS
OTHER
MINERALS
INORGANIC
CONTENT
SODIUM
POTASSIUM
FLOURIDE

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MICROSCOPIC STRUCTURE
SUPRAGINGIVAL PLAQUE
 Typically demonstrates a stratified organization of the bacterial
morphotypes.
Gram-positive cocci and short rods predominate at the tooth
surface
Gram-negative rods and filaments ,spirochetes predominate in
the outer surface of the mature plaque mass.
Supra gingival plaque can have a structured architecture
polymer containing channel or pores have been observed that
link the plaque/oral environment interface to the tooth surface (
Wood et al 2000,Auschillet al 2001,Zaura Arite et al 2001)

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Thin section of supragingival plaque
GRAM POSITIVE BACTERIA IN
PALISADING ARRANGEMENT

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SUBGINGIVAL PLAQUE
Between sub gingival plaque and the tooth an electron dense
organic material is interposed , termed as cuticle.
Gingival crevicular fluid, -contains many substances that the
bacteria may use as nutrients
 Host inflammatory cells and mediators have influence on the
establishment and growth of bacteria in this region.
DENTA PLAQUE UNDER
X 400 MAGNIFICATION

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Thin section of plaque in a deep pocket
FILAMENTS
RODS
COCCI

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DEVELOPMENT OF DENTAL
PLAQUE
The formation of the
pellicle on the tooth
surface
Initial adhesion and
attachment of
bacteria
Colonization and
plaque maturation
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I. Formation of the pellicle
Vigorous tooth brushing – nanoseconds – acquired pellicle .
Acquired pellicle - a homogenous, membranous, acellular film that
covers the tooth surface and frequently form the interface between
the tooth ,the dental plaque and calculus. (Schluger)
`A fully established pellicle - 30 min, within 24 hr- 0.8 µm in
diameter.
Derived from components of saliva and crevicular fluid as well as
bacterial and host tissue cell products and food debris.
12/27/2011
Transmission electron micrograph (TEM) of the acquired pellicle on an enamel surface

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ULTRA STRUCTURE OF DENTAL PELLICLE
 Salivary pellicle can be detected on clean enamel surfaces
within 1 minute.
 By 2 hours, the pellicle is essentially in equilibrium.
 Thickness - 30 - 100 nm
 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
(Panacea for Periodontology: Basic Tissue, Etiology and Pathogenesis
By Dr. Priyam Mishra)
12/27/2011

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Studies shows ( 2 hours) enamel pellicle, its amino acids
composition differs from that of saliva, indicating that the
pellicle forms by selective adsorption of the environmental
macromolecules. (Scannapieo FA et al , “ saliva and dental pellicles’”
contemporary periodontics, 1990)
Mechanism involved are:
 Electrostatic forces
 Van der waals
 Hydrophobic forces
12/27/2011

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CHEMICAL COMPOSITION OF ACQUIRED PELLICLE
(Mayhell & Butller 1976, Sonju 1975)
Amino acids -
4.6%
Pellicle contains more hydrophobic and less neutral
amino acids than whole saliva (ie more leucine,
alamine, tyrosine and sereine than saliva)
Hexosamines -
2.7%
Glucosamine - 18%, Galactosamine -18%
Carbohydrates -
14%
Glucose - 20%, Galactose - 27%
Mannose - 9% Fructose - 18%
Salivary Molecules Mucins
Proline rich proteins - statherins
Cystatins, Amylases
Ductal & stromal products
Lactoferrin & Lysozyme

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SIGNIFICANCE
OF PELLICLE
PROTECTIVE
provide barrier
against acids thus
may reduce dental
caries attack.
LUBRICATIONke
p surface moist
prevent drying.
NIDUS FOR
BACTERIA:
Plaque formation
by adherence of
microorganisms.
ATTACHEMENT
CALCULUS: A
of calculus
attachment.

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II. Initial Adhesion and Attachment of
Bacteria
TRANSPORT TO
SURFACE
INITIALADHESION
ATTACHMENT
COLONIZATION OF
SURFACE & BIOFILM
FORMATION

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PHASE I. Transport to the surface
RANDOM CONTACTS
OCCUR THROUGH:
Brownian
motion ( 40
µm/hour)
Sedimentation of
organisms
Liquid flow
Active bacterial
movement
(chemotactic
activity)
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PHASE II. INITIAL ADHESION
Transport
to surface
Initial
adhesion
Attachment
Colonization
of the
surface and
biofilm
formation
 Reversible adhesion of the
bacterium and the surface.
Physical phase
 Initiated by interactions b/w bacterium and surface through long
range and short range forces, including
 Van der Waals attractive forces
 Electrostatic repulsive forces

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DLVO theory
Derjaguin, Landau, Verwey & Overbeek (DLVO) have postulated
that above a separation distance of 1nm, the summation of previous
two forces describes total range interaction also called as Total
Gibbs Energy (GTOT).
The result of summation (GTOT= GA+GE) is function of a
separation distance between negatively charged particle and a
negatively charged surface in a medium ionic strength suspension
medium.

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 Three stages
1. Secondary minimum (reversible attraction)
2. Positive maximum (energy barrier)
3. Primary minimum (irreversible attraction)

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PHASE III. Attachment
A firm anchorage between bacterium and surface will be
established by specific interactions ( ionic, covalent, or hydrogen
bonding)
This follows direct contact or bridging true extra cellular
filamentous appendages (with length up to 10nm).
12/27/2011

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On a rough surface, bacteria are better protected against shear
forces so that a change from reversible to irreversible bonding
occurs more easily and more frequently.
The bonding between bacteria and pellicle is mediated by
specific extracellular proteinaceous components (adhesions) of
the organism and complementary receptors (proteins,
glycoproteins, polysaccharides) on the surface (pellicle) and is
species specific.

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Streptococci (mainly S. sanguis) – Primary colonizer - binds to
acidic proline-rich-proteins
 α-amylase
 sialic acid.
Actinomyces - Primary colonizers, eg A. viscosus possesses
fimbrae - adhesins - specifically bind to proline-rich proteins of
dental pellicle.
A. viscosus - reognises cryptic segments [cryptiotopes] of proline
rich proteins, which are only available in adsorbed molecules.
( with lock &key mech.)
( Mergenhagen et al 1987)
Receptors in pellicle

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Selected Bacterial Adhesins & Target Substrates
ATTACHMENT
SURFACE
SUBSTRATE BACTERIAL
SPECIES
ADHESIN SUBSTRATE
RECEPTOR
Tooth Saliva coated
surfaces
A.Viscsus
S.Mitis
F.Nucleatum
Fimbriae
Proline rich
proteins.
Saliva treated
hydroxyapatite
Tissue Epithelial cells
Fibroblasts
PMN`S
Connective tissue
P.Gingivalis
A.Viscosus
T.Denticola
A.Viscosus
A.Naeslundii
P.Gingivalis
P.intermedia
Fimbriae
Fimbriae
Surface protein
Fimbriae
Membrane protein
Galactosyl
residues
Galactosyl /
Mannose
residues
Fibrinogen/
fibronectin
Pre existing
plaque mass
S.Sanguis
A.Naeslundii
A.Israelii
S.Sanguis
A.Israelii
P.Gingivalis
C.Ochracea
P.Loescheii
F.Nucleatum
Heat sensitive
protein
Fimbrial protein
Outer membrane
protein
Rhamnose/
fucose/ N-acetyl
neura acid
Galactosyl
residues

39. Page  39
III. Colonization and plaque
maturation
Mainly by 2
mechanisms
COAGREGGATION. COADHESION
12/27/2011
Transport
to surface
Initial
adhesion
Attachment
Colonization
of the
surface and
biofilm
formation

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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.
12/27/2011
SECONDARY COLONIZERS
 They do not initially colonize the clean tooth surface but adhere to
bacteria already in the plaque mass.
 Including Prevotella intermedia, Prevotella loescheii,
Capnocytophaga spp., Fusobacterium nucleatum, and
Porphyromonas gingivalis.

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 Co-aggregation is the interaction
between planktonic micro-organisms
of a different strain or species
 Co-adhesion is the interaction
between a sessile, already adhering
organism and planktonic micro-
oganisms of a different strain or
species

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Co- Aggregation
It was described by Gibbsons & Nygaard
Cell to cell recognition of a genetically distinct partner cell type.
Occurs primarily through
1. Highly specific interaction of
protiens and carbohydrate
molecules located on the bacterial
cell surfaces.
2. Less specific interaction resulting
from hydrophobic electrostatic &
van der waals forces.

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 Well characterized interaction include the coaggregation of:
• Fusobacterium nucleatum S. sanguis,
• Prevotella loescheii A. viscosus
• Capnocytophaga ochraceus A. viscosus
• Streptococci show intrageneric co-aggregation  bind to
the nascent monolayer of already bound streptococci.
 Later stages – coaggregation between different Gram negative
species seen – F. nucleatum & P. gingivalis or T. denticola.
43

44. Page  44
Coaggregation Bridges:
 Formed when the common partner bears two or more types of coaggregation
mediators.
 Mediators can be various types of receptor polysaccharides, or various types
of adhesins, or a mixture of the two.
 Bridging is usually considered to be a cooperative event that brings three or
more cell types into close proximity and fosters symbiotic relationships.
 Bridging can also be an antagonistic event which brings together organisms
that compete with each other for nutrient or other needs.

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Thus most coaggregation among strains of different genera are
mediated by lectin-like adhesin & can be inhibited by lactose &
other glycosides.

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• F.nucleatum is central to the mechanism - since this
organism can co aggregate with numerous other species.
• Examples
F.nucleatum:
 S.sanguis
 P. loescheii
 A.viscous
 Capnocytophaga
 P.gingivalis
 B.forsythus
 T.denticola
12/27/2011

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COAGGREGATION COMPETITION:
 Competition occurs when multiple cell types recognize the same
coaggregation mediator on the common coaggregation partner.
Model depicting competition for binding sites
on Streptococcus oralis .

49. Page  49
 Test tube brush:
 Composed of a central axis of a filamentous
bacterium with perpendicularly associated
short filaments.
 Commonly seen in the subgingival plaque of
teeth associated with periodontitis
 Detected between filaments of bacteria to
which gram –ve rods adhere.
 Corncob formation:
 Feature of plaque present on teeth
associated with gingivitis .
 Rod-shaped bacterial cells eg.
Bacterionema matruchotii or
Actinomyces sp. that forms inner core
of the structure and coccal cells eg.
Streptococci or P. gingivalis that attach
along the surface of the rod shaped
cells.
Described by Gibbsons and Nygaard

50. Page  50
S.mitis
S.oralis
S.sanguis
Streptococcus sps
S.gorondi,
S.intermedius
E
A
R
L
Y
C
O
L
O
N
I
Z
E
R
S
V.parvula
A.odontolyticus
P.intermedia
P.nigrescens
P.micros
F.nucleatum
C.rectus
E.nodatum
C.showae
E.corrodens
Capnocytophaga sps
A.actinomycetocomitans
P.gingivalis
T.forsythus
T.denticola
CLOSELY ASSOCIATED
COMPLEXES IN THE ORAL
CAVITY
LATE COLONIZERS
12/27/2011
Socransky et al (1998)

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Distribution of different complexes in subgingival plaque
sample
Kigure et al (1995)

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CO-ADHESION
• Some bacteria are unable to bind directly to the conditioning
film, but are able to interact with molecules on bacteria that
are already attached (co-adhesion), also by adhesin-receptor
interactions.
• One bacterium, Fusobacterium nucleatum, can co-adhere with
almost all other bacteria found in dental plaque, and is
considered to be a key bridging organism between early and
later colonisers.

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Development of dental plaque on a clean enamel surface. Coccal bacteria attach to the enamel pellicle as pioneer species
(A) and multiply to form microcolonies (B), eventually resulting in confluent growth (biofilm formation) embedded in a
matrix of extracellular polymers of bacterial and salivary origin (C). With time, the diversity of the microflora increases, and
rod and filament-shaped bacteria colonize (D and E). In the climax community, many unusual associations between
different bacterial populations can be seen, including ‘corn-cob’ formations (F). (Magnification approx. × 1150)

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