dental plaque - part 1

DENTAL PLAQUE

GUIDED BY:DR. RUPINDER KAURDR. DIVYA JAGGI

PRESENTED BY:

DR.MALVIKA THAKUR

PG II YEAR

CONTENTS

1. Introduction2. Classification of soft deposits3. Definitions of dental plaque4. History of dental plaque5. Classification of dental

plaque6. Composition & Structure of

dental plaque7. 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

INTRODUCTIONHuman 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.

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]

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

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 coccoidalmicroorganisms 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

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.

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.

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

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

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

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

Micro-organisms

70%

•Bacterial•Non-bacterial

Intercellular Matrix20%-30%

•Organic material•Inorganic materials

MICROORGANISM

INTERCELLULAR MATRIX

PLAQUE

SOLIDS 20-30%

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.mutansStrep.sanguisA.viscosus

Gram -ve A.actinomycetemcomitansCapnocytophypa sp.Ekinella corrodens

P.GingivalisF.nucleatumP.intermediaB.forsythusC.rectus

Spirochetes T.denticola

VIRUSESYEAST

PROTOZOA MYCOPLASMA

NON BACTERIAL

NON BACTERIAL PORTION

ORGANIC CONTENT

CARBOHYDRATES30%

PROTEINS30%

LIPIDS15%

INTERCELLULAR MATRIX

Accounts for 20% to 30% of the plaque mass Organic and inorganic material.. Derived from – Saliva , Gingival crevicular fluid and Bacterial products.

CALCIUM

PHOSPHO

RUS

OTHER MINERALS

INORGANIC CONTENT

SODIUMPOTASSIUMFLOURIDE

MICROSCOPIC STRUCTURESUPRAGINGIVAL 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)

Thin section of supragingival plaque

GRAM POSITIVE BACTERIA IN

PALISADING ARRANGEMENT

SUBGINGIVAL PLAQUEBetween 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

Thin section of plaque in a deep pocket

FILAMENTS

RODS

COCCI

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 pellicleVigorous 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.

12/27/2011Transmission electron micrograph (TEM) of the acquired pellicle on an enamel surface

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 PathogenesisBy Dr. Priyam Mishra)

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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

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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 - statherinsCystatins, AmylasesDuctal & stromal productsLactoferrin & Lysozyme

SIGNIFICANCE OF PELLICLEPROTECTIVE provide barrier against acids thus may reduce dental caries attack.

LUBRICATIONkeep surface moist prevent drying.

NIDUS FOR BACTERIA: Plaque formation by adherence of microorganisms.

ATTACHEMENT OF CALCULUS: A mode of calculus attachment.

II. Initial Adhesion and Attachment of Bacteria

TRANSPORT TO SURFACE

INITIAL ADHESION

ATTACHMENT

COLONIZATION OF SURFACE & BIOFILM FORMATION

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

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.

Three stages

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

PHASE III. AttachmentA 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).

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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.

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

Selected Bacterial Adhesins & Target SubstratesATTACHMENT SURFACE

SUBSTRATE BACTERIAL SPECIES

ADHESIN SUBSTRATE RECEPTOR

Tooth Saliva coated surfaces

A.ViscsusS.MitisF.Nucleatum

FimbriaeProline rich proteins.Saliva treated hydroxyapatite

Tissue Epithelial cells

FibroblastsPMN`S

Connective tissue

P.GingivalisA.ViscosusT.DenticolaA.ViscosusA.NaeslundiiP.GingivalisP.intermedia

FimbriaeFimbriaeSurface proteinFimbriae

Membrane protein

Galactosyl residuesGalactosyl / Mannose residuesFibrinogen/ fibronectin

Pre existing plaque mass

S.SanguisA.NaeslundiiA.IsraeliiS.SanguisA.IsraeliiP.Gingivalis

C.Ochracea

P.Loescheii

F.Nucleatum

Heat sensitive protein

Fimbrial protein

Outer membrane protein

Rhamnose/ fucose/ N-acetyl neura acidGalactosyl residues

III. Colonization and plaque maturation

Mainly by 2 mechanisms COAGREGGATION. COADHESION

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Transport to surface

Initial adhesion

Attachment

Colonization of the surface and biofilm formation

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.

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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.

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

Co- Aggregation

It was described by Gibbsons & NygaardCell 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.

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.

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

• 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

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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 .

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

S.mitisS.oralis

S.sanguis

Streptococcus spsS.gorondi,S.intermedius

EARLY

COLONIZERS

V.parvulaA.odontolyticus

P.intermediaP.nigrescensP.microsF.nucleatum

C.rectus

E.nodatum

C.showae

E.corrodens Capnocytophaga spsA.actinomycetocomitans

P.gingivalisT.forsythusT.denticola

CLOSELY ASSOCIATEDCOMPLEXES IN THE ORAL CAVITY

LATE COLONIZERS

12/27/2011 Socransky et al (1998)

Distribution of different complexes in subgingival plaque sample

Kigure et al (1995)

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.

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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dental plaque - part 1

Science