Dental Plaque: Structure, Formation, and Its Role in Periodontal Disease

Stages Of Dental Plaque Formation And Development Dental Plaque in Periodontal Disease Structure/Morphogenesis

Supragingival Plaque

• It is adherent to tooth structure and consists of gram-positive cocci, gram-negative rods and filaments.
• Morphologic arrangement of flora in supragingival plaque is described as corncob formation.
• Corncob formation has a central core which consists of rod shaped bacterial cells which attaches along the surface of the rod-shaped cell.

Subgingival Plaque

• It has many large filaments with flagella and is rich in spirochetes.
• Tooth-associated plaque is same as supraginigival plaque while tissue associated plaque is covered with flagellated bacteria and numerous bristle brush formations. Extracellular matrix is not well Defined. This arrangement is called as test tube brush formation.
• Test-tube brush formation is characterized by large filaments that form long axis and short filaments or gram-negative rods embedded in an amorphous matrix.

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Formation of Dental Plaque

Formation of Organic Pellicle

• Pellicle is the initial phase of plaque development that forms on all the surface of teeth and prosthesis.
• The first stage of pellicle formation is derived from component of saliva and crevicular fluid as well as bacterial and host tissue cell products and debris. Pellicle consists of glycoproteins, proline rich proteins, phosphoproteins, histidine-rich proteins, enzymes as well as various other molecules, which act as adhesion site for the bacteria.
• There is adsorption of the positively charged salivary fluid, crevicular fluid and various other environmental molecules to the negatively charged hydroxyapatite surfaces of teeth via electrostatic, Van der Waals and hydrophobic forces.
• Pellicle functions as a protective barrier providing lubrication for the surface and preventing tissue desiccation. Pellicle is a non-shedding hard surface that provides a substrate on which bacteria progressively accumulated to form a dental plaque.

Dental Plaque vs Tartar: Differences And Effects On Oral Health Initial Colonization Of Bacteria On Tooth Surface

• Within a few hours, bacteria are formed on a dental pellicle. The initial bacteria which colonize on pellicle coated tooth surface are predominantly gram positive facultative microorganisms such as S. sanguinis, S. mitis and Actinomyces species.
• Adherence of bacteria via various specific attachments, i.e. extracellular polymeric substances and specific molecules, i.e. adhesions, which attach to receptors at dental pellicle.
• Each of the oral bacteria has different cell surface binding site for attachment and multiplication.

Following are the various sequences which shows the attachment of bacteria to the tooth surface.

First phase: Transport to Surface

This phase consists of initial transport of bacteria to the tooth surface. Various contacts can occur via chemotactic activity, Brownian motion, sedimentation of microorganisms, etc.

Second phase: Initial Adhesion

This phase consists of initial reverse adhesion of bacterial which get initiated by integration of bacteria and tooth surface from a distance through long range or short range forces which consists of Van der Waals forces and electrostatic forces.

Third Phase: Attachment

• As initial adhesion finishes, firm adhesion between bacteria and tooth surface occur via covalent, ionic and hydrogen bonding.
• If there is presence of rough surface, bacteria protect themselves against the shear forces and the bonding becomes irreversible.

Fourth phase: Colonization of surface and biofilm formation

As firmly attached bacteria starts their growth, newly formed bacterial clusters remain attached to microcolonies or there is a development of a biofilm.

Effective Methods For Removing Dental Plaque At home Secondary Colonization And Plaque Maturation

• Initial colonizers use the available oxygen, which causes decrease in the levels of oxygen as well as redox potential which favors growth of gram-negative anaerobic organisms i.e. Fusobacterium nucleatum and Capnocytophaga species.
• Now these microorganisms adhere to the cell surface receptors of initial colonizers as they vave poor ability of attachment directly to pellicle, so as plaque mature number of gram-negative bacteria increases.
• These microorganisms adhere to cells of bacteria already in the plaque mass by a process known as coaggregation and this play very important role in secondary colonization.
• During early stages of plaque formation interaction between gram-positive and Gram negative bacteria occur which is followed by coaggregation in the later stages between gram-negative organisms.
• Within the plaque matrix nutrients are required so that there is growth of bacteria in plaque matrix. Main source of nutrient is saliva.
• If plaque is established substances produced by various species become nutrients which are essential for growth of other organisms.
• Long-standing supragingival plaque demonstrates corncob as well as test-tube brush arrangement.
• Corncob formation are observed between rod-shaped bacterial cells which forms the inner structure and the coccal cells which attach along the surface of rod-shaped cell while the test-tube brush arrangement consists of filamentous bacteria to which gram-negative rods adhere.
• Early colonizers which lead to plaque formation lie in yellow and purple complex while secondary colonizers lie in green, orange and red complexes.

How To Control Dental Plaque To Prevent Gum Inflammation Microbiology Of Dental Plaque

The organisms associated with plaque formation are:

Gram +ve

• Actinomyces viscosus
• Streptococcus sanguinis

Gram –ve

• Actinobacillus actinomycetemcomitans
• Bacteroides forsythus
• Capnocytophaga species
• Porphyromonas gingivalis
• Prevotella intermedia
• Treponema denticola
• Fusobacterium nucleatum

Red Complex

• Porphyromonas gingivalis
• Treponema denticola
• Bacteroides forsythus

Purple Complex

• Veillonella parvula
• Actinomyces odontolyticus

Yellow Complex

• Streptococcus mitis
• Streptococcus oralis
• Streptococcus sanguinis
• Streptococcus gordonii
• Streptococcus intermedius

Green Complex

• Actinobacillus actinomycetemcomitans
• Capnocytophaga species
• Eikenella corrodens

Orange Complex

• Prevotella intermedia
• P. nigrescens
• Peptostreptococcus micros
• Fusobacterium nucleatum
• C. Showae
• E. nodatum
• Early colonizers which lead to plaque formation lie in yellow and purple complex while secondary colonizers lie in green, orange and red complexes.