Introduction to Dental Plaque

Question 1

Define Dental Plaque.

Answer 1

-Structure, resilient yellow-greyish substance that adheres to intraoral handsurfaces, including removable and fixed restorations.

Question 2

Define dental biofilm.

Answer 2

• Complex microbial community that develops on a tooth surface, and other hard non-shedding materials, embedded in a matrix of polymers of bacterial and salivary origin.

Question 3

What is the link between caries and plaque?

Answer 3

• Plaque requires a tooth surface, time and sugar to develop
• Caries requires a tooth surface, plaque, time and sugar
• Streptococcus mutans bacteria causes caries

Question 4

How does long does it take for gingivitis to occur because of plaque accumulation?

Answer 4

• Symptoms of gingivitis present within 21 days - subsidided in a week after tooth cleaning.

Question 5

What are the different types of dental plaque?

Answer 5

• Supragingival plaque (found at or above gingival margin)
• Marginal plaque (found in contact with gingival margin)
• Subgingival plaque (found below gingival margin, between tooth and gingival pocket epithelium)

Question 6

Outline the composition of dental plaque biofilm

Answer 6

• 70-80% bacteria
• 20-30% intracellular matrix
• Water channels

Question 7

What are the organic components of plaque?

Answer 7

• Glycoproteins from saliva
• Polysaccharides produced by saliva
• Proteins
• Lipids

Question 8

What are the inorganic components of plaque?

Answer 8

• Mainly calcium and phosphorus
• Minerals like sodium, potassium and fluoride

Question 9

What are the sources of inorganic components in different types of dental plaque?

Answer 9

• Saliva is the source in supragingival plaque
• Gingival crevical fluid is the source in subgingival plaque

Question 10

How does the mineral content change the plaque?

Answer 10

• Increasing mineral content changes the plaque mass to become calculus as it is calcified

Question 11

What are the 3 phases of dental plaque formation?

Answer 11

• Formation of pellicle on tooth surface
• Initial adhesion of bacteria
• Colonisation/maturation

Question 12

Outline stage 1 of dental plaque formation

Answer 12

• Forms in seconds after teeth have been cleaned
• Contains 180+ peptides, proteins and glycoproteins e.g. keratin, mucins and other adhesion sites for bacteria - bacteria bind to pellicle, not tooth directly.

Question 13

Outline stage 2 of dental plaque formation

Answer 13

• Adhesin molecules on microbial cell surface interact with receptors in pellicle and adhere to it (primary colonisers)
• Over 4-8 hours, 60-80% of bacteria present are members of Streptococcus genus, rest are obligate aerobes and faculative anaerobes

Question 14

Outline stage 3 of dental plaque formation (coadhesion)

Answer 14

• Coadhesion - primary colonisers provide new binding sites for secondary colonisers
• Oxygen removed, primary colonisers provide conditions for obligate anaerobes growth

Question 15

Outline stage 3 of dental plaque formation (coaggregation)

Answer 15

• Genetically distinct bacteria become attached to one another via specific molecules
• Coadhesion + coaggregation develop complex microcolonies, eventually forming mature biofilm

Question 16

How does dental plaque shift from early to mature plaque?

Answer 16

• Shift in microbial population from mainly gram positive organisms, to mainly gram negative organisms

Question 17

What are the differences between gram positive and gram negative bacteria?

Answer 17

• Gram+ stain crystal violet, gram- stain red or pink
• Gram+ have no outer cell membrane, gram- do
• Gram- have a cell wall high in peptidoglycans (retains crystal violet dye), making them more resistant to antibodies

Question 18

What is the corncob structure seen in supragingival plaque?

Answer 18

• Found in supragingival plaque near gingival margin
• Cocci held together by an extracellular polysaccharide matrix with web of central filamentous micro-organisms

Question 19

How does rate of formation and location of plaque vary between individuals?

Answer 19

• Influenced by age, diet, salivary secretion, oral hygiene, tooth alignment, systemic disease and host factors
• Gram+ cocci and short rods predominate at tooth surface
• Gram- rods predominate in outer surface of mature plaque

Question 20

What are the natural factors that aid plaque retention?

Answer 20

• Calculus
• Enamel projections
• Tooth fissures, grooves, pits and cracks
• Cervical and root caries
• Tooth crowding