Oral Microbiology

Question 1

Describe how dental plaque forms on tooth enamel

Answer 1

After 2 seconds aquired enamel pellicle forms
Within 2 minutes, pioneer bacteria ie, streptococci adhere to the pellicle
Within 2 hours, Microcolonies of bacteria, Biosynthesis of Extracellular Polysaccharides and Biofilm development
Within 2 days we have mature plaque

Question 2

What is dental plaque

Answer 2

Dental plaque is a matrix of bacteria that adheres to the tooth surface, creating a biofilm. If not removed, the biofilm continues growing, becoming a site that can harbour multiple bacteria. An example of this is streptococcus mutans, a gram positive, cariogenic bacteria involved in the development and progression of dental caries

Question 3

what is supragingival plaque

Answer 3

above gingival margin
bathed in saliva
carbohydrate fermentation
micro-aerophilic (can tolerate oxygen but prefers not)
gram positive
can progress to dental caries

Question 4

what is subgingival plaque

Answer 4

below gingival margin
bathed in gingival crevicular fluid
protein breakdown
anaerobic (oxygen free)
gram negative
can progress to periodontal disease

Question 5

Describe the virulence factors that allow Streptococcus mutans to cause dental caries (4)

Answer 5

1/ extracellular polysaccharide production, s.mutans produce polysaccharides and make chains of glucose that facilitate retention of acids.
2/ carbohydrate fermentation, s.mutans ferments carbs from our diet releasing lactic acid as a biproduct. Sits on tooth surface and demineralises enamel, resulting in loss of calcium and phosphate ions.
3/ s.mutans is aciduric, meaning it can survive a low pH and have success in an acidic environment.
4/intracellular polysaccharide storage, allowing to continue the fermentation process even when carbs are not present in oral cavity.