Question

Name the bacterial and yeast polysaccharide that is found in dental plaque on the surface of teeth.

• A. Glycogen
• B. Peptidoglycan
• C. Agar
• D. Dextran

Hint:

Sucrose is the key dietary driver of dental caries because it is the only sugar that can be converted by bacterial glucansucrases into sticky, plaque-forming dextrans.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Dental plaque is a structured biofilm that forms on teeth surfaces, composed of bacterial cells embedded within an extracellular polymeric substance (EPS) matrix.
This matrix helps bacteria adhere to the enamel and shields the biofilm from physical and chemical clearing mechanisms.

Step 2: Detailed Explanation:
The primary bacterium associated with dental plaque formation is Streptococcus mutans.
When dietary sucrose is consumed, S. mutans uses extracellular enzymes called glucansucrases (dextransucrases) to cleave sucrose into glucose and fructose.
The enzyme polymerizes the glucose units into high-molecular-weight, highly branched glucan polymers known as dextrans.
The chemical structure of dextran consists of a backbone of \(\alpha\)-(1\(\rightarrow\)6) glucosidic linkages with \(\alpha\)-(1\(\rightarrow\)3) and occasionally \(\alpha\)-(1\(\rightarrow\)4) or \(\alpha\)-(1\(\rightarrow\)2) branch points.
This insoluble, sticky polysaccharide forms the structural core of dental plaque, enabling bacterial colonization and acid localization, which leads to dental caries.

Step 3: Final Answer:
The polysaccharide found in dental plaque on the surface of teeth is dextran.