Dental Caries and Oral Bacteria Quiz

Development of Dental Caries

• 4 factors required: teeth, bacteria in plaque, fermentable carbohydrate in diet, and time

Nutrient Sources for Bacteria

• Saliva
• Gingival crevicular fluid
• Host diet

Main Bacteria in Caries

• Streptococcus mutans
• Lactobacillus
• Veillonella

Acidogenic and Aciduric

• Acidogenic: produces high levels of acid
• Aciduric: can survive and flourish in low pH conditions
• S. mutans is both acidogenic and aciduric, allowing it to keep producing acid in low pH conditions

Virulence Factors for S. mutans

• Antigen I/II (enables adherence to surfaces)
• Glucosyl transferases (produce glucan polymers from sucrose)
• Glucan binding proteins (enable bacteria with glucan to bind to oral mucosa)

Lactobacillus

• Found in other parts of the body and in fermented foods
• Opportunistic organism that requires low pH habitat
• Colonizes existing lesions, does not initiate caries

Veillonella

• Gram-negative anaerobic cocci
• Grow using lactate as a substrate for growth
• Beneficial in caries, using lactate produced by streptococci and lactobacilli

Other Acidogenic Species

• Scardovia wiggsiae
• Propionibacterium acidfaciens
• Bifidobacteria

Plaque Hypothesis

• 3 stages: dynamic stability, acidogenic, and aciduric
• Dynamic stability: acid production, followed by alkalization phase
• Acidogenic stage: repeated sugar intake, poor oral hygiene, and reduced salivary flow
• Aciduric stage: selection of aciduric bacteria, environmental change, and shift in microbiota

Saliva's Role in Caries

• Amylase is critical in plaque and caries
• Alpha-Amylase hydrolyzes starch to glucose and maltose, making them available for fermentation
• Binds with high affinity to oral streptococci, retaining activity when bound

Sugar Sources

• Host diet
• Salivary components (sucrose, maltose, and maltooligosaccharides)

Sugar Transport and Glycolysis

• Sugars transported to interior of cells via the phosphotransferase system (PTS)
• Glycolysis results in pyruvate and 2 ATP molecules

Extracellular Polysaccharides (EPS)

• Formed from bacterial metabolism of sucrose
• Become part of the plaque matrix
• 3 roles: sticky polymers contributing to bacterial adherence, resistance to washing away, and source of sugars for metabolism when nutrients are limited

Intracellular Polysaccharides (IPS)

• Formed by S. mutans
• Storage molecules for later use

Glucosyl Transferases

• 3 produced by S. mutans: GTFB, GTFC, and GTFD
• GTFB and GTFC produce water-insoluble glucans
• GTFD produces water-soluble glucans

Glucan Synthesis and Hydrolysis

• Glucan synthesised by glucosyl transferase
• Glucan hydrolyzed by glucanase

Fructan Synthesis and Hydrolysis

• Fructan synthesised by fructosyl transferase
• Fructan hydrolyzed by fructanase