Dental Caries and Oral Microbiology

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Questions and Answers

What is the primary function of glucosyl transferases in Streptococcus mutans?

Breakdown of lactate to produce energy

Increasing the pH of the oral environment

Enabling the bacteria to adhere to surfaces

Producing glucan polymers from sucrose (correct)

What is the characteristic of Lactobacillus that differentiates it from other oral bacteria?

It is an acidogenic and aciduric bacterium

It produces glucan polymers from sucrose

It is a Gram-negative anaerobic cocci

It can be found in other parts of the body and in fermented foods (correct)

What is the role of Veillonella in the development of dental caries?

It colonizes existing lesions (correct)

It produces acid from lactate

It initiates the development of caries

It competes with other bacteria for nutrients

What is the term for the ability of bacteria to survive and flourish in low pH conditions?

Aciduric Signup and view all the answers

What is the function of antigen I/II in Streptococcus mutans?

It enables the bacteria to adhere to surfaces Signup and view all the answers

What is the primary source of nutrients for bacteria in the oral mucosa?

Saliva and gingival crevicular fluid Signup and view all the answers

What is the primary source of sugars that can be used by bacteria in the plaque?

Host diet Signup and view all the answers

What is the primary role of alpha-amylase in plaque and caries?

Hydrolysing starch to glucose Signup and view all the answers

What is the result of glycolysis?

Pyruvate and 2 ATP molecules Signup and view all the answers

What is the primary function of extracellular polysaccharides (EPS) in plaque?

Forming a sticky matrix Signup and view all the answers

Which enzyme is responsible for synthesising glucan?

Glucosyl transferase Signup and view all the answers

What is the role of enolase in glycolysis?

Catalysing the penultimate step of glycolysis Signup and view all the answers

What is the effect of fluoride on the glycolysis cycle?

Inhibits enolase Signup and view all the answers

Which stage of the plaque hypothesis involves the buffering capacity of saliva being lost?

Aciduric stage Signup and view all the answers

What is the role of Scardovia wiggsiae in carious lesions?

An acidogenic species associated with carious lesions Signup and view all the answers

What is the primary function of IPS in S.mutans?

Storing sugars for later use Signup and view all the answers

Study Notes

Dental Caries Development

Four factors required for dental caries development: teeth, bacteria in plaque, fermentable carbohydrate in diet, and time.

Nutrient Sources for Oral Bacteria

Three sources of nutrients for bacteria in the oral mucosa: saliva, gingival crevicular fluid, and host diet.

Main Bacteria in Caries

Three main bacteria found in caries: Streptococcus mutans, Lactobacillus, and Veillonella.

Acidogenic and Aciduric Bacteria

Acidogenic bacteria produce high levels of acid.
Aciduric bacteria can survive and flourish in low pH conditions.
Streptococcus mutans is both acidogenic and aciduric, allowing it to thrive in low pH environments.

Streptococcus mutans Virulence Factors

Three virulence factors for Streptococcus mutans: Antigen I/II (enables adherence to surfaces), glucosyl transferases (produces glucan polymers from sucrose), and glucan binding proteins (enables bacteria with glucan to bind to oral mucosa).

Lactobacillus Characteristics

Lactobacillus can be found in other parts of the body and fermented foods.
Lactobacillus is an opportunist organism that requires a low pH habitat and colonizes existing lesions.

Veillonella Characteristics

Veillonella is a Gram-negative anaerobic coccus.
Veillonella grows using lactate as a substrate for growth and thrives in carious lesions where lactate is present.

Plaque Hypothesis Stages

Three stages in the plaque hypothesis: dynamic stability, acidogenic, and aciduric.
Dynamic stability stage involves acid production from sugars, followed by an alkalisation phase.
Acidogenic stage involves repeated sugar intake, poor oral hygiene, and reduced salivary flow, leading to acid production by non-mutans streptococci and Actinomyces.
Aciduric stage involves the selection of aciduric bacteria, such as S. mutans, Lactobacillus, and some Bifidobacterium and Propionibacterium species, due to the loss of buffering capacity and change in the microbiota.

Saliva's Role in Plaque and Caries

Amylase is a critical component of saliva in plaque and caries.
Alpha-amylase hydrolyses starch to glucose and maltose, making them available for fermentation, and binds with high affinity to oral streptococci, facilitating glucose uptake.

Sugar Sources and Transport

Sugars can be derived from the host diet and salivary components.
Sugars are transported to the interior of cells via the phosphotransferase system (PTS) for glycolysis.

Glycolysis and Extracellular Polysaccharides

Glycolysis results in pyruvate and 2 ATP molecules.
Extracellular polysaccharides (EPS) are formed from bacterial metabolism of sucrose and become part of the plaque matrix.

Intracellular Polysaccharides and Glucosyl Transferases

Intracellular polysaccharides (IPS) are formed by S. mutans and serve as storage molecules for later use.
Three glucosyl transferases produced by S. mutans: GTFB and GTFC (form water-insoluble glucans), and GTFD (forms water-soluble glucans).

EPS Roles and Glucan Synthesis

EPS is sticky and contributes to bacterial adherence to the pellicle and plaque.
EPS makes bacteria more resistant to being washed away by food and drink.
EPS serves as a source of sugars for metabolism when nutrients are limited.
Glucan synthesis involves glucosyl transferase, sucrose, and glucan primer.
Glucan is hydrolysed by glucanase.

Fructan Synthesis and Hydrolysis

Fructan synthesis involves fructosyl transferase, sucrose, and fructan primer.
Fructan is hydrolysed by fructanase.

Enolase and Fluoride's Effect on Glycolysis

Enolase is a key regulatory enzyme in glycolysis.
Fluoride inhibits enolase, reducing sugar transport and acid production.

Xylitol and Probiotics

Xylitol is used to replace sugar and inhibits S. mutans growth in vitro.
Xylitol is transported into S. mutans cells, but enters a futile cycle of phosphorylation, dephosphorylation, and export, using energy without producing ATP.
Xylitol inhibits glycosyl transferase and is used to replace sucrose.
Probiotics inhibit disease-associated oral bacteria.

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Description

Quiz about the factors required for dental caries, sources of nutrients for bacteria, and types of bacteria found in caries. Also, defines acidogenic and aciduric terms.