L12.Dental Plaque & Caries

Question 1

Acquired Enamel Pellicle?

Answer 1

Resultant layer on tooth surface derived from specific interactions b/t dental enamel surfaces and macromolecules (both host & microbial derived) present in saliva that are selectively absorbed.
-Irregular surface. Provides surface for easier attachment of bacteria (adhesins). Can become cariogenic when env’t correct (=presence of sucrose).

Question 2

Exopolysaccharides (EPS)?

Answer 2

Proteins, lipids, nucleic acids, amyloid fibre, have been identified in the matrices of various biofilms.

• Key component of matrix of cariogenic oral biofilms. Recognized virulence factors involved in the pathogenesis of dental caries.
• Bacterial-derived matrix Present in ALL cariogenic biofilms. If eliminated GREATLY reduces growth.

Question 3

Sucrose breakdown in S. Mutans.

Answer 3

Facilitated by Fructosyl Transferase and Glucosyl Transferase (Gtfs-very imp). Produce fructose and Glucose; both used in glycolysis (intermediates make more Gtfs and Ftfs and as well as Glucan Binding Proteins.
-Gtfs produce GLUCAN. Formation catalyzed by the Gibbs free energy produced during hydrolysis of sucrose. NOTE: This means glucan NOT produced when only simple monomer sugars available b/c no large energy release.

Question 4

Glucosyltransferases (Gtfs). Role in pellicle formation?

Answer 4

Adsorbed onto TOOTH SURFACE. Doesn’t need pellicle! Once on tooth surface, produces glucan, which S. mutans, with their Glucan Binding Proteins, can easily bind.

Question 5

Exopolysacharide derived in absence of sucrose vs. Gtf derived EPS?

Answer 5

Biofilm matrix formed w/o sucrose presennt has very few cariogenic organisms, and shows limited vertical build up.
Gtf derived EPS has high concentration of Glucan –> S. Mutans binding easily –> Other virulent, acid-tolerant bacteria.

Question 6

How does the PhosphoTransferase System (PTS) contribute to caries?

Answer 6

S. mutans transport multiple fermentable carbohydrates very effectively accros their membranes via PTS –> increased rates of glycolysis & production of acids from fermentable carbs through the fermentation pathway

Question 7

3 mechanisms by which S. mutans and other acid tolerant bacteria survive in low pH env’ts?

Answer 7

1. Increase activity of PROTON-TRANSLOCATING ATPase (pumps H+ out of cell
2. low pH induces increased DNA repair pathways
3. Changes in mambrane fatty acid composition

Question 8

GtfC & GtfB?

Answer 8

GtfC: Deposits glucan on HA
GtfB: on bacterial surface