integuments

Question 1

what are dental integuments?

examples?

Answer 1

‘substances that form on the surface of teeth ‘

• Coating of developmental origin
  
  • Cuticle, reduced enamel epithelium, coronal epithelium
• Acquired coatings
  
  • Pellicle, plaque, calculus

Question 2

what is the pellicle?

what are its components?

Answer 2

Protein layer on the enamel surface formed very quickly

components

• proteins from
  
  • saliva, GCF, serum
  • bacteria and their metabolic products
  • connective tissue metabolites

Question 3

how is the pellicle layer developed?

Answer 3

• First layer forms in <5 seconds
  
  • Strong interactions
• Low molecular weight proteins laid down first
• Pellicle layer matures over days
• Mature pellicle is 10µm thick with surface and subsurface layers

Question 4

what proteins are found in the dental pellicle?

Answer 4

• Lactoferrin
• IgA
• Salivary amylase
• Histatin
• Statherin
• Cystatin
• Acidic proline rich phosphoprotein
• Albumin
• MG1

Question 5

which forces lead to pellicle formation on enamel??

Answer 5

adhesive forces

• Ionic interactions
• Van der Waals forces
• Hydrogen bonds
• Hydrophobic interactions

Question 6

how are salivary proteins attached to the enamel surface by ionic bonds?

Answer 6

Electrostatic attraction between ionised groups:

• negative groups COO- or PO43- on protein to Ca2+, HPO42- on Hydroxyapatite (HAP) surface
• Strong binding

Question 7

what does ionic bonding between the salivary proteins and enamel surface cause?

what are the consequences of this?

Answer 7

• Interaction between hydroxyapatite and calcium ions leads to change in conformation of the phosphoprotein
  
  • Exposes hydrophobic regions
  • Often binding regions for bacterial receptors

Question 8

what are the functions of the pellicle?

Answer 8

• Acid protection
• Enamel protection
• Assists in re-calcification of enamel defects
• Provides a continuous layer of protein at the enamel-gingival interface
• Provides a surface for the adsorption of bacteria
  
  • bacterial colonisation of the pellicle

Question 9

what are the stages of plaque formation?

Answer 9

1. Initial transport of bacteria to tooth surface
2. Reversible adsorption of the bacteria onto pellicle surface
3. Less reversible attachment of bacteria & matrix synthesis by bacteria

• Sugar matrix with cross linked sugars
• Attachment becomes less reversible

4. Growth of attached organisms forming a bacterial community containing many “distinct” species.

Question 10

describe the transport of bacteria to the tooth surface

Answer 10

Transport of micro-organisms to pellicle-coated tooth via passive means

• Local variations in the chemical composition of pellicle can influence the pattern of microbial deposition

Question 11

describe the initial interactions between the micro-organisms and the enamel surface

Answer 11

reversible interactions

• formation of long-range physico-chemical interactions between micro-organisms and pellicle proteins
  
  • electrostatic (ionic and H-bonds)
  • van der Waals forces (induced dipole formation)
• micro-organisms are usually negatively charged
• acidic proteins usually in pellicle
  
  • interactions - formation of calcium bridging

Question 12

describe the short range interactions between bacteria and pellicle

Answer 12

Less reversible attachment of bacteria to tooth surface

• short range interaction between
  
  • adhesins on microbial surface
  • proteins in pellicle
• usually specific
• usually very strong
  
  • irreversible

Question 13

what is required for bacteria to bind to the pellicle proteins?

Answer 13

• For plaque formation to proceed it is necessary that not all bacteria aggregate in saliva before they reach the tooth surface
• Conformational changes of proteins on adsorbed surfaces allows bacteria to bind
  
  • Pellicle protein binds to enamel surface and exposes the binding site for bacteria

Question 14

what bacterial binding proteins are there?

Answer 14

• bacterial adhesins
  
  • serin-rich repear proteins (Srr)
  • antigen I/II polypeptides (Ag I/II)
• Pili/fibrillar adhesion proteins

Question 15

how do bacterial adhesins cause bacterial binding?

what is their structure

Answer 15

• Specialised ‘glue’ proteins
• General concept of substrate recognition by bacterial adhesins
• Interactions with pellicle proteins

Question 16

how do serine-rich repear proteins (Srr) cause bacterial adhesion?

Answer 16

• contains large amount of serine residues
• has recognition site for sialic acid in the mucin MG2
• leads to adsorption of streptococci to enamel surface
• drop in pH -> alters adhesive properties

Question 17

how do antigen I/II polypeptides (Ag I/II) cause bacterial adhesion?

Answer 17

• gp-340 = immunity scavenger receptor & pattern recognition molecule
  
  • bound to enamel
  • recognised by bacterial antigen I/II polypeptides
    
    • causes adhesion to enamel surface
  • has different variants
    
    • can increase adhesion and caries risk
• isopeptide bond stabilises the structure of the protein
• peptide was used to vaccinate caries

Question 18

which binding protein was used for vaccinations for caries?

was this successful?

Answer 18

antigen i/II polypeptides (Ag I/II)

• unsuccessful
  
  • Multiple adhesion receptors on the streptococci
  • Targeting one receptor is not sufficient to prevent disease

Question 19

how do Pili/Fibrillar adhesion proteins cause bacterial adhesion to the enamel surface?

Answer 19

• Composed of 3 subunits
• Found on Gram + and – bacteria
  
  • 3 distinct protein subunits
  • up to 3 micrometre long (very large)
  • can bind to extracellular matrix and cell surfaces
  • some bind to salivary pellicle proteins, i.e. proline rich protein
• Also type 2 FimA binds Gal-GalNAc-containing surfaces
  
  • host cells
  • oral microbiota
• Required for complex biofilm formation

Question 20

describe the F. nucleatum and Strep. Mutants complex

Answer 20

• Adhesin required for strep.mutants interaction
• adhesin RadD recognises strep.mutants
• Complex is formed between strep.mutants and F.nucleatum
• foundation is laid for the building of the cities of slime….
• Interaction between RadD and strep.mutants can be interrupted with arginine, a positively charged amino acid.
• P.gingivalis can coaggregate to this complex
  
  • Occurs through FomA protein
  • Implications for periodontal disease
  • Initiates inflammation of the gingiva