OE L29 Integuments Flashcards
What are integuments?
Substances that form on the surfaces of teeth.
Give examples of coatings with developmental origins.
- Cuticle
- Reduced enamel epithelium
- Coronal cementum
Give examples of acquired coatings.
- Enamel pellicle
- Plaque (colonisation by bacteria)
- Calculus
Describe the pellicle.
- A protein layer on the enamel surface, to which bacterial species and their metabolic products can adhere to.
- Predominantly present close to the ginigval margin.
What are the main contibutors to the pellicle?
- Proteins from saliva, GCF, serum
- CT metabolites
- Bacterial products/metabolites
- Cellular products/metabolites
Describe the development of the pellicle.
- Extremely quick
- First layer forms in less than 5 seconds
- Low molec. weight proteins laid down first
- Pellicle matures over several days and becomes 10um thick
- Has surface and subsurface layers
What proteins are found in the pellicle?
- Mucins
- Amylase
- Cystatin
- Statherin
- Histatins
- Proline rich proteins
What are the main adhesive forces involved in pellicle formation?
- Ionic interactions (main force)
- Van der Waals forces
- Hydrogen bonds
- Hydrophobic interactions
Which molecules interact with calcium ions in HAP?
- Sulphated glycoproteins e.g. mucins
- Phosphoproteins (directly or via phosphor-calcium bridge)
How can calcium binding cause increased bacterial binding?
- Sometimes, the interaction between the phosphoprotein and calcium causes a conformational change in shape of the protein
- This can expose hydrophobic regions which can be used for bacterial receptor binding
What are the major functions of the pellicle?
- Protection against acids
- Protects enamel from abrasion
- Assists in re-calcification of enamel defects
- Provides a continous layer of protective proteins at enamel-gingival interface to protect from decay
- Provides surface for the absorption of bacteria
Outline bacterial colonisation of the pellicle.
Proteins stick to the tooth; bacteria stick to proteins.
Formation of a matrix which stabilises interactions between the pellicle and bacteria.
Describe the 4 stages of plaque formation.
- Transport of bacteria to tooth surface
- Reversible adsorption of bacteria onto pellicle surface (passive means)
- Attachment of bacteria becomes less reversible, a matrix of cross linked sugars is synthesised by bacteria to stabilise themselves
- Growth of different organisms, diverse bacterial community of many species established
Describe the initial reversible interactions between pellicle proteins and microorganisms.
- Long-range interactions form between proteins and microorganisms
- These interactions are electrostatic (ionic and hydrogen) and van der Waals forces
- Interactions usually occur via calcium bridging
Describe the less reversible attachment of bacteria (later stages of plaque formation).
- Short-range interactions between adhesins on microbial surface and proteins in the acquired pellicle
- Very strong and specific
Which 2 other factors can allow bacterial adhesion?
- Confirmational changes of proteins on adsorbed surfaces can allow bacteria to bind
- Bacterial neuraminidase action can remove sialic acid, facilitating bacterial adhesion
Describe the main functions of bacterial adhesion proteins.
- Surface of bacteria, e.g. streptoccoi have long adhesion proteins which have n-terminal binding sites for mucins on the pellicle
- There are variants of adhesion proteins which have different recognition motifs for pellicle proteins e.g. serine-rich repeat proteins recognise sialic acid in mucin
Which receptor on streptococci can bind to gp-340 thus preventing bacterial aggregation?
Antigen I/II polypeptides (Ag I/II)
Describe pili and fibrillar adhesion proteins.
- Further type of adhesin
- Can be very long (up to 3um)
- Can bind to ECM and cell surfaces, some bind to salivary pellicle proteins
- They are required for complex biofilm formation
What are fimbriae?
Long filamentous polymeric protein structures located at the surface of bacterial cells.
Fimbrae can have one or more adhesive domains.
Distinct fimbrae allow interactions with specific components, give examples of these interactions.
- S.gordonii with amylase
- A.naeslundii with statherin
- S.mutans and P.gingivalis can interact with HAP treated with proline-rich proteins (PRPs)
What do hydrophobic fimbrae interact with?
Hydrophobic portions of salivary proteins.
Some bacterial proteins are “lectin-like”, what can they bind to?
- Carbohydrates or oligosaccharides within salivary glycoproteins
Describe the basis of colonisation.
- There are early colonisers e.g. streptoccoi
- Bridge colonisers act as a bridge between early and late colonisers e.g. F.nucleatum has adhesins to connect to S.mutans
- Late colonisers .e.g P.gingivalis can bind to F.nucleatum
Have vaccines against F.nucleatum been successful in preventing gingivitis?
Yes in mice studies there was reduced gingival inflammation.
