Composition of saliva and acquired pellicle Flashcards

1
Q

What are the immune and non-immune defense mechanisms of saliva?

A
  • Protection
  • Buffering
  • Pellicle formation
  • Maintenance of tooth integrity
  • Antimicrobial action
  • Digestion
  • Taste
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2
Q

Briefly describe the constituents of saliva

A

99.5% water and 0.5% electrolytes

Contains the following proteins:

  • Enzymes
  • Lysozymes
  • Defensins
  • Mucins
  • Histatins
  • Statherin
  • Lactoferrin
  • Small organic molecules
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3
Q

Name some enzymes in saliva

A

‣ amylase, peroxidase, and salivary lipase

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4
Q

What are defensins?

A

proteins of the immune system

‣ Assist in killing phagocytosed microbes by forming pores in membrane to efflux essential nutrients

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5
Q

What are mucins and what do they do?

A

glycosylated proteins produced by epithelial tissues.

‣ Produced by the mucous acinus

‣ They form gel secretions so serve provide lubrication

‣ Protection in oral cavity

‣ Cell signalling

‣ Form chemical barriers – over enamel(pellicle)/mucosa

‣ Aggregation of bacteria

‣ Overexpression of mucin proteins (MUC1) can be associated with cancers e.g. adenocarcinomas and lung diseases

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6
Q

What are histatins?

A

antimicrobial peptides in the oral cavity

‣ Histatin 1 and histatin 2 = wound-closing factors in saliva – enhance initial epithelial cell migration

‣ Secreted by Von Ebners’ glands (minor glands)

‣ Encoded for by 2 genes: HTN1, HTN3

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7
Q

What does statherin do?

A

Prevents calcium-phosphate precipitation in saliva, maintaining high Ca2+ level in saliva for remineralsation/ PO43- for buffering

‣ STATH gene ‣ SIgA (secretory IgA) – antibody in mucous secretions

‣ Tears saliva GIT, respiratory epithelium

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8
Q

What does lactoferrin do?

A

Antimicrobial globular glycoprotein in secretory fluids

‣ Binding and transport of iron ions

‣ Binds to bacterial cell walls, affecting permeability and causing lysis ‣ Binds to viral proteins and stops penetration into cell/ replication

‣ Also anti-fungal and anticarcinogenic

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9
Q

Give examples of small organic molecules in saliva

A

Glucose, urea, lipids, amino acids

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10
Q
A
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11
Q

What is the dental pellicle and when does it form?

A

Dental pellicle is a protein film that forms on the surface enamel by selective binding of glycoproteins from saliva that prevents continuous deposition of salivary calcium phosphate.

It forms seconds after a tooth is cleaned

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12
Q

What does the acquired pellicle protect the tooth from?

A

It is also protective to the tooth from the acids produced by oral microorganisms after consuming the available carbohydrates

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13
Q

What does chlorohexidine do?

A

Chlorhexidine prevents adhesion of calculus to the tooth

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14
Q

What are some of the components of the acquired pellicle?

A

macromolecules such as lysozyme, alpha-amylase, perioxidase, immunoglobulin A, immunoglobulin G, glycosyltransferase, proline-rich proteins, mucins, albumin and breakdown products from macromolecules from both saliva and bacteria

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15
Q

What is ‘plaque’ and what does it contribute to?

A

Plaque is an adherent microbial biofilm attached to teeth and the primary aetiological agent of dental caries and periodontal disease. 1000-25000 species involved in plaque.

• The microbial composition reflects the site of formation and the host diet

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16
Q

Outline the 4 stages of plaque formation

A
  1. Colonisation by pioneer species
  2. Outgrowth
  3. Secondary colonisation
  4. Climax community
17
Q

What are the major sites of plaque formation in the oral cavity?

A

Major sites of plaque formation are fissures, interproximal areas and the gum margin

18
Q

Which microbes are the early colonisers in plaque formation?

A

The species most able to colonise are: Streptococcus oralis, Steptococcus mitis and Streptococcus sanguis = 90% of the flora in the first few hours. Replicate in oxygen rich environment

‣ Actinomyces and Neisseria – early colonisers

19
Q

What occurs in ‘outgrowth’?

A

multiplies spreads in the plane of the surface and then upwards

20
Q

What happens during secondary colonisation?

A

• Secondary colonisation occurs by gram positive and gram negative, by the process of co-aggregation (aggregation between different species) leading to an increase in diversity. Proportion of streptococci decreases

‣ Co-aggregation occurs when colonising microbes attach to cells part of the developing biofilm.

‣ At 24 hours plaque contains a wide variety of bacteria and interspecies associations

21
Q

What occurs during the ‘climax community’ stage?

A

Plaque matures to form a stable climax community – bacterial succession. Colonies->corncobs->anaerobic environment

22
Q

What is the adhesion of a microbe to a surface governed by?

A

The adhesion of a microbe to a surface including another microbe is governed by shear force which sweeps bacteria away from a surface, and electrostatic repulsion with Van de Waal’s forces that provide areas of weak attraction

23
Q

Define asaccharolytic

A

Bacteria that can’t breakdown charbohydrates, so instead break down proteins

24
Q

What are the predominant species in supragingival plaque?

How do they contribute to the formation of dental caries?

A

Streptococcus and Actinomyces species are predominant in the supra gingival area. They can adhere the saliva-coated tooth surface by attachment between adhesins (located on bacterial cell surfaces) and receptors (contained mainly in the salivary coating on tooth surfaces) and are known to utilise salivary components as nutrients.

These bacteria are saccharolytic and degrade carbohydrates derived from foods to form lactic, formic acid, acetic, succinic and other organic acids, and concomitantly consume oxygen by NADH oxidase. Taken together, these activities create acidic and anaerobic conditions. The acidification is rapid and the supragingival pH can reach around 4 within several minutes

25
Q

Where do subgingival bacteria get their nutrients from?

A

• Subgingival sites (stable tooth and unstable epithelial surface) are bathed with a continuous efflux of gingival crevicular fluid (GCF), derived from blood plasma and thus nutritionally rich in nitrogenous compounds such as amino acids, peptides and proteins

26
Q

What species of bacteria are located subgingivally and what are the conditions of their environment?

A

As a gingival crevice deepens, the environmental factors in the subgingival site become more stable, i.e. neutral pH and anaerobic.

‣ Under these conditions, asaccharolytic and anaerobic and/or proteolytic bacteria such as Fusobacterium, Eubacterium, Campylobacter, Prevotella and Porphyromonas are found.

27
Q

How do saccharolytic and assacharolytic bacteria differ?

A

Saccharolytic bacteria share the same main metbaolic pathway, whereas assacharolytic bacteria have different metabolic pathways

28
Q

What is GCF?

A

Fluid/exudate occurring in the gingival crevice with a composition similar to saliva

  • Associated with inflammatory response against infection – it is not a product of healthy tissue. Calculus can form from it.
  • Contains leukocytes, lymphocytes, monocytes + organic ions
  • Functions: ‣ Clearance of bacteria/cleansing of sulcus ‣ Antimicrobial action of antibodies
29
Q

What are the names of the three plaque hypotheses?

A
  1. non-specific
  2. specific
  3. ecological
30
Q

What is the non-specific plaque hypothesis?

A

Disease results from interactions among all bacterial species of plaque. More plaque -> more disease. QUANTITY not quality

31
Q

What is the specific plaque hypothesis?

A

Limited number of pathogens are responsible for disease so therapies can target them (non-specific was abandoned in 20th century)

32
Q

What is the ecological plaque hypothesis?

A

Environmental factors controlling flora and disease results from shift in balance of resident species

33
Q
A