the oral cavity as a microbial habitat - dental bioflims

Mucosal surfaces

Lips, cheek, palate and tongue

Hard surfaces/non-shedding surfaces

Teeth

Biggest reason why we need dentistry

Bc nothing is minimizing the microbial load on the hard tissue

Hardest known substance

Enamel

Two types of fluids produced in mouth

Saliva & GCF

Resting saliva

Saliva in the mouth rn

Stimulated saliva

When you see food/smell food; larger quantities and more diluted liquid

Saliva has a large buffer bc

Of the salts and bicarbonates

Important salts in saliva

Sodium, potassium, calcium, magnesium, phosphate, bicarbonate

Other constituents in saliva

Protein, IgA, IgG, IgM, C3, amylase, lysozyme, albumin

Factors affecting microbial growth in the oral cavity

Temperature, redox potential, pH, nutrients, host defenses, host genetics, antimicrobial agents and inhibitors

Normal temperature

35-36 C

periodontal pockets with inflammation can increase the temp to?

39 C

Temperature change can?

Regulate gene expression in bacteria for genes encoding enzymes (protease, SOD) and frimbriae

When changing the hosts temperature what can it make the bacteria?

Can make them more virulent

Oxygen tension on tongue varies from

12-16%

Buccal folds oxygen content

.3 - .4%

Most oral organism are?

Facultative or obligate anaerobes

Earlier colonizers vs late colonizers

Arerotolerant; more anaerobic

pH of palate

7.34

pH of buccal mucosa

6.3

pH is regulated by?

Saliva due to the buffer capacity

Healthy gingival crevice pH

6.9

Disease gingival crevice pH

7.4 +

Bacteria that likes high pH

P. Gingivalus (periodontal disease)

Bacteria that likes low pH

Strept. Mucans

Consumption of sugar will?

The pH will be lowered due to fermentation of the sugars to acids and bacteria love low pH so they will feed off it

Endogenous nutrients

Already present in your mouth; saliva, GCF, Bactria products

Exogenous nutrients

Food you eat; dietary

Host defense

Immune system fights infection but could have a defect

Host genetics

Some people are genetically more prone to diseases; Nuetropenic - lack the neutrophils to fight candida

Antimicrobial agents and inhibitors

Antibodies and toothpaste/mouthwash; both kill good and bad bacteria

Saliva flow

Physical removal of microorganisms; swallowing

Mucin/agglutinins

Sticky mucin proteins that grab bacteria and physically remove microorganisms

Lysozyme-protease-anion

Cell lysis - by degrading cell membrane

Lactoferrin

Keeps amount of iron in saliva low so bacteria cant feed on it

Apo-lactoferrin

Cell killing

Sialoperoxidease system

Offers pH tolerance of bacteria: hypocyanous acid (low pH) & hypothiocyanite production (neutral pH)

Histatins

Most anti-fungal protein in the body (lots in saliva)

Defensins (a & B)

Antimicrobial and immunomodulatory activity

Cystantins, SLPI & TMP

Cysteine, serine & metallo-protease inhibitors

Chitinase & chromogranin

Antifungal (kill fungi)

Cathelicidin & calprotectin

Antimicrobial peptides present in saliva

Intra-epithelial lymphocytes & langerhans cells

Cellular barrier to penetrating bacteria and/or antigens

sIgA

Primary antibody in oral cavity (saliva); prevents microbial adhesion & metabolism

IgG, IgA, IgM

Prevent microbial adhesion; opsonins; complement activators

Complement

Activates neutrophils

Neutrophils/macrophages

Phagocytosis

How do bacteria cell colonize?

With adherence properties, synergistic bacteria, nutritional substrates, temperature and moisture

How bacterial cell die or expel out

Agglutination, antimicrobial properties of saliva, mechanical shearing, antagonistic bacteria

Antimicrobial agents

Fluoride, chlorhexidine, antibiotics

Biofilms

A cluster of microbial cells composed in a gooey mess (matrix enclosed) and the whole thing adheres to biological and non-biological surfaces

Biofilm development

Surface attachment; microcolonies; macrocolonies

Surface attachment

Reversible & irreversible

Microcolonies

Cell proliferation & Coaggregation

Macrocolonies

Mushroom and tower-like structures & cell detachment

Macrocolonies

Mushroom and tower-like structures & cell detachment

Conditioning films

Layer of sticky proteins and sugars

Higher mass of bio films leads to

More limitation of nutrients & oxygen movement into biofilms

Quorum sensing

Intercellular signaling as a regulatory mechanism that plays a significant role in coordinating various stages of biofilm formation

Responds to population density

When a critical mass of population is reached, bacteria are very intuitive and will see the lack of nutrients/oxygen. At this point some bacteria will choose to die and secrete molecules that signal other bacteria to die

Auto-inducers

Cell secreting it can also be induced by it

Peptide autoinducer

Streptococcus mutans

Fungal QS molecules auto-inducer

Famesol - produced by candida

Plaque - dental biofilms

A complex microbial community on the surface of teeth

Stages of dental plaque formation

1. Pellicle formation

2. Reversible attachment

3. Adhesion-receptor; irreversible, specific short range

4. Coadhesions

Unique precursor in dental biofilms

Acquired enamel pellicle

Enamel pellicle is composed of

Salivary proteins and glycoproteins & bacterial components

Examples of salivary proteins and glycoproteins

Salic acid, proline-rich proteins, mucins, agglutinin, amylase

Examples of bacterial components

Glucan, glucosyltransferases

Bacterial rarely come in direct contact with the tooth enamel

True

How quickly does the pellicle form?

Formation initiations in seconds of any clean surface being introduced in the oral cavity

Association

Least intimate form of surface interaction; weak, reversible attachment

Adhesion

More intimate form of attachment than association; stable, irreversible attachment; adhesions interact with complementary moles on the host surfaces

Invasion

Penetration of the mucosal barrier by bacteria

Adhesion

Interaction between bacterial adhesion and pellicle or cell receptor

Coaggregation/coadhesion

Interbacterial interaction

Beneficial (synergistic) microbial interactions in a plaque

Enzyme complementation , food chains, coadhesion, cell-cell signaling, gene transfer

Enzyme complementation

Bacteria can lend enzymes to each other

Food chains (food webs)

Bacteria can produce food that other bacteria need to eat to survive

Coadhesion

Bacteria can bind to other bacteria

Cell-cell signaling

Bacteria send signals to each other to help each other

Gene transfer

Conjugation, transduction, transformation

Antagonistic microbial interactions in a plaque

Bacteriocins, hydrogen peroxide, organic acids, low pH and nutrient competition

Bacteriocins

Peptide antibodies are produced by one bacteria to kill other bacteria

Hydrogen peroxide

Bacteria can produce hydrogen peroxide that kill other bacteria by creating oxidative stress

Organic acids and low pH

Bacteria will produce organic acids that lower pH and if other bacteria don’t like it then they will die

Nutrient competition

Competing for food

Microbial succession

As dental plaque biofilms develops, local environment changes

Synergistic and antagonistic effects