Cariology Lecture 2

Why do only some species colonize?

the oral cavity will become home to those species that can utilize, and efficiently compete for, the nutritional sources available, and withstand host defense mechanisms

______ is almost always a prerequisite for colonization, though retentive sites such as fissures of teeth may obviate that need

adhesion

what is the name of the bacteria that first adhere to the pellicle

early colonizers

are early colonizers gram positive or negative

gram positive

cell shape of early plaque

cocci

cell type of early colonizers

facultative anaerobes

• grow in presence or absence of oxygen

what are the names of the organisms that adhere to the primary colonizers

secondary colonizers

the oral microbiome consists of multiple different ______

niches

As the plaque matures, are the microorganisms more gram positive or negative

increasing gram negative, but still a mix of negative and positive

cell type of later colonizers

facultative anaerobes and obligate anaerobes

gram type for supragingival plaque

gram - and +

cell shape for supragingival plaque

cocci and rods

gram type subgingival plaque

higher proportion of gram -

shape of cells in subgingival plaque

more gram - rods and spirochetes

physical means of plaque control

flow of saliva, movement of tongue, chewing, sloughing if cheek epithelial cells

what do plaque do to counter mechanical removal

adhesion mechanisms that keep them tightly bound

saliva harbors anti-______ factors

microbial

what is the most abundant isotype in saliva

IgAwhat

how does IgA defend against plaque

agglutinates bacteria to interfere with adhesion

Which of the following is NOT a means by which the host keeps the oral commensal microbiota in check?

1. Salivary Flow

2. Fever

3. Cationic peptides and defensins

4. Lysozyme

2

The mechanism by which sIgA can prevent adhesion of supragingival plaque organisms is:

1. By changing the surface from negative to positive

2. Byopsonization that facilitates phagocytosis

3. by inducing autolysis of the bacteria

4. by agglutinating the bacteria so they are swallowed before they can adhere

5. all of the above

4

When does oral microbiota acquisition begin?

Likely begins before birth via microbial antigens crossing the placenta; continues at birth and throughout infancy.

How does the mode of birth affect the microbiota?

Vaginal delivery results in greater bacterial diversity than Cesarean section.

Main sources of bacterial transmission to infants

Saliva from mother or caregivers, milk, skin, food, and environment.

What is vertical transmission?

Passing bacteria from mother to child.

Why do only some bacterial species colonize the mouth?

Only bacteria that can adhere, compete for nutrients, and resist host defenses persist.

What role does adhesion play in colonization?

Adhesion allows bacteria to attach to oral surfaces, preventing removal by saliva and movement.

What are nonspecific adhesion forces?

Weak interactions such as

van der Waals,

electrostatic,

hydrophobic, and

hydrogen bonds that allow close contact.

What are specific adhesion interactions?

Bacterial adhesins bind to complementary host receptors such as proteins or carbohydrates on the pellicle.

What is a bacterial adhesin?

A molecule on the bacterial surface such as a protein, lipoprotein, or fimbriae that binds host receptors.

What is the pellicle?

A thin protein-rich film on tooth surfaces made of salivary glycoproteins and other molecules that serves as a receptor surface for bacterial adhesion.

What is coaggregation?

Bacteria adhering to other bacteria already attached to host receptors, forming complex communities.

What are primary plaque colonizers?

Early colonizing bacteria, such as Streptococcus and Actinomyces, that bind directly to the pellicle.

What are secondary or late plaque colonizers?

Bacteria that attach to early colonizers and thrive as oxygen levels decrease.

What determines which bacteria colonize first?

Adhesion ability, available receptors, and environmental conditions such as oxygen levels.

What do biofilms protect bacteria from

antibiotics and host defenses

Who first described dental plaque as a biofilm?

Antonie van Leeuwenhoek, who observed plaque under a microscope.

Major niches in the oral cavity

Supragingival plaque, subgingival plaque, tongue, buccal mucosa, and saliva.

Do individuals have the same oral microbiome?

Broadly similar patterns but large interpersonal differences in specific species and abundance.

What are microbial interactions within plaque?

Cooperation such as enzyme sharing and coaggregation,

competition through acid

nutrient rivalry.

what can cause the microbiome to shift

diet, smoking, age, and environment.

Physical mechanisms limiting plaque

Saliva flow, swallowing, tongue movement, chewing, and epithelial shedding.

What does lysozyme do?

Breaks bacterial cell walls, agglutinates bacteria, and may trigger self-lysis.

What does lactoferrin do?

Binds iron to prevent bacterial growth and can directly damage bacteria.

what do histadins do?

act as antibacterial and antifungal

What do neutrophils do?

engulf pathogens

what do mucin and agglutins do

trap and clump bacterial for clearance

What is the role of defensins and antimicrobial peptides?

Disrupt bacterial membranes and are found in saliva and crevicular fluid.

What immune factors operate in the gingival crevice?

Immunoglobulins such as IgA, IgG, and IgM, neutrophils

lymphocytes

What is sIgA's role?

Agglutinates bacteria to block adhesion but can also aid adhesion if bound to the pellicle.

Why can't the adaptive immune system fully eliminate plaque?

Many pathogens originate from normal flora and are tolerated by the host immune system.

Behavioral controls of plaque

Diet, brushing, flossing, mouth rinses, and professional cleanings.

How fast does plaque regrow after cleaning?

two to three days.