What is herd immunity?

# At what point is herd immunity to a given disease observed?
A. After 100% of a population has developed a primary immune response
B. After antibiotics have treated all known cases of disease in a population
C. After 100% of a population has developed a secondary immune response
D. Immediately after 100% of a population has been Immunized
E. After enough people in a population have developed a primary immune response so that spread of an infectious agent is curtailed

The correct answer is E. After enough people in a population have developed a primary immune response so that spread of an infectious agent is curtailed. 

Herd immunity does not require that 100%

of a population be immune. Herd immunity

requires that enough people in the population have elicited memory cells.

Should the pathogen enter the population,

the number of people infected will be small

because the immunized population will not

be able to contract or spread the infection

to the non-immunized population. This

keeps the number of pathogens to a

minimum, for the protection of all.

Extend the life of a Tungsten Carbide bur

# To extend the life of a tungsten carbide bur, the bur should...
A. Be moving slow before contacting tooth structure
B. Be sterilized with heat sterilization
C. Contact tooth structure before rotating
D. Be moving fast before contacting tooth structure

The correct answer is D. Be moving fast before contacting tooth structure.

The lifespan of a tungsten carbide bur can
be extended by bringing the bur up to speed  before contacting tooth structure, because it decreases the friction between the bur and the tooth structure thereby decreasing damage to the bur and the pulp.

Sufficient rotating speed makes the cutting
edge of the bur more efficient even with
using light pressure.

Heat sterilization corrodes the carbon steel
and anneals the cutting edge of the bur.

Rubber Dam

# In Which dental procedure is a rubber dam most indicated?
A. Deep caries
B. Direct pulp capping
C. Indirect pulp capping
D. Preparing a crown

The correct answer is: B. Direct Pulp capping. 

In direct pulp capping, it is essential to have adequate access, visibility, and isolation of the operating field.

Direct pulp capping is indicated if a pin-point pulp exposure is made during cavity preparation.

Teeth should be properly isolated to avoid saliva and bacterial contamination during direct pulp caps.

Proper isolation of the operating field also allows proper sealing of the cavity of the tooth. 

Single most important factor in producing cariogenic plaque

# The single most important factor in producing cariogenic plaque is:
A. High amount of glucose exposure
B. High frequency of glucose exposure
C. High amount of sucrose exposure
D. High frequency of sucrose exposure

The correct answer is: D. High frequency of sucrose exposure.

High-frequency exposure to fermentable carbohydrates such as sucrose may be the most important factor in producing cariogenic biofilm and ultimately caries lesions. Frequent ingestion of fermentable carbohydrates begins a series of changes in the local tooth environment, essentially changing the composition of the biofilm, thus favoring the growth of highly acidogenic bacteria that eventually leads to caries lesion formation. In contrast, when ingestion of fermentable carbohydrates is severely restricted or absent, biofilm growth typically does not lead to caries lesions.

Sucrose in particular allows the formation of extracellular polysaccharides, which render the biofilm viscous and sticky. Because the eventual metabolic product of cariogenic diet is acid, in addition to caries lesions the exposure to acidity from other sources (e.g., dried fruits, fruit drinks, or other acidic foods and drinks) also may result in dental erosion.

Liquid system of glass ionomer restorative material

# The liquid system of glass ionomer restorative material is essentially:
A. Polyalkanoic acid
B. Phosphoric acid
C. Polyacrylic-itaconic acid
D. Hydrochloric acid

The correct answer is C. Polyacrylic-itaconic acid.

COMPOSITION OF GLASS IONOMER CEMENTS

Powder/liquid materials

Powder -  Sodium aluminosilicate glass with about 20% CaF and other minor additives

Liquid - Aqueous solution of acrylic acid/itaconic acid copolymer or Aqueous solution of maleic acid polymer or maleic/acrylic copolymer and Tartaric acid in some products to control setting characteristics

Powder/water materials

Powder - Glass (as above) + vacuum-dried polyacid (acrylic, maleic or copolymers)

Liquid - Manufacturers supply a dropper bottle which the operator fills with water or The manufacturer supplies a dilute aqueous solution of tartaric acid

Toothbrush trauma usually occurs on:

# Toothbrush trauma (cervical abrasion) usually occurs on:
A. Centrals and laterals
B. Canines and premolars
C. Second and third molar
D. First and second molars

The correct answer is: B. Canines and premolars.

Toothbrush trauma (abrasion) usually occurs on teeth that are the most prominent in the dental arch.

Trauma from toothbrushing may result in the following:

• Recession of the marginal gingiva

• Lacerations of the soft tissues including the attached gingiva and the alveolar mucosa

• V-shaped notches in the cervical areas of teeth

• Gingival clefts: which are narrow grooves that extend from the crest of the gingiva to the attached gingiva

The location of the above alterations is frequently inversely related to the right or left handedness of the patient.

Gingival enlargement without destruction of the underlying periodontal tissues

# Which type of pocket is formed by gingival enlargement without destruction of the underlying periodontal tissues?
A. Gingival pocket
B. Periodontal pocket
C. Suprabony pocket
D. Infrabony pocket

The correct answer is A. Gingival pocket.

Deepening of the gingival sulcus may occur by coronal movement of the gingival margin, apical displacement of the gingival attachment, or a combination of the two processes.

Pockets can be classified as follows:

• Gingival pocket (pseudopocket): this type of pocket is formed by gingival enlargement without destruction of the underlying periodontal tissues. All gingival pockets are suprabony (the base of the pocket is coronal to the crest of the alveolar bone). The sulcus is deepened because of the increased bulk of the gingiva.

•Periodontal pocket: this type of pocket occurs with destruction of the supporting periodontal

tissues. Progressive pocket deepening leads to destruction of the supporting periodontal tissues and loosening and exfoliation of the teeth. 

Two types of periodontal pockets exist:

• Intrabony (infrabony, subcrestal, or intraalveolar): in which the bottom of the pocket is apical to the level of the adjacent alveolar bone

• Supra bony (supracrestal or supraalveolar): in which the bottom of the pocket is coronal to the underlying alveolar bone.