NBDHE Scientific Basis of Practice 2

Question 1

Which immunoglobulin class is the most abundant in gingival crevicular fluid (GCF) and plays a primary role in local periodontal defense?

Accepted Answer

IgG

Answer

IgA

Answer

IgM

Answer

IgE

Question 2

In research design, a randomized controlled trial (RCT) is considered the gold standard because it:

Accepted Answer

Randomly assigns subjects to experimental and control groups, minimizing selection bias and confounding variables

Answer

Is the least expensive study design

Answer

Does not require a control group

Answer

Always uses a double-blind design

Question 3

The cariogenic bacterium Streptococcus mutans produces which key virulence factor that enables its colonization of smooth tooth surfaces?

Accepted Answer

Glucosyltransferases (GTFs) that synthesize insoluble glucans from sucrose for biofilm adhesion

Answer

Collagenase for tissue invasion

Answer

Proteases that destroy immunoglobulins

Answer

Endotoxin (lipopolysaccharide)

Question 4

When calculating the sensitivity of a diagnostic test for periodontitis, which value represents the percentage of people WITH the disease who test positive?

Accepted Answer

True positive / (True positive + False negative) × 100

Answer

True negative / (True negative + False positive) × 100

Answer

True positive / (True positive + False positive) × 100

Answer

True negative / (True negative + False negative) × 100

Question 5

The Gram stain differentiates bacteria based on cell wall composition. Which characteristic is the basis of the Gram-positive reaction (purple/violet staining)?

Accepted Answer

A thick peptidoglycan cell wall that retains the crystal violet-iodine complex during decolorization

Answer

Presence of an outer membrane lipopolysaccharide layer

Answer

High lipid content in the cell membrane

Answer

Spore formation within the cell

Question 6

Which mineral is primarily responsible for the calcification of calculus, and from which oral fluid is it primarily derived?

Accepted Answer

Calcium phosphate (as hydroxyapatite, brushite, and whitlockite), primarily derived from saliva for supragingival calculus and from GCF for subgingival calculus

Answer

Calcium carbonate from dietary sources

Answer

Fluorapatite from fluoride treatments only

Answer

Magnesium phosphate from plaque bacteria