Scientific Basis of Practice Flashcards

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

Answer: IgG

IgG is the predominant immunoglobulin in GCF, derived from plasma cells in the inflamed gingival connective tissue and periodontal ligament, where it functions in opsonization and complement activation against periodontal pathogens.

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

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

Randomization ensures that both known and unknown confounding variables are distributed equally between groups by chance, making the RCT the most powerful design for establishing causality.

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

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

S. mutans produces glucosyltransferases (GTFs) that catalyze the synthesis of insoluble glucan polymers from sucrose, enabling firm adhesion to smooth tooth surfaces and forming the scaffold of cariogenic biofilm.

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

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

Sensitivity = TP / (TP + FN) × 100 — the proportion of diseased patients correctly identified as positive; high sensitivity minimizes false negatives.

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

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

Gram-positive bacteria have a thick, multilayered peptidoglycan cell wall that traps the crystal violet-iodine mordant complex during the alcohol decolorization step, resulting in a purple/violet color.

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

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

Calculus is primarily calcium phosphate (mostly hydroxyapatite, octacalcium phosphate, brushite); supragingival calculus mineralizes from salivary calcium/phosphate, while subgingival calculus mineralizes from GCF.