Scientific Basis of Practice 1 Flashcards

Which triad of bacteria comprises the 'red complex,' most strongly associated with deep periodontal pockets and clinical attachment loss in chronic periodontitis?

Answer: Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola

Socransky's landmark cluster analysis identified P. gingivalis, T. forsythia (formerly B. forsythus), and T. denticola as the red complex — the bacterial group most strongly correlated with clinical measures of periodontitis severity such as increased probing depth, bleeding on probing, and attachment loss.

A new salivary biomarker test for early caries detection yields 80 true negatives and 20 false positives among 100 disease-free individuals. What is the specificity of this test?

Answer: 80%

Specificity = TN / (TN + FP) = 80 / (80 + 20) = 80%. Specificity measures how accurately a test identifies those WITHOUT disease (the true negative rate), thereby minimizing false positives and avoiding unnecessary treatment.

Which mechanism BEST explains how fluoride reduces enamel susceptibility to acid dissolution by cariogenic bacteria?

Answer: Fluoride substitutes for hydroxyl ions in hydroxyapatite, forming fluorapatite with a lower critical pH (~4.5)

Fluoride substitutes for hydroxyl groups in the hydroxyapatite crystal lattice to form fluorapatite, which has a critical pH of approximately 4.5 compared to 5.5 for hydroxyapatite. This structurally more stable mineral is significantly more resistant to acid attack from bacterial metabolic byproducts.

A dental hygienist develops erythema and vesicles on her hands 48 hours after contact with latex gloves. This reaction is BEST classified as which type of hypersensitivity?

Answer: Type IV — T-cell–mediated delayed hypersensitivity

The 48-hour delay and contact dermatitis presentation are hallmarks of Type IV (delayed-type) hypersensitivity, mediated by sensitized CD4+ T lymphocytes rather than antibodies. Contact dermatitis to latex chemical additives follows this timeline, in contrast to Type I reactions (urticaria, anaphylaxis) triggered by latex proteins within minutes.

Which prostaglandin is considered the PRIMARY lipid mediator of alveolar bone resorption in chronic inflammatory periodontal disease?

Answer: Prostaglandin E2 (PGE2)

PGE2 is the predominant prostaglandin detected at elevated concentrations in gingival crevicular fluid at active periodontitis sites. It stimulates osteoclast differentiation and activity by upregulating the RANK/RANKL pathway, making it the principal arachidonic acid–derived mediator of bone destruction in periodontal disease.

When evaluating literature to support a clinical guideline on subgingival scaling frequency, which study design provides the HIGHEST level of evidence?

Answer: A systematic review with meta-analysis of multiple randomized controlled trials

The evidence hierarchy places systematic reviews with meta-analysis of RCTs at the apex because they synthesize findings across multiple high-quality trials, reducing random error, increasing statistical power, and improving generalizability. A single RCT, while strong, ranks below this pooled synthesis of the best available individual studies.