Endodontic Microbiology and Pathology Flashcards

Calcium hydroxide's antimicrobial mechanism in root canals is primarily due to:

Answer: The high pH (~12.5) causing membrane damage and enzyme inactivation

Ca(OH)2 produces a strongly alkaline environment (pH ~12.5) that disrupts bacterial cytoplasmic membranes and denatures essential enzymes.

Which cytokine plays a DUAL role in apical periodontitis — promoting inflammation in early stages but also stimulating osteoblast activity and bone repair in healing phases?

Answer: Interleukin-6 (IL-6)

IL-6 has pleiotropic effects — it promotes acute inflammation and B-cell differentiation but also stimulates osteoblasts and contributes to bone healing after infection control.

Fusobacterium nucleatum's role in endodontic infections is best described as a:

Answer: Bridge organism connecting early and late colonizers in polymicrobial biofilms

F. nucleatum acts as a bridge species in polymicrobial biofilms, co-aggregating with early colonizers (streptococci) and late colonizers (Porphyromonas, Prevotella), facilitating complex community development.

A tooth that has undergone root canal treatment is still symptomatic 6 months post-treatment. A periapical biopsy reveals hyphae and yeast forms. The most likely causative organism is:

Answer: Candida albicans

Candida albicans is the most commonly identified fungal species in persistent endodontic infections, demonstrating both yeast and hyphal (dimorphic) forms.

The periapical rarefaction seen radiographically in chronic apical periodontitis results primarily from:

Answer: Osteoclastic bone resorption driven by RANKL/OPG imbalance

RANKL (from activated T cells and fibroblasts) promotes osteoclast differentiation and activity, while inflammatory cytokines suppress OPG, leading to net bone resorption visible as periapical radiolucency.

Which property makes Treponema denticola particularly virulent in endodontic infections?

Answer: Production of a dentilisin protease that degrades host defense proteins and penetrates dentin tubules

T. denticola produces dentilisin, a protease complex that degrades fibronectin, fibrinogen, and complement proteins, enabling tissue invasion and immune evasion.

An internal resorption defect noted on CBCT is histologically characterized by:

Answer: Odontoclasts within dentinal tubules resorbing dentin from the canal lumen outward

Internal resorption is caused by odontoclasts (clastic cells) present within the pulp space that resorb dentin from the canal walls outward.