Etiology
Most commonly arise from acute exacerbation of pre-existing periodontitis: the pocket orifice becomes occluded (by food impaction, calculus, foreign body — classically popcorn husks), trapping anaerobic bacteria. Increased bacterial virulence plus impaired drainage → rapid purulent accumulation.
PRECIPITATING FACTORS: SRP can push bacteria apically or cause swelling that seals the pocket orifice. Incomplete antibiotic course (suppresses surface bacteria, allows deep biofilm to continue). Foreign body impaction. Immunosuppressive medications.
MICROBIOLOGY: Predominantly anaerobic gram-negative rods — Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum. Pus contains >10⁸ bacteria/mL.