Endodontic Microbiology and Infection Control
This section rewards precise microbiology plus practical aseptic discipline.
Primary versus secondary infection
- Primary infection: mixed obligate anaerobes, mainly gram-negative rods (Porphyromonas, Prevotella, Fusobacterium, Tannerella), gram-positive anaerobic cocci such as Parvimonas micra, plus facultative streptococci.
- Secondary or persistent infection after failure: Enterococcus faecalis, Candida albicans, Actinomyces, Lactobacillus, often in biofilms in isthmuses and the apical third.
- Extraradicular infection (Actinomyces, Propionibacterium propionicum) is biofilm on the external root surface, does not respond to instrumentation, and requires surgery.
Biofilm consequences
Biofilm bacteria are far more resistant to disinfectants than planktonic cells and hide in dentinal tubules, lateral canals and uninstrumented fins. Mechanical preparation alone cannot disinfect; irrigation, activation and an intracanal medicament are required.
Asepsis and sterilization
Rubber dam with a well-adapted clamp; single-use needles and files; steam autoclave at 134 degrees C for 3-4 minutes or 121 degrees C for 15-20 minutes. Biological spore indicators at least weekly, chemical indicators per load. Repeated autoclaving increases NiTi fatigue. Surface disinfection with a tuberculocidal agent, plus barriers and eye protection.
Chemical adjuncts
Sodium hypochlorite 0.5-5.25% dissolves tissue and is bactericidal; chlorhexidine 2% is substantive but cannot be mixed with hypochlorite (brown precipitate); EDTA 17% removes smear layer.
Antibiotics
Not indicated for irreversible pulpitis or a localized abscess without systemic signs. Indicated for fever, spreading cellulitis, or impaired host defence, always alongside drainage and root canal treatment.
Traps
Using antibiotics instead of drainage; assuming hypochlorite sterilizes isthmuses; skipping autoclave spore monitoring.