Endodontics
What the exam tests
Pulp and periapical diagnosis, correct determination of working length, chemo-mechanical disinfection, and the judgement call between conservative treatment, retreatment and extraction.
Core rules
- Diagnose with sensibility testing (cold, EPT), percussion, palpation and radiographs. Irreversible pulpitis = spontaneous or lingering pain; symptomatic apical periodontitis = pain on percussion; asymptomatic apical periodontitis = radiolucency without symptoms; necrosis = no response.
- Working length is 0.5-1.0 mm short of the radiographic apex, confirmed with an electronic apex locator in a dry-ish canal.
- Negotiate a glide path before rotary shaping; crown-down preparation reduces the risk of ledging and transportation.
- Irrigate with sodium hypochlorite (0.5-5.25%) for tissue dissolution and antimicrobial effect, EDTA 17% to remove the smear layer, and chlorhexidine as an alternative where hypochlorite is unacceptable. Never combine hypochlorite and chlorhexidine directly - a brown precipitate forms.
- Obturate with a well-adapted cone and sealer; warm vertical or Schilder condensation is an accepted alternative to lateral condensation. Coronal seal matters as much as the apical one.
- Antibiotics are not indicated for pulpitis or for a necrotic tooth with a drainable abscess; NSAIDs and drainage handle the pain.
Worked example
A 35-year-old has a necrotic lower first molar with a periapical radiolucency and mild swelling. Reasoning: the diagnosis is necrotic pulp with symptomatic apical periodontitis and a localised abscess. Access, full canal debridement, drainage through the canal, and a temporary restoration are indicated; incision is added if fluctuation is present. No systemic antibiotic is given unless there is spreading infection, fever or systemic involvement.
Traps that cost marks
- Prescribing antibiotics instead of performing pulpectomy.
- Over-instrumenting beyond the foramen and extruding irrigant; a hypochlorite accident causes sudden severe pain and swelling.
- Restoring before the canal is truly dry.