Operative Dentistry and Endodontics
Operative dentistry and endodontics: questions focus on the next clinical step, the correct material at each interface, and the pulpally-driven decision between preserving, extirpating or extracting a tooth. Diagnosis comes first; technique questions follow from it.
Core rules
- Pulpal diagnosis drives treatment: reversible pulpitis (sharp pain, provoked, resolves in seconds) - remove the cause and protect the pulp; irreversible pulpitis (spontaneous or nocturnal pain, lingering cold response) - extirpation then complete root canal treatment; necrotic pulp with apical periodontitis - root canal treatment.
- Enamel bonding uses 30–37% phosphoric acid for 15–30 s; dentine etch is shorter (about 15 s) and moist dentine should not be desiccated, or the collagen network collapses.
- Composite shrinks on polymerisation. The C-factor is the ratio of bonded to unbonded surface and is highest in class I cavities; incremental layering or controlled bulk-fill placement limits marginal stress.
- Rubber dam is standard for endodontics: airway protection plus a dry field.
- Working length ends 0.5–1.0 mm short of the radiographic apex.
- Sodium hypochlorite dissolves tissue and kills biofilm; 17% EDTA removes the smear layer. Never mix NaOCl and chlorhexidine directly - an orange precipitate forms.
- Calcium hydroxide is the usual interappointment medicament; obturate with gutta-percha and sealer to a verified cone fit.
Worked example
A patient reports spontaneous night pain in a lower first molar that lingers for minutes after cold, and the tooth is now tender to percussion. Spontaneous, lingering pain means irreversible pulpitis; percussion tenderness suggests early apical involvement. Management is pulpectomy for pain relief, then full root canal treatment under rubber dam with working length and obturation to the radiographic apex minus about 0.5 mm. A restoration alone would not address the diagnosis.
Traps
- Prescribing antibiotics for pulpal pain; analgesia plus definitive treatment is the answer.
- Long working length, which injures periapical tissues, or short, which leaves infected canal.
- Etching dentine and drying it thoroughly before adhesive application.
- Obturating without verifying cone fit, leaving voids or overextension.