Conservative Dentistry and Endodontics
What this domain tests
Cavity design logic, adhesive dentistry, pulp diagnosis, and the technical sequence of root canal treatment with its biological rationale.
Core rules
- Cavity classification: Class I pits and fissures; II proximal posterior; III proximal anterior without incisal involvement; IV proximal anterior with incisal involvement; V cervical third.
- Retention and resistance form must be balanced; undermined enamel is removed, and the cavosurface margin should be in sound enamel where possible.
- Bonding: etch-and-rinse (phosphoric acid, 30–40% for enamel, then primer and adhesive) versus self-etch (non-rinsed acidic primer). Enamel bonds best with phosphoric acid etch; dentine requires wet bonding to avoid collagen collapse.
- Pulp diagnosis: a cold test or electric pulp test assesses vitality; a lingering response to cold suggests irreversible pulpitis; no response with a periapical radiolucency suggests necrotic pulp with asymptomatic apical periodontitis.
- Working length is set about 0.5–1.0 mm short of the radiographic apex, confirmed with an apex locator.
- Irrigation: sodium hypochlorite dissolves organic tissue and disinfects; EDTA removes the smear layer; a rubber dam is mandatory.
Worked example
A mandibular first molar is tender to percussion, has a deep caries lesion, no response to cold, and a 3 mm periapical radiolucency. Reasoning: no response means a necrotic pulp; the periapical radiolucency without symptoms corresponds to asymptomatic apical periodontitis. The plan is root canal treatment with rubber dam isolation.
Traps
- Calling a tooth "vital" after a false-negative electric pulp test caused by poor contact.
- Extruding irrigant beyond the apex.
- Confusing reversible pulpitis (sharp, brief, provoked) with irreversible (spontaneous, lingering).