Restorative and Operative Dentistry
What this domain tests
Operative dentistry tests caries removal, cavity design, adhesion, isolation and restoration of form and function. The exam favours clinical decisions: when to seal, when to restore, which material and why.
Core rules
- Caries is managed by risk assessment. Non-cavitated lesions may be sealed or remineralised; cavitated dentin lesions need restoration.
- Enamel bonding uses 35-37% phosphoric acid to create microporosity. Dentin bonding requires etching, priming and adhesive infiltration to form the hybrid layer.
- Etch-and-rinse uses a separate acid step. Self-etch acidic primers condition and prime simultaneously; they are less technique-sensitive but bond less strongly to enamel.
- Polymerisation shrinkage creates stress. The configuration factor is the bonded-to-unbonded surface ratio; high C-factor in Class I cavities increases debonding and postoperative sensitivity.
- Incremental placement, soft-start curing and sectional matrices reduce shrinkage effects and restore proximal contour.
- Amalgam requires mechanical retention and no bevel. Composite requires an enamel bevel and adhesive isolation.
- In deep caries, selectively remove to soft dentin at the pulp floor and avoid exposure; use calcium hydroxide or glass ionomer as a liner when needed.
- Rubber dam is standard for endodontics and recommended for adhesive work.
Worked example
A Class II cavity on a mandibular first molar has a deep proximal box and a wide occlusal outline. The C-factor is high because most surfaces are bonded. One large increment would concentrate shrinkage stress at the gingival margin. Correct approach: sectional matrix and ring, enamel bevel, adhesive, then 2-mm increments cured separately, with the first increment against the gingival floor.
Traps
- Do not bevel an amalgam cavity; it weakens marginal enamel.
- Eugenol-containing temporary materials can inhibit composite polymerisation.
- Do not air-dry etched dentin aggressively; collapsed collagen reduces bonding.
- A radiograph does not determine whether caries is active; use visual and tactile criteria.